Tunnel Watching

Tunnel Watching

Edmund W. Jupp intellect

Tunnel Watching

Edmund W. Jupp

intellectTM Bristol, UK Portland OR, USA

First Published in Paperback in UK in 2002 by Intellect Books, PO Box 862, Bristol BS99 1DE, UK First Published in USA in 2000 by Intellect Books, ISBS, 5804 N.E. Hassalo St, Portland, Oregon 97213-3644, USA Copyright © 2000 Intellect Ltd All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission.

Consulting Editor: Masoud Yazdani Production and Cover Design: Vishal Panjwani Production Assistant Peter Singh

A catalogue record for this book is available from the British Library ISBN 1-84150-807-1

Printed and bound in Great Britain by Cromwell Press, Wiltshire

Contents Preface

iv

The Problem

1

The Materials

10

Some Solutions

20

Methods

34

Examples

46

Glossary

50

Bibliography

52

iii

Preface The reader might be forgiven for wondering what there is to be "watched" about tunnels. After all, the greater part of a tunnel lies out of sight underground, and only the entrance and exit can be seen. Even these may not be easily accessible. Again, when under construction these burrowings may not be something the passer- by would find worthy of a second glance. So those whose knowledge lies in other fields may feel that there is no attraction in seeking them out just to look at them. When most people walked, instead of riding in vehicles, a hole dug in the road could attract a small crowd of interested passers-by, to see what the workers were doing. Tunnels are much larger excavations, and if you know a little about how they are conceived and built the knowledge can increase your interest in what bits there are to be seen. Moving about the world, you come across all kinds of holes running along beneath the ground; and although they have this one thing in common, that they are for the most part hidden from sight, yet there are many differences, too. Size is not the only thing that makes one tunnel differ from another. The methods of making the bore itself have changed over the centuries and are still developing. The styles of the entrances have altered, too. New materials have become available. A modern tunnel doesn't look the same as an ancient one. If you know something about tunnels, and if you look carefully you can see the differences. Enjoy tunnel-watching So here we hope to look at some of the facts that make tunnels rather more intriguing than they might seem at first. The technical aspects will be dealt with lightly, (without, I hope, "talking down" to the reader), and those who tremble at the very thought of mathematics have nothing to fear. Indeed, many of those competent in the delights of mathematics and physics may well shudder a little at some of the liberties I shall take with aspects that perhaps deserve a more rigorous treatment. Well, this isn't for them. It is for those who have a little time to stand and stare, or even to sit and stare, to muse and contemplate, to luxuriate in the pleasant occupation of idle thoughts.

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Tunnel Watching

I do hope you will enjoy your watching, and will be led to look a little more closely at such tunnels as you may meet in your wanderings. Some people find pleasure in taking photographs and some like to sketch or paint, because tunnel mouths are often set in lovely countryside. A train emerging from a hole in the side of a hill makes a good picture, in any weather conditions, whether as a photograph or a painting. On the other hand some people like to just look, without recording the sight. Whichever may be your choice, I wish you happy tunnel-watching. Tunnel or bridge?

Perhaps the first question that you will ask is "Why a tunnel at all?" The answer is most easily put in the words "To cope with an obstacle to progress". For example, when a road or railway is laid out in such a way that it meets an obstruction like a hill or a stretch of water the engineers must choose whether it is cheaper or better to go over or under, or round, i.e. to plan a bridge or a tunnel, or a diversion.

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Tunnel Watching There are other reasons for tunnelling, such as providing an approach for men and materials, to get at something not otherwise accessible from the surface, escaping from a prison, robbing a bank, or following a seam of mineral deposits, perhaps to carry water or other liquids from one place to another.

Smugglers and rebels in the past were well aware of the security offered by tunnels in the cliff face leading to safe houses, the entrances being well concealed; and children can always find compelling reasons for the hazardous game of tunnelling in sand at the seaside. < However, we shall consider generally those tunnels whose purpose is to provide transport below ground for people, and services, the kind of thing that any watchful person might come across in the course of travel. What determines the choice will be discussed in the next section. Just for now it may be enough to glance at the general points that we shall have to discuss, such as distance to be covered, the environment, possible future requirements, and so on. Ingenious tunnels The bright young men who dug tunnels to escape from prisoner- of-war camps displayed brilliant ingenuity, managing to reach high levels of safety, ventilation, maintenance of direction, removal and disposal of material, and so on. They developed high standards of good tunnelling practice, and descriptions of their work make fascinating reading. They had little in the way of tools or materials, and what they managed to do with odd bits of beds and Red Cross parcels is amazing.

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Tunnel Watching

Early tunnel making Lots of the tunnels already in existence were built many years, even centuries ago. Some never survived flood and earthquake, but those that we can still see are a tribute to the skill of those early excavators. Methods available to the people who burrow beneath the ground have changed very little over the ages, but the means to dig have taken a sudden spurt forward during the last century. Modern tunnelling equipment is powerful, ingenious and, inevitably, expensive. The work is not undertaken lightly. Safe tunnel watching Most of your tunnel-watching will be above ground; but if there are opportunities for some observation inside a tunnel, you would be well advised not only to have authority for entering, but never to go alone. It is a fascinating occupation, and perilous only if you make it so. As you extend your knowledge during tunnel-watching sessions I wish you well. You may also be drawn to some of the literature on the subject, either easy introductory material like this or more technical treatment, leading you along fascinating lines of learning. Go forth and enjoy this free entertainment.

