Rock control in geomorphology

ROCK CONTROL IN GEOMORPHOLOGY

Skeleton 920

Lake

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MUSKOKA, ant, Canada Contour interval 100 feet, elevations in feet above mean sea level (Courtesy of the Department of Mines and Technical Surveys, Canada)

12

14 km

ROCK CONTROL IN GEOMORPHOLOGY

by EIJU

YATSU

SOZOSHA

8, 3-chome, Kandanishikicho, Chiyodaku, Tokyo

1966

Copyright 1966 Sozosha

PREFACE

ALL RIGHTS RESERVED This book or any part thereof must not be reproduced in any form without the written permission of the publisher.

Printed in Japan

Geomorphologists too long have shied away from investigating . basic processes associated with landform origin and development. Few have gone beyond regarding them in amateurish or superficial ways. In doing so, they have delayed unduly the time when their field becomes truly scientific and useful to persons in allied disciplines. How many engineers, geologists, mineralogists, pedologists, ecologists, foresters, chemists, physicists, or agriculturists turn to geomorphological literature for information that might aid them in solving problems related to the earth's land surface? Should they do so, how often would their efforts be rewarded by finding useful information? It is a sad commentary, but in all probability their harvest would reveal few grains of corn embedded in huge volumes of chaff. This is a condition that Professor Yatsu hopes to correct. The intent of this short book by no means is an attempt to explain or catalogue a wide variety of examples where rock control has produced or is reflected in scientific land forms. Rather, it emphasizes the importance of physiochemical and mechanical processes that affect rock properties, and hence, secondarily, resulting land forms. It deals with fundamental, but largely unsolved, problems in rock dynamics. A style that at times is deliberately provocative is used in the hope that it will stimulate open and youthful minds to develop a truly scientific geomorphology. The fact that the text asks more questions than it answers points up the need for more penetrating research than geomorphologists are likely to deem essential. The hope is that a science hardly advanced beyond the swaddling clothes stage will mature and on the basis of merit attain its potential of being sound, respected, and useful. It should not continue to follow degenerative paths toward becoming little more than an aid in describing scenery. This viewpoint is similar to one that I expressed in presidential addresses before the Association of Americ:m Geographers and the Geological Society of America. My concluding statement in the Hitchcock Lectures at the University of California in 1965 repeated the hope.

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The effect of the influence of William Morris Davis, who is usually considered as the father of American geomorphology, was to divert students away from truly scientific research, such as was rather characteristic of the nineteenth century, into superficial inquiries centered on stages of development in cycles of erosion, a scheme that Davis advocated for many decades with much precise logic. Research was concerned with end products, hypothetical forms of the surface, while the investigation of datails of morphological processes lapsed into almost complete somnolence. Professor Yatsu specifically commends Filip Hjulstrom, Sundborg, Strahler, Wolman and Miller, Leopold and Langbein, Chorley, Glover, Dury, and Hack for their contributions toward developing a more meaningful geomorphology. But the emphasis in the book centers on the contributions of people such as H. W. Anderson, P. F. Kerr, F. J. Turner, F. Birch, D. Griggs, T. V. Karman, A. W. Skempton, L. Bjerrum, R. Grim, M. A. Melton, E. Penner, D. J. Varnes, and Karl Terzaghi. In addition many Japanese are cited, most of whom have published in English. While some of these names will be recognized by' American geomorphologists, probably few have intimate knowledge of their contributions. It is high time that they do! In progressing from superficial "explanatory descriptions," advocated by Davis, toward more meaningful studies of land forms, many geomorphologists, indeed, have struck out in new directions. Climatic geomorphology, currently in vogue in Europe and to some extent in America, is regarded by Professor Yatsu as but one interesting approach, rather than an end in itself. Its practitioners are likely to be concerned with broad features of landscapes and to regard rock types and structures as interesting only because they influence forms of micro-relief. Interpretations of aerial photographs, and we might add, other forms of remote sensing, although useful, will never provide the information needed to understand the origin of land forms. Dependence on mathematical elegance offers little more than the highly logical deductive approach of Davis, at least until sufficient knowledge has accumulated concerning all processes involved. This requires detailed observation and analysis, both on the ground and in the laboratory, where it requires the use of modern equipment. To develop anything like an ultimate geomorphology it is

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necessary to solve essential, fundamental problems underlying the dynamics of rock deformation. This is something where most progress to date has been made by specialists in other fields, many of whom have been engaged in penetrating inquiries. It is not enough to know the physics and chemistry of bedrock, nor how rock behaves when subjected to mechanical tests. Research must emphasize underlying causes, extending into the physical chemistry of minerals on the scale of examining their crystal lattices, and into changes related to time as well as to local environments. Rock alterability ordinarily depends on the fact that minerals are stable in the environments where they originated, but are altered readily when the environment is changed. In the case of a metamorphic rock formed at considerable depth and later brought to the surface, for example, it is necessary to realize that such generalizations must be accepted with caution, because numerous exceptions may be cited. While it is generally true that sedimentary rocks of the orthoquartzite series are more stable than those of the arkose-graywacke series in surface environments, specific examples must be subjected to a variety of inquiries and tests before one knows whether the rule is being followed. Professor Yatsu is by no means suggesting that geomorphology must be developed by people in other disciplines. He notes that while the main contributors of fundamental information to date have been people such as chemists, geophysicists, pedologists, and mechanical engineers, once the geomorphologists get down to business and think in terms of fundamental processes, their contributions will surpass in value those of allied specialists. It is sincerely hoped that this text will be found on the shelves of all institutions where geology, geomorphology, or engineering are included in the curriculum. Its content should be understood by all advanced students in geomorphology and by civil or architectural engineers concerned with the design of structures resting on the ground, the location of highways, railways, tunnels, and dams, as well as mining engineers involved in planning underground workings or open-pit excavations. Its bibliography contains about seventeen pages of useful references, and in itself is an excellent guide to the acquisition of useful information. While serving as a visiting professor in the Department of

IV

Geography of Louisiana State University, Professor Yatsu at no time hesitated to exceed the "call of duty." His enthusiasm inoculated students fortunate enough to participate in his course on geomorphology, and on many occasions they requested him to present extra-curricular lectures and discussions; requests that he invariably accepted. I felt honored when he asked me to contribute this preface to the revised edition of a manuscript which originally was written for the purpose of presentation to his students and faculty members in our department, as a token of appreciation. If the seed planted by Professor Yatsu results in serious consideration of processes involved in rock alterability and bears fruit, we may anticipate the development of a truly scientific geomorphology, a goal that is both highly desirable and by no means out of reach. The book is not a compendium. Although it provides many examples where rock control is evident as influencing landform development, its aim is to suggest directions that investigators may follow with profit. If it results in the realization of many of Professor Yatsu's ideals, a compendium may be anticipated at some future date; and in all probability the professor, with his boundless energy and extreme enthusiasm, may be expected to be a major contributor. R. J. Russell

AUTHOR'S PREFACE The purpose of the present book is to point out some of the basic principles necessary for an exact understanding of rock control problems in geomorphology. It is intended for use as a supplementary reading. Some puzzling expressions and therefore humorou~ narrations are used to encourage and stimulate young students In geomorphological thinking. The book has been developed from my lectures in geomor?h~logy . at the Louisiana State University where I was kindly Invited In 1965. I wish to express my gratitude to the faculty ~:mbers for their kindness and generosity. In July 1966, I JOIned the Department of Geography, University of Ottawa. In this c.omfortable home-like atmosphere, I finished the manuscript of thiS book by supplementing the temporary printing with some explanations and figures. lowe a particular debt of gratitude to the faculty here. I am most grateful to Professor Richard J. Russell, director the Coastal Studies Institute, Louisiana State University, who kIndly honoured me by writing the preface to this book and by enco~raging me to publish it. I would also like to express my gratitude to the following persons: Mr. Kogi Yamaguchi, former teacher of the Ibaraki Normal School, Dr. Yanosuke O~~uka, .late Professor of the University of Tokyo, Professor Filip HJulstrom, l)"niversity of Uppsala, Dr. Yokichi Mino Emeritus Professor of the Tokyo University of Education Dr' Fumio Tada, Emer~tus Professor of the University of T~kYo: Professor Jean Tncart, University of Strasbourg, Professor Arthur N. ~t~ahler, Columbia University, Professor Harley J. W~lker,. LOUISiana. ~tate University, Professor J. Ross Mackay, University of BntIsh Columbia, Professor Mark A. Melton University of British Columbia, Professor Harishankar Prasad Srivastava, University of Ottawa, and Professor Hiroshi Nakano Chuo University, all of whom have exerted a great influenc~ on my work and life. I wish to acknowledge the reasonable criticism by my colleague, Dr. Takasuke Suzuki, Lecturer of Chuo University concerning "The Rock Control Theory" Applied Geography:

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No.5, 1964. The present book is, so to speak, a collection of vindication and apology for those papers. In this sense, he prompted me to write it and kindly helped me in reading the proof. I highly appreciate the valuable suggestions from Professor David Erskine of the University of Ottawa in preparing the manuscript. I am greatly indebted to many authors for their data, tables, and figures that I have referred to, in this book. Those, whose sources are not referred to have been prepared by myself. Finally, I wish to acknowledge my debt to Mr. Kazuyoshi Izawa, Sozosha Publishing Co., for his generosity in taking charge of a pUblication that runs a risk of being financially unprofitable and for his valuable help in correcting the proof.

Department of Geography University of Ottawa July 28, 1966 EIJU YATSU

CONTENTS

Preface .................................. .................... ..... ...... ...... . i Author's Preface ·· ···· ........... ... .... ... .. ... .. ...... ...... .. ..... . ...... V I.

SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGy··· ······ ·· ······ ·· ······ ···· ·· ·· ··· ·················· ..... . 1.1. Geomorphology and its Methods ··· ·········· ··········· ··· ······· ·· 1 1.1.1. Geomorphology··· ............ .. ............... ..... .. ... ........ . 1.1.2. Domains of Geomorphology and its Methods ........ . 1.2. Rock Control Problems .... .. ..... . ..... . . .. .. . . ... .. .... .. .. .. .. ...... 4 1.2.1. Rock Control Problems and its Former Researches 4 1.2.2. Air Photo Interpretation of Geological Structure .. ' 10 1.2.3. Rock Control in Relation to Processes ............ ······11 1.2.4. An Approach to the Rock Control Problems ·········12

II. EROSION AND SURFACE MATERIALS OF THE EARTH··· 15 2.1. Alterability of Rocks······ ·· ······ ·········· ······ ····· ·· ···· ···· ··· ·· ·· ·· 15 2.1.1. Alterability······································ ········ ·· ··· ·· ·· · '15 2.1.2. Methods of Studying Alterability·········· ·· ··· ····· · ······17 2.1.3. Some Problems on the Alteration···· ........ ... .. ..... . ····18 2.2. Erosibility······ .. . ........... ... ...................................... .. ..... '19 2.2.1. Soil Properties and Soil Erosion··· ·· · .................. .. .... 20 2.2.2. Landslips and Slope Rupture················· ····· ·· ·· ···· ·· · 23 2.2.3. Glacial Erosion and Erosibility of Rocks .............. . 34 2.2.4. Denudation and Erosibility of Rocks .... .. ............... 34 2.2.5. Wear of Rocks············· ··· ·· ····· ·······························35 III. MECHANICS OF SOLID ROCKS .... ..... ..... .......... .. ...... . .... .. 45 3.1. Strength of Solid Rocks .. .. ............................................ 45 3.1.1. Definition of Strength ... .... .. ....... .. ............ .. .......... 45 3.1.2. Classification of Disintegration .. ... .. .. ......... ... ......... 45 3.2. Failure of Rocks by Static Load·· ··· ········ ·········· ·· ···· ···· ··· 46 3.2.1. Rheological Behavior of Rocks .............................. 46 3.2.2. Theories of Fracture of Rocks ... .. ... .......... ............ 47 3.2.3. Time Dependance of Deformation and Fracture ·· ···· 47 3.2.4. Conditions which influence the Strength of Rocks··· 51

Vill

3.3. Impulsive Fracture and Others··· ·········· ·· ····· ................... 51 3.4. Cohesion of Rocks .. ········· .. ·· .. ·· ··· ·· ·· ··· .. ·· ········ ···· ·· ... .. ..... 60 3.5. Plasticity of Rocks and Salt Domes ........ · ................. . ...... 61 3.5.1. Plasticity of Rocks· ...................................... · ........ 61 3.5.2. Salt Domes .................... ...... ..... .. ...... .. ... ... ... . ... ... 64 3.6. Wear ....... ......................................... .. ... ....... ... ............ 66 3.6.1. Friction and Wear · ............ .... .. · .. · .. · .. ...... .... .......... 66 3.6.2. Various Wear Mechanism ................. .. .. ............... 67 3.7. Rock Mechanics and Geology ................ · .. · ...... · ............ 70

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IV. MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS ..................... ... ....... ..... .. ...... .... ........... . ··· .. · .. · .. · ·· · ·· · 79 4.1. Mechanics of Weathered Bedrock and Systems of Large Debris ........ ..... ..... ........................... .. ... .......... ... 79 4.1.1. Application of Soil Mechanics to Weathered Bedrock and Systems of Large Debris ......... ... .... .. 79 4.1.2. Some Examples of Field Measurements .. · ............ · .. 81 4.1.3. Some Problems on Unconsolidated or Fractured Rock ............ .... .. ...... ........................ ............... ··· 81 4.2. Mechanics of Fine Debris such as Soils ............. ........... 94 4.2.1. Physical Properties of Soils ................ .. .................. 94 4.2.2. Mechanical Experiments on Soils ............ · .............. 95 4.2.3. Properties of Some Erosible Sandy Soil I, Shirasu··· 96 4.2.4. Properties of Some Erosible Sandy Soil II, Masa ... 98 4.2.5. Stability of Slope ......... .................................. .. 102 4.3. Mechanics of Micronized Debris such as Clays .......... .. 104 4.3.1. Clayey Soils ........ ........................ ...................... 104 4.3.2. Mechanics of Clay .................................... ·........ 104 4.3.3. Thixotropy and Mudflows ................................. 106 4.3.4. Properties of Some Clayey Soil I, Kanto Loam ... 107 4.3.5. Properties of Some Clayey Soil II, Post-glacial Marine Soils ........................... ..... .................... .. 111 V. CONCLUSION

...... .......... ..... .. ..... .... ........ .... ... .. ........ .. ... .

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Author Index .............. .. .................................. .... ...... Subject Index ..... ... ............. ... ...... ... ... ...... .. ......... .. .....

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SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGY

., 1.1. Geomorphology and its Methods 1.1.1. Geomorphology. This natural science is concerned with land forms, namely with the forms of land surfaces. It is very difficult to define exactly the last two words of the preceding sentence. The term "land surface" is thought of as the boundary between the solid and the fluid such as the hydrosphere or the atmosphere. In this case, the word "boundary" implies its meaning not in the size of atoms or molecules but in macroscopic size. Consider the soil covering the bedrock of the earth; it is composed of soil particles, air and water. Water and air exist between soil particles or on their surfaces. Also, in the case of bedrock, air and water are included in cracks, joints and cleavages. These contact surfaces between the solid and air or water are not called the earth's surface. Therefore the word "land surface" is the one which covers the uppermost particles of soil or of bed rocks. Exogenic processes occur intensively at or near such boundaries between the solids and fluids. One portion of consolidated solids are separated; abstracted into fluids, namely liquids and air; transported by them; and then deposited. On the other hand, the fluids invade the solids and alter them. This is an aspect of the weathering phenomena. Altered solids change their kinetic characteristics and begin to deform themselves or to slide and creep. The rupture and slip of the earth slope are examples of such mass wasting phenomena. Endogenic processes derived from the energy of the earth's interior contribute much to the deformation and displacement of the surface of the earth. Orogenic or epeirogenic movements and volcanism play this role; they join in the deformation and displacement of the earth's surface together with the exogenic processes.

1.1.2. Domains of Geomorphology and its Methods. It is intended here neither to describe the history of the development of

SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGY

Geomorphology and its Methods

geomorphology nor to treat in detail the methods of geomorphology. In this connection, several textbooks are very easily accessible so that the author wishes to leave the trifling and delicate details to them, and he intends only to summarize his personal opinions about the problems. Such a brief epitome might be necessary, preliminary to the following discussions of section 1. 2. Considering the development of geomorphology, it was a topology of forms of land surface and had devoted itself to the definitions and classifications of land forms, just as phytology, which used to be taxonomy or plant morphology in its first stage. It is a matter for congratulation that our geomorphology has developed into comparative embryology as phytology has done into embryology and then into physiology. But alas! Our geomorphology has strayed into that fanciful theory of Davis. What a deplorable thing this is for the appropriate development of geomorphology! The principal role of gemorphology is, of course, in studying the evolution of land forms. The history of the development of land forms is thought of as consisting of two forces-an endogenic process or endogenic factor, for example, crustal movements and intrusion of igneous body; and an exogenic process, such as erosion, transportation and sedimentation. These two forces, moreover, have changed their intensity in the course of the development of the earth. Exogenic processes are especially influenced by climatic environments which change as time passes. It is true that there is a land form of fault. Everybody agrees readily and without any hesitation that a shatter zone is weak and likely to be erosible. Then, why is the shatter zone weak? How is it eroded? On what does this weakness depend? Furthermore, what is the mechanism of erosion? In answering these questions, many geomorphologists cheat their students, flourishing their abstract explanations or their own imaginations without any intention of scrutinizing the true nature of the matter. Do they not have any ability of understanding the true nature of matters? Or do they have any eagerness to do so? Are they not ashamed of themselves as scientists? Professor Filip Hjulstrom (1935) should be worthy of our greatest respect, for he has built up the school of Uppsala with his lofty ideal for science and integrity, doing researches into exogenic process and its application to geomorphology, especially

to fluvial geomorphology, while a crowd of geomorphologists became apostles of Davis. So we look forward to the researches by young students of this school (Sundborg, 1956). Recently a group of American geomorphologists have intensively developed analytical and dynamic researches in this science, and it seems to be a resurgence of Gilbert's idea (1914) and the influence of a late American engineer, Horton (1945). Their contribution in two decades should be highly appreciated (Strahler, 1952 ; Wolman and Miller, 1960; Leopold and Langbein, 1962; Chorley, 1962; Glover, 1964; Dury, 1964; Hack, 1965) . It is true that climatic geomorphology, which has been quite in vogue recently, has contributed greatly to the study of geomorphology. It is, of course, a very excellent approach to this science. However, the writer wonders whether this method, popular in recent times, is not merely a systematization of simple observations, and he feels that there is some limitation to this approach. In the domain of geomorphology, there are many phenomena very difficult to observe or measure in a short while, so it is natural that we should use the historical approach to the study of geomorphology. Most of the researchers occupied with this kind of historical approach, however, are sadly lacking in the sense of modern science, and have no knowledge of 19th century chemistry and do not even understand the Mechanics of Newton. And how many of these researchers there are in the world! Their theory is composed of mere deductions. They fall into a chain reaction of empty imaginations, though trying to shake themselves out of Davis' theory. The writer contributed to the first number of Applied Geography on how applied geomorphology should be, under the title of "Les caracteres fondamentaux de la geomorphologie appliquee" (Yatsu, 1959). At present, some researchers of applied geomorphology seem very enthusiastic about drawing maps of land form classification or geomorphological maps and seeking the way of their expression. It might be very handy to the users of those maps. But, if they were too much concerned with the way of expression and too much fascinated with the beauty of color in maps, they might be artists. It is as if they were practicing flower arrangement(Ikebana) . Geomorphological maps would be of little use unless they contained not only classifications of land forms, but also dynamic and physical characteristics of the matters that compose land forms. Those

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SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGY

would be, as it were, maps needed for travelers or useless guidebooks for those engineers who are to do some work with them. It might be better for geomorphologists to be indulged in fantasy with those maps on their laps, to make some guesses at land forms looking at air photograph, to observe sometimes outcrops in the fields, or to take a survey of the whole panorama of land forms from the top of mountains. But be careful! They need to be careful not to degrade into studying the "Science of Scenery}' It is necessary to introduce dynamics into geomorphology so that this science may rank among modern sciences. It is natural, of course, that geomorphology cannot be explained in every respect by dynamics, but at least, dynamics is essential to the explanation of processes of exogenic agents. Geomorphology should be much obliged to mathematicians and hydrodynamists for their participation in the study of it. In their case, it is absolutely necessary that they should use their mathematical approaches but only after they have understood the full intrinsic 'phenomena of geomorphology. If not, their approaches would be a science of fantasy. The system of the study of geomorphology has no need for smartness or elegance. It is the fundamental nature of land forms that should be made clear (Yatsu, 1964). 1.2. Rock Control Problems 1.2.1. Rock Control Problems and its Former Researches. In brief, rock control theory is concerned with the influences of rock properties on the formation of land forms. The problem of rock control has been considered as a geomorphological concept for a very long time, and the writer believes it began with the start of geomorphology; therefore it is not a new concept. However, according to many books and reports on this subject, it is, strictly speaking, treated as structure control such as distribution of strata, folds, faults, unconformities and so forth, although the reports sometimes deal with the physical and chemical properties of rocks which compose layers. Their treatment of this difficult subject is considerably rough, and some of those researchers, even while saying with a nonchalant air that geological structure is a dominant control factor in the evolution of land forms and is reflected in them, have no intention

Rock Control Problems

5

of studying the properties of rocks. Some have declared that the general features of land forms are determined by climatic environments and have insisted that rock control is only important in micro-configuration. Davis thought that structures, processes and stage are the dominant factors in the formation of topography (Davis, 1899). This concept was correct and adequate. His concept of the. term stage, however, was of imaginary time in a fanciful cycle. He deceived his followers, giving merely verbal descriptions to various processes which were easily accepted. This trend was an extremely regrettable digression and forced the advancement of geomorphology to be enormously retarded compared with the advancements of the other natural sciences. Many books juggle to substitute the concept of structure control for that of rock control, or consider the latter to be a factor of lower degree than the former, although they distinguish them from each other. Is it really adequate to depreciate the problems of rock control in comparison with structural control? To this question the writer wishes to reply with this antagonistic question. Imagine the thick deposition of completely homogeneous and isotropic strata followed by diastrophisms such as tilting, folding, faulting, etc. Consider that these strata do not lose the characteristics of their homogeneity and isotropy in spite of such crustal movements. Is any structure reflected in the topography in this case? It is common in nature that strata different in physico-chemical characteristics alternate, and that these strata are deformed by diastrophism to produce folds, faults, cracks, joints, shatter zones and so on, which give anisotropic parts to these strata. Furthermore, two kinds of rocks or strata of different strength are commonly in contact with each other unconformably. This is the reason why structures are reflected in land forms. In other words, it results from the anisotropy and non-homogeneity of the materials forming land forms that the structures give the important influences upon the topography. The existence of the anisotropy and non-homogeneity, namely differences in rock properties, enables us to acknowledge the structures. Is this not a correct opinion? It is more general and more adequate to state that the structures are reflected in land form because of the differ~nce in strength or erosibility of rocks; therefore

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SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGY

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Rock Control Problems

SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGY

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oti.lJ...l.J=J...]:,j,.ij

- 8 -6-4- 2024

Fig. 2-c.

ESCARPMENT LINE L BOUNDARY OF GRAVEL

SECTION LINE

Fig. 2-a.

r

-2 0 2 4 6

Cumulative-frequency curve of alluvial fan deposits.

Yatsu studied the fluvial deposits of many rivers in Japan and found that the grain size distribution shows bimodality, the geomorphological significance of which is of great importance. He concluded that this characteristic of fluvial deposits must be reflected in the discontinuity of the longitudinal profile of graded river which is not expressed by one exponential curve but by two in the great majority of cases. By and large, an abrupt change of slope is noticed in fans at their margins, whether the alluvial fan be large or small. In view of the existence of discontinuity in graded river profiles, discontinuous slope change at fan margins is easily understood. Of course, the origin of such a phenomenon is bimodality of the grain size distribution of fan deposits. If the differentiation of land forms by ' the different quality of various rocks is rock control, then uniform features caused by homogeneity of their materials should also be rock controlled topography. Is there any difficulty, if so, in thinking that general phenomena in land forms which are due to universal characteristics of rocks should be rock control itself? Therefore, the discontinuity of slopes in graded rivers and at fan margins must be a kind of rock control

~ MOUNTAIN AREA

SAMPLING STATION

- 6- 4- 2024

Y

Topography of Echi River Fan and Inugami River Fan.

phenomena. E

-

----~

140 1

20 - - - - - + " < ; , : - - - - - - , - - -----,--- - - - - 1

'I

,

"r--....

-----_

100r------------+~~~--~------~--~~-~_----+-----------~

r------+---~-~- ~-=-=_~---------~-~-~--~-== __~_-~ -----------. Fig. 2-b.

Radial profiles of Echi River Fan and Inugami River Fan.

the topography is controlled by rocks. Such a way of thinking changes the point of view about whether rocks or structures should be stressed. The conversion of a point of view sometimes makes a great advancement of science in general. Without any correct understanding of the relation between rock control and structure control, many morphologists use the word "rock control" as a magic cloak, easily saying "that depends on the differences in rocks, this part remains not eroded because of hardness, that part is hard because it remains protrusive as you can see." They don't want to clarify the mechanism of

I

I

10

SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGY

rock control. If they don't somehow inhibit this circular thinking, they cannot expect the development of this science, and the way of advancement still remains closed for geomorphologists. Concerning rock control problems many text books of geomorphology take such instances as follows: Cuesta Structural bench Some knick point and fall maker Permeability of soils which influence the stream texture Dike ridge Mesa, Hogback Inversion of topography Structural plain Karst topography, etc. Concerning these items, is there any investigation that clarifies the essential problems of rock control, going beyond naive descriptions of simple observations and conjectures? Although reports are often seen on the chemical analysis of limestone cave water, there are very few which deal with the erosibility and other physico-chemical, mechanical properties of rocks for the purpose of geomorphological investigations. Recently some papers have treated these properties of rocks, and someone investigated the discontinuous frequency distribution of grain size of fluvial sediments and explained the discontinuity of slopes at fan margins (Yatsu, 1954, 1957), or tried to introduce the methods of soil mechanics as an approach to dynamic geomorphology (Yatsu, 1957). 1.2.2 Air Photo Interpretation of Geological Structure. In recent times, air photographs have been .used in the study of the geological structure, namely air photo interpretation has become very popular. Numerous books and periodicals on air photo interpretation are published in many countries. How is it possible to guess the geological structures from air photographs? These are taken from high altitudes above the ground, and on such pictures the topography, vegetation and other objects of the surface of the area concerned are developed. Many kinds of properties of the earth's surface appear in light and dark. Deduction processes of geological structure interpretations are mainly in such a way as follows:

Rock Control Problems

11

air photograph

interpretation of topography

prediction of geological structure

This scheme is very fundamental. The possibility of this thinking process simply depends on the fact that the topography is controlled by the situation of distribution and arrangements of physico-chemical, mechanical properties of rocks or its assemblage. In this connection, an intensive study of these properties should be indispensable. If there should be anyone who thinks that air photographs and geological maps provide enough information for studying the problems of rock control, he should be guilty of the above-mentioned circular reasoning. The interpretation of geological structure will result from the exact and abundant information concerning the mechanism of rock control. Some statistical conclusions obtained from the juxtaposition of air photographs and geological maps are merely prospective hypotheses, absolutely apparent and sometimes deceptive. The problem is to examine these hypotheses and fundamentally resolve the problems of mechanism and processes of rock control. 1.2.3. Rock Control in Relation to Processes. As to strength of rocks, it is important to elucidate how different types of rock strength control and condition the features of the land surface. Moreover the strength value of the same rocks differs according to processes. Even if the processes and rocks are same, the strength is not the same if the rate of processes differs. Therefore the problems of rock control should be understood in relation to geomorphological processes. The latter remarkably depends on the condition of circumstances. In this meaning, climatic geomorphology should be thought of as an approach to geomorphology. Even the same rock changes its erosibility with different types of processes, as in the case of limestones, a well-known example. The same materials will naturally have different

SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGY

REFERENCES

forms due to the kind and magnitude of forces, velocity and duration of their application. It is, therefore, very ridiculous and meaningless that the properties of the materials that constitute land forms should be treated independently of the agents acting on them.

mechanical characteristics of rocks, soil, clay and so forth. It may be a good idea to perform ordinary mechanical experiments. That is the first step in our research anyway, although we should not remain satisfied with these experiments. We must solve the fundamental and essential problems that underlie apparent mechanical characters, the problems of mechanism of rupture of solids, of cohesion and repulsion, of electrical double layer structure in the colloidal state, of · adsorption, etc. Based upon physics of solid state, surface chemistry and the quantum theory of matter, we must study the surface materials of the earth to solve the above-mentioned problems. This approach will not only develop the rock control theory, but also will offer accurate information about surface materials of the earth, which is needed by engineers. This is the rock control theory in its real sense.

12

I

I'

1.2.4. An Approach to the Rock Control Problems. We must return to the subject of rock control. Indeed, the study of exogenic processes is remarkably advanced, but the writer doubts if surface materials of the earth affected by processes are taken up dynamically and physico-chemically in the light of modern science. Such an approach might be very difficult, of course. When even the same rocks are affected by different forces, their resistance and strength become different according to the kind or quantity of forces as mentioned above. The study of rocks like elastic bodies or visco-elastic bodies has been made by many researchers. Dynamics takes up and studies the stress and strain of rocks as isotropic and sometimes orthotropic materials. Rocks .behave as elastic bodies with a rapid application of forces, but when they are affected by gradual forces, they undergo plastic deformation. The former case results in faulting, whereas the latter case results in folding. How do surface materials of the earth behave themselves toward the exogenic forces? What about soil? What about clay? In what categories of British Rheologist's Club can we put them? The writer, however, cannot be quite satisfied with rheology itself unless it has a close connection with molecular theory. In general, dynamics takes up a small portion of mass, calculates the equilibrium in that small portion, estimates the deformation, and solves the differential equations of this small portion as a continuous body. Thus it presupposes the continuity of materials, but it is a macro-view or a simple statistical method. It is true that in hydrodynamics we might not need to take into consideration behaviors of a water molecule one by one. But in the case of mechanics of rupture, creep and sloppy mud, a macroview cannot solve various problems. Soil mechanics and rock mechanics are now both deadlocked. Is there anyone who wants to struggle in order to find some key to these difficult problems? It is essential for geomorphologists, especially for those who deal with problems of rock control, to be acquainted with the

13

A doodle: Geomorphologists have been trying to answer the what, where, and when of things, but they have seldom tried to ask how. And they have never asked why. It is a great mystery why they have never asked why.

REFERENCES

CHORLEY, RI., 1962, Geomorphology and general systems theory, U.S.G.S. Prof. Paper, 500B, p.10. DAVIS, W.M., 1899, The geographical cycle, Geogr. Jour., vol. 14, pp. 481SOL DURY, G.H., 1964, Principles of underfit streams, U.S.G.S. Prof. Paper, 452 A, p.67. GILBERT, G.K., 1914, The transportation of debris by running water, U.S. G.S. Prof. Paper, 86, p. 363. GLOVER, RE., 1964, Dispersion of dissolved or suspended materials in flowing streams, U.S.G.s. Prof. Paper, 433B, p. 32. HACK, I.T., 1965, Geomorphology of Shenandoah Valley Virginia and Origin of the residual ore deposits, U. S. G. S. Prof. Paper, 484, p.84. HJULSTRiiM, F., 1935, Studies of the morphological activity of rivers as illustrated by the River Fyris, Bull. Geol. Inst. Uppsala, vol. 25, pp. 321-532. HORTON, RE., 1945, Erosional development of streams and their drainage basins ; hydrophysical approach to quantitaive morphology,

14

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" I I'

I'!

I

I,

SIGNIFICANCE OF ROCK CONTROL IN GEOMORPHOLOGY

Bull. Geol. Soc. Am., vol. 56, pp. 275-370. HOWARD, A.D., 1965, Geomorphological systems-equilibrium and dynamics, Am. Jour. Sci., vol. 263, pp. 302-312. LEOPOLD, L.B., and LANGBEIN, W.B., 1962, The concept of entropy in landscape evolution, U.S.G.S. Prof. Paper, 500A, p.20. MELTON, M.A., 1958, Geometric properties of mature drainage systems and their representation in an E4 phase space, Jour. Geol., vol. 66, pp. 35-54. MELTON,M.A, 1958, Correlation structure of morphometric properties of drainage systems and their controlling agents, Jour. Geol.. vol. 66, pp. 442-460. SCHUMM, S.A, and LICHTY, R.W., 1965. Time, space, and ::ausality in geomorphology, Am. Jour. Sci .• vol. 263, pp.110-119. STRAHLER, AN., 1952, Dynamic basis of geomorphology, Geol. Soc. Am. Bul!., vol. 63, pp. 923-938. SUNDBORG, A., 1956, The River Klaralven, a study of fluvial processes, Geografiska Annaler, vol. 38, pp. 127-316. TANNER, W.F., 1959, Examples of departure from the gaussian in geomorphic analysis, Am. Jour. Sci., vol. 257, pp.458-460. WOLMAN, M.G., and MILLER, J .P., 1960, Magnitude and frequency of forces in geomorphic processes, Jour. Geo!., vol. 68, pp.54-74. YATSU, E., 1955, On the longitudinal profile of the graded river, Am. Geophy. Union, Trans., vol. 36, pp.655-663. YATSU, E ., 1957, On the discontinuity of grain-size frequency distribution of fluvial deposits and its geomorphological significance, Proc. of 1GU Regional Conference in Japan, 1957, pp.224-237. YATSU, E., 1957, On the application of the method of soil mechanics to the investigation on the erosibility of the bare mountain area in Japan, an approach to the dynamic geomorphology, Miscellaneous Rept. Res. 1nst. Nat. Resources, Tokyo, no. 45, pp. 1-8. YATSU, E., 1959, Les caracteres fondarr.entaux de la georr.orphologie appliquee, Applied Geography, no. '1, pp.13-28. YATSU, E., 1964, An approach to the rock control theory, Applied Geography, no. 5, pp. 3-6.

II EROSION OF SURFACE MATERIALS OF THE EARTH

(

Concerning . depositional topography, there are probably many problems of rock control such as the occurrence of slope discontinuity at fan margins due to the bimodality in grain size frequency of the fluvial sediments, as noted in the first chapter. However, problems of rock control on the depositional land forms have not been discussed frequently. In this chapter the main subject is the erosibiIity of the surface materials of the earth, which is the fundamental problem of rock control on erosional land forms. Surface materials in this case imply the materials at and near the earth's surface. 2.1. Altere bility of Rocks 2.1.1. Altere bility. By the action of weathering, solid rocks change in chemical composition and become debris of various particle size. Namely, the weathering processes cause the decomposition and fragmentation of bedrock, and, generally speaking, these processes provide the preparation for erosion by previously weakening the bedrock. For instance, there is no erosion of rocky coasts by mere wave erosion; weathering processes always participate in and aid the processes of marine denudation. Valleys are not, of course, merely the products of deepening and lateral erosion by stream processes. Valley walls suffer from weathering processes, and the detritus produced by weathering is transferred to the valley bottom by mass wasting such as landslips and rupture of slopes (c/. 4. 2. 5) and is then transported by rivers. The main role of river processes ( is considered to be transportation rather than erosion. Therefore, the erosibility of rocks in any region depends primarily on the problem of whether or not the rocks in the region are easily weathered and are ready to . undergo fragmentation and lose the force of coagulation as massive rocks. Consequently, rock control makes its appearance through the medium of weathering processes. Weathering is generally defined as the disintegration or

16

Ii:I

I

EROSION OF SURFACE MATERIALS OF THE EARTH

A:lterability of Rocks

decomposition of rock in place by external forces. In view of the fact that the materials become more easily eroded, the changes in the properties of rocks by endogenic agents such as hydrothermal alteration and diastrophism, which causes the fragmentation of rocks, are as much worthy of attention as the fragmentation and wearing resulting from movements ih the flowing media. Therefore, whether changes occur in place or during transportation, or whether by exogenic or endogenic forces, we must study all of the phenomena of these changes in the chemical and mechanical properties of rocks and debris; that is, all transitions from materials difficult to be eroded into the highly erosible ones. Such a transition is called alteration, and the ease of this transition might be designated "alterability." The writer does not like to coin a new word, because so many geomorphologists are patients of definition-mania that a serious confusion of technical terms occurs . in geomorphology. Davis was the most grave case. We must control the issuance of licenses for technical jargon and discard them. Most textbooks on geomorphology divide the geomorphological processes in two parts, exogenic and endogenic, and consider the processes of weathering, erosion, transportation and deposition as the former, and crustal movements (epeirogenic and orogenic) and volcanism as the latter. The above usage has overlooked the decomposition and fragmentation by hydrothermal reaction and diastrophism, since geomorphologists are not so much interested in the actual materials which form the · topography. Is this not a great mistake of geomorphologists, who pretend to be much interested in facts of rock control by verbal expressions, but who will not try to really recognize the rock control itself? Alteration naturally includes such processes as: 1. Weathering, 2. Wear, disintegration by impaction and decomposition, 3. Production of mylonite, breccia, gouge, and formation of fissures and joints by various stresses, 4. Alteration of minerals by hydrothermal reactions and formation of clay minerals with a resulting decrease in the strength of rocks. When minerals and rocks undergo these processes, their attitudes depend not only upon their species but upon the function of the kind, intensity, duration, and circumstance of action. Whether the processes are continuous or intermittent assumes great

importance. For example, repeating stresses may introduce fatigue failure. The problems are complicated but interesting. There are few articles which discuss the resistance of rocks to shattering action. It is possible to compare their relative resistance in areas where various kinds of rocks are exposed near each other and where they are broken by the same faulting action. Mudstone, shale, and limestone easily undergo plastic deformation and are usually not shattered. On the other hand, such hard but brittle rocks as slate, granite, and diorite are conspicuously shattered. Rock mechanics will offer experimental data about these problems. Although extensive precise studies are often revealed in the mineralogical literature, they always concern merely the problems of successive changes of minerals. Very few articles (Takahashi et at., 1963) discuss the strength changes as the rocks undergo hydrothermal alterations. This problem is also very interesting to geomorphologists who must be well acquainted with mechanical and engineering methods to investigate it.

17

2.1.2. Methods of Studying Alterability. In order to study the degree of alteration, the following characteristics are very useful and effective: 1. Changes of chemical composition and optical properties, 2. Degree of fragmentation, 3. Elasticity or velocity of dilatational waves in fresh bedrock compared with those of their weathered parts. Weathering of minerals is also investigated by X-ray analysis and electron diffraction by electron microscope, all of which reveal changes in the crystal lattice. In the processes of alteration, unstable minerals disappear very early, whereas the resistant minerals remain until a later stage. Sedimentary rocks are C(jlmposed of resistant allogenic and authigenic minerals. The latter is thought of as stable during diagenesis, although generally unstable during the processes of weathering. It is very difficult to measure the velocity of weathering in natural conditions. Geomorphology always depends upon very questionable velocity values in respect to this point. The investigations of old buildings, walls and monuments of various kinds of rocks, the date of inauguration of which are known

' ;<

18

exactly, will give the data for this question to some degree. Some 80 years ago Geikie (1880) already made a survey of dated tombstones in Edinburgh. Volcanic rocks, ashes and recent moraines are good materials to investigate to measure the velocity of weathering processes. Soil scientists seem to have been more interested in this problem and to have made more researches than geomorphologists (Jenny, 1940).

I II

Erosibility

EROSION OF SURFACE MATERIALS OF THE EARTH

2.1.3. Some Problems on the Alteration. Concerning the problems of hydrothermal alteration, some papers have discussed those in Hawaii, U. S. A. and Japan. The clay derived from this reaction sometimes is given attention from the engineering point of view because of its swelling properties. Clays such as montmorillonite or mixed layer minerals of montmorillonite and illite or others in the Hakone volcanic region give rise to the rupture· of tunnel linings and to the occurrence of landslides. Turner explained in detail the structure of metamorphic tectonite and his book is very useful for geomorphologists in understanding the formation of tectonite by the stresses of shearing, compression and tension (Turner and Weiss, 1963). Keller (1955) summarized many papers on chemical weathering. Some selected references, which the students have to scan will be given at the end of this chapter. Solubility of rock forming minerals depends on their components. Monovalent ions are leached out more quickly than divalent ones; the latter more quickly than trivalent ones, and Al and Si remain to form clay minerals. The hydrogen ion concentration of environments, however, has great importance in this case. The larger the surface per unit mass and the higher the temperature, the quicker the chemical reaction is in general. A unit of mass will acquire a larger surface if it is crushed into finer particles. Chemical reaction occurs on the surface of the material, thus the finer materials pulverized by processes of mechanical weathering undergo various chemical reactions very easily. The platy voids in the solid whose surfaces are parallel to crystal lattice planes are called cleavage. If the voids in the solid have linear or irregular forms, this solid is referred to as porous. If water contained in the voids is frozen, the solids are extremely disintegrated. The BET method is the most convenient and exact one for determining the specific surface (Brunauer et at., 1938).

19

The stability of minerals will be mentioned briefly. In case of the weathering processes of igneous rocks, olivines most easily undergo chemical alteration, followed in increasing order· of stability by pyroxenes, hornblendes and biotites among mafic minerals. This order is thought to be the same as the crystal differentiation series. Concerning feldspar, calcic plagioclases are more easily affected by chemical weathering than alkali feldspars such as albites and orthoclases, and microclines are also considered stable. Quartz and muscovite are conspicuously durable to weathering processes. Silicate minerals formed at low temperature are relatively stable, whereas those formed at high pressure and temperature are, to the contrary, unstable in the circumstance of the ordinary temperature and pressure at or near the earth's surface. However, it is not correct to consider these series as adequate under every condition. For instance, calcite is very easily dissolved in humid regions that are rich in vegetation and water, whereas calcite plays the role of a resistant mineral in dry regions without vegetation. Among the clay minerals produced by weathering processes as stable residuals, kaolinites are stable in acid environments, while montmorillonites remain unchanged in alkali condition. These two clay minerals, however, are unstable during diagenesis under sea water and are gradually converted into illites or chlorites. Authigenic minerals such as gypsum, apatite, glauconite, zeolite, chlorite, albite, etc. are stable during diagenesis, whereas they are unstable during weathering as mentioned above. Throughout the processes of weathering, transportation, deposition, and diagenesis, the stable minerals are clay minerals, quartz, chert, muscovite, tourmaline, zircon, brookite, and anatase, which occur either as allogenic or as authigenic minerals in the sediments. 2.2. Erosibility

In the preceding section, the alterability or its antonym, stability of rock forming minerals were discussed. This section will deal with the susceptibility to erosion, namely erosibility of the mass of disintegrated particles pulverized and decomposed from fresh rocks. Moreover, the behavior of solid rocks to various agents will be illustrated by some examples.

( :A

~ )!. i

21

EROSION OF SURFACE MATERIALS OF THE EARTH

Erosibility

2.2.1. Soil Properties and Soil Erosion. Human activities often accelerate geological erosion of the surface materials of the earth. This accelerated erosion is called soil erosion. There are several types of soil erosion such as rain wash erosion, gully erosion, and wind deflation. Soil scientists have contributed much more to this problem than geomorphologists. As Baver (1956) has stated, soil erosion of the first type is due to dispersive action and transporting power of rain wash water which is affected by rainfall characteristics, slope and area of the land, vegetation cover, and soil properties. From this relationship, we obtain the partial derivative with respect to soil properties as the subject of this section. When rainfall intensity exceeds infiltration capacity (Horton, 1933), runoff occurs. Many geomorphologists stress the relationship between infiltration capacity and drainage texture. According to Baver, the effect of soil factors on erosion may be summarized as follows:

dispersion, called the ultimate silt plus clay. Also, he measured the colloid percent by the water vapor absorption method and moisture equivalent. These physical measurements · were expressed as a percentage of the dry weight of the soil fraction, less than 2 mm in diameter. His dispersion ratio and erosion ratio are as follows: suspension percent Dispersion ratio ultimate silt plus clay · t' dispersion ratio E rOSIOn ra IO = ratIo . 0 f co ll'd . t ure eqUlva . Ient 01 percent to mOis Anderson studied 14 watersheds of the Coast Range in southern California, and he expressed the relationship between erosibility and physical characteristics of soils as in Table 1. The physical measurements suggested by Middleton, he noticed, could be recommended as a good index of soil erosibility. He illustrated the aptness of his equation by comparing the calculated erosion to measured erosion for some watersheds as in Fig. 3.

E=K~D­ APp where K: proportionality constant D: an index of the ease of dispersion A: an expression of the infiltration 'capacity of the soil surface P: permeability of the soil profile p: size of soil particles Musgrave (1947) has stressed the difficulty of expressing the erosibility of soils by single numerals. Woodburn and Kozachyn (1956) studied Mississippi gully soils and stated as follows: it appears that soils vary widely in their resistance to erosion as determined by any method· .. loose sandy material from different geologic sources had about the same erosion potential regardless of the method of evaluation. In general splash erosion increased with an increase in sand content of the soil. Aggregate stability decreased with increasing sand content. Anderson (1951) expressed the erosibility of soils by using Middleton's dispersion ratio and erosion ratio. A correct concept is very important in researches, although it seems to be extremely rudimentary and simple at first. What is Middleton's idea? Middleton (1930) determined the silt plus clay in the soil in the absence of chemical or mechanical dispersion, called the suspension percent, and the silt plus clay after standard

Table 1. Equations relating physical characteristics of soils and cover density to erosion (after Anderson, 1951).

20

Equation No.

Equation 1

Correlation coefficient

1. Log Es=3. 073-2. 430 log C+3. 427 log DR 2. Log Es=4. 786-2. 486 log C+2. 473 log ER 3. Log Es=l1. 461-2. 524 log C+2.189Iog S-3. 288Iog(si+cl) Coll 4. Log Es=2. 127-2. 341 logC+3.861 logDR+1. 353 Iog ME 5. Log Es = 10.279 -1. 788 log C+ 1. 151 log S-3. 164 log Coll

.888 .878 .849 .890 .854

lEs=Average suspended sediment content of stream flow in ppm; C= average cover density on watershed, per cent; DR=Dispersion Ratio, ER= Erosion Ratio; S=Suspension; si+cl= Ultimate Silt plus Clay; Coll = Colloid, ME=Moisture Equivalent; and log= logarithms to base 10.

Anderson (1954) defined the surface-aggregation ratio as follows: surface area on soil particles of sand and coarser size ( >0.05 mm in diameter) divided by the aggregated silt plus clay; surface area is obtained by considering the particles as spheres and assigning mean diameters of 7. 5, 3. 5 and O. 9 mm to greater than 5. 0, 2. 0 to 5. 0, and O. 05 to 2. 0 mm particle-size classes respectively; aggregated silt plus clay is the ultimate silt plus clay minus the suspension percent. He applied the same method to the investigation of soil erosion in . western Oregon and northern California (1961) and concluded that the soil erosibility index is significantly related to soil-geologic rock

22

Erosibility

EROSION OF SURFACE MATERIALS OF THE EARTH 400

~200

\

1/

w

o

z

~100 §' SO >- 60 0

0

Vo

0

0

0

0

1/

1 ;/

0 B 6

2~ 11

Fig. 3.

1/

Note: -

m ~~~~I\~~et vai~~~e a1.j tlo

11111

2 4 6810 20 406080100 @MEASURED SUSPENDED SEDI MENT-IN THOUSANDS ppm

200

Relation of calculated erosion to measured erosion for some south coastal watersheds in California (after Anderson, 1951).

Table 2. Soil-geologic sequences of physical soil characteristics and erosibility for major soil-geologic types: Santa Maria and Santa Ynez Basin, California (after Anderson, 1951) . Geology' Miocene Continental (sandstones) Quaternary terrace deposits (limestone) Upper Cretac· eous sediments (shale) Middle Mio·

~:dfm~nat~ine (shales and sandstone) Upper Eocene marine sediments (shale) Lower Cretac-

:~drm~:{;ne

jSuspen- Ultimate Silt

type and that the surface-aggregation ratio is also related to vegetation and geographic zones in these regions (1961). Although his studies of course succeeded very much in clarifying the erosibility of soil, there remain still many problems. What determines the value of aggregated silt plus clay, suspension percent, ultimate silt plus clay, etc? What kind of clay minerals exist in this soil? How much is the cation exchange capacity of that soil? How about the absorbed ions? What is the aggregation? It seems to be indispensable for studying soil erosibility to solve the clay-mineralogical and physico-chemical problems on erosibility itself. If not, the erosion ratio is merely a simple, apparent, and statistical thing. There is much qualitative and indirect evidence that high fe rtility does reduce soil erosion losses. It is, as Peterson (1961) pointed out, partly because fertile soils can grow excellent vegetation cover that reduces erosion, and on the other hand, because highly fertile soils generally have better tillage than their depleted counterparts. Higher fertility moreover will reduce soil erosion through more organic residues, more active soil flora and fauna, and higher soil organic matter contents. Regarding wind erosion of soils, three major factors are involved; wind velocity, nature of the surface, and soil properties. Among the last two, the most important factors are the aggregation of soils which undergoes soil erosion and the conditions of the state of soils, especially soil water content, because erosion by wind only occurs in dry regions. Aggregation of soils depends upon the content of clay and organic materials, clay mineral species, and physico-chemical properties of soils. We will skip their considerations.

1

/

V

23

Moisture Dispersion Erosion Relative Colloid equivalent Ratio Ratio erosibility2 Percent Percent

sion Percent

plus Clay Percent

19.5

39.3

11. 3

11. 9

49.6

52.2

100

16.1

37.9

19.5

14.5

42.5

31. 6

59

22.4

61. 3

27.5

26.5

36.6

35 . 2

35

15. 1

66.1

36.0

25.8

'23.2

16.8

7.4'

15.2

94. 1

39.0

23.4

16.1

9.6

2.12

5.1

36.2

31.4

16.3

14.1

7.3

1.34

(shale)

'From Geologic Map of California, Jenkins, 1938. Parenthetical expressions were from field observations at th~ particular places where soil samples were taken. 'From Equation 1, Table 1, with Miocene Continental geology taken as 100. 'The standard deviation of the Dispersion Ratios of this soil·geologic type, with five replications, was 2. 1, that is about 9 percent of the mean, indicating little variation within the geologic type.

2.2.2. Landslips and Slope Rupture. Both terms indicate different types of slope failure. Civil engineers commonly combine them into one term, landslide, whose meaning is different from Sharpe's concept (1938). The word "landslip" is almost the same as "earth flow" in Sharpe's classification of mass wasting. In section 4. 2. 5., the reason why the writer challenges the use of Sharpe's terminology will be demonstrated. Landslips imply plastic deformation and flow of the mass wastes that compose the slopes of the protuberant parts of the earth. Even landslips with much aspect of flow are extremely different from the behavior of volcanic mud flows or mud flows in arid zones..

(

24

EROSION OF SURFACE MATERIALS OF THE EARTH

A slope rupture looks like the failure of brittle materials overpassing their elastic limits, while a landslip is similar to the plastic deformation and creep failure of ductile materials. Koide (1955) has classified the landslips in Japan into three groups: (1) Landslips in tertiary regions, (2) Landslips in shatter zones, (3) Landslips in thermal spring areas. His conventional classification is very convenient for practical use, and so agricultural or forestry engineers have voluntarily applied it to their work. In his classification, however, the overlapping conceptions induce terrible confusion and requires a traffic cop to control its usage, as the writer recently indicated (Yatsu, 1965 a). In the phenomenon of landslips, day minerals seem to play important and fundamental roles of rock control. Clay minerals neither occur nor participate in slope failures of the rupture type. Slip planes or slip surfaces sometimes exist very distinctly, irrespective of the forms they may assume, and along these planes occur clayey materials which some call landslip clay. The writer is rather inclined to name this "slip surface clay" and reserve "landslip clay" for the clay minerals in the landmass or waste of landslips and in the bedrocks, including the slip surface clay. When it is realized that from the mineralogical point of view, there is no difference between the clay minerals of slip surfaces and those in the waste or in bedrock, it becomes evident that it is probably more convenient to lump them together and call them landslip clays rather than to restrict this term to the clays occurring at the landslip surface. The appearance of slip surface clay indeed has a real aspect of plastic materials so apprehensible that geomorphologists, geologists and civil engineers have grown accustomed to paying attention exclusively and short-sightedly to these clays and not to understanding that they have nothing but some clayey aspects because of their being kneaded at the shear planes called landslip surfaces. Although geological conditions are acknowledged to be a predisposition to landslips, there are more important aspects than overly comprehensive and superficial concepts such as geologic conditions. What type of rocks in general form those landslip areas? Why? How are those rocks decomposed? What kind of surface-chemical

25

Erosibility

:i fl

><'" ~

»

.D -0 OJ

;.c; B en en

:~

~ u

...9 -0 C

'"

co .