vii

The Problem When people began to move about the country, in ancient times, it was along paths, following tracks through forests or across open spaces; and these were along the best routes, not always the shortest, with changing steepness here and there. These tracks ran over hills and valleys as convenient, for a man might move up and down hill with little difficulty. There was no problem about siting the paths. They just followed the trails long established by generations of feet trampling the ground as they went about their business. They often had to dodge round obstacles like large trees, deep holes, dangerous areas, and marshy ground, so the ways were rarely direct or straight. They wriggled their way along from place to place. These paths became well-established in time, and in some cases were eventually made more permanent, perhaps having laid upon them some hard-wearing material. Sometimes the swerving lines persisted long after the original obstacles had vanished, as is clear from the twisty lanes to be seen in the countryside today. In recentlydeveloped countries, modern machinery deals easily with obstructions, sweeping them away to provide straight swathes along which roads are built. So one usually finds straighter roads in modern countries and rather less direct routes in older- established areas. Roads follow old trails Where development has been slow, and when buildings have been erected along the old ways new roads have had to follow the twists of the trails to minimise demolition work of earlier buildings. In some cases the havoc wrought by war has flattened large areas, so that new construction work has been able to take advantage of this to plan more direct routes. When getting around no longer depended upon walking only, i.e., when men began to use animals, these could manage the smaller hills generally with little discomfort. However, even sturdy nimble pack animals could not cope with very steep places, and they had to find ways round; so there were inevitable kinks in the routes; and when draught animals were used, pulling carts and wagons of various kinds, even the gentler gradients or narrow passes often entailed detours. Steep gradients were formidable obstacles. So more kinks developed, and the wagons followed slow and twisty routes to get from one place to another. Need for direct routes For movements of people and goods there was little call for going underground. Only for providing shelter, or getting at the wealth of mineral deposits was it necessary to start digging. Tunnelling into the sides of mountains could bring rich rewards for those willing to take risks. Archaeology is revealing much of what went on in those days, and 1

Tunnel Watching we have been able to reconstruct the methods of the early tunnellers from remains of the people and the tools they used. When man, faced with hills and mountains, began to seek more direct routes his thoughts turned to making holes through the obstructions. There have always been problems when working beneath the earth's surface, even when it consisted of little more than scratching away at soft surfaces to make a hole and then slowly enlarging and lengthening it; and the overall challenge of drilling large holes consists of a large number of related problems, some of which require the attention of specialists. The gradient problem In more modern days, with the coming of canals and the spread of road and railway systems, steepness became the principal problem. Road traffic could manage fairly steep stretches; and it wasn't too hard a problem to ease the slopes for motor- driven transport. The road itself could be built with curves so as to wind about a little thus reducing the effective rate of climb. A gradient is defined by the amount of height gained or lost in unit distance traversed along the route, so that any increase in distance horizontally for a given rise decreases the gradient. Negotiating mountains When a road skirted a particularly steep mountain side the builder was forced to tunnel through here and there, as in the Alps, and in the Rockies of North America, and this was to avoid running the road too near a precipitous edge. A good example of a road tunnel is that through Mont Blanc. Here a great mountain blocked the direct route for a road connecting Switzerland and Italy. No road system could climb over the obstruction, and a tunnel was the only solution. A great hole was bored through the mountain, and traffic now flows freely along its length. There are many more like this. With the railways, even more limited by the inability of locomotives to drag heavy trains up steep gradients, many hills and valleys presented a daunting problem. Here was the need to begin tunnelling on a huge scale. The short answer Striving to connect places by the shortest and most direct route, transport engineers were compelled to tackle head on the challenge of hills and mountains, valleys and lakes. Crossing many stretches of water could generally be achieved with bridging, but hills demanded detours or tunnelling. Crossing the Channel In some cases, such as the rail link under the English Channel, connecting Britain with France, there was not much choice. It was either a bridge or a tunnel. To tunnel under a wide stretch of water like the English Channel was an enormous undertaking; but the 2

Tunnel Watching alternative solution of a bridge was rejected in favour of the ambitious and adventurous boring under the sea. It had already been attempted on several occasions, but abandoned each time in face of financial and other difficulties. Eventually it was completed, and now finds favour with the travelling public, who enjoy smooth and rapid riding between Britain and France. Any bridge would have had to allow a way through for the very busy maritime traffic, and the exposed site would have called upon much ingenuity on the part of the designers of a suitable bridge. This does not rule out forever a Channel Bridge, of course, to complement the tunnel, but this must lie some years ahead. It will be an exciting project for some future bridge engineer, and some clever financial wriggling, too! Canal locks and gradients Along the routes of canals a hill could be negotiated by the use of locks, chambers which could be filled and emptied as required to lift or lower the waterborne traffic. Locks were expensive to build and maintain, and slowed up the traffic as the great barges queued up to go through. High hills called for a long series of locks, and these caused slow movement of goods. In some places, therefore, it was found more economical to take the canal underground. This was especially sound when the levels at each side of the hill did not differ very much. Locks are not built within the tunnel itself, but on the approaches; so the canal traffic traverses a level stretch within the tunnel. Hence the bore is a level one for canals, and usually straight, too. Canals underground The problem when taking canals underground is much like that for underground viaducts or water pipes of large bore except for the matter of scale. In Roman Britain some interesting work was carried out to carry water from place to place, and much of the construction is still in evidence. Before the internal combustion engine was invented and brought into use, you could get a barge through a canal tunnel with a low roof by men lying on their backs on top of the barges and "walking" the craft through. Pushing with their feet upon the invert or roof was a commendably cheap, effective, and efficient method. Perhaps men who ran their own canal businesses as a family concern found this a harmonious way of keeping family and friends occupied, and used up some of the spare energy of the adolescents on board.

3

Tunnel Watching Brickwork canal linings Because of the sometimes soft and crumbly nature of the soil these tunnels were strengthened by linings of brick. Millions were required to cope with the spreading network of canals. So the construction of tunnels had a good effect on the numerous brickyards throughout the country. Many of the bricks were themselves taken by canal barge to the sites, a cheap and efficient way of dealing with the heavy loads. Canals are much less in vogue nowadays, except for the increase in holiday and recreational purposes. In many ways it offers a much better way of dealing with very heavy loads, but at a much slower speed than the modern lorry. There are no new canal tunnels being built at this time. If there were, they would be much more rapidly completed than the earlier ones. Meanwhile, thousands of people every year enjoy the peace and quiet of a canal holiday, puttering along through pleasant countryside, in a well-equipped floating home.

Nature's tunneller The mole is a charming little velvety creature that spends most of its life below ground, continuously creating tunnels. It is an efficient and tireless digger, sustained in its efforts by the need to eat an enormous amount of food each day; but it can manage only comparatively soft soil, as gardeners know to their sorrow. Geological obstacles Tunnel engineers encounter hard rock, as well as crumbly material, and they have to find ways of dealing with difficult routes around a curve underground, or cutting from both ends, to meet in precise alignment for the join. Cutting holes in the earth costs a lot of money, and those who settle the bills ask for quick results, at a reasonable charge.

4

Tunnel Watching Here then is the problem in general for, say, a railway line. Given a line drawn on a map, straight or curved, it is required to drill a hole through the ground to follow that line faithfully, and to keep within the limits of slope that a locomotive can manage when drawing a train, hauling goods and passenger rolling stock.