'"

",

bJJ

.5

a.E 'en" '+<

0

en

:~

'...9" u

-0 C

~

.0

OJ

en

\':

3u

OJ

..c II)

'"c

-5'" ~

OJ

~ 2 w

.2-

-;;;

-0 C

2

'-

0

c

.9

:;

.D

'5en

is

""M

~

,0

~

Table 3.

Rocks and clay minerals in landslip areas in Japan. Clay minerals of landslip areas which consist of shales and tuffs

~ Q')

( 1)

Locality

No.

Other clay minerals

Mixed layer minerals

14;\ -Minerals

Primary minerals tTl

I. 2.

Tenguyama, Rumoi-gun, Hokkaido

3.

Tappu, Rumoi-gun, Hokkaido Kirinai, Kitaakita-gun, Akita-ken

4.

Oami, Higashida-gun, Yamagata-ken

5.

Sugishita, Higashimurayama-gun, Yamagata-ken

6.

Shiroishi, Shiroishi-shi, M iyagi-ken Ojiya, Ojiya-shi, Niigata-ken

7. S. 9.

10. II. 12. 13. 14. 15.

Kotaki, Himi-shi, Toyama-ken Kakefuda, Himi-shi, Toyama-ken Chausuyama, Shinonoi-shi, Nagano-ken Shimojuni, Kama-gun, Gumma-ken Gohachi, Nishiyashiro-gun, Yamanashi-ken Iwama, Nishiyashiro-gun, Yamanashi-ken Shimogawara, Minamikoma-gun, Yamanashi-ken Yui, Ihara-gun, Shizuoka-ken

- - -

L

sw. ChI.

Chl.~L

L

M. M. sw. ChI. M. M.

16. Honden, Kanaya, Shizuoka-ken 17. Mae, Onsenmachi, Hyogo-ken IS. Imafuku, Matsuura-shi, Nagasaki-ken 19.

M. "ChI. M. M. M. M. M. *Chl. M. *Chl. M. M. M. M. M. M. M.

Akedo, Hirato-shi, Nagasaki-ken

-

-

-

-

L *L

-

-

-

-

*Cr Q. *Cr. *F. Q.

L*H.

- -

*L

-

H.

-

---

Z

o'<j

Q. *Z

-

(3

- -

- -

orn

Q.

H. -

--

--

;.;

Q.

H.

'<j

:»

()

0:1

~

Q.

-

:» >-l ;.;

Q.

*L *H. *H.

~ ;.;

0:1

--

;;

M.~L

L *H.

Q.

rn

M . ~L

L *H.

Q.

M.+L

L L

M.~L

L

'<j

>-l

Q.

::<: 0:1

Q. Q.

H.

M.~L

r

o

K.

~ ~

>-l

::<:

Q. Q.

H.

*F

Q.

I.

Q.

Table 3.. Continued. ( 2 ) Clay minerals of landslip areas in metamorphosed crystalline rocks. No.

Locality

20.

Kanezaki, Chichibu-gun, Saitama-ken Okunoi, Higashiiyayama, Tokushima-ken

2I. 22. 23.

Mugiudo, Higashiiyayama, Tokushima-ken Takano, Higashiiyayama, Tokushima-ken (3)

Kamogawa, Awa-gun, Chiba-ken

25.

Soro, Awa-gun, Chiba-ken Akamatsu, Shimada-shi Shizuoka-ken ( 4)

27.

-ChI. M. *25;\ sw. l4k ChI. *M? ChI. sw. ChI *25;\ *M? ChI. sw. ChI *25;\

Sounzan, Hakone, Kanagawa-ken 29. Kirishima, Aira-gun, Kagoshima-ken

Primary minerals T

*H.

I. I. I.

--

Chr. Chr.

--- -

-- -

- -

sw. 14k ChI.

Chl.+sw. 14;\

Chl.~L

- -

gJ

oen

[ ~

- - -

*Cr

*Z

--

*24~2S;\

*AI F. *Cr

H.

Clay minerals of landslip areas in other rocks.

Yoshino, Mihara-gun, Hyogo-ken

Legend

- -

M. *M? ChI.

M. M. M.

2S.

30.

I

Clay minerals of landslip areas suffered from hydrothermal reaction.

Kindaichi, Ninohe, Iwate-ken

(5)

Other clay minerals

Mixed layer minerals

Clay minerals of landslip areas which consist of serpentines.

24. 26.

l4;\-Minerals

I

ChI. sw. 14A I *25;\

IL

Al : Alunite ChI : Chlorite Chr: Chrysot ile Cr: Cristobalite F: Feldspar H .. Halloysite I : Illite K: Kaolinite M: Montmorillonite Q: Quartz T: Talc Z : Zeolite + : Regular mixed layer minerals ~: Irregular mixed layer minerals Goth ic: Principal component *: Minor component

I

Q.

~

--J

28

Erosibility

EROSION OF SURFACE MATERIALS OF THE EARTH

and mechanical behaviors are debris exhibiting? These are really fundamental characteristics of geological predispositions. A mere 10 percent clay content in soils may completely change their mechanical behavior (Mori, 1964). They depend upon the content value and species of clay minerals, absorbed ions, and surface-chemical characteristics of the boundary between clays and water. If this is realized, there is no doubt for the necessity of mineralogical, physico-chemical and mechanical researches on landslip clays. Yatsu (1965 b) described the landslip clay minerals in Japan as follows: (1) Clay minerals of landslip areas which consist of shales and tuffs; dominant minerals are montmorillonites, of which 001 diffraction is reduced up to some 12.5 A by NH 4NO a, swell by water or ethylene glycol up to 20-18 A, subordinate minerals are halloysites and primary minerals, very often occur the mixed layer minerals of montmorillonites and illites, and sometimes swelling chlorite appears. (2) Clay minerals of landslip areas in metamorphosed crystalline rocks; dominant minerals are illites or chlorites, subordinate minerals are mixed layer minerals with basal diffraction of 25 A, swelling chlorites and montmorillonites with basal diffraction of 14 A, the clay minerals of landslip areas in the mesozoic Izumi sandstone are very similar to those of crystalline rocks because the former were derived from the latter. (3) Clay minerals of landslip areas of other rocks; in the landslip clays of serpentine regions, chrysotiles, chlorites, illites, mixed layer minerals, montmorillonites or swelling chlorites are observed. In the landslip clays derived from volcanic rocks subjected to hydrothermal reactions, dominant minerals are montmorillonites; subordinate minerals are zeolites, halloysites, cristobalites and alunites. We will consider the clay minerals of landslips in the world. In the landslip area of the upper part of the Queyras River in the French Alps, sericite, chlorite, and swelling chlorite were

Fig. 5-a.

Landslip area of the upper part of the Queyras River in the French Alps.

Fig. 5-b.

Structure of landslip debris of Fig. 5-a.

29

J

30

EROSION OF SURFACE MATERIALS OF THE EARTH

r, M <.D

en ,....,

'"

"'5 H

<1)

f-< H

l! oJ

'-' oJ

;.0 0

..c

E oJ

U

+0

0 C

..c: f-<

Fig. 7-a . Regular mixed layer clay minerals of illite and intermediate clay mineral of (V-M) . These are the clay minerals that presented great difficulties in the construction of the earth dam at Prek Thnot (after Teruta, 1963)

..!<: <1)

~

"8"' <1)

c

§ >.

oJ

)

U b.O

:.§ OJ

:;: 00

.....0 00 <1)

u

!l H

2:i E <1)

Dried in ai r

.8u oJ H

:::::

;.0

>.

oJ

';<

:x:

<.D t>D

Swelled with H 2 0

ii:

o

5 10 LI__~__~__L-~_ _-LI__~__~~__~__~I

o

Fig. 7-b.

28

Ka

X-ray diffractometer traces of swelling clay minerals, Prek Thnot (after Teruta, 1963)

---~-- ------~------------------------------------------------------------~--

32

Erosibil ity

EROSION OF SURFACE MATERIALS OF THE EARTH

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33

detected by Yatsu (1965 b). He also examined the glacial tills near Solleftea in central Sweden and observed chlorites as dominant minerals and illites as subordinate ones by X-ray diffraction. According to Kerr (1963) , clay minerals in glacial tills are illites, montmorillonites, chlorites and kaolinites. Glacial tills are very different from each other in mineral composition, even in adjacent areas. Leda clay near Ottawa consists mainly of illites ; · clay minerals of landslip areas in Manitoba consists of illites and montmorillonites (Warkentin, 1961) . Leda clay is said to be a marine deposit saturated with calcium and magnesium ions. Mechanical experiments with quick clays indicate a very low value of interval friction angle (Bjerrum, 1961). However, it seems more reasonable to classify the flowslide of post-glacial clays in terms of mudflows (4. 2. 5., 4. 3. 5.) . In general, swelling clay minerals are more or less contained in the landslip clays. Even though its value is small it is anticipated that this one should change the mechanical characteristics of clays. Clays typical in Israel show a seasonal swelling, and their liquid limit is 81 and the plastic index is 54. These clays consist mainly of montmorillonite, thus the foundation of these areas is very unstable (Geitlen and Komornik, 1961). The badland areas that supply large amounts of debris to the Jordan River (Shattner, 1960) probably have the same type of clay minerals and are a probable area of landslips. The swelling clay minerals in the Transvaal region of South Africa and clay consisting mainly of montmorillonites in the Black Cotton soil area of India cause difficult problems from the civil engineering point of view. The Prek Thnot earth dam encountered very difficult problems of swelling soils (The Prek Thnot Investigation Team, 1962), and a part of the construction method had to be changed. Teruta (1963) investigated this clay which was derived from Triassic arkose sandstone. The yellow clays of this area are covered by lateritic surface soils. She concluded that the clayey soil is composed mainly of montmorillonites (speaking in detail, intermediate clay minerals between montmorillonites and vermiculites, namely with both characteristics of the two kinds of clay minerals) and mixed layer minerals of the above-mentioned montmorillonites and illites, and these minerals are considered to be responsible for the swelling characteristics of this soil. The utilization of

EROSION OF SURFACE MATERIALS OF THE EARTH

Erosibility

this soil as material for an earth dike will carry a great risk of slumping. Most clay mineralogists have no interest in the mechanical behaviors of clays, while civil engineers are occupied with mechanical experiments of heavy soil and making blueprints. Chemists investigate clay minerals from the viewpoint of surface chemistry or ceramics. The problems of landslips will remain unsolved without the collaboration of geologists, geomorphologists, chemists, and civil engineers in order to investigate the boundary regions of their sciences. Fig. 4 and Table 3 give the distribution of landslip areas in Japan and the general concept concerning their clay minerals (Yatsu, 1964). Slope rupture cannot be attributed to some special component of debris such as montmorillonites in the case of landslips. It happens everywhere, if the following conditions are satisfied: accumulation of debris, increase in weight of masses by infiltrating water, decrease of shear strength by infiltrating water, degree of slope, etc. Conditions of rocks are reflected in the formation of debris and in the characteristics of the debris itself, for example, permeability and strength of debris. Rupture of slopes occurs especially in the regions of unconsolidated and fresh volcanic sand (Shirasu in Japanese, 4.2.3.), strata of gravels and sands, and decomposed debris derived from granitoides (M asa in Japanese, 4.2.4.). In the Tama River drainage area near Tokyo, granite regions are more susceptible to this type of erosion than the regions of sandstones or slates.

wear called abrasion. Amounts of cracks are important. Sandstone (extremely consolidated) and crystalline rocks are more resistant than shales, tuffaceous rocks and other sedimentary layers in general. Chalk is very soft and is easily eroded by waves. Yamanouchi (1964) evaluated the erosibility of rocks to wave erosion by the dropping hammer test. The Schmidt hammer test perhaps supplies good data. The comparison of penetration depth or carved volume by nail gun test probably might be appropriate for the field survey. Many strength tests such as compression, tension and percussion as well as the measurement of hardness and weathering tests should be performed for a discussion of this problem in detail.

34

2.2.3. Glacial Erosion and Erosibility of Rocks. Many geomorphologists, impressed by large scale erosion and deposition of glacial processes, pay little attention to the lithological effects on glacial topography. At least, it is reasonably anticipated that differences of strength, hardness, amount of cracks, porosity, etc. influence glacial topography (c/. Frontispiece). 2.2.4. Denudation and Erosibility of Rocks. Erosional forces of waves and offshore currents as well as the weathering processes along coasts play important roles in coastal geomorphological processes. Waves act in many modes of destructive effects such as compression, fatigue by reciprocating stress, cavitation and

35

2.2.5. Wear of rocks. Processes of wear are important during the transportation of debris by flowing water (Russell, 1938) and by wind in arid regions or in the case of wave erosion. Regarding the grain size of fluvial sediments, Sternberg (1875) proposed the following formula: Y=Y o e- lX where Y =diameter of debris x =distance which debris traveled Yo=Y at x=O and A be designated as the coefficient of abrasion. Morris and Fan (1962) applied an experimental abrasion test to arkose sands. Mixtures of quartz and potash feldspar grains, varying in size, were placed in a group of oscillating tubes for a maximum of 30 hours. The samples were analyzed at 10hour intervals and weight loss computed for each component. Potash feldspars of course are more susceptive to wear than quartz. Observing their data in detail, weight seems to decrease in exponential curve of time t, W=W o e- pt where W =weight t =duration of experiment Wo=W at t=O and fl corresponds to A in Sternberg's formula. The greater the hardness, especially scratching hardness, the smaller the coefficients of abrasion)' and fl. Quartzites, siliceous sandstones and hornfels are more resistant to abrasive effects while slates, shales and limestones are easily worn. The modes of wear at

36

I I

I

EROSION OF SURFACE MATERIALS OF THE EARTH

beaches are somewhat different from those in streams (Nakayama, 1965; Aramaki and Suzuki, 1962). Gravels on beaches become flatter and more smooth than those in rivers because in the latter case gravels are rolled during transportation more than in the former. What is wear? What is the mechanism of wear? This problem is very difficult. Explanations will be given in the ) next chapter. The decrease in grain size of fluvial sediments during their transportation is not attributed entirely to wear in the rivers but also to disintegration by impaction. It probably might be adequate to say that the impaction effect is greater than attrition. Sternberg's formula involved these two processes, but neither explained the mechanism of wear nor gave its When we analyze the fluvial deposits physical meaning. comprising gravel, sand and silt, we can easily observe very often the binominal distribution on the grain size frequency curve and one minimum frequency always rests at the grain size of 4-2 mm. Yatsu (1955) thought that these deposits consist of two populations of gravel and sand, and they are lacking in the grains of granules. Thus he inferred that granule size particles are unstable and susceptible to disintegration. The strata mainly consisting of this size indeed seem to be rare in many series of sedimentation. In tests of aggregates of concretes, testing machines of Deval or Los Angeles type are ordinarily used to measure the rate of wear. Such test methods can be applied to determine the erosibility of rocks to some degree. The topography associated with faults and structures has been very frequently described partly because of the spectacular nature of some scarps and ridges, and also because of the ease of apprehension. It is necessary to keep in mind that geological structure consists of stratified rocks that vary in susceptibility to erosion. If geomorphologists. however, will not study the problems of rock control itself, they leave many things shrouded in doubt. When it is realized how scientists of the other fields have striven to investigate the properties of materials, it becomes evident that this phase of geomorphological studies has been neglected, even though geomorphologists have emphasized the importance of rock effects.

REFERENCES

37

REFERENCES

ADAMS, J . E., HENDERSON, R c., and SMITH, R M., 1959, Interpretations of runoff and erosion from field scale plots on Texas Blackland Soil, Soil Sci., vol 87, pp. 232-238. , ALLING, H. L., 1951, Abrasion of nine minerals of sand size in ."'ball mills, Am. Jour. Sci., vol. 249, pp. 569-590. ANDERSON, H. W., 1951. Physical characteristics of soils related to erosion, Jour. Soil and Water Conservation, vol. 6, pp. 129-133. ANDERSON, H. W., 1954, Suspended sediment discharge as related to streamflow, topography, soil, and land use, Trans. Am. Geophys. Union, vol. 35, pp. 268-281. ANDRE, J. E., and ANDERSON, H. W., 1961, Variation of soil erosibility with geology, geographic zone, elevation, and vegetation type in northern California wildlands, Jour. Geophy. Res., vol. 66, pp. 3351-3358. AOMINE, S., and WADA, K, 1962, Differential weathering of volcanic ash and pumice, resulting in formation of hydrated halloysite, Amer. Mineralogist, vol. 47, pp. 1024-1048. ARAMAKI, M. , and SUZUKI, T., 1962, The prevailing direction and mechanics of beach drift inferred from variation series of beach sediments along the Sagami Bay coast, Japan, Geog. Rev. Japan, vol. 35, pp. 17-34. BAILEY, S. W., CAMERON, E. N., SPEDDEN, H. R, and WEEGE, R]., 1956, The alteration of ilmenite in beach sands, Econ. Geol., vol. 51, pp. 263-279. BARTRUM, J. A.. 1947. The rate of rounding of beach boulders, Jour. Geol., vol. 55, pp. 514-515. BAVER, L. D., 1956, Soil physics, 3 rd edition, p. 429, John Wiley & Sons. BAYLISS, P., and LOUGHNAN, F. C., 1963, Mineralogical evidence for the penecontemporaneous lateritization of the basalts from New England, N. S. W., Amer. Mineralogist, vol. 48, pp. 410-414. BIRMAN, J. H., 1952, Pleistocene clastic dikes in weathered granite-gneiss, Rhode Island, Am. Jour. Sci., vol. 250, pp. 721-734. BJERRUM, L., 1961, The effective shear strength parameters of sensitive clays, Proc. 5 th I. C. S. M. F. E., Paris, vol. 1, pp. 23-28. BRANNOCK, W. W., FIX, P. F., GIANELLA, V. P., and WHITE, D. E ., 1948, Preliminary geochemical results at Steamboat Springs, Nevada, Trans. Am. Geophy. Union, vol. 29, pp. 211-226. BROCK, R W., 1943, Weathering of igneous rocks near Hong Kong, Bull. Geol. Soc. Amer., vol. 54, pp. 717-738. BRUNAUER, S., EMMETT, P. H., and TELLER, E., 1938, Adsorption of gases

38

EROSION OF SURFACE MATERIALS OF THE EARTH

in multimolecular layers, Jour. Am. Chern. Soc., vol. 60, pp. 309-319. CHEPIL, W. S., 1954, Factors that influence clod structure and erodibility of soil by wind: III, calcium carbonate and decomposed organic matter, Soil Sci., vol. 77, pp. 473-480. CHEPIL, W. S., 1955, Factors that influence clod structure and erodibility of soil by wind : IV, sand, silt, and clay, Soil Sci., vol. 80, pp. 155-162. CHEPIL, W . S., 1955, Factors that influence clod structure and erodibility of soil by wind: V, Organic matter at various states of decomposition, Soil Sci., vol. 80, pp. 413-421. CHEPIL, W . S., 1957, Sedimentary characteristics of dust storms: I, II, III, Am. Jour. Sci., vol. 255, pp. 12-22, 104-114, 206-213. COOMBS, H. A., 1942, Expansion of concrete due to reaction between andesitic aggregate and cement, Am. Jour. Sci., vol. 240, pp. 288-297. DODGE, T . A., 1947, An example of exfoliation caused by chemical weathering, Jour. Geol., vol. 55, pp. 38-42. EMERY, K. 0., 1960, Weathering of the Great Pyramid, Jour. Sed. Pet., vol. 30, pp. 140-143. EVERETT, D. H., 1961, The thermodynamics of frost damage to porous solids, Trans. Faraday Soc., vol. 57, pp. 1541- 1551. FAIRBAIRN, H. W., 1951, Hydrothermal·differential pressure equipment for experimental studies in low·grade rock metamorphism, Bull. Geol. Soc. Am., vol. 62, pp. 39-44. FENNER, C. N., 1936, Bore·hole investigations in Yellowstone Park, Jour. Geol., vol. 44, pp. 225- 315. FLINT, R. F., 1949, Leaching of carbonates in glacial drift and loess as a basis for age correlation, Journ. Geol., vol. 57, pp, 297-303. FREDERICKSON, A. F., 1951, Mechanism of weathering, Bull. Geol. Soc. Am., vol. 62, pp. 221-232. GEIKIE, S. A., 1880, Rockweathering, as illustrated in Edinburgh churchyards, Proc. Roy. Soc. Edinburgh, vol. 10, pp. 518-532. GEITLEN, J. G. and KOMORNIK, A., 1961, Deformation and moisture movements in expansive clay, Proc. 5 th 1. C. S. M. F. E., Paris, vol. I, pp. 873-879. GLENN, R. C., and NASH, V. E., 1964, Weathering relationships between gibbsite, kaolinite, chlorite, and expansible layer silicates in selected soils from the lower Mississippi Coastal Plain, Twelfth Nat, Con£. on Clays and Clay minerals. XII, pp. 529-548. GOLDTHWAIT, J. W ., and KRUGER, F . C., 1938, Weathered rock ill and under the drift in New Hampshire, Bull. Geol. Soc. Amer., vol. 49, pp. 1183-1198. GRANT, W . H., 1964, Chemical weathering of biotite-plagioclase gneiss,

REFERENCES .J

39

Twelfth Nat. Con£. on Clay and Clay Minerals, XII, pp.455463. GWYNNE, C. S., 1950, Terraced highway side slopes in loess, Southwestern Iowa, Bull. Geol. Soc. Am., vol. 61, pp. 1347-1354. HAMROL, A. , 1961, A quantitative classification of the weathering and weatherability of rocks, Proc. 5 th, 1. C. S. M. F. E., Paris, vol. 2, pp. 771-774. HAY, R. L., 1960, Rate of clay formtaion and minerals alteration in a 4000year old volcanic ash soil on St. Vincent, B_ W. 1., Am. Jour. Sci., vol. 258, pp. 354-368. HILL, D. E., and TEDROW, J. C. F., 1961, Weathering and soil formation in the arctic environment, Am. Jour. Sci., vol. 259, pp. 84-101. HORTON, R. E ., 1933, The role of infiltration in the hydrologic cycle, Trans. 14 th Ann. Meeting Am. Geophys. Union, pp. 446460. ICHINOSE, Y., 1957, Geomorphological Studies of landslides in the case of the Tama Valley, Miscellaneous Reports of the Research Institute for Natural Resources, no. 45, pp. 8- 18. IRELAND, H. A., 1955, Surface tension as a factor in gradation, Am. Jour. Sci., vol. 253, pp. 162-172. IWAGAKI, Y., and TSUCHIYA, Y., 1957, On the detachment and the transportation of soil by rain water flow, Trans. Japan Soc. Civil Eng., No. 51, pp. 34-40. IWASAKI, I., HIRAYAMA, M., KATSURA, T., OZAWA, T., OSAKA, 1., KAMADA, M., and MATSUMOTO, H., 1964, Alteration of rock by volcanic gas in Japan, Bull. volcanologique, organe de l'Association de volcanologie de l'Union geodesique et geophysique internationale, Tome 27, pp. 1-:16. JENNY, H., 1940, Factors of soil formation, A system of quantitative pedology, p. 281, McGraw-Hill. JUDSON, S., 1949, Rock-fragment slopes caused by past frost action in the Jura Mountain (Ain), France, Jour. Geol., vol. 57, pp. 137142. KARKHANAVALA, M. D., 1960, Alteration of ilmenite and "Arizonite," Econ. Geol., vol. 55, pp. 843-844. KASHlWAGI , H., 1963, Study on the weathering of granite, Rept. Hiroshima Univ., no. 12, pp. 319-342 (in Japanese). KELLER, W. D., and FREDERICKSON, A. F., 1952, Role of plants and colloidal acids in the mechanism of weathering, Am. Jour. Sci., vol. 250, pp. 594-608. KELLER, W. D., 1955, The Principles of chemical weathering, .p. 88, Lucas Brother Publishers, Columbia, Missouri. KELLY, W. C., and ZUMBERGE, J. H. , 1961, Weathering of a quartz diorite at Marble Point, McMurdo Sound, Antarctica, Jour. Geol., vol. 69,pp. 433-446.

'y

EROSION OF SURFACE MATERIALS OF THE EARTH

REFERENCES

KERR, P. F ., KULP, J. L. , PATTERSON, C. M., and WRIGHT, R J., 1950, Hydrothermal alteration at Santa Rita, New Mexico. Bull. Geol. Soc. Am., vol. 61,pp. 275-347. KERR, P. F ., 1955, Hydrothermal alteration and weathering, Geol. Soc. Am. Special Paper 62, pp. 525- 543. KERR, P. F ., 1964, Quick clay, Scientific American, pp. 132-141. KIELY, P. V., and JACKSON, M . L. , 1964, Selective dissolutions of mIcas from potassium feldspars by sodium pyrosulfate fusion of soils and sediments, Amer. Mineralogist, vol. 49, pp. 1648-1659. KOIDE, H., 1955, Landslips in Japan ( in Japanese), Toyo-keizai-shimpo-sha, Tokyo. Kopp, O. c., HARRIS, L. A. , and CLARK, G. W ., 1961, The hydrothermal conversion of Muscovite to kalsilite and an iron-rich mica, Amer. Mineralogist, vol. 46, pp. 719-727. LAUDlSE, R A., and KOLB, E. D., 1963, The solubility of zincite m basic hydrothermal solvents, Amer. Mineralogist, vol. 48, pp. 642648. LEGRAND, H. E., 1952, Solution depressions in diorite in North Carolina, Am. Jour. Sci., vo\. 250, pp. 566-585. LEONARD, R J., 1927, The hydrothermal alteration of certain silicate minerals, Econ. Geo\., vo\. 22, pp. 18-43. LEROY, P. G., 1954, Correlation of copper mineralization with hydrothermal alteration in the Santa Rita porphyry copper deposit, New Mexico, Bull. Geol. Soc. Amer., vol. 65, pp. 739-768. LOUGHMAN, F. C. L., 1962, Some considerations in the weathering of the silicate minerals, Jour. Sed. Pet., vo\. 32, pp. 284-290. MACDONALD, G. A., 1944, Solfataric alteration of rocks at K ilauea Volcano, Am. Jour. Sci., vol. 242, pp. 496-505. MASON, B., 1947, Oxidation and reduction in geochemistry, Jour. Geol., vol. 57, pp. 62- 72MCINTYRE, D. S., 1958, Soil splash and the formation of surface crust by raindrop impact, Soil Sci., vol. 85, pp. 261- 266. MERRITT, R S., and MULLER, E. H ., 1959, Depth of leaching in relation to carbonate content of till in central New York State, Am. Jour. Sci., vol. 257, pp. 465-480. MOREY, G. W ., and FOURNIER, R 0., The decomposition of microcline, albite and nepheline in hot water, Amer. Mineralogist, vol. 46, pp. 688- 699. MORI, R, 1964, Some problems on the chemical stability of soils, Committee of Soil Chemistry, Association of Electrochemistry, Tokyo. MORRIS, W. J., and FAN, P. F ., 1962, Abrasion effects on arkose mixtures, Jour. Sed. Pet., vol. 32, pp. 226-230. MURAKAMI, K, 1956, Landslips in Volcano Akagi, Gumma Prefecture, Geogr. Rev. Japan, vol. 29, pp. 209-217. MUSGRAVE, G. W., 1947, The quantitative evaluation of factors in water

erosion, a first approximation, Jour. Soil and Water Conservation, vol. 2, pp. 133-138. NAKAYAMA, M., and MIURA, T ., 1962, Roundness of pebbles in the course of rivers in Japan, Geogr. Rev. Japan, vol. 37, pp. 115-130. NAKAYAMA, M., 1965, Analyses of the size, roundness, and flatness of beach pebbles, Geogr. Rev. Japan, vol. 38, pp. 103-120. OLLIER, C. D., 1963, Insolation weathering : examples from Central Australia, Am. Jour. Sci., vol. 261, pp. 376-381. PANABOKKE, C. R, and QUIRK, J . P., 1954, Effect of initial water content on stability of soil aggregates in water, Soil Sci., vol. 77, pp. 185-195. PARIZEK, E . J., and WOODRUFF, J. E., 1957, Mass wasting and the deformation of trees, Am. Jour. Sci., vol. 255, pp. 63-70. PAYNE, J. H., and MAU, K T. , 1946, A Study of the chemical alteration of basalt in the Kilauea Region of Hawaii, Jour. Geol., vol. 54, pp. 345-358. PETERSON, J . B., 1964, The relation of soil fertility to soil erosion, Jour. Soil and Water Conservation, vol. 19, pp. 15-19. PURl, B. R, SINGH, D. D., and MYER, Y. P., 1957, Freezing points of liquids absorbed on porous solids, Trans. Faraday Soc., vol. 53, pp. 530-534. RAMBERG, H., 1954, A theoretical approach to the thermal stabilities of hydrous minerals. 1. General principles as revealed by studies of hydroxides and oxyacids. Jour. Geo\., vol. 62, pp. 388-398. RUSSELL, RD., 1939, Effects of transportation on sedimentary particles, Recent Marine Sediments (edited by P. D. Trask), Am. Assoc. Petroleum Geo\. , Tulsa, pp. 32-47. RUSSELL, R J., and RUSSELL, RD., 1939, Deposits associated wi th strand line, Mississippi River Delta sedimentation, Recent Marine Sediments( edited by P.D. Trask), Am. Assoc. Petroleum Geol., Tulsa, pp. 153-177. SCHATTNER, 1., 1960, The bad land-zone of the Jordan as a source area of its riverload and a conditioning factor of the meandering hab it of the river, Abstracts of Papers, International Congress, Norden, 1960, pp. 255-256. SCHLOCKER, J ., and VAN HORN, R, 1958, Alteration of volcanic ash near Denver, Colorado, Jour. Sed. Pet., vol. 28, pp. 31-35. SCHWARTZ, G. M ., 1939, H ydrothermal alteration of igneous rock, Bull. Geol., Soc. Am., vol. 50, pp. 181-238. SCHWARTZ, G. M., 1958, Alteration of biotite under mesothermal conditions, Econ. Geo\., vol. 53, pp. 164-177. SHARPE, C. F. S., 1938, Landslides and related phenomena, Columbia University Press. SHIMA, H., 1961, The relationship between weathering and geomorphology in granitic regions, Geographical Studies presented to Prof

40

41

42

EROSION OF SURFACE MATERIALS OF THE EARTH

Taro Tsujimura in honor of his 70th birthday, pp.201-214. SINGEWALD, J. T., 1932, Weathering and albitization of the Wissahickon schist at the Prettyboy Dam, Baltimore County, Maryland, Bull. Geol. Soc. Amer., vol. 43, pp. 449-468. SMEDES, H. W., and LANG, A. J.. 1955, Basalt column rinds caused by deuteric alteration, Am. Jour. Sci., vol. 253, pp. 173-181. STERNBERG, H., 1875, Untersuchungen iiber Lingen-und Querprofil geschiebe-fiirende Fliisse. ZS. Bauwesen, vol. 25, pp. 483-506. STEINER, A., 1953, Hydrothermal rock alteration at Wairakei, New Zealand, Econ. Geol., vol. 48, pp. 1-13. STRINGHAM, B., 1952, Fields of formation of some common hydrothermalalteration minerals. Econ. Geol., vol. 47, pp. 661-664. STRINGHAM, B., 1953, Granitization and hydrothermal alteration at Bingham, Utah, Bull. Geol. Soc. Am., vol. 64, pp. 945-992. TAKAHASHI, H., IIZUKA, A., YOSHIKAWA, K., and TAKAGI, M., 1963, Swelling and loads on steel supports in solfataric clay (OnsenYodo in Japanese name), New Tanna Tunnel, Railway Technical Research Report No. 371, pp. 1-28. TANAKA, Shig., 1952, An experimental formula concerning soil-losses at steep-slope-erosion, Jour. Japan Soc. Civil Eng., vol. 37, pp. 519-522. TANAKA, Shin.,1957, The drainage-density and rocks (granitic and paleozoic) in the Setouchi Sea coast region, Western Japan, Geogr. Rev. Japan, vol. 30, pp. 564-578. THE PREK THNOT INVESTIGATION TEAM, 1962, Feasibility report on the Prek Thnot project, Cambodia. TERUTA, Y., 1963, Recherche sur l'argile de Prek Thnot, Cambodge, Applied Geography, No.4, pp. 27-37. TOYOSHIMA, Y., 1956, On wave-cut benches along the south coast of the Miura Peninsula, Kanagawa Prefecture, Geogr. Rev. Japan, vol. 29, pp. 240-252. TSUCHlYA, Y., 1958, Some hydraulic considerations on the water erosion of land surface, Trans. Japan Soc. Civil Eng., no. 59, pp. 32-38. TURNER, F. J., and WEISS, L. E., 1963, Structural analysis of metamorphic tectonites, p. 545, McGraw-Hill. VER STEEG, K., 1947, The influence of geologic structure on the drainage pattern in northeastern Minnesota, Jour. Geol., vol. 55, pp. 353-361. VICKERS, R. c., 1957, Alteration of sandstone .as a guide to uranium deposits and their origin, Northern Black Hill, South Dakota Econ. Geol., vol. 52, pp. 599-611. WAHLSTROM, E. E ., 1948, Pre-fountain and recent weathering on Flagstaff Mountain near Boulder, Colorado, Bull. Geol. Soc. Am., vol. 59, pp. 1173-1190. WARKENTIN, B. P., 1961, Shrinking and swelling properties of two Canadian

REFERENCES

43

clay. Proc. 5 th I. C. S. M. F. E., Paris, vol. I, pp. 851-855. WEAVER, C. E., 1953, Mineralogy and petrology of some ordovician K-bentonites and related limestones, Bull. Geol. Soc. Am., vol. 64, pp. 921-944. WILSHIRE, H. G., 1958, Alteration of olivine and orthopyroxene in basic lavas and shallow intrusions, Amer. Mineralogist, vol. 43, pp. 120-147. WOODBURN, R., and KOZACHYN, J., 1956, A study of relative erodibility of a group of Mississippi gully soils, Tran. Am. Geophys. Union, vol. 37, pp. 749-753. YAMANO, T ., 1964, On the degree of weathering of debris, Monthly, Doboku Shikenjo Hokkaido, no. 135, pp. 20-24. YAMANOUCHI, H., 1964, On the retreat of the sea cliff along the Pacific Coast at Haranomachi, Japan, Geogr. Rev. Japan, vol. 37, pp. 138-146. YATSU, E ., 1955, On the longitudinal profile of the graded river, Tran. Am. Geophys. Union, vol. 36, pp. 655-663. YATSU, E., 1964, Sur Ie gonflement des roches par l' imbibition de l'eau, Applied Geography, no. 5, pp. 7-30. YATSU, E., 1965, Classification of landslips (in Japanese), Chikyukagaku (Journal of the Association of Geological Collaboration in Japan), no. 76, pp. 34-37. YATSU, E ., 1965, Landslip clay minerals in Japan ( in Japanese), Clay Mineral Science. vol. 4, pp. 54-66.

III

MECHANICS OF SOLID ROCKS

Rocks undergo various kinds of geomorphological processes. Resistances to such destructive forces are called the strength of rocks. In this chapter, strength, failure and wear phenomena of solid rocks will be discussed. This knowledge is indispensable not only for researchers of earth science such as geomorphologists and geologists but also for mining, architectural, and civil engineers. 3.1. Strength of Solid Rocks 3.1.1. Definition of Strength. Strength of rocks is their property of resistance and durability to the forces applied on them. Here the discussions are restricted to mechanical problems and exclude chemical processes. As many rocks commonly manifest themselves as anisotropic bodies, irrespective of their being igneous, metamorphic or sedimentary rocks, the problems become very intricate. 3.1.2. Classification of Disintegration. What types of disintegration are happening in geomorphological processes? What kinds of processes attribute to a given type of disintegration of rocks? To such problems Thornbury (1954) and Strahler (1952) gave their excellent answers. Table 5 shows the agents and their destructions: Table 5.

Agents involved and their destruction

[Agents] [Type of Destruction] Running water ······ ······(l)Wear (2)Impaction failure Waves and currents····· ·(l)Wear (2)Impaction failure (3)Compression and tension failure (4)Fatigue failure Wind ·········:··············(l)Wear (2)Impaction failure Glacier ·····················(l)Wear (2)Compression failure Endogenic agents······ ···(l)Compression failure (2)Tension failure (3)Shear failure

MECHANICS OF SOLID ROCKS

Failure of Rocks by Static Load

Therefore, discussions are unequivocally requisite on the relation between failure and . stresses such as compression, tension and shear, and on the problems of fatigue failure and wear in detail.

application of uniaxial compression without lateral compression behave as a typical brittle material and collapse at their elastic limits. Proportionately with an increase of lateral pressure, elastic strain slightly decreases, the domain of deformations such as those perceptible in ductile materials increases, and at last the failure occurs. The more the increase of lateral pressure, the larger the domain of plastic or flow strain. In hydrostatic pressure where the pressure is equal in any direction ( 171=172=173), plastic deformation does not occur.

46

3.2. Failure of Rocks by Static Load 3.2.1. Rheological Behavior of Rocks. An external force exerted on a body is called load from the engineering point of view. Loads are classified as static loads and dynamic loads due to speed of loading. The latter comprises repeated loads, alternate loads, moving loads, impact or impulsive loads, etc. Imagine the state in which an impulsive load is applied to one end of a bar. In this situation, the bar does not exert the resistant force as a whole, but the stress exerted by impulsive force is transmitted from one end where impulsive force is applied to the other one. It is an impulsive load that gives rise to such a state. On the other hand, a load might be called high speed static load if the equilibrium between the load and the stress in this bar can be imagined from the point of view of statics, even though the static load is commonly defined as the load which applies very slowly. In general, three kinds of behavior of materials will be observed when uniaxial tests are applied to solid bodies. In the domain of minor strains, they behave as elastic bodies and the relation between stresses and strains is reversible. Some bodies break down when strains overstep their elastic limits; others show a gradual transition from the elastic to the plastic stage, manifest many times of strains in the elastic stage and at last undergo failure. If a body experiences three phases when subject to a sufficient load, this body is called ductile. If a body does not have a plastic stage and collapses at the point of its elastic limit, this body is named brittle. Without remarkable necking, brittle materials fall into failure very suddenly. In general, rocks are classified. as brittle materials. However, such classification as ductile and brittle materials is not adequate for all states of the same materials. It is more accurate to say that so-and-so material is in a brittle or plastic state. Karman (1911) applied tri-axial compression tests to columnar test pieces of limestone with various rates of lateral pressure, and proved that the behaviors of test pieces depend upon the mechanical state of stress. That is to say, test pieces, upon

47

3.2.2. Theories of Fracture of Rocks. The theories of fracture are classified into three categories: a. Stress theory, b. Strain theory, c. Energy theory, We can enumerate many theories of fracture as follows: a. Maximum stress theory, b. Maximum strain theory, c. Maximum shear theory, d. Maximum octahedral stress theory, e. Maximum energy theory, f. Maximum energy of distortion theory, g. Mohr's general theory of failure. Among of them, maximum octahedral shear theory seems to have a superiority over others in order to explain the fracture of brittle materials. Mohr's theory is the most fascinating one for engineers, except that this theory ignored the intermediate principle stress. According to this theory, the limiting state of failure is expressed by the equation: r = f (a), and this equation is the envelope of stress circles of Mohr, determined by experiments. Many researchers have performed a great number of experiments on various rocks, some of which are listed in references of this chapter. 3.2.3. Time Dependence of Deformation and Fracture. It is well established that the result of experiments on rock strength depends upon the speed and duration of loading. In 1939 and 1940, Griggs reported the creep of rocks. In 1959, Hardy reported the recent advancements of rock mechanics in Canada, under the title of "Time Dependent Deformation and Failure of Geological Materials."

48

Failure of Rocks by Static Load

MECHANICS OF SOLID ROCKS

1 ELEMENT

@ DEFINING , EQUATION

basic

+

Maxwell Unit Fig. 8.

rh~ological

element

I

I

Viscouc, . P Sv = Tj

Elastic P SE =E

S=p Cl +l + l (1 - e- tl ') E. 1J. E where ~=-'l E S: Strain P : applied stress t : time after the application of the stress ~ : retardation time E. and E : elastic element 1J. and 1J: viscous element

Inert ial " P SI =m

@

Voigt Unit

Basic rheological element and unit.

Griggs experimented using the Solenhofen limestone and drew the time-strain curves. He thought of them as elasticoviscous and consisting of two parts: a. pseudoviscous flow or deformation of definite velocity, expressed by Ct, b. elastic flow or deformation decreasing logarithmically in time, expressed by B log t. Thus the total strain S is expressed as following equation: S = A + B log t + Ct in which, t = time, A,B,C are respectively constant due to each rock, and the recovery curve after unloading is expressed as follows : S' = A' - B log t. Many papers recently appeared which explained the mechanical behaviors of rock phenomenologically by using the rheological models such as shown in Fig. 8. Combination of elements gives units such as the Maxwell unit and the Voigt

1

E'

(l)----T--Maxwell unit

'I.

(2)

P3 =ES P4 ='lS

P = ES + 1JS

E

S,lP, t) = t(l-e-t/ l), where ~=t

Fig. 9.

Burgers' rheological model.

50

Impulsive Fracture and Others

MECHANICS OF SOLID ROCKS

unit (Kelvin unit) . Those papers want to explain the mechanical behaviors as the combination of these elements and units. Fig. 9 shows Burgers' rheological model and its mathematical expression. In this case, the behavior of rocks is considered as viscoelastic, and is better represented by a model consisting of four elements. The total deformation of rocks consists of an instantaneous elastic deformation, delayed or retarded elastic deformation, and a viscous deformation. The first two deformations are recoverable on the removal of the load, and the third one results in a permanent strain in the rock. According to Hardy (1959), under a low value of applied stress (where the strain does not exceed 10- 3 in/ in), Burgers' viscoelastic model is assumed to hold to a first approximation, whereas at a higher value of applied stress, it is postulated that the viscoelastic behavior is retained to some extent but microfractures begin to develop and propagate. As the applied stress increases the fracture system develops to such an extent that complete failure of the specimen occurs.

kg/em' -<=

2500

2:'

2400

0

Serpentine, Tase Dam.

2300

•

Weathered se rpentine , Iwanebashi .

QQ c

(/)

2200

0

III

Serpentine, near Tase Dam.

o Shale, Kodomari.

2100 kg/em '

2000 1900

•

Shale, Sengan Tunne l.

@

Shale,

Sankebetsu.

.. Shale, Kamihaboro .

1800

0

b Mylonite, Sengan Tunnel.

1700

•

1600

A My lonite, Maebar a Pa ss.

Mylonite, Shinkoshirazu.

x Tuff, Shirakawa.

1500

•

1400

+

Tuff, Kodomari ,

1B Slate,

near Tase Dam,

1300 1200 1100

51

III

3.2.4. Conditions which influence the Strength of Rocks. Water content of rocks has a great influence upon the strength of rocks. Dry rock is much stronger than wet rock. In considering their strength with the greatest safety, the experiments should be done in conditions of maximum water content. It has been well known for a long time that the strength of rocks depends upon the velocity of loading. According to Horibe and Kobayashi (1964), the ratio of high-speed compressive strength (3. o~ 12 x 105 kg. cm- 2 sec-I ) to the low-speed one (9. 5~ 10 x 10- 2 kg. cm- 2 sec-I) is about 1. 6 for sandstone, 1.9 for marble, and 1. 5 for cement mortar, and the Poisson's number for each rock decreases with an increase in the cOlDpressive load, but this number on the same compressive stress has a tendency to increase as the loading-rate increases.

••

•

0

1000 900 800 700

400 300 200

+

100

•

o

t\~ " •©Q) 5

+

®., .,l'

.

o

I

10

15 -

Fig. 10.

+

20 Water Content

Strength of various rocks and their water content.

25%

3.3. Impulsive Fracture and Others

The mechanism of impulsive or fatigue fracture is quite different from those described in the preceding sections. Livingston's energy transfer theory (1956) may be useful to understand the mechanism of impUlsive fracture. According to this theory, when the solid no longer is capable of transferring

52

Impulsive Fracture and Others

MECHANICS OF SOLID ROCKS

·energy in excess of that liberated by the critical weight of ·explosive from the explosion cavity into the mass of the solid, impulsive fracture occurs. Impulsive waves transmit, refract and reflect strain energy. If the impulsive waves refracted or reflected meet with succeeding waves, they are composed. Thus the resultant strain energy surpasses the elastic energy of this solid, and then fracture ·occurs. This is the strain energy theory. Rinehart (1959) explained the role of stress waves in comminution. There exist very little information regarding the fatigue failure of rocks. Rock fracture by insolation must be a good ·example of this phenomenon. A thermal stress due to temperature gradient occurs in rocks, and it is repeated reciprocally by heating and cooling. It may be the most mechanical explanation that such a repeated load is attributed to the occurrence ·of fatigue failure of rocks, which is commonly called insolation fracture. Fig. l1·a and Fig. 11-b show one method of measuring the dynamic elastic modulus Ed of rocks, which is obtained as follows: Ed V'p(1 + 11) (1- 211) (1 - 11) where p =dens ity of the material in question, V =L/t, 11 = Poisson's ratio of this material, L = length of rod, and t = transit time_ It will be also interesting and instructive to state briefly the anisotropic properties of rocks. Fig. 12-a and Fig. 12-b show the stressstrain curves of Shimizu slate. The commonest, and in most cases best, method of measuring the strain employs electric resistance-strain gauges. In case of Shimizu slate, the loading direction does not greatly affect Young's modulus and Poisson's ratio; however, the resid ual strains in the hysteresis loops are remarkably different from each other. The compress ive load parallel with the bedding plane, cause larger residual strains in slate than that perpendicular to the bedding plane. In the latter case, the specimen recovers elastically without residual strains after the removal of stress, while in the former case, it is presumable that the basal plane of clays in slate easily separate and in such tiny flaws, the edges of the clay minerals are sq ueezed. The clay minerals usually are less res istant to the tens ion in the direction of c-axis than to the compression in that direction. This phenomenon of res idual strain must be creep or fatigue failure of a very slight quantity. In this connection, a more elaborate investigation is needed.

53

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MECHANICS OF SOLID ROCKS

Impulsive Fracture and Others

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(em ) 1 'tOOZ ""

(OOZ ) D' (~£I 'ZOl ) 1 ym (ZOI) D ¥6ZZ (alI) 0 '(lEI '~Ol ) 1ywz

Fig. 12-a.

Stress-strain loops. The loading direction bedding plane (1), Shimizu Permian slate.

lS

perpendicular to the

(IEI tre ) 1' (ZOl ) 148 yasZ

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0.30

yavvl'

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N

Fig. 14-a.

Shimizu Permian slate, parallel with bedding plane.

Fig. 14-b.

Shimizu Permian slate, perpendicular to bedding plane.

Fig. IS.,.a. Takakurayama Permian or Triassic slate, parallel with bedding plane.

Fig. IS-b.

Takakurayama Permian or Triassic slate, perpendicular to bedding plane.

60

MECHANICS OF SOLID ROCKS

Plasticity of Rocks and Salt Domes

As mentioned above, most rocks except some igneous rocks display anisotropic characteristics to such a marked degree that the importance of their micro-structure, which seems to be the origin of an isotropy, cannot be overemphasized. It is easily expected that in slate, clay minerals should have parallel orientation if the compression was great enough during the diagenesis stage. Such stratification must be very clearly examined by recourse to X-rays. If the stratification be perfect, only the (001) reflection will be observed in the X-ray diffractometer traces, when X-rays are applied to the surface parallel with the bedding plane, while X-rays incident upon the surface perpendicular to the bedding plane will cause only the (hkO) reflection. If the stratification of clay minerals is not perfect, the (hkO) reflection will be not iced in X-ray diffractometer traces, even though X-rays are applied to the surface parallel with the bedding plane. Fig. 13 discloses the perfect parallelism of clay minerals in Shimizu slate and the imperfect one in Takakurayama slate. Photographs taken by electron microscope (Fig. 14-15) w ill g reatly assist in understanding the deg ree of stratification of the clay minerals in slates.

boundaries of minerals or in minerals themselves. In the latter case, the fracture usually occurs along the cleavage of minerals. It is evidently natural that the fractures occur along the grain boundaries and in grains if the intergranular bond is equal to the cohesion of grains. In a well solidified concrete specimen, the fracture surfaces always truncate the hard gravels of aggregates, whereas in poorly cast concrete, sometimes aggregates are not cut. Specimens of concrete will give a good model for the fracture of rocks.

61

3.5. Plasticity of Rocks and Salt Domes 3.5.1. Plasticity of Rocks.

Rocks display the plastic properties

3.4. Cohesion of Rocks

The cohesion of rock as a polycrystal body is attributed to the bond of chemical reaction, consolidation by crystal growth, mutual inclusion of crystals, intermolecular force, adhesion due to adsorption, etc. The cohesion of single crystals has been calculated by physicists. The data resulting from experiments on the real single crystals are far smaller than the values theoretically estimated, so that Griffith (1924) proposed his theory that there exist minor cracks in crystals and that they grow by stresses to form fractures. Such assumed cracks in homogeneous brittle solid are named Griffith flaw. Evidence that the observed yield stress causing slip in crystals is much lower than the theoretical estimate of the shear cohesion as mentioned above introduced the dislocation theory, which has become a star player in the explanation of this discrepancy. Every crystal contains imperfections from which slip can start at a low stress. These imperfections may be due to vacant lattice sites, interstitial atoms, dislocations, gross defects and so forth. Fractures in polycrystal rocks occur either along the grain

I

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64

MECHANICS OF SOLID ROCKS

under confined condition as mentioned above. Folding of strata is a pertinent evidence of this phenomenon. Limestone has been especially known as a plastic material and very intensively studied by many researchers. Rock salt is also quite famous for its plastic behavior which is the principal cause of the formation of salt domes. 3.5.2. Salt Domes. They are small domal structures produced by intrusion of masses of salt into rock strata, and have been known in many areas, especially in the Gulf Coast Plain of Louisiana and Texas in the United States. The description of salt dome topography will be relegated to the text books of geomorphology and one example of their internal structure will be presented. Kupfer (1962) thoroughly investigated the salt dome of Weeks Island, Iberia Parish, Louisiana. The geologic structures of ceiling at 660 feet below sea level were shown on the map as reproduced in Fig. 17. He recognized that all axes are essentially vertical (81°-90° plunge), therefore walls show vertical bands and ceilings show intricate fold patterns. As possible origin of such structures, he considered the intrusion of plastic salt into a restricted opening, which caused the lineation parallel to the direction of flow. Formations of rock salt may not have definite values of the plastic limit K p , as their plasticity increases with increase of the triaxial compression. In addition to instantaneous yielding deformation, rock salt is also subject to pseudoviscous flow which is defined as gradual creep deformation when constant pressure is applied below the elastic limit Ke. For a long duration of loading, such a viscous deformation in rock salt can attain to a considerable value. Serata and Gloyna (1960) applied the theory of plasticity to the evaluation of stress and strain conditions of the salt cavity. The whole question of the deformation of evaporites has recently been dealt with at considerable length by Borchert and Muir (1964). According to them, the ease of deformation in response to tectonic stress increases in the following order: limestone / dolomite<marl
Slip lines and lineation of radiation damages. Specimen: KCl single crystal (Harshaw). The photograph is parallel with the loading direction. Radiation : 3.6 X 10' roentgen of r·ray. Compressive strain: 8 %.