Shaping a tunnel The bore, whether circular, or of some other section, must be big enough to provide good clearance all round for the outline of a locomotive and its train of wagons or carriages, and needs to have a flat floor to take the track. Tunnel ventilation When most railway traffic was hauled by steam locomotives the tunnels would fill with smoke and steam, and although the trains themselves helped to "pump" this out of the tunnel by their passage, still a ventilation problem remained, especially with many trains following one another at short intervals, perhaps with traffic in both directions. If a train were stopped inside a tunnel the air would soon be a little difficult to breathe. The old steam locomotive, much loved though it is, could be a smoky kind of beast, particularly when pulling a long and heavy train up a long steep incline. Locomotives and gradients Climbing any gradient within the bore calls for more work from the engine, and hence more pollution of the air. Effectively, the locomotive has to lift the whole load through the difference in level between the ends of the incline. This is why a steam engine tends to huff and puff on a steep bit of line, and why such slopes are usually avoided as far as possible in railway networks. The little white posts beside the line indicate the rates of climb and descent, and they show gradients that are nothing like as steep as those along roads.

5

Tunnel Watching Coal, even the best steam coal, is a fuel that has some particularly dirty residue and produces pollution that is unpopular among many people. This has changed with the coming of electrical and diesel-powered locos, but the keen tunnel- watcher can still see traces of soot on the walls of older tunnels, giving some indication of what it was like in the past. Planning for getting rid of the polluted air is an important demand on the resources of the designers. So adequate ventilation is yet another part of the overall problem; and this must be done without in any way weakening the structure. Tunnel recesses At one time the railways employed great numbers of linesmen to inspect the lines frequently, and to correct malalignment, shifting of ballast, slackening of fixings and so on. Little gangs of workmen were often to be seen, working on the track, with a lookout man keeping an eye on the line for approaching traffic.

With trains nearly filling the bore, provision had to be made for people working on the line to dodge out of the way of passing traffic. This was all part of the design requirements. There has to be adequate access to the hole during the excavation, for men, materials and machinery, both entering and leaving the works. This entails proper provision of approach arrangements. At any one time there might be two streams of material and personnel, one going in and one coming out. Tunnelling hazards Other problems call for attention, too. The safety of people must always be considered; means of dealing with the excavated material is needed, and precautions against collapse of the roof are essential. Straight or curved, the hole must emerge exactly where required; or if excavation is carried out from both ends at the same time the two 6

Tunnel Watching parts of the hole must meet precisely. Again, one ought not to forget the requirement to provide suitable fare for celebrations when the junction is made.

Weather conditions or tidal action on some sites may provoke difficult decisions. Severe cold or unexpected shortage of labour, cloudbursts causing flooding at the approaches, all kinds of hardly foreseeable problems add to the overall picture. The electricity supply may fail, a belt may jam or break, the labour force may strike, a sub-contractor may go bankrupt, the chief engineer might be taken ill, food poisoning can put the whole staff out of commission, and so on. Cost of tunnelling Above all, the engineers must have costs constantly in mind, for grossly exceeding the budget can produce a great deal of unhappiness for those involved. Tunnels don't come cheap, and serious overspending is not readily forgiven. This is a formidable list of contributory possibilities, and it all adds up to a "problem". It is not a complete list, either. If you talk with an experienced tunnel man you may get a long list of additions, culled from past experience. Training engineers Well, problems do not usually lead to despair among engineers. Their training is directed towards the solution of problems. Their studies involve mathematics, and physics, as well as specialist subjects like soil mechanics, fluids, theory of machines, theory of structures and so on subjects which may be thought of as tools of the profession. Engineers are not turned out in a few minutes. Even on completion of their formal education many years are spent in a kind of "apprenticeship" with experienced engineers, so that in time they are competent to tackle the specialised demands of ground penetration for tunnels. 7

Tunnel Watching Developing expertise Firms that undertake the construction of tunnels are usually specialised companies that have long years of experience and have acquired a staff of experts in the field, wise in the ways of ground-boring, up-to-date in the latest techniques. Because of this they can usually submit a more attractive quote for undertaking the work than less-experienced competitors, and can handle problems as they arise. Planning an approach The siting of the work is pretty well fixed by the approaches to the obstruction as well as the nature of the obstacle itself. It is of interest to the tunnel-watcher to look at the approach roads or railways at the ends of a tunnel seen in his or her travels. Not only the plan view, but the variation in elevation or height, should be considered, so that the way in which the approach problem was handled when the tunnel was designed can be appreciated. Range of problems You can see that with tunnelling there is not just one big problem, but a whole lot of smaller ones, of different kinds, all adding up to the overall difficulty. Although it is the engineer who carries the main responsibility, there is a range of specialists in other disciplines, too, each responsible for dealing with problems in their own fields. Lawyers, accountants, clerks, typists, computer experts, financial analysts, geologists and so on are needed to raise the money, keep clear of legal disputes, deal with records and mail, oversee safety arrangements, and in general manage the whole enterprise. Some engineers regard all these others as so much "sand in the bearings" but without them the project cannot proceed. Teamwork There are people to make the tea, or run the canteen, provide first aid, clean the huts, transport men and materials to and from the site, order the daily requisites, operate the lavatories, and so on; and all these details demand close attention. They are part of the total many-faced problem. The assembly of all this expertise requires substantial knowledge of what is involved to deal with sub-contractors, local government officials, "men from the ministry" and other interested parties; and a great deal of work is done before the first little bit of material is dug out at the site. Large tunnels involve thousands of people at many different levels of specialisation, and part of the overall problem is managing this formidable team, so that it all slots in smoothly.

8

Tunnel Watching Social impact The effect upon the local population, employment, and the prosperity of the shops and suppliers in the vicinity may be significant. It is temporary, of course, but those responsible have to know about the social impact brought about by massive civil engineering undertakings like long tunnels, and any possible long-term effects. An examination of the area surrounding a tunnelling site, both during construction and after completion, can be revealing. For example, at a major site it might be necessary to provide temporary housing for staff, and there may be traces of this, abandoned after completion of the contract, to be seen by the keen tunnel-watcher. From this one can see the kind of problem this presented at the time it was built. Getting more information In many cases, you can get hold of literature about the construction of particular tunnels. Papers published by the engineering institutions in many countries give details of how difficulties were tackled when certain major tunnels were drilled. It is worth reading these, especially those about the earlier cases, and then visiting the tunnels themselves. Some of the technical papers, though they may use terms unfamiliar to the non-technical reader, will provide good background information. Picking one's way through can yield nuggets of interest, whatever the reader's speciality, or background. In the next chapter we shall look at some solutions to the problems referred to above. There are occasions when there may be several different solutions, each with its own appeal. Here it is the experienced man who can best decide which way out will be the best in the long run.