66

Wear

MECHANICS OF SOLID ROCKS

is applied, the greater is the deformation produced. If the temperature increases slightly, halite and sylvite remarkably increase their mobility which is very important in accounting for the formation of a salt dome. Under quasistatic loading at room temperature, pressure of only 150-200kgj cm 2 suffices to produce the flowage deformation of rock salts. In passing, it is very interesting that in general the purer the crystal, the lower the yielding stress, and impurity and crystal defects such as radiation damage increase the strength of the crystal. In this direction, countless works are reported in periodicals such as the Journal of Applied Physics, Philosophical Magazine and so on. Akimoto (1963) reported that single crystals of sylvite produced by the Harshaw Co. undergo flowage deformation under a stress less than 100kgj cm2. However, in case of sylvite rock salts, the stress sufficient to produce the flowage deformation is considered by Dreyer (1955) to be about 250kgj cm2. The discrepancy between the very high calculated strength of a crystal and that one experimentally measured, is fully solved by the dislocation theory, concerning which it is particularly deisrable to consult books on solid state physics (3.4.) . 3.6. Wear 3.6.1. Friction and Wear. Geomorphologists as well as sed imentologists have an interest in the phenomenon of wear, but it seems that they do not investigate this phenomenon itself. The problems of friction and wear of materials, especially metals, are so very important that researchers of engineering materials are fully occupied in clarifying such phenomena. Though it might be thought very commonly that the greater the friction, the more extensive the wear, this is not always correct. We have to completely separate the two terms. Wear usually implies several phenomena as follows: a. Wear due to sliding between two contact bodies, adhesive or galling wear, abrasive and cutting wear, b. Wear due to surface fatigue, pitting (flaking) , c. Cavitation, etc.

67

Wear due to solid particles in moving liquid is abrasive wear as observed in rivers and shores. We will skip the explanation of cavitation in the next section. 3.6.2. Various Wear Mechanism. Mechanical engineers usually consider corrosion as corrosion wear, whereas geologists and geomorphologists exclude it from wear phenomena. a. Adhesive wear. Formerly, friction was attributed to the gearing of ruggedness of two contact surface and its value was thought to be determined by the value of work to lift up to the height of protuberance. Recently the theory of adhesion has become popular. According to this theory, some parts of contact surfaces approach each other by the distance of a molecule, thus adhesive forces occur. Friction is attributed to the force which shears the adhesive parts. In the case of metals, the following explanation is given for the mechanism of adhesive wear. On the actual surface loaded with value of W, plastic deformation occurs around the contact points, thus the contact surface increases to the extent in which the load W becomes in equilibrium with the product of the increased contact surface A times the yield stress of materials P, then we can obtain the next equation,

A=Y'L P where P is considered as micro-Vickers hardness H (kgj mm 2) . Therefore,

A=Y'L H The value of adhesive wear V is proportional to this A and the distance of slide L, then V=k AL =k Y'LL=k' WL

H If both sides of this equation are divided by apparent contact

area Ao, average depth of wear h is as follows, - V -k' W L h -A Ao o=k' PoL

where Po= W Ao ' Po is named design pressure, and k' coefficient of adhesive wear. Fig. 19 shows the mechanism of adhesive

68

Fig. 19.

limit of"Blauumschlag"

Mechanism of adhesive wear.

Two materials M, and M, are in contact with each other. Consider the shear strength of M, to be greater than that of M, and the hatched area , ABCD to undergo work hardening. (1) If the shear strength of the adhesive part AB IS smaller than both those of M, and M" the part AB will be sheared. (2) If its ' value is greater than that of milder material M" M, will be sheared along the surface CD in M,. The work necessary for this shear is equal to the friction and the part ABCD is the adhesive wear.

wear. Concerning the work hardening of rocks, experiments on the indentation pressure or hardness by Brace (1960) must be referred to here. He reasonably concluded as follows: Rock salt deforms predominantly by gliding and becomes harder with increased deformation, and the hardening characterizes both individual grains and polycrystalline aggregate. Anhydrite, limestone and marble deform by combination of fracture and gliding; the bulk hardness decreased from the normal value outside the deformation zone to a small fraction of this just under the indentation) however, the hardness of individual grains, for the marble at least, increased toward the center of the deformation zone. The writer does not know whether work hardening occurs so often in rocks. Wear of rocks and minerals may result mainly from the processes described in the following section. b. Abrasive and cutting wear. This wear is mechanical cutting in which one of two surfaces in contact is rougher and harder than the other, and the former directly cuts the latter. The material which undergoes this type of wear least is the one with great hardness and a small Young's modulus. It is usually admitted that the greater the elastic limit of strain E e,

69

Wear

MECHANICS OF SOLID ROCKS

Fig. 20-a.

Contours of bulk hardness in sectioned indentation in rock salt. Normal hardness is 17kgjmm' (after Brace, 1960).

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Distance below

(a)

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Bulk and grain hardness in the deformed region of anhydrite and marble (after Brace, 1960) .

70

MECHANICS OF SOLID ROCKS

the less the abrasive and cutting wear. Ee is equal to the quotient of elastic limit of stress fIe divided by Young's modulus E, and fIe is considered to be in proportion with the hardness of material H, therefore, E -~ ex: H e- E E and elastic energy per unit volume E g , 1 fIe2 H2 Eg=Z - E- ex: E

thus we can conclude that the greater the value of E g , the less the abrasive and cutting wear. c. Wear due to surface fatigue. This type of wear occurs when boulders roll down onto bedrock. If the contact pressure exceeds some critical limit and repeating contact occurs more often than some critical frequency, large numbers of small pits occur on the bedrocks, and the value of wear increases rapidly. This type of wear is known as pitting or flaking. It is due to a kind of fatigue by repeating contact, but the quantitative relation of this wear remains unknown. 3.7. Rock Mechanics and Geology

Even geomorphologists, especially those interested in erosion, might not be forced to be occupied with the investigation on the mechanism of occurrence of cracks, cleavages, etc. and on their systematic distribution itself, because geomorphologists can start their work considering the fractures of rocks and minerals as a given condition. Many geologists have engaged in the research of rock mechanics to clarify the mechanisms of structural movements such as folding and faulting, and the occurrence of cleavages and tectonites. Geophysicists, mining engineers and civil engineers might be more acquainted with rock mechanics than geomorphologists in general. Some of their works are listed in references which will be useful to the students of geomorphology.

REFERENCES

AKIMOTO, K, 1963, Hardening of potassium chloride single crystal by

REFERENCES

71

quenching and irradiation, Jour. Appl. Phys., vol. 34, pp. 1767-1770. AKIMOTO, K, and YATSU, E., 1965, Electron microscopic observation of radiation damage in KCI and NaCI single crystals, Eightieth Anniversary Bulletin of Chuo University, pp. 55-66. BERG, c.A., 1965, Deformation of fine cracks under high pressure and shear, Jour. Geophys. Research, vol. 70, pp. 3447-3452. BIRCH, F., and Dow, R.B., 1936, Compressibility of rocks and glasses at high temperature and pressures: seismological application, Bull. Geol. Soc. Am., vol. 47, pp. 1235-1255. BIRCH, F ., and BANCROFT, D., 1939, The elasticity of certain rocks and massive minerals, Am. Jour. Sci., vol. 237, pp. 1-6. BIRCH, F., and BANCROFT, D., 1942, The elasticity of glass at high temperature, and the vitreous basaltic substratum, Am. Jour. Sci., vol. 240, pp. 457-490. BIRCH, F., 1943, Elasticity of igneous rocks at high temperatures and pressures, Bull. Geol. Soc. Am., vol. 54, pp. 263-286. BIRCH, F., 1960, The velocity of compressional waves in rock to 10 Kilobars, part 1, Jour. Geophys. Research, vol. 65, pp. 1083-110l. BLANCHET, P.H., 1957, Development of fracture analysis as exploration method, Bull. Am. Assoc. Petroleum Geol., vol. 41, pp. 17481759. BLOSS, F .D., 1957, Anisotropy of fracture in quartz, Am. Jour. Sci., vol. 255, pp. 214- 225. BLOSS, F.D., and GIBBS, G.V., 1963, Cleavage in quartz, Amer. Mineralogist, vol. 48, pp. 821-838. BOOZER, G.D., HILLER, KH., and SERDENGECTI, S., 1962, Effects of pore fluids on the deformation behavior of rock subjected to triaxial compression, Rock Mechanics edited by C. Faircrust, Pergamon Press, pp. 579-625. BORCHERT, H., and MUIR, R., 1964, Salt deposits, p. 338, D. Van Nostrand Co., London. BRACE, W.F., 1955, Quartzite pebble deformation in central Vermont, Am. Jour. Sci., vol. 253, pp. 129-145. BRACE, W.F., 1960, Behavior of rock salt, limestone, and anhydrite during indentation, Jour. Geophys. Res., vol. 65, pp. 1773-1788. BRACE, W.F., 1960, An extension of the Griffith Theory of Fracture to rocks, Jour. Geophys. Rerearch, vol. 65, pp. 3477-3480. BRACE, W.F., 1965, Some new measurements of linear compressibility of rocks, Jour. Geophys. Research, vol. 70, pp. 391-398. BRACE, W.F., 1965, Relation of elastic properties of rocks to fabrics, Jour. Geophys. Research, vol. 70, pp. 5657-5667. BROUGHTON, J.G., 1946, An example of the development of cleavage, Jour. Geol., vol. 54, pp. 1-18. BURGERS, J.M., and others, 1935, First report on viscosity and plasticity,

MECHANICS OF SOLID ROCKS

72

Amsterdam, Academy of Science. CHAMPBELL, J.D., 1951, Some aspects of rock folding by shearing deformation, Am. Jour. Sci., vol. 249, pp. 625-639. CHRISTIE, J.M., 1958, Dynamic interpretation of the fabrics of a dolomite from the Moine Thrust-Zone in north-west Scotland, Am. J our. Sci., vol. 256, pp. 159-170. COHEN, M., ed., 1954, Dislocation in metals, Am. Inst. Min. Met. Eng., p. 200. COOK, M.A. , PACK, D.H., and MCEWAN, W .S., 1960, Promotion of shock initiation of detonation by metallic surfaces, Trans. Faraday Soc., vol. 56, pp. 1028-1038. COTTREL, A.H., 1953, Dislocation and plastic flow in crystals, Oxford Clarendon Press, p. 223. DREYER, W ., 1955, Uber das Festigkeitsverhalten sehr verschiedenartigen Gestein, Bergbauwiss., vol. 2, pp. 187. DVORAK, A., and Doz, P.P., 1961, Field test on soils and rocks, Proc. 5 th 1.C.S.M.F.E., Paris, vol. 1, pp. 453-460. ENDERBY, J.A., 1955, The domain model of hysteresis, part 1, independent domains, Trans. Faraday Soc., vol. 51, pp. 835-848. EVERETT, D.H., and WHITTON, W.1., 1952, A general approach to h ysteresis, Trans. Faraday Soc., vol. 48, pp. 749-757. EVERETT, D.H. , and SMITH, F .W ., 1954, A general approach to hysteresis, part 2, development of the domain theory, Trans. Faraday Soc., vol. 50, 1954, pp. 187-197. EVERETT, D.H., 1954, A general approach to hysteresis, part 3, a formal treatment of the independent domain model of hysteresis, Trans. Faraday Soc., vol. 50, pp. 1077-1096. EVISON, F.F., 1956, The seismic determination of Young's modulus and Poisson's ratio for rocks in situ, Geotechnique, vol. 6, pp. 118-123. GORUM, A.E ., PARKER, E .R., and PASK, J.A., 1958, Effect of surface conditions on room-temperature ductility of ionic crystals, Jour. Am. Cer. Soc., vol. 41, pp. 161-164. GREGORY, A.R., 1962, Shear wave velocity measurements of sedimentary rock sample under compression, Rock Mechanics edited by C. Faircrust, Pergamon Press, pp. 439-471. GRIFFITH, A.A., 1921, The phenomena of rupture and flow in solids, Phil. Trans. Roy. Soc. London, A. vol. 221, pp. 163-198. GRIGGS, D.T., 1936, Deformation of rocks under high confining pressures, 1. experiment at room temperature, Jour. Geol., vol. 44, pp. 541-577. GRIGGS, D., 1939, Creep of rocks, Jour. Geol. , vol. 47, pp. 225-251. GRIGGS, D., 1940, Experimental flow of rocks under conditions favouring recrystallization, Bull. Geol. Soc. Am., vol. 51, pp. 10011022.

REFERENCES

73

GRIGGS, D., TURNER, FJ., BORG, 1., and SOSOKA, J.. 1951, Deformation of Yule Marble, part IV -effects at 150°C., Bull. Geol. Soc. Am., vol. 62, pp. 1385-1406. GRIGGS, D., and MILLER, W.B., 1951, Deformation of Yule Marble: part I, compression and extension experiments on dry Yule Marble at 1000 atmospheres confining pressure, room temerature, Bull. Geol. Soc. Am., vol. 62, pp. 853-862. HAMMOND, M.L., and RAVITZ, S.F., 1963, Influence of environment on brittle fracture of silicate, Jour. Am. Cer. Soc., vol. 46, pp. 329-332. HANDlN, J ., and HAGER, R.V., 1957, Experimental deformation on sedimentary rocks under confining pressure : test at room temperature on dry samples, Bull. Amer. Assoc. Petrol., vol. 41, pp. 1-50. HANDlN, J. , 1960, Flow, fracture and strength of rocks in laboratory, Trans. A.G.u.. vol. 41, pp. 162-165. HANDlN, J., HAGER, R.V., FRIEDMAN, M ., and FEATHER, J.N., 1963, Experimental deformation of sedimentary rocks under confining pressure ; pore pressure test, Bull. Am. Assoc. Petroleum Geol., vol. 47, pp. 717-755. HARDY, H.R., 1959, Time-dependent deformation and failure of geologic materials, Quart. Jour. Colorado Sch. Mines, vol. 54, no. 3, pp. 135-175. HARRIS, J.F., TAYLOR, G.L., and WALPER, J.L., 1960, Relation of deformational fractures in sedimentary rocks to regional and local structure, Bull. Am. Assoc. Petroleum Geol., vol. 44, pp. 1853-1873. HODGSON, R.A., 1961, Classification of structures on joint surfaces, Am. Jour. Sci., vol. 259, pp. 493-502. HORIBE, T., and KOBAYASHI, R., 1964, On mechanical behaviors of rocks under various loading-rate~, Proceedings of Rock Mechanics, 1964 in Japan, pp. 1-10. HORN, A., 1963, Die Standsicherheit steiler Felsboschungen in hart en unverwittertem gestein, Bautechnik, 10, z. 259-362. HUGHES, D.S., and JONES, HJ., 1950, Variation of elastic moduli of igneous rocks with pressure and temperature, Bull. Geol. Soc. Am., vol. 61, pp. 843-856. ISHIHARA, K., 1965, Effect of rate of loading on the modulus of deformation of materials exhibiting viscoelastic behaviors, Trans. Japan Soc. Civil Eng., no. 117, pp. 35-51. KARMAN, T.V., 1911, Festigkeitsversuche unter allseitigen Druck, Zeitschr. Ver. Deutsche Ingenieure, vol. 55, pp. 1749-1757. KANEKO. S., 1955, Geological structure of the Tertiary deposits in the Itsukaichi Basin, Tokyo Prefecture, Japan, Jour. Geol. Soc. Japan, vol. 61, pp. 471-480.

MECHANICS OF SOLID ROCKS

REFERENCES

KAPOLYI, L., 1963, Die Ahnlichkeitsbedingung der gesteinsmechanischen optischen Spannungsuntersuchung, Berichte der Internationalen Konferenz fur Baugrundmechanik und Grundbau, Budapest, 1963, pp. 473-485. KNUDSEN, F.P., 1959, Dependence of mechanical strength of brittle polycrystalling specimens on porosity and grain size, Jour. Am. Cer. Soc., vol. 42, pp. 376-387. KOBAYASHI, y., IIZUKA, A, and KUMAGAI, K., 1965, Shear srength of rocks along weak planes·· ·case of schist, mudstone and granite, Eng. Geol., vol, 6, pp. 159-181. KUPFER, D.H., 1961, Structure of salt in Gulf Coast domes, 1st Symposium on Salt, Cleveland, Ohio, 1961, pp. 104-123. KUPFER, D.H., 1962, Structure of Morten Salt Company Mine, Weeks Island Salt Dome, Louisiana, Bull. Am. Assoc. Petroleum Geologist, vol. 46, pp. 1460-1467. LIVINGSTON, e.W., 1956, Fundarr.ental concepts of rock failure, Quart. Jour. Colorado Sch. Mines, vol. 51, no. 3, pp. 1-11. MATSUSHIMA, S., 1960, On the f low and fracture of igneous rocks, Disaster Prevention Research Institute Kyoto Univ. Bull, no. 36, pp.

PRICE, N.J., 1958, A study of rock properties in conditions of triaxial stress, Mechanical Properties of Non-Metallic Brittle Materials, Butterworths Science Publications, London, (edited by W.H. Walton), pp. 106-122. RAMBERG, H., 1963, Fluid dynamics of viscous buckling applicable to folding of layered rocks, Bull. Amer. Assoc. Petroleum Geol., vol. 47, pp. 484-505. RINEHART, lS., 1959, The role of stress waves in comminution, Quart. Jour. Colorado Sch. Mines, vol. 54, no. 3, pp. 61-76. ROBERTS, lC., 1961, Feather-fracture, and the mechanism of rock-jointing, Am. Jour. Sci., vol. 259. pp. 481-492. SAKUMA, S., 1952, Elastic and viscous properties of volcanic rocks at elevated temperature, part I, Bull. Earthquake Research Inst. Tokyo Univ., vol. 30. pp. 270- 278. SAKUMA, S., 1953, Elastic and viscous properties of volcanic rocks at elevated temperature, part 2, 3, Bull. Earthquake Research Inst. Tokyo Univ., vol. 31, pp. 63-70, 291-303. SELDENRATH, T.R, and GRAMBERG, J., 1958, Stress-strain relations and breakage of rocks, Mechanical Properties of Non-Metallic Brittle Materials, edited by W. H. Walton, Butterworths Scientific Publications, London, pp. 79-105. SERAFIM, lL., 1961, "In situ" shear tests and triaxial tests of foundation rocks of concrete dams. Proc. 5th I.C.S.M.F.E., Paris, vol. 1, pp. 533-539. SERATA, S., and GLOYNA, E.F., 1960, Principles of structural stability of underground salt cavities, Jour. Geophys. Res., vol. 65, pp. 2979-2987. SHIMOZURU, D., 1952, Dynamic measurements of the elastic constants of rocks subjected to initial stresses, 1. measurement of Young's modulus under uniaxial compression. Bull. Earthquake Research Inst. Tokyo Univ., vol. 30, pp. 63-69. SHIMOMURA, Y. and TAKATA, A, 1958. Research on relations of the physical properties of rocks and the drilling rates of diamondboring, Jour. Min. Metallur. Inst. Japan, vol. 74, pp. 852-860. SIMMONS, G., 1964, Velocity of shear wave in rocks to 10 Kilobar, 1, Jour. Geophys. Research, vol. 69, pp. 1123-1130. SIMMON, G., and BRACE, W .F., 1965, Comparison of static and dyamic measurements of compressibility of rocks, Jour. Geophys. Res., vol. 70, pp. 5649-5656. SKEMPTON, A.W., 1961, Effective stress in soils, concrete and rocks, Pore Pressure and Suction in Soils, Butterworths, London, pp. 416. STEPHENS, D.R, 1964, The hydrostatic compression of eight rocks, Jour. Geophys. Resarch, vol. 69, pp. 2967-2978. STOKES, RJ., and LI, C.H., 1963, Dislocation and the tensile strength of

74

2-9. MATSUSHIMA, S., 1960, On the deformation and fracture of granite under high confining pressure, Disaster Prevention Research Institute Kyoto Univ. Bull., no. 36, pp. 11-20. MAXWELL, le., 1962, Origin of slaty and fracture cleavage in the, Delaware Water Gap Area, New Jersey and Pennsylvania, Petrological Studies: a volume to honor AF. Buddington, pp. 281-311. MOGI, K., 1959, Experimental study of deformation and fracture of marble, On the fluctuation of compression strength of marble and relation to the rate of stress application. Bull. Earthquake Research Inst. Tokyo Univ., vol. 37, pp. 155-170. MOLLER, I.L.. 1963, Der Felsbau, Erster Band, Theoretischer Teil, Ferdinand Enke Verlarg, Stuttgart, p. 624. NADEAU, lS., 1964, Radiation hardening in alkali-halide crystals, Jour. Appl. Phys., vol. 35, pp. 1248-1255. ODE, H., 1956, A note concerning the rr.echanism of artificial and natural hydraulic fracture system, Quart. Jour. Colorado Sch. Mines, vol. 51, no. 3, pp. 19-33. PATERSON, S., 1958, the partition of energy in a blasting shot, Mechanical Properties of Non-Metallic Brittle Materials (edited by W_ H. Walton), Butterworths Scientific Publications, London, pp. 348- 364. PESELNICK, L., and OUTERBRIDGE, W.F., 1961, Internal friction in shear and shear modulus of Solenhofen Lirr.estone over a frequency range of 10' cycle per second, Jour. Geophys. Research, vol. 66, pp. 581-588.

75

MECHANICS OF SOLID ROCKS

REFERENCES

magnesium oxide, Jour. Am. Cer. Soc.. vol., 46, pp. 423-434. SUTHERLAND, RB., 1962, Some dynamic and static properties of rock, Rock Mechanics edited by C. Faircrust, Pergamon Press, pp. 473-

ZELENY, R., and PIRET, E.L., 1959, Studies on the energy requirements for crushing, Quart. Colorado Sch. Mine, vol. 54, no. 3, pp. 33-42.

76

491. TALOBRE, ]., 1957, La Mecanique des roches, appliquee aux travaux publics, Dunod, p. 444. TAYLOR, G.!., 1938, Plastic strain in metals, Jour. Inst. Metals, vol. 57, no. 1, pp. 307-324. TURNER, FJ. and WEISS, L.E., 1963, Structural analysis of metamorphic tectonites, McGraw-Hili, p. 545. VANZANT, B.W., 1962, Dynamic rock penetration test at atmospheric pressure, Rock Mechanics edited by C. Faircrust, Pergamon Press, pp. 61-91. VENABLES, lA., 1964, The electron microscope of deforrration twinning, Jour. Phys. Chern. Solids, vol. 25, pp. 685-692. WALSH, J.B., 1965, The effect of cracks on the compressibility of rock, Jour. Geophys. Research, vol. 70, pp. 381-389. WALSH, lB., 1965, The effect of cracks on the uniaxial elastic compression of rocks, Jour. Geophys. Research, vol. 70, pp. 399-411. WALTON, W.H., 1958, Porosity and strength of brittle solids (with particular reference to gypsum), Mechanical Properties oj NonMetallic Brittle Materials, Butterworths Scientific Publications, London (edited by W.H. Walton), pp. 35-49. WAYLAND, RG., 1939, Optical orientation in elongate clastic quartz, Am. Jour. Sci., vol. 237, pp. 99-109. WEISS, L.E., 1955, Fabric analysis of a triclinic tectonite and its bearing on the geometry of flow in rocks, Am. Jour. Sci., vol. 253, pp. 225-236. WILSON, S.D., 1959, Application of the principles of soil mechanics to open-pit mining, Quart. Colorado Sch. Mine, vol. 54, pp. 93113. WISSER, E., 1957, Deformation in the cordilleran region of western United States, Quart. Colorado Sch. Mines, vol. 52, no. 3, pp. 55-73. WUERKER, RG., 1959, Influence of stress rate and other factors on strength and elastic properties of rocks, Quart. Colorado Sch. Mines, vol. 54, no. 3, pp. 3-31. YAMAGUCHI, T., 1965, Tectonic study of rock fracture, Jour. Geol. Soc. Japan, vol. 71, pp. 257-275. YATSU, E., 1964, Est-ce qu'il y a la necessite de faire la recherche sur Ie monocristal pour la solution des problemes geomorphologiques? Applied Geography, vol. 5, pp. 31-34. YATSU, E., 1964, Sorr.e experimental data of static and dynamic characteristics of the Permian slate in the southern region of the Kitakami Mountains in Japan, Applied Geography, no. 5, pp. 57-64.

77

IV

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

Soils as treated in soil mechanics, aggregates of boulders, gravel, sand, silt, and clay are all considered rocks, that is unconsolidated or fracture<;t rocks, in geology. This chapter is concerned with the mechanics and mechanical properties of large sized debris in talus, bedrock with abundant fractures, weathered or unconsolidated strata, soils, and aggregates of clays. However, space restricts us to phenomena that are especially related to geomorphology. 4.1. Mechanics of Weathered Bedrock and Systems of Large Debris 4.1.1. Application of Soil Mechanics to Weathered Bedrock and Systems of Large Debris. Some attempts have been made to deal

with this subject (Wilson, 1959; Muller, 1959). For example, the approach of soil mechanics was applied to problems of slope stability in open-pit mining. The mechanics of this system would be most important for geomorphologists. Theories of elasticity and plasticity have been applied to solid bedrock and these approaches have succeeded to some extent. Soil mechanics was founded by Terzaghi and brilliant progress has been made by the efforts of his followers. However, large sized debris is not included in their experiments in soil mechanics. Consequently, it is not quite adequate to apply soil and rock mechanics without any _modification to systems of large-sized debris and weathered bedrock. The method of mechanical approach in this domain is extremely retarded irrespective of its great importance, due to the difficulty of experimentation and calculation. Experimental methods concerning systems of large sized debris should be modified and improved in order to fit these systems. For example, the sample size of various experiments in soil mechanics is too small, moreover N-values in penetration tests and consistencies could not be determined. And so field experiments using large size test pieces should be developed.

80

Mechanics of W eathered Bedrock and Systems of Large Debr is

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

1l

"'""~ if>

..:.: u

8

:;; .S

.gf 0 <1)

.<::

b

vi

if>

" e .D " Po<

'I

81

4.1.2. Some Examples of Field Measurements. The following methods are used to estimate the mechanical properties of partially weathered bedrock with many joints, and systems of large debris: a. The ratio of the length of the solid boring core obtained, to the entire length of the borehole, b. Measurements of elastic modulus, comparison of velocities of elastic waves in unweathered samples and in bedrock with fractures or in weathered rock, c. Measurements of elastic modulus by the methods of water chamber or jack method (or perhaps more proper to say, measurement of deformation coefficient) , d. Shearing test by large size testing machine in field , e. Loading test, f. Comparison of drilling velocities by rock drills, g. Comparison of volume of explosives (converted to the explosion power of standard explosive) necessary for excavation of unit volume of rocks, etc. In this domain, new methods should be developed because the theoretical system has not been completely evolved.