9

The Materials No tunnel-watcher can fully appreciate what has gone into the design and construction of any of these underground enterprises without some knowledge of the material that has to be dug out of the ground during the making of the hole. After all, the whole business of digging a tunnel consists of cutting away at the rock and taking it away, leaving a long hole in the ground. Substances are not all the same, and the variations affect the approach to the problem of penetration. So we now look at the materials that we have to move when carrying out such work. Geological considerations Our world is made up from fluids and solids, of many different kinds, and in order to understand them we shall have to dip gently into the subjects of geology and soil mechanics. In all of this we shall try to avoid as far as possible the more technical aspects of these topics; but for those of an adventurous turn of mind there are many splendid books and papers available, enough to satisfy the most avid reader. Although neither of these areas of study are static, yet even the older books are not without interest, so we don't have to reject a book just because it is dated. Indeed, some of the more ancient tomes are of added interest because of the light they throw on the way our ancestors thought. Some of these books may well be too specialised for many readers, who don't need to be concerned with all the niceties; but there are some popular ones as well. Geology especially is well catered for, since there are many amateur geologists, and some have written engagingly about their hobby. Reading well-written books on the subject may become addictive, but so much the better. Many an amateur geologist started by picking up some odd attractive stones, and then reading to satisfy a niggling curiosity. Soil mechanics The books on soil mechanics may prove daunting to those with little mathematical skill, and few have been written on this specialist subject for the layman. However, tunnel watching doesn't call for a deep knowledge in this field, and it is hoped that the rather skimpy treatment it suffers here will be enough to understand the implications, and to whet the appetite for more. Besides books and papers, the reader may find helpful some of the splendidly produced Open University programmes; and if these are at inconvenient times there are some very good schools programmes expounding the subjects in easily-digested bites. There is a lot of well-presented information for those prepared to dig it out. There is also, of course, an immense amount of information on the Internet for those with access.

10

Tunnel Watching Global dimensions Tunnellers are not concerned with the central core of the earth, consisting of magma, except in so far as it affects what we find on and near the surface. The globe is never static, and the fluid magma under great pressure spurts up towards, and sometimes penetrates, the layers we call the crust. Volcanic action is the outcome of stresses far below the surface, sending up masses of hot rock, often molten, and gases, which break through the crust. The layers above the magma, which can be thought of as areas of rock floating around on it, consist of a number of large plates which are forever on the move, though the movements are generally so slow that they do not need to be considered when planning the excavation. From time to time these movements can lead to catastrophic collisions, and then earthquakes occur. Tunnelling in areas liable to such disturbances would be hazardous and unprofitable. Shifting structure What has happened in the past determines what may be expected by those who dig, even in apparently virgin soil. The geology of an area is the result of millions of years of shifting and easing of the physical stresses arising in the world, great temperatures and pressures bringing about changes not only in position but in physical characteristics too. These are on a gigantic scale, and although there are some spectacular sudden movements most of them are slow, the time scale of changes measured by millions of years. Our earth is by no means a permanent structure, save when measured by a human's life scale; and the tunnels we dig are no more than tiny worm holes compared with the size of the globe. Even our largest tunnels are no more than a pinprick in the crust, and the deepest ones don't penetrate much below the surface. The diameter of the earth is about 12,000 kilometres, say 8,000 miles; and the deepest drilling to date is less than one thousandth of that. So with all our efforts we have barely scratched the surface. Mapping the job The geologist can provide maps of the rocks, not only on but below the surface, of great interest to those about to dig down. Planning an excavation of large extent requires as much information as possible about what kind of material is likely to be met in the region. Maps showing the type of rock at different depths in particular areas are consulted before deciding upon the route of a tunnel. Then it may be necessary to weigh the costs of direct route against the cost of dodging any specially difficult bits.

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Tunnel Watching Gathering geological data Methods of getting at geological data have grown over the centuries, with a sudden burst when the computer could be used. Vertical bores can be used to obtain cores, from which the materials at various depths can be seen. There are ways of using sound waves; and variations in magnetic fields can provide clues about the extent of the underlying rock. When direct information is scarce a sound knowledge of the subject can enable the skilled geologist to make inspired guesses and then to confirm or disprove them by instrumental means. The accumulated data over many years is available to those interested in the subterranean world. A visit to the local library will reveal a useful collection of geological literature. It will soon be seen that there is plenty of knowledge about any given area; there are maps of rock formations below the earth, and the history of them. It all adds up to a fascinating story. You may find yourself getting very involved in the subject.

What is the magma? In general the materials of which the earth consists can be roughly divided into hard stuff and soft stuff. Thus, when digging down past the topsoil we may meet hard rock like granite, firm chalk or crumbly sandstone. There are all kinds of other interesting materials, too, as well as underground rivers and huge cavities. If we were to go deep enough we should run into the magma at the centre of our sphere; but tunnels don't run as deeply as that, and are unlikely to do so in the foreseeable future, outside schoolboys' science fiction stories. However, the magma does affect the layers where we do dig, for it is very hot and liquid, and where it contacts older rocks can bring about massive changes. This is a much simplified picture of what is a very complicated field, but it will do for our purposes.

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Tunnel Watching Planning the route When we tunnel into the ground we have some idea of what may be easy to dig, and what may be hard. Those who deal with the composition of the earth and its various rocks are the geologists. Good geological information offers us the guidance we need in deciding how to tackle the job. The main strata or layers occur in fairly well-defined areas below the topsoil, and maps prepared by geologists indicate what is where. So when a decision has been taken about building a tunnel a line can be drawn on a map along the proposed route to see what the diggers are likely to meet. Sometimes a section may be drawn for the line, a cut through the earth showing the depths where the different kinds of rock will be encountered.

Rock categories Broadly speaking, once we get below the topsoil there are three kinds of rock, igneous, sedimentary and metamorphic, with different characteristics that influence the work of removal. There is some interchange between the types, and to some extent it might be said that all rocks are metamorphic in one sense, that is they have all been subject to change of one kind or another. Within these broad divisions there are many variations, and it may be that the reader will find much interest in pursuing further the fascinating subject of geology, both practically and theoretically. Testing for hardness One easy outlet is to pick up odd pieces of rock found here and there, and to try them for hardness with a hammer, or a hammer and chisel, (taking great care that personal damage doesn't arise from flying chips or slipping chisel!) Professional geologists can tell much from the look of a piece of rock, the way it has broken, and its colour. In the laboratory there are testing machines which can be used to find out in detail the behaviour of the material under direct crushing and shear loading. In all, the findings can be of great interest to those planning the work, or designing the tools.

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Tunnel Watching Hardest Rock Looking first at igneous rock, this is solidified material that was at one time liquid, at very high temperatures. When it cooled down it formed dense hard layers which can be broken up only by the exertion of a great deal of energy. It is easily recognised, and presents the engineer with special features, some good and some bad. The first good point is that when a hole is cut in hard rock it stays that way, and the roof is unlikely to fall unless the boring approaches too close to the limit of the rock. So props and various kinds of support are in general not required, representing a financial saving in labour and materials.

Recycling potential Trimmed to the required shape of the bore the hole may not need to be lined. Further, such material as is removed might fetch a good price. (Look into a garden centre, and note what it costs to buy even a little lump of stone for the rockery.)

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Tunnel Watching So boring through hard rock can offer some attraction. On the other hand, penetration isn't easy. At one time the only means of cutting it out usually involved the use of wedges or explosives. This is discussed in the chapter on Methods. Detecting from evidence The result of the use of explosives or other methods of breaking the rock is to produce lots of irregular lumps of this hard material. It is possible sometimes to identify a tunnel that has been bored through igneous rock, for outcrops of the rock often protrude above ground, and there may be the remains of spoil heaps of the material. It is always worth looking at a geological map of the area round a tunnel, noting the significance of the various rocks along the track. Being very dense, pieces of igneous rock are heavy, and handling them was very hard work before the introduction of modern machinery. Hauling it calls for stout wagons, or conveyor belts, to transport the awkward heavy lumps. Modern machinery can cut it, but it is costly in cutting tools, which are expensive to buy and which wear rapidly. So meeting hard rocks is a mixed blessing. When the geological survey is studied it may call for some difficult decisions if the way offers alternative paths through hard and soft rock. The engineer may feel the need to consult financial advisers when this kind of decision has to be made.

Sedimentary layers Sedimentary means "having been formed as a sediment", laid down or deposited in ancient rivers, or seas, sometimes drifted by ancient winds. The various sands that have accumulated in large volumes and then been squeezed by the enormous pressure from the material lying above it come under this heading. There is more sedimentary rock about than the other two main types. Those rocks that have formed from biological origins, such as coal, have special value, and are unlikely to be encountered when tunnelling for transport routes. The coal will 15

Tunnel Watching have been mined as a valuable mineral, and the tunnels made during such mining operations are usually left to collapse after extraction is complete and the workings abandoned. Rock characteristics In general it is not difficult to excavate sedimentary rock, and transporting it is relatively straightforward. Much of it is used in buildings, and a glance at many rural churches shows the warm colours of the sandstones from different regions. The expression "metamorphic material" refers to substances that have undergone change. Minerals contained in rocks are stable only under certain conditions of pressure and temperature. When big alterations in pressure squeeze or relieve the mass, or when major changes in temperature occur, re-crystallization can result, changing the characteristics of the rock. Rocks are in the solid state when metamorphosed, so the minerals undergo stress in a particular direction, sometimes leading to lines which are often visible as streaks. Metamorphism can change any kind of rock, igneous, sedimentary or even metamorphic, and in this way a wide variety of rock can be produced. So the three principal types of rock can be formed from one another. Igneous rock, for example, can be broken by weathering, and fracture from gross distortion, until it consists of small grains, when it can be laid down as sedimentary material.

In some areas one comes across lumps of very hard stuff, flint, as inclusions in softer material like chalk. They are not usually very large, and are dug out without much difficulty. In earlier days they had some value for producing fire, which anyone can readily verify by striking a flint to observe the sparks produced.

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Tunnel Watching

Tools for tunnelling Many of the earlier tools, too, were made from flints. They take a keen hard-wearing edge. Used either in the hand, or fitted to a shaft, excellent tools and weapons could be produced by our forefathers. Many such tools and weapons have been found at sites where early man lived. If you have the time you may see for yourself how good a flint axe can be. Tie one having a sharp edge to the end of a wooden handle, and you can see how easily it cuts even hard wood. Do remember though that flint chips easily. Our ancient forefathers didn't have goggles, and no doubt suffered accordingly; but there is no reason why you should. Shift in proportions The principal interest of flint and flint-like substances to the tunnel-watcher is the linking of this kind of inclusion to the damage they can sometimes cause to modern tools. Roughly speaking, the total rock content of the earth is, like the volume of the earth itself, constant; but over long periods major changes can take place, so that the relative proportions of the different sorts of rock are not constant nor the positions of the masses. Gigantic lumps of rock can rise or descend amid the other layers, so that the whole earth is in a constant slow dance, far from the placid scene we see in one lifetime. Many rock qualities are of no direct interest to the tunnel watcher. It is the "tunnelability" that determines how the tunnel shall be built. This means, after geological survey, how the tunnel is to be aligned, within the limits imposed by the area where the hole is required.

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Tunnel Watching Site constraints Often the line of a tunnel is determined entirely by the constraints at the site, the line of approach at both ends of the proposed excavation, and the levels. When the route of the tunnel has been decided geological conditions may cause a review of the proposals; but usually the work just has to go ahead, tackling the problems of the material which will be part of the job. Past disasters Some of the earlier tunnels were made without the facilities that are now so much taken for granted. There was at one time little or no geological knowledge of what the tunneller might expect during the penetration. In consequence, boring into the earth was a much more risky affair. Further, early excavation was a matter of pick and shovel, which might result in sudden roof collapse and other dangers. There have been some terrible disasters in the distant past, some of which are unrecorded, during the time when men were learning how to tunnel. Now much more is known about conditions underground at a given site, and the behaviour of the rock likely to be met at each stage of the work is predictable. Understanding the old and the new Geology and soil mechanics are not static subjects. Modern research continues to increase the available knowledge of conditions underground. For the tunnel-watcher, the appeal lies in appreciating the work in old as well as new tunnels. Knowing what kind of rock the contractors met underground during construction provides some insight into what was involved in the "cut-and-haul" process for a particular bore.