<1)

:::i\"

.~ c 0

>-. E

'-H

0

::::

:l

u:l ....

ci5 .-<

N

'2Jl

""

4 . 1.3. Some Problems on Unconsolidated or Fractured Rock. The swelling of bedrock with many fractures or soft rocks such as mudstone and shale is a very interesting phenomenon from the point of view of construction engineering as well as geomorphology and applied geology (Yatsu, 1964). Numerous papers have described the difficulties that occurred with rock swelling in the course of construction projects ; for example, tunnel excavation in mountains consisting of montmorillonitic shales, and construction work in the regions containing solfataric clay ( OnsenYodo ) and serpentine. Bedrock of cataclasite or mylonite also manifest swelling phenomena. Mylonites which increase in clay content as the degree of cataclastic action increase, present some of the most difficult problems to resolve, and are especially formidable in dam sites and tunnel projects. The writer's investigation of the notorious Malpasset Dam failure in France showed that the collapsed dam was constructed on a zone of mylonite. This mylonite was derived from gneiss and still contains the original gneiss in Augen. Besides quartz as the primary mineral, this mylonite contains illite as a dominant component, chlorite, and mixed

1 ,

82

Mechanics of Weathered Bedrock and Systems of Large Debris

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

83

6

'"

Q

.;

;:;

t)

0.

'"0-;

::>

k

.~ ....

if> if>

::;;;

4-<

.:;

0

E

..0

'"

'" ., '0-" -;

Q

~

if> if>

::;;;

'+<

0

.,~

~

.,'"

-5 ~

'"

~

.0: 0

>.

E

.s

.,

>

]

N

->:

N

b.O ~

.,c:

.:d

U3 c0 N

b.O ~

(Xl

"" >-rj

r!'i'

:;: t'l

tv

""

()

'" ;:r'aq '" '"'"0 aq

()

~

:»

~

8:'9 ... ::> >-\

Ul

::> '0

:=-

:r:

~o

....., :><

~

o

~

D

"l

~

7.13A

C Z

()

o

'

o

zUl

>-\

'" >-\ '< ... o· ::> p.. _•

.... ::>

::::: >-\ 3 ~

'<

o

~

'"

t-<

8

:» o-l

0

t'l

t:)

03

ro

::> ~. '" '"

'"

>-\

...

0

4.27 A

-~

:»

zt:)

... ... OJ

>-rj ~

:»()

;:r''''

'"0":;;:'" ''"" ...-. '"

o

'"

':l :1'::; 1\

<:

o-l

c:: ~

tt:I

t:)

'" :;: B' '-'" " " '0 '" ... '"'" '"'" ;~ .....,

.

'" '"

;:r'

iO

o()

'"

'"

~

WO

Ul

Dc

>-\

D

"q D

'"q

o

o

o


'"

q

~

'" ::>

;~i

=r

=r

=r

=r

~

~

~

~

p "r;

G)

D

~

= •.••

Table 6. Clay minerals in mylonite at the base of Malpasset Dam. Changes of X-ray diffraction with various treatments. Oriented specimens were used. H 2O

!

E.G.

!

HCI

! NH4 N0 3 ! Dri:fr in /200 o C. 1 h !400°C. 1 h /500 0 C. 1 h /700°C. 1 h !900°C. 1 h !

Mineral (Index)

d , (intensity) d, (intensity) d, (intensity) d, (intensity) d, (intensity)ld , ( intensity) d, (intensity) d, (intensity) ld , ( intensity) d, (intensity) 0

0

29.42A 14.24

Regular mixed layer minerals of swelling Chlorite and Illite

24. OOA( 5) 0

0

0

0

0

0

0

14. 24A(15) 14. 24A( 3) 14. 24A(13) 14.47 (12) 14. 24A(I1) 14. 24A(I1) 14. 24A(1O) 13. 58A(13)

1-. 11. 18

(11) 11. 18

(11)

(13) 10.04

(29) 10.04

(28) 10.04 (24) 10.04

(28) 10.04 (25) 10.04

7.13 (56) 7. 13

(13) 7. 13

(59) 7. 13

(57) 7. 13 (51) 7.13

(52) 7. 13

5.03

(20) 5.06

(8 ) 5.00

(21) 5.03

(19) 5.00 (21 ) 5.00 (19) 5. 03

4.74 (26) 4. 72

(7 ) 4.72

(21) 4.74 (19) 4.72 (25) 4. 71

4.50 (11) 4.27

(41) 4.27

3.56

(40) 3. 54 (14) 3.53

(38)

(15) 5.06 (15)

(33) (35) 3.56

(16) 10.04

x (14)

x

(21) 3. 78

(17) 3. 78 (16) 3. 78

(36) 3. 53

(41) 3.53

(37) 3.54 (26)

Illite (004) Chlorite (003)

(18) 4.50 (20) Illite (020, 110)

(33) 4.27 (36) 4.27 (38) 4.27 (26) 4. 27 (32) 4.25 3. 78

(20) Illite (002) Chlorite (002)

x

4.50 (15) 4.53

(26) 4.27 (28) 4.27

3.78 (13) 3. 78

(19) 4. 74

Chlorite (001) AI-vermiculite

(38) 10.04

10.16

X

x

(33) Quartz (100)

(16) 3.70 (22) Illite (023)

x

Chlorite (004)

3. 35 (100) 3. 35 (100) 3. 35

(100) 3. 35 (100) 3. 35 (100) 3. 35 (100) 3. 35 (100) 3. 35 (100) 3.34 (100) Quartz (101)

3.25 (30) 3.25

(16) 3.23

(34) 3.23

(27) 3.23 (25) 3.24 (23) 3. 23 (18) 3.23

(35) 3.19 (27) 3. 19

(58) 3. 18

(37) 3.20 (37) 3.20 (31) 3.20 (32) 3.20 (32) 3. 20 (27) Illite (114)

3. 14

(17) 3.23

(28) Feldspar (040)

~--.-~

86

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

Mechanics cf Weathered Bedrock and Systems of Large Debris

87

layer minerals of swelling chlorite and illite as a minor component (Fig. 6, Table 5) . The French engineering geologist Talobre (1964) misidentified the mylonite at the base of this fatal dam. At first glance the mylonite looks very hard, but it becomes flaky upon swelling. The origin of failure in this dam should be attributed to the swelling of mixed layer minerals and adsorption of water on the surface of the clay minerals, both of which decreased the strength of the bedrock. Swelling of solfataric clays may cause problems in tunnel constructions such as in the New Tanna Tunnel of the New Tokaido Line (Takahashi et at., 1963) . This tunnel passes very close to Hakone Volcano, which is frequently subject to landslips. Our investigations showed that this tunnel clay consists of montmorillonite, illite, metahalloysite, and mixed layer minerals of montmorillonite and illite and is derived from the Yugashima group by hydrothermal reactions; whereas in the landslip area, the clay minerals are mostly montmorillonite, with halloysite and alunite as minor components, and are derived from andesites in the same way (Nakano et at., 1961) . It is well known that shale and tuffaceous shale containing montmorillonite adsorb water and expand, and that the swelling of these strata give rise to landslips (2. 2. 2.) and many other difficulties in tunnel excavation. At times, troubles due to swelling chlorite have been reported, such as the Yui Tunnel of the New Tokaido Line and the Yui Landslip in Japan. In the western part of the United States, more and more attention is being given to the unique foundation conditions associated with the expansion and shrinkage of clays and clayey bedrock materials (Holz, 1959). Serpentines with abundant fractures will not cause as much trouble for construction works if they do not contain weathered clay minerals. Antigorite and chrysotile are not swelling clay minerals. However, at times, in the clay minerals derived from serpentine rock, montmorillonites or mixed layer minerals of antigorite and montmorillonite which swell a great deal do occur. The Kamogawa and Soro Landslips in Japan are related to montmorillonite in serpentine clay minerals. In some crystalline schist areas, swelling chlorites occur and cause landslips. Swelling chlorites in crystalline schists were first discovered in the Alps and the landslips near the upper end of the Queyras River were caused by such minerals, as

88

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

Mechanics of Weathered Bedrock and Systems of Large Debris

3.0 (%)

2.5

2.0

1.5

1.0

0.5

o

5

10

50

100

500 1000

- - - - - T ime (min.)

Fig. 27. 3. 3/1.

4. 4'. 4/1.

Fig. 26.

Apparatus for measurement of swelling pressure.

6. 6'. 7'. 8. 8'. 9. 9'. 10'. 11. 11'. 12'. 15'.

Free swelling, e-t curve (1).

Shale, Kodomari, 5 x 5 x 5cm' Shale, Kodomari, 7 x 7 x 7cm' Mylonite, Shinkoshirazu Tunnel, 5 x 5 x 5cm' Mylonite, Shinkoshirazu Tunnel, 7 x 7 x 7cm' Mylonite, Shinkoshirazu Tunnel, 3 x 3 x 3cm' Tuff, Kodomari, 5 x 5 x 5cm' Tuff, Kodomari, 3 x 3 x 3cm' Shale, Sankebetsu, 3 x 3 x 3cm' Shale, Sengan Tunnel, 5 x 5 x 5cm' Shale, Sengan Tunnel, 3 x 3 x 3cm' Weathered serpentine, Iwanebashi, 5 x 5 x 5cm' Weathered serpentine, Iwanebashi, 3 x 3 X 3cm' Mylonite, Sengan Tunnel, 3 x 3 x 3cm' Mylonite, Maebara Pass, 5 x 5 x 5cm' Mylonite, Maebara Pass, 3 x 3 x 3cm' Slate, Maebara Pass, 3 x 3 x 3cm' Slate, a little shattered, Sasago Tunnel, 3 x 3 x 3cm'

5000

10000

89

90

Mechanics of Weathered Bedrock and Systems of Large Debris

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

91

300

13.0 12.0

250

11.0 p

(g r/cm 2 )

10.0 ·0

(%)

200

9.0 8.0

150

7.0 6.0

100

5.0 4.0

50

3.0 2.0

o

1.0

500 1000 -----;.- Time (m in. )

Fig. 29. 0

50 ---~S_

Fig. 28. 3'. 5. 5'. 7.

Free swelling, e-t curve (2).

Shale, Shale, Shale, Shale,

Kodomari, 3 x 3 x 3cm' Kamihaboro, 5 x 5 x 5cm' Kamihaboro, 3 x 3 x 3cm' Sankebetsu, 5 x 5 x 5cm'

500 1000 Time (min.)

5000 10000

Pressure increase by swelling with time under confined condition. 3. 4. 6. 7. 8. 9. 10. 11.

Shale, Kodomari Mylonite, Shinkoshirazu Tunnel Tuff, Kodomari Shale, Sengan Tunnel Shale, Sengan Tunnel Weathered serpentine, Iwanebashi Mylonite, Maebara Pass Mylonite, Maebara Pass

5000 10000

Mechanics of Fine Debris such as Soils

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

92

93

3.00

700

2.00

600

500

1 : Shale, Sankebetsu Tunnel

p

Po= 250.0 gr Icm 2

1.00

k= 155 x 10- 4

(gr Icm 2 )

2 : Mylonite, Sengan Tunnel

Po- 42.6 gr Icm 2 k= 1.6 X 10- 3

400

500

Fig. 31.

200

100

o Fig 30.

1000

1500

2000

Time(mi n. )

300 -

5

10

50 ---~.- Time (min.)

Pressure increase by swelling with time under confined condition. 5.

Shale, Kamihahoro Tunnel

Relation between swelling pressure and time.

were those in Shikoku Island, Japan. Swelling clay minerals seem to be an inherent factor in landslips, from many observations in Japan, whereas shattered zone or bedrock without any swelling clay minerals are more likely to undergo the mass wasting characteristic of the slope rupture type. An apparatus as shown in Fig. 26 is convenient to measure swelling pressures. Some example of swelling-time curves are shown in Fig. 27~31. Volume increase of free swelling and swelling pressure in confined volume are functions of time. They may be expressed by the equation of first-order reaction velocity, in which P is swelling pressure, Po the limiting pressure of swelling, thus P=Po (1 -e- kt ) , where t is time in minutes, and k is a coefficient. Po and k depend on the kind and contents of clays in the samples. In general, rocks decrease in strength if they adsorb water to some degree. Now we will go into the reason for swelling pressure. The adsorption of water by the surface of solids or powders of solids, is called the phenomenon of wetting of boundary surfaces. This

94

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

phenomenon is caused by a decrease in the surface energy of solids. The type of adsorption described above is immersional wetting, which occurs at the boundary surface of the powders of solids, or in porous systems. A good illustration is the case of wetting on the inner wall of a glass tube by water. The free energy decrease, Wi, in the case of immersional wetting of solids in liquid is as follows: Wi=aS-al

where as is free energy on the boundary surface of air-solid, and al is free energy on the boundary surface of solid-liquid. This value of Wi is the origin of swelling phenomenon. Such values of energy as 50 to 100 ergs divided by the thickness of one molecule layer 2.5 x lO-scm, is necessary to remove the one molecule layer x 1cm2 of water, from the surface up to the distance of its thickness. This value reaches 4000kg/cm 2 • When 2 molecules are adsorbed at the wall, such energy decreases remarkably. Swelling by adsorption of more than 4 molecules of water is caused by the repulsion of electric double layers. Thus, the swelling of rock is due to the excess of adsorption and repulsion forces compared with the cohesion of rocks. Montmorillonites undergo interlayer adsorption and so they have a tremendously large surface of adsorption. This is the reason why rocks containing montmorillonites are likely to flake down in water. 4.2. Mechanics of Fine Debris such as Soils 4.2.1. Physical Properties of Soils. The methods of soil mechanics are available and are very useful for geomorphologists investigating related problems. Yatsu (1957) attempted to clarify the causes of the unvegetated waste regions in Japan by applying the methods of soil mechanics to his research. His results do not seem to have been fully successful. However, this does not imply that such methods are not appropriate for geomorphological studies. For instance, Chorley (1959))nvestigated the physical properties of Oxford soils and estimated the relative resistance of each soil type. Physical properties of soils, such as soil density, moisture content, permeability, soil consistency and so forth can be measured experimentally. Especially important among them are permeability, which is associated with soil erosion, and consist-

Mechanics of Fine Debris such as Soils

95

ency in the properties of soils when water and soil particles are coexisting. Liquid limit, plastic limit, plasticity index, and shrinkage limits are determined by measuring the water contents of soils under certain critical conditions. If soils contain more water than their liquid limits, they may be considered as liquid, and as they lose their water content, they become plastic, solid bodies. When they attain the conditions of shrinkage limit, they are considered to be in a perfect solid state. Solidification of soils by drying is attributed to the adhesive force of very few molecule layers of water absorbed on the surface of soil particles, as well as under the driest conditions to the cohesion of soil aggregates due to the crystallization of ions formerly dissolved in the soil water, and to intermolecular forces, mainly Van der Waal's force. As the water content increases, soil particles become dispersed in water and interparticle cohesion is weakened. It is Atterberg's contention that the mechanical behavior of soils, such as elastic, plastic, and liquid states should be attributed to the water content. 4.2.2. Mechanical Experiments on Soils. In measuring the n:echanical properties of soils, various methods such as compresSlOn tests and shearing tests are applied. The results of experiments on the same soil differ from each other depending upon the methods of testing, static or dynamic loading, and the soil specimen, moulded or undisturbed. The undisturbed soil specimen has the original structure of natural soil, while the moulded one has lost it. Dynamic loading tests accompanied by vibration furnish results that are not predicted by static loading tests. The tremendous boiling condition of the sandy soils which was caused by the Niigata Earthquake in 1964 severely damaged structures built . on the silty alluvial lowland in Niigata. This was due to a great mistake on the part of construction engineers who in designing earthquake-proof buildings did not adequately consider the foundation on which the building rested. Though they might have studied the foundation material by experiments of static loading and accounted for the bearing capacity of foundations, they dismissed the acceleration of earthquakes, which destroyed the structure of bearing strata.

96

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

Mechanics of Fine Debris such as Soils

%

11

100 90

.-1-

70 60 50 40

I I N

d

Fig. 32.

'"

o

8

/

I

10

~

II I

20

9

,/

! ,

30

8

10

V

.80

o

97

V

-

LOlD"COO'lrl

o d

/

N

7

0

Eu

...

o

J:f 5

d

N

(I')

¢

lJ1W"O'JOl O

0

o

.,

00

I

Particle size in mm

4

",-

Grain size distribution of shirasu (after Matsuo et ai, 1953).

3

2

The word Shirasu means volcanic sandy soils which cover very broadly the southern part of Kyushu, Japan. Their mechanical properties are so extremely unfavorable that this region is subject every year to serious damage from rupture of slopes, gully erosion, and so on. This soil is very sandy and about 90% of it belongs to the range of sand grain size as shown in Fig. 32. Matsuo et at. (1953) studied this soil and summarized the results of physical experiments on shirasu at Yunomata in Kagoshima Prefecture. 4.2.3. Properties of Some Erosible Sandy Soil I, Shirasu.

e~

1.132

o

Yd ~ 1.099g/cm 3

o

6

........

l"1.q-lCli,O"a)O'l ......

o o

••-...............e.

0.-oo _ -

~

8

5 • I

--

4 --;;,

'"

........

3~ 2

0-

X

6

_

6

,,.p.

1-

• 12 '"'" 0 Ol~~~~~~~~~~~~~ 4 6 8 10 '" "' . 14 16 '1 (%)

3

X

~t~

t:. 6

'"

'"

5


4

S X

3

6

2

",«

xX

x"

~

I

'"

)<

~

10

Table 7. Results of physical experiments on shirasu (after Matsuo et ai, 1953). Specific gravity Liquid limit Plasticity index Dispersion ratio Natural angle of repose

o o

12

14

16

0

(%)

2.38 44

6.0 5.0

o

Nri 4.0

62% 32°46'

........

!! 3.0 ... 2.0

Some remarkable characteristics are the high value of the dispersion ratio and the extremely low value of the plasticity index which indicate high susceptibility to erosion by rain wash and running waters. However, in the shirasu region, almost vertical cliffs several tens of meters in height exist very commonly. Fujimoto (1965) carried out triaxial tests and concluded that the apparent cohesion Cu is caused by the interlocking of volcanic sand and ashes, and by the dilatancy during shear tests. This special interlocking in shirasu seems to be the factor that plays an important role in slope stability.

Fig. 33.

Triaxial tests on shirasu (after Fujimoto, 1965). a. Difference of normal stresses (dl-da), ratio of normal stre. sses ((d l/d3) - 1), volume change (t:.v/vo) and difference of void ratio (e-em). b. Mohr stress circle at failure conditions of shirasu, undrained t est.

98

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

Sand or sandy soils of decomposed granitic rocks are designated Masa in Japanese. They have an apparent texture just like granite, even though biotites are decomposed and altered into chloritic clay minerals, and feldspars into kaolinite. The shirasu abovementioned is restricted to volcanic regions of acidic rocks where broad areas are covered by acidic siliceous volcanic ashes, while masa seems to be very common in the world. This simple word masa will be used from now on for decomposed granitic sandy soils in order to save space and time. In Japan, masa has a deep profile of twenty or thirty meters in some places. It has not been decided whether masa is formed under present climatic conditions or a dissimilar one during some stage of the Pleistocene. SOme masa are observed to be covered by Pleistocene deposits. If the vegetation cover is lost, deep profiles of masa will completely undergo devastation by erosion, and a scenery of badlands and bare mountains like that of a granite dome will be observed. From the point of view of soil conservation and geomorphology, adequate measurement of properties of masa and good judgment in the interpretation are prime requisites that deserve much more consideration than is often given to them. Yatsu (1957) studied the masa region in Setouchi and inferred that to the extremely low value of the plastic index (almost always 0) more than to any other cause, must be attributed the high erosibility of masa. Tanaka (1957) carried on the geomorphological investigations and measurements on the mechanical properties of masa. In these studies, carried out at the same time and in about the same area, it was clearly realized that masa shows a higher internal friction angle and a lower cohesion value than soils derived from Palaeozoic sedimentary rocks. The low value of the internal friction angle of sandy soil derived from quartz porphyry seems to the writer to be caused by the existence of clay minerals, into which quartz porphyry is more easily decomposed than granitic rocks. Tanaka concluded that the infiltration capacity of soil derived from Palaeozoic rocks is in general higher than that of granitic soils (masa), but this conclusion must be erroneous. Very reasonably, Shibuya (1960) recommended the measurement of porosity to determine the degree of weathering of granite. Shima (1961) carried on

Mechanics of Fine Debris such as Soils

4.2.4. Properties of Some Erosible Sandy Soil II, Masa.

99

1.5,----r--------,----------,--------,

1

10.28

]f

~

0;,

~ 1.0r------r-------------+---------7~~~~~------~

0~-_7ry_----_7~----~~----~

1.7

1.8

~

y

1J Dry

density

1.9

20

(g/cm 3 )

Dry density - unconfined compression strength curves (3-1ayer)

2 . 0,--------~~~-~----_,----__,

~E

u

1.9

'Ol) >,
C

1\

Q)

"U

1.8

>,

0

1.7 6

lP

S;) Fig. 34-a.

Water content

(%)

Compaction curves (3-1ayer)

Compaction tests on masa (3-1ayer compaction, after Tanimoto and Nishi, 1963).

--- ----- ---------------------------------------------------------~-----------------------------------------------------------

100

Mechanics of Fine Debris such as Soils

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

3.0,-----------,---------,,---------,

101

80

~ 60 o

xl--/

;;;:

2.5r--;::=====::;---t----I--~51I

>-

(a)

10.(-

6 40

xV' ~....... V-


~ 2 0 f - - -- - - f - - - - - - f - --+-----,1--T

~,

"/ x . VvA~A~_ v';

i= (j')

E

V,X 'A-Line

0: 20

.. Z:: ~

~/

,/

i/: ~~ xxV"'"

o

40

20

60

v'

80

LIQUID LIMIT

1-

100

80

.

, ,

V

~ 60 o z >40 (b)

x/

i= (j')

o~

O~--------~--------~~------~~ 1.7 1.8 1.9 2.0 Dry density

2.0 80

~ ~

1.9

25

~

.~

'"

:. 1.8

c5 1.7L.-------~=~===~:--~--,i 6

Water content

(%)

Compaction curves (5-layer) Fig. 34-b.

Compaction tests on masa (5-layer compaction, after Tanimoto and Nishi, 1963).

...-

j..-"

/

...-

I

" j..- "

V 20

...-

40

i 60

CLAY CONTENT

(g/cm 3 )

Dry density - unconfined compression strength curves (5-layer)

,/

x

/


0: 20

Kaolin (SKEMPTON)

/x

6

80

100

::!,

(a) Plasticity index versus liquid limit; (b) Plasticity index versus clay content

Fig. 35.

Plasticity index of fine fractions of decomposed granitic soil, Hong Kong (after Lumb, 1962).

seismic prospecting at many places in granitic regions and concluded that the velocity of longitudinal waves in masa is 0.5 to 1. 0 km/sec, while those of fresh granites fall in the range of 4.0 to 5.4 km/sec. Many tests on the mechanical properties of masa were done by Tanimoto and Nishi (1963) from the standpoint of enlarging utilization of this soil for large-scale construction works. According to them, a specimen compacted to the highest dry density does not have the highest strength, and in order to give masa the highest strength compaction process is most effective at water contents slightly lower than the optimum water content for the highest dry density. In addition, they acknowledged that the angle of internal friction of the loosest sample is almost equal to the angle of repose; however, more elaborate investigation is greatly needed in this connection.

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

Mechanics of Fine Debris such as Soils

Decomposed granitic soil in Hong Kong was studied by Lumb (1962) . Plasticity indices of the fine fractions are shown in Fig. 35. The results lie on or above the A-line and noticeably above the values quoted by Vargas (1953) for decomposed granite in Brazil. The average activity is 0.93 which would put the soil into the normal activity group, and except in two samples, plasticity indices are higher than that of kaolinite, presumably because of the appreciable content of mica in these .fractions. However, this soil behaves essentially as a coarse grained soil.

occur at a slope more gentle than that of slope rupture which does not need the existence of clay minerals for its occurrence. It is fundamentally a problem of rock control that landslips can occur on a gentle slope where rupture of slope cannot.

102

4.2.5. Stability of Slope.

This item forms one chapter in every text book of soil mechanics. The control of stability of slopes, natural or excavated, is an important aspect of civil engineering. For geomorphologists, slope problems are the focus of interest because any topographic feature is composed merely of two elements, slope and altitude. (Consider slope S, altitude A and position P, then, topography = f (S, A) , where A = f (P) , S = dA/ dP. This is a fundamenal geomorphological concept) . Thus mass wasting on slopes should have been a matter of primary concern for geomorphologists. However, they have indulged in their fantastic imagination about slopes, saying convex, concave, aufsteigende Entwicklung, absteigende Entwicklung, retreat of slopes, and so on. This approach has had its time. Geomorphologists have at long last had to come, hat in hand, before the civil engineers to beg instruction in the matter of slope stability, a matter long understood by the engineers. However, don't take this too sorely to heart. With little effort we can not only catch up but also surpass them. Soil mechanics has come to a standstill in a certain sense. Among the problems of slope stability, some opinions about mass wasting will be presented. The well-known classification of mass wasting by Sharpe is very systematic but very puzzling because it lacks explanation of mechanisms from a mechanical point of view. Recently a new classification of landslides have been presented by a civil engineer (Varnes, 1958) , and it seems to be much better. The writer wishes to propose a tentative classification of mass wasting which emphasizes the mechanisms of such phenomena and ignores their shapes and so forth (Table 8) . Landslips have a relationship to swelling clay minerals and

Table 8.

103

Classification of mass wasting.

1. Fall

Mass travels through the air.

Soil fall , rock fall , needle ice eroSIon

2. Creep

Plastic deformation without clear shear plane.

Soil creep

3. Rupture (YAMA-KUZURE)

Abrupt brittle fail ure of slope with clear shear plane.

Rock slide, slump, g lide

4. Slip ( JISUBERI)

Slow plastic flow with clear shear plane.

Landslip ( Earth flow)

5. Flow

Liquid flow, high content of water more than liquid limit

Mud flow Flowslide in quick clay

6. Others

Complex type, transitional type or other

Solifluction

When civil engineers calculate the stability of slope, they usually assume the slip surface to be circular. However, shear surfaces do not seem to be as simple in nature. Nevertheless, shearing stress , is expressed by angle of internal friction ifJ and cohesion C, as follows: , = u tanifJ + C where u is normal stress. Sandy soil without cohesion lacks C, whereas in clay ifJ becomes O. Geomorphologists must perform experiments on shearing, and take up the problems of what type of rocks make a particular kind of soil from the point of view of soil mechanics. In regions that are subject to earthquakes, their effects should be accounted for in the stability of slopes. If the acceleration of earthquakes attains several hundred gals, slope rupture occurs everywhere and mountain slopes lose their debris. The effects of earthquakes are caused not only by their acceleration but also by changes in the fundamental physical properties of soils and conditions of pore pressure. In soil that has an angle of internal friction <jJ, this value decreases with the degree of vibration as follows: ifJ k= ifJ - tan-!

v\

104

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

where cP k is cp in the time duration of earthquakes and k is the magnitude of the earthquake. 4.3. Mechanics of Micronized Debris such as Clays 4.3.1. Clayey Soils. In general, soils which have 20~30% clay components are called sandy clay loam, clay loam, or silty clay loam, and when the clay content surpasses 30%, these soils are called clays. However, soils are thought recently to behave as clayey soils, if 10% of their components are clays. The Norwegian applied geologist Rosenqvist (1958) said, as the general reporter, that the physical, .chemical, and mineralogical properties of the materials dealt with in soil mechanics are of extreme importance for the fundamental understanding of the subjects we are dealing with in the scientific and in the engineering approach. Concerning the important roles of clay minerals in soil mechanics, Grim (1962) has summarized in his book much data that seems to be useful for geomorphologists. 4.3.2. Mechanics of Clay. The ratio of clay to water, namely water content ratio, the type of clay minerals, and absorbed cations on the surface of caly minerals, are reflected in the mechanical properties of clays or clayey soils. We will discuss some important aspects. Plastic limits differ in different kinds of clay minerals and even in the same species, and they depend on the differences in crystal structure, lattice defects, and absorbed ions. In general. plastic limits decrease in the order of attapulgite. montmorillonite, halloysite 4H 20 , illite, halloysite, and kaolinite. Allophanes in natural condition have a high value of plastic limit which they lose when dried up. Plasticity indices, namely the differences of liquid and plastic limits, decrease in the order of montmorillonite, attapulgite, illite, halloysite, and kaolinite. Grain sizes naturally influence Atterberg's limits because the finer the grain, the larger the total surface of clays per unit weight. Atterberg's limits usually decrease markedly when clayey soils dry up. It is extremely remarkable in the lateritic soils containing ferric hydroxide and aluminum hydroxide. If the organic materials and content of R 20 a undergo dehydration,

Mechanics of Micronized Debris such as Clays

'II

105

they combine very firmly to prevent the intrusion of water, namely to resist hydration. The changes of relations in the clay-water system should be considered as being irreversible. The repeating of moderate wetting and drying makes some clay minerals, such as illite, chlorite, and kaolinite, in contrast to their normal decrease, increase their plastic properties. It is likely to be considered that such a reciprocation causes the pulverization of particles and changes of exchangeable cations and soluble salts. Skempton (1953) defined "activity" as the ratio of the plastic index to the volume of components of grain size less than 2/1, i. e. the volume of clays, and classified as follows: Group 1. Inactive with activity less than 0. 5 Group 2. Inactive with activity 0. 5 to 0.75 Group 3. Normal with activity 0. 75 to 1. 25 Group 4. Active with activity 1. 25 to 2 Group 5. Active with activity greater than 2 Various kinds of clays have their activity as follows: Montmorillonite . 0. 5-7 Attapulgite 0.5-1. 3 0.2-0. 6 Illite Kaolinite 0.1-0.4 Halloysite O. 1-0. 2 Allophane in Japan 2 3 Allophane in New Zealand The activity of chlorite is considered to be the same as kaolinite or illite. Uniaxial compression strength d~ pends upon the components of clay minerals. volume of non-clay materials, distribution of grain size, shape of particles, structure of aggregation, hysteresis effects on compression. exchangeable cations. water content. and so on. The addition of clay minerals to some degree makes silt and soil increase their compressi(;m strength. and montmorillonites have the most eminent effects of this kind. Montmorillonite is hardly subject to consolidation. and the clays with Na-adsorbed ions undergo the effect of consolidation with greater difficulty than the same clay minerals with Al and Ca ions. The same factors as described in the case of uniaxial compression are important in considering shearing strength. In the ranges of small water content, this strength is mainly influenced

MECHANICS OF UNCONSOLlDA TED AND FRACTURED ROCKS

Mechanics of Micronized Debris such as Clays

by water content, while with relatively larger water content, the kind of clay minerals and exchangeable ions play an important role in this property. Attention must be paid to the time effect which is reflected greatly in the strength of shear. Terzaghi (1944) defined the concept of sensitivity as the ratio of the strength of soil in an undisturbed condition to the remolded material at the same water content. Skempton et at. (1952) classified the sensitivity of clays as follows: [Group] [Sensitivity] Insensitive clays <1 1-2 Low sensitive clays Medium sensitive clays 2-4 Sensitive clays 4-8 Extra sensitive clays 8-16 Quick clays 16 A soil composed of allophane has been described (Grad well and Birrell, 1954) as having a sensitivity of 7. The sensitivity of allophane is due to the substantial differences in textural characteristcs and accordingly in strength between the soil test pieces in their natural state and those in a remolded state, as shown by Yatsu (1964 b) . In general, the more irreversible the hydration and dehydration of clay minerals, the greater their sensitivity. The work of remolding destroys the structure of aggregation and changes the state of hydration that is hardly ever regained. If the strength is recovered after a remolding of test pieces for some duration, such a property is named thixotropy.

flows in that the orientation of particles is not instantaneous under shearing stress and needs a definite time lag for structural recovery. These time lags depend upon the concentration of the suspension, namely, the higher the concentration, the lesser the time lag because the average intergranular distance is less, with consequent greatness of intergranular attractive force. Thus structural recovery soon occurs. Bentonite, chiefly composed of montmorillonite and some glacial till clay called quick clay, has striking characteristics of thixotropy. The amount of thixotropic regain of strength in remolded test pieces of soils is greatest in clayey materials with high activity, namely in clays containing chiefly momtmorillonite. It results from the extremely small particle size of montmorillonite and its high water· adsorbing capacity which favors the development of oriented water on clay minerals. The regain in strength is considerable for montmorillonite, moderate to small for illite and practically nil for kaolinite. Grim (1962) opined that quick clays do not show any appre· ciable regain in strength on standing after remolding and con· sequently thixotropic hardening does not provide an explanation for their sensitivity, and Kerr (1963) supported this opinion. A great number of landslides (Mudflow in Table 8) in Scandinavia result from the properties of quick clays that were inten· sively studied by Bjerrum (1961), Kjellman (1954) and others. The landslides at Anchorage caused by the Alaskan Earthquake (1964) and the one at Maseguchi (1947) belonged to the category of mudflows. Quick clays lose their strength by shocks and vibrations, assume a liquid state, and begin to flow. Many mudflows in volcanic regions seem to have the same origin, because of the occurrence of a great deal of montmorillonite clay from hydrothermal reactions.

106

>

4.3.3. Thixotropy and Mudflows. The term "thixotropy" OrIgInally was given to the property of certain suspensions that causes them to become fluid on agitation but set to gel when undisturbed. A characteristic behavior of thixotropic materials manifests itself in a hysteresis loop when they are tested in a rotational viscometer (rheometer) under varying rates of shear. At increasing rates of shear, the structure is continuously broken down and the up-curve is shifted toward larger stresses, indicating a decrease in flow resistance, whereas the down-curve determined at decreasing rate of shear is shifted toward smaller stresses. Thixotropy, like other non-Newtonian types of flow, results from the change of structures when materials are subjected to shear stress, but it differs from the non-Newtonian

107

4.3.4. Properties of Some Cloy,ey . Soil I, Konto Loom. The socalled Kanto Loam is not a" real loam in the soil classification, but is the traditionaL common name which was given to the altered volcanic ashes, covering the Diluvial terraces and hilly lands in the Kanto Basin, Japan. Soils of a similar type cover broad areas in Central and North-east Honshu Island. Several hundred works have been contributed to clarify its origin and nature from various points of view, geological, pedological, agricultural, technical and so forth. However, some problems

108

Mechanics of Micronized Debris such as Clays

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

still remain obscure. From the geomorphological point of view, Kanto Loam is very interesting, in that it makes steep, in many cases almost vertical cliffs, and undergoes so little rain wash erosion that in some place, geomorphological inversion seems to be observed. Some part of the hilly land of Tertiary sandy shale, e. g., near Tsurukawa, probably was covered by Kanto Loam just as was the Sagami Diluvial Terrace, but Kanto Loam on this hill was easily eroded because of its locality of deposition and the bed rock thereafter has been exposed to erosion due to its lower value of permeability than that of Kanto Loam. It is a matter for deep regret that most geomorphologists in this country do not accord special attention to problems of land forms in which the nature of Kanto Loam plays an important part. Kanto Loam consist of small particle of crystals, clay minerals and amorphous allophane. The original materials of this soil are andesitic volcanic ashes of silica, feldspar, hornblende, hypersthene, augite, volcanic glass and so on (Kato, 1965). Clay minerals and allophane in Kanto Loam will be discussed later. Grain size analysis of this soil is very difficult, because the results depend extremely on the dispersion methods. A low percentage of clay content, sometimes less than 30%, has been reported but this seems to result from an imperfect dispersion. A combined treatment by adequate deflocculating agents and ultrasonic wave dispersion method, is recommended to determine the grain size distribution. The Kanto Loam Study Group (1964) summarized the engineering properties at the end part of its bulky volume, most of which is devoted to the origin and correlation of four layers: Tachikawa Loam, Musashino Loam, Shimosueyoshi Loam and Tama Loam, in sequence from upper to lower. Many researches have been done on the engineering properties of Tachikawa Loam and Musashino Loam, however very few on Shimosueyoshi Loam and Tama Loam because of their restricted distribution. Here will be mentioned some properties of the upper two Loams. Kanto Loam has high void ratio and they are about 3 to 5. remarkably higher than those of Alluvial soils and almost equal to the void ratio of humus-rich clayey soils. Other remarkable properties are the high value of water content, almost always 100 to 180%, and the very high content of non-free water in

109

2.o1----i\\\---+--+---l--+-- +---J-..------j---1----l----l--....j 1.9 - - - I--'I.\S-l---l---+-- +--+--+~E 1.81--+-~~::--+--+--+--+--+"'I-

:r:

1.71--+---+'