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What to do with the waste In some cases, notably the tunnel under the English Channel, considerable publicity has been given to the project, and generous details are readily available regarding the materials removed. Disposal of the mammoth amounts of material from the Channel Tunnel presented an unusual problem. The geological knowledge at hand when the project was planned enabled the engineers to proceed with confidence. Knowing the nature of the material enabled them to choose what machinery was going to be needed to cut and transport the types of rock that would be met during the work. Roof prop development If the material is friable, demanding frequent support, consideration needs to be given to the kind of roof props readily available, short tunnels might be lined at the sides and the roof with slabs of stone; but long pieces were scarce. Later, with the invention of the arch, it was easier to cope with softer material overhead. Local research When looking at some tunnels then, arm yourself with a local geological map of the area, and see if you might discover the sort of material confronting the tunneller when the work was done. If you are not within your own locality, a visit to the local library will usually furnish you with all the geological information you might need for the vicinity. Librarians are helpful and knowledgeable people and will probably be able to deal with your problem at once. 19

Some Solutions When the general problem of tunnelling was discussed earlier we saw that there were many parts to the overall challenge. Not all of these apply to every contract, for each presents its own particular combination of interesting possibilities. Finding solutions to these constitutes the intriguing work of engineers. So in this chapter we look at some of these solutions. As the years pass along so more difficult enterprises are tackled. These in turn sometimes lead to more solutions, often to better answers to old problems. For the tunnel-watcher the results of these solutions can often be seen and are of great interest. Trail of discovery As we study each tunnel that we come across we can imagine what things were like before it was built, what the problems might have been and how they were handled. Sometimes we can look at an old map and notice how the road or rail ran before work began, and from local history sources we can see how the demand for a tunnel arose in the first place. Often it was the coming of the railway that led to work being undertaken to pierce a hill previously easy for road traffic. Sometimes it was the needs of a canal. We start by thinking about the construction of a shallow tunnel, running just below the surface of the earth, say one for an underground train, built to avoid buildings and road traffic. The problem here is how to avoid caving in of the necessarily thin crust between tunnel roof and surface.

The solution is one of the simplest ways of tunnelling. Unsuitable for deep work, it applies only when the bore is to run very near to the surface, as in parts of the Metro in Paris, and similar works elsewhere. In some places it is used when a road is to pass under a square in a city road network, and there is no need to go deep.

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Tunnel Watching Using the trench method The method is to dig a suitable trench, large enough to take the proposed tunnel, and then to build a tube of suitable dimensions, or lay a prefabricated tube along the trench; when all is in place the material that was removed is used to cover it all up again, with nothing to show but a hump in the ground. Sometimes there is not even a hump, for the soil can be taken elsewhere. This approach is possible only when the tunnel is not a deep one, and when the site offers enough space to store the stuff which has been dug out either alongside the proposed tunnel or near enough for it to be easily transported and poured back on top of the tube, when it is time to fill the trench and bury the tube. Dealing with the spoil If the spoil is to be stored on the ground by the sides of the trench, it will form either one or two long heaps with sloping faces, that is either one heap alongside or, if convenient, one each side of the trench. The nature of the soil as well as the size of the hole will determine how much ground is needed on each side to accommodate the material.

A mound of sugar When a mound of granular material is formed the slope of the faces of the mound will depend upon what is known as the "angle of repose", that is the natural angle of slope for that material. Pouring sugar onto a plate provides a simple illustration of this. As more and more sugar is poured onto the heap it piles up; but when the steepness reaches a certain value the added material trickles down the sides, so as to maintain a constant slope; the heap increases in height and base area, but the side slope stays the same.

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A mound of flour, showing a greater angle of repose than the sugar. Angle of repose There is a limiting angle for every substance. Different materials form heaps with differently sloped sides. Comparing several different substances such as salt, sugar, and breakfast cereal, or even potatoes can provide a simple illustration of this. For fine powders or small grains the angle of repose may be affected by the moisture content. This can be tested with dry and wet sand for example. We can use an equation to work out the width needed for the heaps; but if equations don't appeal to you, then you can skip the next few paragraphs without losing the general trend of the chapter.

If the sides are not restrained then the section is triangular, and of height h say. The section has an area A, given by A=bh /2

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Tunnel Watching where b is the width of the heap at the base. Then, if V is the volume of the material, and L is the length of the heap, we have V = LA i.e. V= Lbh /2 If the length of the heap is the same as that of the trench, then the volume of the heap, i.e. of the excavation, has a base width b from b = 2V/Lh If the material can be placed evenly on both sides of the trench, each pile would take half the volume, so each heap would need a base of width V/Lh. The quantity V is known from the shape, width and depth of the excavation. So an area of width V/Lh has to be cleared on each side of the trench. If we simplify matters by taking the angle of repose as 45 , the base is twice the height h, and we find h and b from the relationships h = ÷(V/L) b = 2÷(V/L)

Shoring up sides If the sides of the trench are not shored up they should have the same slope as the heaps, though the uncut material may have a different angle of repose, probably steeper because of the compacted nature of the uncut soil. Further, the section will in general be trapezoidal, that is with a flat base rather than triangular. However, this will give some rough idea of what is involved. Boarding up the sides is expensive and so is digging, so both need to be costed carefully if there is a choice. When shoring or shuttering is to be used it is because at that particular site this is cheaper than digging a wide hole with sloping sides or sometimes because there just isn't enough room.

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Tunnel Watching Estimating the slopes Then along come the diggers. The trench is dug, and the soil put into these long piles. A tunnel-watcher can estimate the slopes of different kinds of spoil at any site where excavation is taking place. If you can view the pile end on you can hold up a protractor with its zero line parallel with the slope of the heap; then hang a little weight on a string through its middle, to register along one of the radial lines. This will indicate the angle of repose for the heap. Safely finished After the tunnel material is in place it is then covered up again using the same machinery, a very straight forward job. Under these conditions many of the problems of deep tunnelling vanish. No supports are needed, no venting, and safety is much more readily achieved. However, the method is of limited application, for shallow work of this kind is not often required. We get something very near to this when a road is dug up to lay a cable, but this does not normally involve a tunnel as such.

Effective ventilation Keeping the air fresh underground is part of the overall problem of all tunnels, unless they are very short. The pumping action of passing traffic, whether road, rail or water borne, moves the air and this may sometimes be enough. The problem increases with the length. In general, air circulation can be achieved by building ventilation shafts at suitable intervals along the line of excavation, connecting directly with the outside air. The tunnel-watcher should be on the look-out for these. They mark at ground level the line of the tunnel. Their appearance depends upon conditions at the surface, of course, and it is sometimes necessary to disguise them so as not to interfere unduly with the appearance of the environment. They didn't worry much about this in the early days of the railways, when the country was less densely populated, so they may still be seen along the routes of some of the earlier lines. 24

Tunnel Watching The principle of interconnection In mine workings the interconnecting tunnels are so arranged as to maintain a constant flow of air along the network of holes, and fans are generally necessary to make sure there is proper circulation. In short road and railway tunnels, we usually rely upon the movement of lorries, cars, and trains to get the air moving, and this is often enough. Large tunnels are often duplicated, and interconnected, as in the Channel Tunnel, joining Britain to France. Natural self-ventilation Good circulation is achieved without the use of fans in many of the tunnels likely to be seen. If there is a difference in level between the ends, a tunnel can be self-ventilating, the air flowing downhill towards one end, though the circulation may not always be sufficient, and might need extra help. Again, in some areas there may be a fairly constant wind parallel with the bore that provides a cheap natural ventilation system. So the ventilation problem can be solved usually without very much difficulty, when the amount of regular use is known. Explosive solutions The major challenge is usually the rock itself. Very hard rock is costly to cut, whatever method is used. It is normally a job for the specialist. The old miners used picks and shovels to cut and clear away the material, though nowadays there is not much of that going on. Substances like coal are comparatively soft, but stuff like granite will not yield to a pick. To cope with granite and similar materials explosives can be used, rammed into holes before being detonated so as to split the rock. Any method that subjects the rock to severe stress can push aside parts of the rock, splitting it along lines of weakness. It may at first appear to be a somewhat hit-and-miss affair, not boasting any great degree of accuracy; but the skilled tunneller who really knows his job can produce surprisingly good results. Breaking it down to size Breaking hard rock into large pieces entails more work before it can be removed, so the tunneller aims at producing lumps of a size easily handled by the means available. These can then be loaded onto trucks or conveyor belts which carry it along to the mouth, where sometimes fleets of lorries are waiting. Softer rock does not present the same kind of problem, but with this, of course, special precautions must be taken against collapse of the roof before the lining is in place. Two points may be noted here. Firstly, props may be fitted to press against the roof, opposing the downward crushing forces from the overlying material; secondly, the 25

Tunnel Watching lining may be carried out close to the working face, so that only a very short part of the roof is exposed at any one time.

From shield to cutter head One solution was the invention of the tunnelling shield, a device that filled the tunnel at the working face, with a number of cells in it, in each of which a workman excavated, the shield being advanced as the work progressed, and lining material was placed over the cut surface. Modern methods are a step forward from this, where the machinery consists of a large rotating cutter head eating its way forward, the lining being placed continuously as it advances. In the past clay bricks were widely used for lining, but pre-fabricated reinforced concrete segments can be made off site, and are easily handled and fed to the face. Here they can be slotted together and grouted to form the continuous lining Health and Safety Factors The problem of danger has always existed, but over the years steps have been taken to reduce the risks, and the modern worker has much less to fear than his predecessors. Nevertheless, safety is still part of the challenge faced by the engineer whenever civil engineering works are undertaken. For dealing with the unexpected the most that can be done is to presume the nastiest and take whatever steps are possible to avoid injury or worse. So for extensive work it is usual to appoint a Safety Officer whose task it is to prepare for emergencies and ensure that personnel are at all times protected. Governments often lay down regulations and appoint inspectors to ensure that firms comply with every aspect of them.

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Completed tunnels rarely retain features showing what measures were taken during construction, but occasionally from a slow-moving train one can see little recesses in the walls of a tunnel like shallow sentry boxes. They are one feature of safety precautions, and provide sanctuary for workers whilst vehicles or trains pass, both during construction and in the working life of the tunnel. Tunnel Linings Linings may be metallic or of brick or concrete. At the ends it isn't always easy to see what has been used, for there is often some architectural feature to embellish entrance and exit. Many are relatively plain, but the Victorians ensured that their masterpieces were suitably adorned. These are a delight to the tunnel-watcher. The primary purpose of the lining is to sustain the compressive forces of the surrounding material. In the early tunnels millions of bricks were used. They were easily transported and laid, a skilled bricklayer carrying out the work with impressive speed. Concrete is well suited to the job, too, for it is strong in compression. The lining may be faced with white tiles, to improve the lighting, and in some cases, notably pedestrian access to underground trains, the spacious surfaces can be adorned by advertisers' posters. Cost and diameter Disposal of the stuff dug out is always a problem demanding careful preparation. (If you hate equations, jump forward a few sentences here.) Earlier we spoke of shallow tunnels and the resulting spoil heaps. If we now think about a hole of length L, circular in section and of diameter D, then the volume V to be handled is given by the equation 27

Tunnel Watching V = (pLD_)/4 or V LD2 The thing to note about this is that the volume goes up rapidly as the diameter increases. As the volume increases so does the cost of cutting and hauling the material from the tunnel. So financial problems can grow with larger diameters. The solution here is to design with the minimum acceptable diameter. However, one cannot be too niggardly with constructions like tunnels. Once constructed, it is rather expensive to make changes! Note that, although we have used the word "diameter", not all tunnels are circular in section. The circular shape is from some points of view the most economical; but other considerations may influence the engineer to adopt oval sections, sometimes with a flattened base to suit the proposed road or track. Again, in some of the pioneer mining, such as tunnelling for minerals in densely forested areas a square or rectangular shape was chosen, largely because shoring and supporting the roof was readily achieved with baulks of timber, plentifully available on site. Over or Under Some of these old workings are still to be seen in remote areas, in regions where timber was readily available, for example in Canada and the United States of America. Gradients within tunnels are slight, especially in those for rail traffic, so they do not normally present much of a problem. Roads, though, may climb more steeply, and it might be better to start the dig from one end rather than the other. Also, when passing below a river the line may dip at each end to get down to a safe level. Except for underground railway systems therefore, in large cities many of the roads may pass below the river whilst the railways run over bridges. The alignment of the bore is a matter calling for careful attention. The public is often surprised to see pictures of tunnelling breakthroughs so precisely achieved, but it is not really a major difficulty Straight lines and offsets can be as readily dealt with below ground as on the surface. A theodolite, or adjustable telescope, can be sighted along the desired direction; but nowadays, with laser beams, life is generally much easier. Spectacular tunnels It is not often that a curve is needed in a railway tunnel, but there is a magnificent exception in the Canadian Rockies, where a helical bore has been cut in the mountain, a truly wonderful achievement. It is as if a giant corkscrew has been used to penetrate the rock, so that a train can within a comparatively short distance descend a gentle gradient 28