: o

~~~d )

Clay

.

AllUVium

• Peat • Kanto Loam

<.9

W 1.61--+--+-~~

3:

~

1.51-- +---1----+

:::J

1.41--+---+-------.:+--~~'1i::

l.311-11-----j-f~~~~~f~~;Jg~j 1.2 1----t---t--t------t---t---r---;-F~~ci-'=~~~ti

1.10L - - L - . - L - . - L - - . L2----L----.L 3 ----.L--4L----1--=~5=~---.::......J VOID RATIO

Fig. 36-a.

Unit weight of soil-void ratio relationship of Kanto Loam and Alluvial soils in Tokyo and its vicinity (after Soc. Arch. and Soc. S.M.F .E .• 1959) .

120r--~----~----~----~----~----~----~--~----_,

100

• Kanlo Loam x o

x

Sill} Alluvium Clay

..

80 1---+--~--+---~--+-~4-~~~~~~~~

w

o

z

r60 1-----I-----+----_+---,-+--~~~~P+~~~~-+_--~ ]-

<:5 ~

o. :.

540 1---~------+~--_+~ ,~~~~~~~o~ . -. ~---_+-~ D...

201------4--0L---~~--~----~----~80~--~1~00~--7.12~O--~1~4~O--~lW~--~180 LIQUID LIMIT

Fig. 36-b.

-

%

Plasticity chart of Kanto Loam and Alluvial soils in Tokyo and its vicinity (after Soc. Arc. and Soc. S.M.F.E ., 1959).

110

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

1.100

\

-"~

1.000

)\ rf p 1~

® 0.900

~

0

~ ®

:Y

0. 700

'?-o.-

;\~~.<&

Cf

0.600

0. 50 0

',,-

@n J , u

20

40

60

80

~cr

100

120

~

140

60 .

w:% Fig. 37. Effect of in it ial water content on the opt imum water content of compac t ion test, Kanto Loam ( smaller than 0.85mm in diameter). P. 1 to P. 5 are in sequence from dry to wet initial condition. P . 1: sample dried in an oven, P . 2-5 : samples dried in air ( after Kuno, 1962).

the range of PF, more than 4. 2. The consistency of Kanto Loam, determined by the ordinary method using the air-dried sample, is very similar to those of Alluvial soils as illustrated in Fig. 36-b. However, these results give an utterly false image for the consistency of this soil. The drying treatment once done, this soil does not recover its original properties, even if water be added, i. e., the drying and wetting processes are irreversible. Kanto Loam decreases its plastic and liquid limits with the decrease of water content by drying in the air. This phenomenon presumably is caused by the existence of allophane. The shearing test shows that the value of cohesion is about 0.3 to 0. 5kg/cm2, almost equal to that of Alluvial clays, but its angle of internal friction is 25° to 30°. The bearing capacity estimated by the penetration test is 3 to 8 t / m2, however, when calculated by load-settlement relation attains to 10 to 15 t / m2. This discrepancy should originate from the special structure of this soil. It must deserve special consideration that the method of

l

Mechanics of Micronized Debris such as Clays

111

controlling the water content of the specimens strongly affects the optimum water content on the compaction test. Fig. 37 shows this phenomenon (Kuno, 1962). Many reports concern clay minerals in Kanto Loam. In this field, Sudo (1956) and his followers studied intensively the alteration of volcanic glass fragments. Through the efforts of mineralogists and pedologists, the components are clarified as follows: Tachikawa Loam dominant in allophane, auxiliary hydrated halloysite. Musashino Loam allophane and hydrated halloysite . Shimosueyoshi Loam hydrated halloysite and halloysite. Tama Loam halloysite. Yoshinaga and Aomine (1962) observed a fibrous clay mineral in Kyushu named "Imogolite", which seems to be a type transitional between amorphous allophane and crystalline clay minerals. Imogolite is observed in Kanto Loam. Yatsu discovered filmy allophane in Tachikawa Loam at the Kasugacho Campus of Chuo University. This filmy allophane is very unstable and he ('onverted it to crystalline halloysite by collision with carbon vapor in high vacuum (Yatsu, 1964) . New Zealand has a temperate humid climate, as does Japan. The physical and soil engineering properties of volcanic clayey soils there are very similar to those in Japan. Gradwell and Birrell (1954) and Fieldes et at. (1955a, 1955b, 1956, 1957) have contributed to the research on this type of soil. 4.3.5. Properties of some clayey soil II, post-glacial marine soils.

During post-glacial transgressions, very broad areas were submerged by marine water under which a huge volume of sediments were deposited. In many regions, these marine deposits subsequently have been covered by fluvial sediments and form the substrata of fluvial plains and deltas. In regions, depressed under the ice load in the period of glaciation, the post-glacial transgression was followed by the uplift of lands which raised the post-glacial marine soils to their present elevation above sea level. In eastern Canada, most flow slides have occurred in the valleys of the Ottawa and the St. Lawrence Rivers where clays (called Leda clay) and silts have been deposited in the Champlain Sea and now raised generally up to 300 feet above sea level. In Norway, fjord lowlands near

......

...... tv

~ to

()

:I:

> Z

oen o

"l

~

()

o Z

en r

o

6

> >-l to

'=' > Z '=' "rj ~

>

()

>-l

c:: ~

to

'=' ;;0 o() ~

en

Fig, 38-a,

Allophane (round) and imogolite (fibrous) in Tachikawa Loam at the Kasugacho Campus, Chuo University,

...

~ ~

::r-

'"" ' ri '"

o ..... ~ ri'

a "

~.

0..

tJ

r1>

:r en' '"c(') ::r'"'"

o

Ii)

'<

'"

Fig, 38-b,

Allophane (filmy), at the Kasugacho Campus, ChuD University,

...... ......

w

..... ..... ",.

...

2::: t
"

()

:I:

:> Z

0

Ul

0

."

c:: Z ()

0

Z

Ul

0

r

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t
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z

0

,.." ~

:> () >-l

c:: ~

•

•

• Fig. 38-c.

•

/',1),

t
0

()

:>1

Ul

I • Allophane (filmy ), at the IKasugac ho Camr;us, Chuo University.

2:::

~ oo ::l ri'

::rif>

8.,

2::: q. o

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N' (1)

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Fig. 38-d.

Halloysite converted from filmy allophanes shown in Fig. 38-c by collision cf carbon vapor in high vac uum.

..... ,.... (Jl

116

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

~ ~ Soil ' Elev. Description ft { Surface

y

<7

Fill

~ Water Content. 20

%

40 60

~ Undrained Shear Strength and Preconsolidation Pressure, tift 2 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

lOH==l=+==+~=+=+=+=+=+=!==l==l==l==l I"'-Ot-+--+~--+--P~--~~-+--t-+--+~--+-~

G -1Ot-+-= >-FH--<'P't---+---+1'~ : B° >-~ ; c9
vP~econlsolid~tion pre~sure ~\

-~t-~=T~+--r~!\:,-\-+-01~~0~-+~r-1--+~+--r-1 LL ,: ~ Jf ective overburden ttl t---

1"

Clay

~

Foraminifera

F -30

°

I' ' I

01

pressure \'

["Yf'"

\

~~ \ n~r'\. -~r-~~~~+'-r~-r~~I-4 ,ro~~~~~ ~ "1 50 I--+.I __ -j-: -,1-+---11-+ \-+ __ 1-+-+ __ °+---, '\~.--t--+--+--I E

jl-'

zones -

Fig. 39.

-60

,\

a'"",,

,

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. : 'I-Shear strength from D - 70f---c;W,fj' "Cw ::':9':-:W:-J +--+--1-\1-\--t--+140 Ivan, tes

"-

o

° on' °"

il/

N

Soil profile and geotechnical test results, Skabo, Oslo (after Kenny, 1964) .

Oslo and Trondheim were covered by marine clay deposits which have been lifted up to about 600 feet. Similarly in Sweden, the valleys of Stockholm and Goteborg undergo numerous flow slides. Meyerhof (1957) summarized the common characteristics of these marine clays. According to him, the sites on which flow slides occurred were mainly underlain by extrasensitive quick clays (4.3.3.). They have a relatively low plasticity and are characterized by a liquid limit of about 25~60, plastic limit of 15~25 and a plasticity index of about 1O~35. Canadian and Swedish deposits are frequently less sensitive and the corresponding Atterberg's limits are somewhat higher than Norwegian ones. Clays and silty clays below a stiff crust have undisturbed shear strength from about O. 1~o. 4 ton/W, and the ratio of shear strength to effective overburden pressure varies from O. 1 ~O. 5 which correspond to an angle of shearing resistance of about 50 to 20 0. After a period of rest the remoulded material recovers its strength by thixotropic hardening but generally never regains its original strength. Recently, Leda Clay has been intensively investigated by the group of Soil Mechanics Section, Division of Building Research, National Research Council of Canada. Table 9 summarizes the characteristics of this clay. Crawford and Eden (1965) are inclined to doubt that Leda Clay was deposited under marine

LO LO

00 CD

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118

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

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\ '1:>

800 .--. U) ~

>-

~

:~

c:

2c:

:2_.....J

g:E".....J

/ \ 0 0

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500

h

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700

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119

Mechanics of Micronized Debris such as Clays

i~- /\ \ Ii

,~,C:/\ Iii ,' , \ .

I/r-..- ~

t::;; ~

~

'(/j

c (])

~

400

V>

'"

(j)

~

300

>'"

200

'" > «'"

OD

•

:."

100

~

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14 , Electrokinetic potential Fig, 40,

E lectro-kinetic potential of undisturbed Leda Clay as a function of sensitivity (after Penner, 1964).

conditions. They acknowledge some differences in the geotechnical properties of this clay from . those of Scandinavian quick clays. Leda Clay is more highly plastic (lp=30~40) , and has lower pore water salt concentration than Scandinavian clays. This Canadian geotechnics school seems to question the existing theory for sensitivity based on the salt-leaching. Penner (1964) measured the electro-kinetic potential in undisturbed samples of Leda Clay. Of particular interest is the fact that the potential increases directly with increasing sensitivity. Surface chemistry must be a powerful method in an attempt at complete solution of sensitivity problems. Fig. 41 and 42 show the geotechnical properties of marine soils in the Thames Estuary, Osaka Bay and Ube, which display the normal consolidation; thereforet he strength of such clays does increase with depth. Alluvial plains are quite often underlain by post-glacial clays that are high in water content and have not yet consolidated enough to afford a large bearing capacity. Construction works such as large buildings, bridges, highways etc. frequently encounter great difficulties because of insufficient strength of

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120

REFERENCES

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS SHEAR STRENGTH

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strata. Consolidations of clay layers is one of the causes of such ground subsidences as observed in Tokyo and Osaka. These are, in a sense, tangible manifestations of the direct rock control over human life. REFERENCES

ANDERSON, PJ., and MURRAY, P ., 1959, Zeta potentials in relat ion to rheo' logical properties of oxide slips, Jour. Am. Ceramic Soc., vol. 42, pp. 70-74. AOMINE, S., and WADA, K, 1962, Differential weathering of volcanic ash and pumice, resulting in formation of hydrated halloysite, Am. Mineralogist, vol. 47, pp. 1024-1048. AVENARD, ].M., 1961, La solifluxion, Centre de Documentation Universitaire, p. 164. BISHOP, A.W., and MORGENSTERN, N., 1960, Stability coefficients for earth slopes, Geotechnique, vol. 10, pp. 129-147. BJERRUM, L., 1954, Geotechnical properties of Norwegian marine clays,

,

121

Geotechnique, vol. 4, pp. 46-69. BJERRUM, L., and KJAERNSKI, B., 1957, Analysis of the stability of some Norwegian natural clay slopes, Geotechnique, vol. 7 pp. 1-16. BJERRUM, L., and SIMONS, N .E ., 1960, Comparison of shear strength charactt"ristics of normal consolidated clays, Norwegian Geotechnical Inst. pub., 35, pp. 13-22. BOWER, T .H., 1951, Mudflow occurrence in Trinidad. B. W. 1., Bull. Am. Assoc. Petroleum Geol., vol. 35, pp. 908-912• CAPPS, S.R., 1941, Observations of the rate of creep in Idaho, Am. Jour. Sci., vol. 239, pp. 25-32. CHORLEY, R.]., 1959, The geomorphic significance of some Oxford soils, Am. Jour. Sci., vol. 257, pp. 503-515. CRAWFORD, C.B., and EDEN, W.J., 1965, A compariron of laboratory results with in-situ properties of Leda Clay, Proc. 6th 1. C. S. M . F. E. 1965, Montreal, vol. 1, pp. 31-35. DAVIS, D.H ., 1954, Estimating porosity of sedimentary rocks from bulk density, Jour. Geol. , vol. 62, pp. 102-107. DEVANATHAN, M .A.V., 1954, A theory of the electrical double layer and the interpretation of differential capacity curves, Trans. Fara· day Soc., vol. 50, pp. 373-385. FIELDES, M ., and WILLIAMSON, K1., 1955, Clay mineralogy of New Zealand soils, I, New Zealand Jour. Sci. Tech., vol. 37, pp. 314335. FIELDES, M ., 1955, Clay mineralogy of New Zealand, II, New Zealand Jour. Sci. Tech., vol. 37, pp. 336-350. FIELDES, M ., WALKER, 1.K and WILLIAMS, P .P ., 1956, Clay mineralogy of New Zealand soils III, New Zealand Jour. Sci. Tech., vol. 38, pp. 31-43. FIELDES, M., 1957, Clay mineralogy of New Zealand soils IV, New Zealand Jour. Sci. Tech., vol. 38, pp. 533-570. FUJIMOTO, H ., 1965, Shearing properties of shirasu, Soil Mechanics and Foundation Engineering, vol. 13, pp. 56-63. GRADWELL, M., and BIRRELL, KS., 1954, Physical properties of certain volcanic clays, New Zealand Jour. Sci. Tech., Sec. B, vol. 36, pp. 108-122. GRATER, R.K, 1945, Landslide in Zion Canyon, Zion National Park, Utah, Jour. Geol., vol. 54, pp. 116-124. GRIM, R.E., 1962, Applied Clay Mineralogy, p. 422, McGraw-Hill. HENKEL, DJ., 1956, The effect of overconsolidation on the behavior of clays during shear, Geotechnique, vol. 6, pp. 139-150. HEMWALL, J .E., and Low, P.F., 1956, The hydrostatic repulsive force m clay swelling, Soil Sci., vol. 82, pp. 135- 145. HIGASHI, T., and AOMINE, S., 1962, Weathering of montmorillonite in soils, Soil Sci. Plant Nutr., vol. 8, pp. 7-12. HOLTZ, W .G., 1959, Expansive clays-properties and problems, Quart. Colo-

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

REFERENCES

rado Sch. Mines., vol. 54, no. 4, pp. 89-125. KANTO LOAM STUDY GROUP, 1964, Kanto Loam, its origin and nature, p. 373, Tsukiji Shokan, Tokyo. KATO, y., 1965, Some problems on parent materials of volcanic ash soil, Pedologist, vol. 9, pp. 13-19. KENNY, T .C., 1964, Sea-level moverr.ents and the geologic histories of the post-glacial marine soils at Boston, Nicolet, Ottawa and Oslo, Geotechnique, vol. 14, pp. 203-230. KERR, P .F ., 1963, Quick clay, Scientific America, 1963, Nov., pp. 132-l42. KJELLMAN, W., 1955, Do slip surfaces exist? Geotechnique, vol. 5, pp. 18-22. KUNO, G., 1962, Soil compaction, Gihodo, Tokyo. LUMB, P., 1962, The properties of decomposed granite, Geotechnique, vol. 12, pp. 226-243. MATSUO, H., MIZUNO, T., UCHIDA, 1., and YAMANOUCHI, .T., 1953, Studies on the characteristics of shirasu, Kyushu Univ. Kogaku Shuho, vol. 26, pp. 79-84. MCMILLEN, E.L., 1932, Thixotropy and plasticity, Jour. Rheol., vol. 3, pp. 75-94. MELTON, M .A., 1965, Debris-coveredhillslopes of the southern Arizona desert, consideration of their stability and sediment contribution. Jour. Geol., vol. 73, pp. 715-729. MEYERHOF, G.G., 1957, The mechanism of flow slides in cohesive soils, Geotechnique, vol. 7, pp. 41-49. MILLIGAN, V., SODERMAN, L.G., and RUTKA, A., 1962, Experience with canadian varve clays, S. M. F. D. Proc. Am. Soc. Civl Eng., 31-67. MOHAN, D., and CHANDRA, S., 1961, Frictional resistance of bored piles in expansive clays, Geotechnique, vol. 11, pp. 294-30l. MORIMOTO, R, 1951, Geology of Imaichi District with, special reference to the earthquake of Dec. 26, 1949 (II), Bull. Earthq. Res. Inst., Tokyo Univ., vol. 29, pp. 349-358. MORIMOTO, R, OSSAKA, J., and FUKUDA, T., 1957, Geology of Imaichi District with special reference to the earthquake of Dec. 26, 1949 (III), Bull. Earthq. Res. Inst. Toky. Univ., vol. 35, pp. 359-375. MULLER, L., 1959, The european approach to slope stability problems, Quart. Colorado Sch. Mimes, vol. 54, no. 3, pp. 115-133. MURAl, 1., 1960, On the mudflows of 1926 eruption of volcano, Tokachidake, Central Hokkaido, Japan, Bull. Earthquake Res. Inst., Tokyo Univ., vol. 38, pp. 55-70. NAKANO, H., YATSU, E., and TERUTA, Y., 1961, On the clay minerals In the landslip-debris in Japan (1), Applied Geography, No.2, pp. 1-24. OHSAKI, Y., 1957, Geotechnical properties of Kanto-Loam and .its anisotropy,

Report of the Building Research Institute, no. 21, pp. 1-14. OLSON, RE., and MITRONOVAS, F ., 1960, Shear strength and consolidation characteristics of calcium and magnesium illite, proc. Ninth. Nat. Conf. Clay and Clay Minerals, pp. 185-209. OLSON, RE., 1962, The shear strength properties of calcium illite, Geotechnique, vol. 12, pp. 23-43. PENNER, E., 1963, Sensitivity in Leda Clay, Nature, vol. 194, pp. 347-348. PENNER, E., 1964, Studies of sensitivity and electro-kinetic potential in Leda Clay, Nature, vol. 204, pp. 808-809. ROSENQVIST, LT., 1953, Sensitivity of Norwegian Quick Clay, Geotechnique, vol. 3, pp. 195-200. ROSENQVIST, LT., 1958, Soil properties and their measurement, Proc. Fourth International Con., S. M. F. E., vol. III, pp. 85, London. SHARP, RP., and NOBLES, L.H., 1953, Mudflow of 1941 at Wrightwood, Southern California, Bull. Geol. Soc. Am., vol. 64, pp. 547560. SHIBUYA, T ., 1960, The weathering of rock and its porosity (on granite), measurement of degree of the weathering at civil engineering work, Engineering Geology, vol. 1, pp. 12-18. SHIMA, H., 1961, The relationship between weathering and geomorphology in granitic regions, Geographical studies presented to Prof. Taro Tsujimura in honor of his 70th birthday, pp. 201214. SKEMPTON, A.W., and NORTHEY, RD., 1952, the sensitivty of clays, Geotechnique, vol. 3, pp. 30-53. SEKMPTON, A.W., 1953, Soil Mechanics in Relation to Geology: Part 1, Proc. Yorkshire Geol. Soc., vol. 29, pp. 33-62. SKEMPTON, A.W., and BROWN, J.D., 1961, A landslide in boulder clay at Selset, Yorkshire, Geotechnique, vol. 11, .pp. 280-293. SKEMPTON, A.W., and HENKEL, D.J., 1961, The post-glacial clays of the Thames Estuary at Tilbury and Shell haven, Proc. 5th 1. C. S. M. F. E., 1961 Paris, Session 3/7, pp. 302-308. SOCIETY of ARCHITECTURE and SOCIETY of SOIL MECHANICS and FOUNDATION ENGINEERING, 1959, Ground of Tokyo, Gihodo, Tokyo. SPENCE, RA., and GLYNN. T.E., 1962, Shear characteristics of a marine clay, Jour. S. M. F. D., Proc. Am. Soc. Civil Eng., pp. 85-104. SUDO, T., 1956, X-ray and thermal data for clay minerals formed by alteration of volcanic materials, Tokyo University of Education, Sci, Rep., Ser. C, no. 43, pp. 39-55. TAKAHASHI, H ., IIZUKA, A., YOSHIKAWA, K., and TAKAGI, M., 1963, Swelling and loads on steel supports in solfataric clay (On senYodo in Japanese name), New Tanna'Tunnel, Railway Technical Research Report No. 371, pp' 1-28. TAKENAKA, J., 1964, Formation of clay layers and their properties (3), Soil mechanics and Foundation Engineering, vol. 12, pp. 33-43.

122

123

l 124

MECHANICS OF UNCONSOLIDATED AND FRACTURED ROCKS

TALOBRE, J .A., 1964, Rock Mechanics and stability of dams, JSCE, vol. 49, pp. 65-70. TANAKA, S., 1957, The drainage-density and rocks (granitic and Palaeozoic) in Setouchi Sea coast region, Western Japan, Geogr. Rev. Japan, vol. 30, pp. 564-578. TANIMOTO, K, and NISHI, M., 1963, On sorr:e properties 6f "masado" ( weathered granite sand), Rep. Construction Eng. Inst., no. 4, pp. 197-214. TAYLOR, D.¥l., 1937, Stability of earth slopes, Jour. Boston Soc. Civil Eng., vol. 24, pp. 337-385. UCHIYAMA, N., MASur,.T., and ONIKURA, Y., 1962, Montmorillonite in a volcanic ash soil, Soil Sci. Plant Nutr., vol. 8, pp. 13- 19. VARGAS, M., 1953, Some engineering properties of residual clay soil occurring in Southern Brazil, Proc. 3rd r.C.S.M.F.E., I, pp. 67-71. VARNES, D.J., 1958, Landslide types and processes, Landslides and Engineering Practice National Academy of Science, National Research Council, Publication 544, pp. 20- 47. WARKENTIN, B.P., and YONG, R.N., 1960, Shear strength of montmorillonite and Kaolinite related to interparticle forces, Ninth Nat. Conf. Clay and Clay Mineralogy, pp. 210-218. WENTWORTH, C.K, 1943, Soil avalanches on Oahu, Hawaii, Bull. Geol. Soc. Am., vol. 54, pp. 53-64. WILSON, S.D., 1959, Application of the principles of soil rr:echanics to openpit mining, Quart. Colorado Sch. Mines, vol. 54, no. 3, pp. 93-113. WINKLER, E.M., 1956, Influence of sun heat on clays, Soil Sci., vol. 82, pp. 193-200. Wu, T.H., DOUGLAS, A.G., and GOUGHNOUR, R.D., 1962, Friction and cohesion of saturated clays, Jour. S. M. F. D., Proc. Am. Soc. Civil Eng., pp. 1-32. YATSU, E., 1957, On the application of the method of soil mechanics to the investigation on the erosibility of bare mountain area in Japan-an approach to the dynamic geomorphology-Miscellaneous Reports of the Research Inst. for Nat. Resources, no. 45, p. 1-8. YATSU, E., 1964, Sur Ie gonflerr:ent des roches par I'imbibition de I'eau, Applied Geography, no. 5, pp. 7-26. YATSU, E., 1946b, Sur l'observation de l'allophane par Ie microscope electronique. Applied Geography, no. 5, pp. 48-56. YOSHINAGA, N., and AOMINE, S., 1962, Allophane in some Ando Soils, Soil Sci. Plant Nutr., vol. 8, pp. 6-13.

V

CONCLUSION

Geomorphology should be constructed on a scientific basis, especially exact dating, correct knowledge of processes, and physico-chemical and mechanical understanding of rocks. The intention of this essay has not been to explain how rock controls are reflected in land forms, but to emphasize the importance of physico-chemical and mechanical understanding of rocks in geomorphological studies and also to explain, to some degree, such thinking and methods of studying. Men live on the Earth. Human lives are controlled directly and indirectly in many ways. Therefore, fundamental studies on the surface materials of the earth must supply essential data for engineers. We should not be wedded to the term geomorphologz'cal method, and we should not be carried off our feet by the trivialities of z'sms and z'cs. We may use any method that leads to the truth of the matter and that is useful for the elucidation of facts, and should the necessity arise, we must develop new methods and apparatus by our original ideas and contrivances. Although the deciphering of reality needs a great deal of painstaking work, we should not flinch from any difficulty. We have to give up living in the Moon of Valencia. YOUNG STUDENTS FULL OF HOPE AND ENERGY WILL PLAY THE MOST ACTIVE PART IN THIS FIELD.

AUTHOR

AKIMOTO, K., 66 ANDERSON, H. W., 20, 21 AOMINE, S., 111 ARAMAKI, M., 35 BAVER, L. D., 20 BIRRELL, K. S., 106, 111 BJERRUM, L., 33, 107 BORCHERT, H., 64 BRACE, W. F., 68, 69 BRUNAUER, S., 18 CHORLEY, R. J., 3, 94 CRAWFORD, C. B., 117, 118 DAVIS, W. M., 2, 3, 5 DREYER, W., 66 DURY, G. H., 3 EDEN, W.

J..

117, 118

FAN, P. F., 35 FIELDES, M., 111 FUJIMOTO, H., 96, 97 GEIKIE, S. A., 18 GEITLEN, L. G., 33 GILBERT, G. K., 3 GLOVER, R. E., 3 GLOYNA, E. F., 64 GRADWELL, M., 106, 111 GRIFFITH, A. A., 60 GRIGGS, G., 47, 48 GRIM, R. E., 107 HACK, J. T., 3 HARDY, H. R., 47 HENKEL, D. J., 119 HJULSTROM, F., 2 HOLZ, W. G., 87

I

d

INDEX

HORIBE, T., 51 HORTON, R. E., 3, 20 JENNY, H., 18 KATO, Y., 108 KARMAN, T. V., 46 KELLER, W. D., 18 KERR, P. F., 33, 107 KJELLMAN, W., 107 KOBAYASHI, Y., 51 KOIDE, H., 24 KOMORNIK, A., 33 KOZACHYN, J., 20 KUNO, G., 110, 111 KUPFER, D. H., 62, 63, 64 LANGBEIN, W. B., 3 LEOPOLD, L. B., 3 LIVINGSTON, C. W., 51 LUMB, P., 101, 102 MATSUO, H., 96 MEYERHOF, G. G., 116 MIDDLETON, H. E., 20, 21 MILLER, J. P., 3 MORI, R., 28 MORRIS, W. J.. 35 MUIR, R., 64 MULLER, L., 79 MUSGRAVE, G. W., 20 NAKANO, H., 87 NAKAYAMA, M., 36 NISHI, M., 99, 100 PENNER, E., 118 PETERSON, J. B., 23 RINEHART,

J.

S., 52

128 ROSENQVIST, 1. T., 104 SERATA, S., 64 SHARPE, C. F. S., 23, 102 SHATTNER, 1., 33 SHIBUYA, T., 98 SHIMA, H., 98 SKEMPTON, A. W ., 105, 106, 119 STERNBERG, H., 35 STRAHLER, A. N., 3, 45 SUDO, T., 111 SUNDBORG, A., 3 SUZUKI, T., 35 TAKAHASHI, H., 17, 87 TAKENAKA, J:-; 120 TANAKA, Shin., 98 TANIMOTO, K., 99, 100 TALOBRE, J. A., 87

TERUTA, Y., 30, 31, 32, 33 TERZAGHI, K., 79, 106 THORNBURY, W. D., 45 TURNER, F . J., 18 VARGAS, M., 102 VARNES, D. ]., 102 WARKENTIN, B. P., 33 WEISS, L. E., 18 WILSON, S. D., 79 WOLMAN, M . G., 3 WOODBURN, R., 20 YAMANOUCHI, H., 35 YATSU, E., 3, 4, 9, 10, 24, 25, 28, 33, 34, 36, 81, 94, 98, 106, 111 YOSHINAGA, N., 111

SUBJECT

Abrasion, 35 abrasion test, 35 coefficient of, 35 Acceleration of earthquake, 103 Activity, 105 Adhesive force, 95 Adsorption, 13, 87, 93, 94 Aggregate stability, 20 Aggregation, 23 Air photo interpretation, 10 Alaskan Earthquake, 107 Albite, 19 Allogenic mineral, 17, 19 Allophane, 104, 106, 108, 110, 111 Alluvial fan deposits, 9 Alluvial clay, 110 Alps, 87 Alterability, 15, 16, 18, 19 Alteration, degree of, 17 method of studying, 17 Alternate load, 46 Alunite, 28, 87 Anatase, 19 Anchorage, 107 Andesite, 87 Anhydrite, 68 anhydritic sediments, 64 Anisotropic, 45 anisotropy, 60 Antigorite, 87 Apatite, 19 Attapulgite, 104 Atterberg's limit, 104, ) 16 Attrition, 36 Augen, 81 Authigenic mineral, 17, 19 Bad land, 98 Basal diffraction, 28

INDEX

Bearing capacity, 110 of foundation, 95 Bentonite, 107 BET method, 18 Biotite, 19, 98 Bischofite, 64 Black Cotton Soil, 33 Boiling condition, 95 Brazil, 102 Breccia, 16 British Rheologist Club, 12 Brittle, 46 brittle rock, 17 brittle material, 24 Brookite, 19 Burgers model, 51 Calcite, 19 California, 21 Cambodia, 30, 32 Canada, 47, 111 Carnalli te, 64 Cataclasite, 81 Cation exchange capacity, 23 Cavitation, 34, 66 Chalk, 35 Champlain Sea, 111 Chert, 19 Chlorite, 19, 33, 81, 105 swelling chlorite, 28, 87 Chrysotile, 28, 86, 87 Clay mineral, 16-19, 24-33, 87, 98, 104 expansion and shrinkage of, 87 swelling clay mineral, 33, 93, 102 Cleavage, 1, 18, 61 Cohesion, 60, 94, 103 Colloidal state, 13 Colloid percentage, 21 Compaction test, 111

--- - - -- ----- - - --- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - . J J j

131

130 optimum water content for, 101 Compression, 18 compression failure, 45 compression test, 95 high speed compression, 51 Consistency, 94, 110 Consolidation, 105 Creep, 1, 12. 103 creep of rocks, 47 creep failure, 24 Cristobalite, 28 Crustal movement, 2, 5, 16 Crystal lattice, 17 Crystalline rock, 35 crystalline schist, 87 Cuesta, 10 Decomposition, 15, 16 Deflation, 20 Deformation, 1 deformation coefficient, 81 elastic deformation, 48 plastic deformation, 12, 17 pseudoviscous deformation, 48 Dehydration, 104 Denudation, 15, 34 Design pressure, 67 Deval type, 36 Diagenesis, 17, 19 Diastrophism, 5, 16 Dike ridge, 10 Dilatancy, 96 Dilatational wave, 17 Diorite, 17 Disintegration, 15, 36 classification, 45 Dislocation theory, 60, 66 Dispersion, 20 dispersion ratio, 21, 96 Divalent ion, 18 Dolomite, 64 Dropping hammer test, 35 Drilling velocity, 81 Ductile, 46 ductile material, 24, 47

Dynamic load, 46

French Alps, 28, 29

Earthflow, 23, 103 Echi River Fan, 8 Edinburgh, 18 Elasticity, 17 elastic body, 12, 46 elastic limit, 24, 46, 64 elastic modulus, 52, 81 Electrical double layer, 13, 94 Electric registance-strain gauge, 52 Electro-kinetic potential, 118 Electron diffraction, 17 Embryology, 2 Endogenic, process, 2 agent, 16 Epeirogenic movement, 1 Erosibility, 5, 15, 19, 20, 34, 35, 98 Erosion, 2, 15, 16. 20 erosion ratio, 20, 21 Evaporite, 64 Exogenic, 16 force, 12 process, 1, 2, 12

Geological structure, 4, 36 photo interpretation, 10 prediction of, 11 Geomorphological, inversion, 10, 108 map, 3 process. 45 Geomorphology, 1, 2, 17 applied geomorphology, 3 climatic geomorphology, 3 dynamic geomorphology, 10 fluvial geomorphology, 3 development, 2 domain, 1 method, 1 Glacial till, 33 Glauconite, 19 Gneiss, 81 Goteborg, 116 Gouge, 16 Graded river, 9 Granite, 17, 98 granite dome, 98 Griffith flaw, 60 Gulf Coast Plain, 64 Gully erosion, 20, 96 Gypsum, 19

Failure, 45, 46, 47 Fall, 103 Fall maker, 10 Fault, 2, 4, 5, 12, 17 Fatigue failure, 17, 45, 52 Feldspar, 19, 35, 98 Field measurement, 81 First-order reaction velocity, 93 Flaking, 66, 70 Flaw, 52,60 Flow, 103 flow strain, 47 flowslide, 33, 103, 116 Fold, 4, 5, 12, 64 Fracture, 60 theory of fracture, 47 Fragmentation, 15 France, 81 Free energy, 94

Hakone, 18 volcano, 87 Halite, 64, 66 Halloysite, 28, 87, 104, 111 hydrated halloysite, 111 Hardness, 67 bulk hardness, 68 scratching hardness, 35 Vickers hardness, 67 Hawaii, 18 Hogback, 10 Hong Kong, 101, 102 Honshu Island, 107 Hornblende, 19 Hydration, 105

Hydrogen ion concentration, 18 Hydrostatic pressure, 47 Hydrothermal, alteration, 16-18 reaction, 28, 87, 107 Hysteresis, 105 hysteresis loop, 106 Iberia Parish, 64 Illite, 18, 19, 28, 33, 81, 87, 104, 105, 107 Imogolite, 111 Impact load, 46 Impaction, 16, 36 impaction failure, 45 Impulsive, fracture, 51 wave, 52 Indentation pressure, 68 India, 33 Infiltration capacity, 20 Insolation fracture, 52 Intergranular attractive force, 107 Interlayer adsorption, 94 Interlocking, 96 Internal friction, 103 Inugami River Fan, 8 Israel, 33 Isotropy, 5 Izumi Sandstone, 28 Jack method, 81 Japan, 18, 24-28, 87, 94-98, 105, 107 Jisuberi , 103 Joint, 1, 5, 16 Jordan River, 33 Kagoshima Prefecture, 96 Kamogawa, 87 Kamogawa Tunnel, 86 Kanto Basin, 107 Kanto Loam, 107-115 Kaolinite, 19, 33, 102, 104, 105, 107 Karst, 10

132 Kelvin unit, 51 Kieseritic rock, 64 Kinu River, 6 Knickpoint, 10 Kyushu, 96, 111 Land form, 1, 2 evolution of, 4 Landslide, 18, 23 Land slip, 15, 23-28, 34, 86, 87, 102, 103 lands lip clay, 24, 33 Lateral erosion, 15 Lateral pressure, 46, 47 Leda Clay, 33, 111, 116-118 Limestone, 17, 35, 46, 64, 68 Liquid limit, 95, 110 Livingston's energy transfer theory, 51 Load, 46 loading test, 81 Loam, 107 Los Angeles type, 36 Louisiana, 61-64 Maebara Pass, 80 Malpasset Dam, 81-85 Manitoba, 33 Marble, 51 Marl, 64 Masa, 34, 98-101 Maseguchi, 107 Mass wasting, 1, 15, 23, 93, 102, 103 Maximum octahedral shear theory, 47 Maxwell unit, 48 Mesa, 10 Metahalloysite, 87 Mica, 102 Microcline, 19 Micro-configulation, 5 Middleton 's dispersion ratio, 20 Mississippi, 20 Mixed layer mineral, 18, 28, 31-33,

133 81, 87 Mohr, stress circle, 97 Mohr's theory, 47 Moisture equivalent, 21 Molecular theory, 12 Monovalent ion, 18 Montmorillonite, 18, 19, 28, 33, 34, 87, 94, 104, 107 Moraine, 18 Moving load, 46 Mudflow, 23, 33, 103, 106 Mudstone, 17, 81 Muscovite, 19 Mylonite, 16, 80, 81, 87 Nail gun test, 35 New Tanna Tunnel, 87 New Zealand, 105, III Niigata Earthquake, 95 Non-newtonian flow, 106 Norway, III N-value, 79 Olivine, 19 Onsen Yodo, 81 Optimum water content for compaction, 101, 110, 111 Oregon, 21 Orogenic movement, 1 Orthoclase, 19 Osaka, 120 Osaka Bay, 118 Oslo, 116 Ottawa, 33, 111 Oxford Soil, 94 Parallel orientation, 60 Penetration test, 110 Permeability, 10, 20, 94 PF-value, 110 Physiology, 2 Phytology, 2 Plagioclase, 19 Plant morphology, 2

Plasticity, 61, 109 plasticity index, 95, 96, 101, 102, 104, 109 plastic deformation, 23, 24, 47 plastic limit, 64, 95, 104, 110 plastic material, 64 plastic stage, 46 plastic strain, 47 Pitting, 66, 70 Poison's, number, 51 ratio, 52 Pore pressure, 103 Post-glacial, clay, 33 marine soil, 111 transgression, 111 Prek Thnot, 30-34 Pseudoviscous flow, 64 Pyroxene, 19 Quantum theory, 13 Quartz, 19, 35, 81 Quartzite, 35 Quartz porphyry, 98 Queyras River, 28, 29, 87 Quick clay, 33, 103, 107, 116 Radiation damage, 65, 66 Rain wash, 20 Regain in strength, 107 Repeating stress, 17 Repeated load, 46 Repulsion, 94 Resid ual strain, 52 Rheology, 12 rheological behavior, 46 rheological element, 48 rheological model, 48 Rheometer, 106 Rock control, 5, 9, 12 depositional land form, 15 relation to processes, 11 rock control theory, 4 approach to rock control theory, 12

Rock drill, 81 Rock salt, 64 Rotational viscometer, 106 Rupture, 12, 103 slope rupture, 1, 15, 23, 24, 34, 96, 103 rupture of solid, 13 Sagami Diluvial Terrace, 108 Salt dome, 61, 64, 66 Sandstone, 35, 51 Schmit hammer test, 35 School of Uppsala, 2 Sensitivity, 106, 118 Sericite, 28 Serpentine, 28, 87 Setouchi, 98 Shale, 17, 28, 35, 81, 87 montmorillonitic shale, 81 Shatter zone, 2, 5, 24, Shear, shear failure , 45 shear strength, 34, 68, 105 shearing, 18 shearing test, 81, 95 shearing stress, 103, 107 Shikoku Island, 93 Shimizu Slate, 52, 54-57 Shirasu, 34, 96, 97 Shrinkage limit, 95 Siliceous sandstone, 35 Slate, 17, 60, 80 Slip, 103 slip plane, 24 slip surface clay, 24 Slumping, 34, 103 Soil erosion, 20 Solenhofen Limestone, 48 Solfataric clay, 81, 87 Solid state, 13 Solifluction, 103 Solleftea, 33 Solo, 87 Solubility, 18 Specific surface, 18

,I

134 Splash erosion, 20 Stockholm, 116 Static load, 46 Sternberg's formula, 35, 36 St. Lawrence, III Strain, 46 strain energy, 52 strain of rocks, 12 strain energy theory, 52 Stratification, 60 Stream text ure, 10 Strength, 45 strength of rocks, 5, 16, 45 strength test, 35 Stress, 18, 46 stress circles of Mohr, 47 Structural, structural bench, 10 structural plain, 10 structural recovery, 107 Structure control, 5, 9 Surface, surface-aggregation ratio, 21 surface chemistry, 34 surface energy, 94 surface fatigue, 70 Suspension percent, 20 Sweden, 33, 116 Swelling, 18, 81 swelling pressure, 88, 93 Sylvite, 64, 66 Takakurayama Slate, 55, 58, 59 Tama River, 34 Taxonomy, 2 Tectonite, 18 Tension, 18 tension failure, 45 Texas, 64 Thames Estuary, 118 Thermal spring, 24 Thermal stress, 52 Thixotropy, 106 thixotropic hardening, 116 Time,

135 time dependence, 47 time effect, 106 time-strain curve, 48 Tokyo, 34, 120 Tourmaline, 19 Transvaal, 33 Triaxial cOrppression, 64 triaxial compression test, 46, 96 Trivalent ion, 18 Trondheim, 116 Tsurukawa, 108 Tuff, 28 tuffaceous rock, 35 tuttaceous shale, 87 Ube, 118 Ultrasonic pulse wave, 53, 108 Unconsolidated rock, 81 Undisturbed soil specimen, 95 Uniaxial test, 46, 47 United States, 87 Van der Vaal's force, 95 Visco-elastic, visco-elastic body, 12 visco-elastic behavior, 51 Viscous deformation, 64 Void, 18 void ratio, 108, 109 Voigt Unit, 48 Volcanism, 1, 16 volcanic ash, 18, 108 volcanic rock, 18 volcanic sand, 34 volcanic sandy soil, 96 Watarase River, 6 Water chamber method, 81 Water content, 108 Wear, 35, 45, 66 abrasive wear, 66 adhesive wear, 67, 68 cavitation wear, 66 cutting wear, 66, 68 galling wear, 66

mechanism of, 67 Weathering, 1, 15-19 velocity of, 18 weathering test, 35 Weeks Island, 61-64 Wetting, 83 immersional wetting, 94 Work hardening, 68 X-ray analysis, 33

X -ray diffraction, 33 Yamakuzure, 103 Young's modulus, 52 Yugashima group, 87 Yui,87 Yunomata, 96 Zeolite, 19, 28 Zircon, 19