Tunnel Watching to reach a level far below, popping in and out of the mountain to the delight of tourist and tunnel-watcher alike. Some of the trains are very long, so that one might see the front of the train emerging from a hole before the tail end vanishes into the other entrance. The men who built the trans-Canada railway system were men of determination and vision, who seemed able to overcome all obstacles. The line across the plains presented little difficulty, but crossing the Rockies called for imagination and determination. Flooding Flooding can be a problem during construction and later, and this is a challenge that has to be firmly faced, especially when working under rivers. During the construction of Brunel's tunnel under the Thames he was confronted with a bad leak, which he tackled with characteristic aplomb. He had himself taken along the tunnel to the site of the leak, and arranged a diving bell to be lowered from above. The story has been told many times, and all good tunnel-watchers should read the account. Modern pumping equipment can deal with large flows of water, and where some flooding is possible preparations can be made to handle it. The occasional unexpected flood is a different matter, but even so modern methods can bring in efficient gear to cope with all but the most disastrous inundations. In the distant past many lives have been lost through flooding, but it is rare nowadays to hear of such catastrophes. Pumping it out There are many different types of pump but almost without exception, those used in tunnelling nowadays are of the centrifugal type. These have a snail-like outer casing, inside which is a rotor with blades. When the rotor is spun it whirls the water around so that it creates what is known as a forced vortex. The characteristic of a forced vortex is that the outer parts tend to rise higher than the centre, like the surface in a tea-cup when stirred. When held inside the casing, the outer parts of the water are at a higher pressure, and it is this that is the basis of the pumping action of a centrifugal pump.

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Tunnel Watching Beam engines

The old beam engines are no more than a tourist attraction now, though they worked with the utmost reliability and minimum maintenance, driving a great piston up and down, sucking up the water from the depth of the workings. Slow moving and powerful, they looked engagingly robust and satisfactory to the eye of the enthusiast, but it is unlikely that the tunnel-watcher will have a chance to see one nowadays save in a museum. They had one very special advantage over modern high-speed pumps. They never seemed to wear out, and would go on doing their duty seemingly forever, requiring only a little squirt of oil occasionally where it mattered.

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Tunnel Watching Their maintenance periods were, it is thought, based on the number of strokes. An instrument called a "kilometer" measured the number of strokes, and registered them in thousands. Every so many thousand strokes what little maintenance was needed was carried out. It is interesting to see that some people pronounce the word "kilometre" (accented first syllable) as though it were "kilometer" (accented second syllable), and in the United States the words are spelt the same. Scheduling the job The problem of access is a question of logistics. Careful planning is needed to ensure that men materials and equipment arrive at the right time, and this may involve the building of special roads and light railway systems when the undertaking is a large one, all carefully time-tabled into the overall plan. Nowadays there are some excellent devices, and computer programs to help solve problems of this kind, and the tunnel- watcher who has the good fortune to see tunnelling work going on can see the results of this, as the flow of men and equipment is steadily maintained Clearing the face The movement of material away from the face is usually achieved by the use of wagons or conveyor belts. A railway system can be laid down to take open wagons, or a long conveyor belt can be installed to run the whole length of the undertaking on sets of rollers. Here again, due thought must be taken about the safety of people making their way along the tunnel. The arrival of waste at the mouth is not the end of the problem, of course. Action from there on will depend upon the kind of material, and plans for its disposal. The tunnel watcher can sometimes see signs of what happened at the time of construction. Occasionally there are piles of broken rock to be seen in the vicinity of the ends, or mounds of soil, often landscaped. If one makes a rough guess at the dimensions of a tunnel, (assumed cylindrical) i.e., the length and diameter, one can arrive at an estimate of the volume of material removed from below the ground. Calculating the waste Suppose a bore of circular section with diameter D, and length L yields material to be dumped in one conical heap of height H. If for the sake of simplicity we assume an angle of repose of, say, 45 , then we can find the height of such a cone by equating the volume of the tunnel to that of the pile, thus p D_L/4 = (p H_)/3 From this, we can get a value for H in terms of the length and diameter. Thus, we have the height of the conical heap given by 31

Tunnel Watching H = (3D_L/4)_/_ Well, if you don't like equations you won't like that! Still, if we put in a few figures it does give an idea of the sort of heap that might be needed.

With the same assumptions, then for a tunnel with a diameter of say 8 metres, for every kilometre of excavation the height of our imaginary heap would be about 36 metres, with a base diameter of over 72 metres! That is rather a lot. Further, the volume of excavated material is in general greater than the volume of the tunnel as the process of breaking it up when digging it out of the earth means that there are more voids or empty spaces between the lumps. So for even a modest hole there is a great deal of material to carry away. Of course, the spoil is not usually dumped in one great heap at 1- kilometre intervals like that; but perhaps this gives some idea of the enormity of the task.

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Tunnel Watching Carting it away Using the same rough figures, the volume of material would be about 64,000 cubic metres. If lorries were hired to take the stuff away, this would require a pretty large fleet, busily running to and fro along the access road. Look at a large lorry, and estimate its capacity from the length width and depth of the usable volume. The immensity of the task of removing rock in this way can be appreciated. The figures used above were deliberately chosen to make the calculation easy. They should help the tunnel-watcher to get some idea of the work entailed for any particular tunnel whose dimensions can be roughly assessed. In all of this we have skimmed lightly over the kind of solutions used to deal with the problems encountered. There are other problems in every undertaking, and other solutions. It is part of the life of the engineer to meet and solve the problems arising in design, construction, and maintenance. In this particular field experience is especially valuable. Those who tender for tunnelling work need an extensive "track record" behind them.

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Methods Over the centuries much has changed with regard to the ways in which digging has been tackled. Man, and woman too, struggling to penetrate the earth, must have fought against the intractable nature of the work. From earliest times the problem has consisted of removing material from the face of the workings, and transporting it back along the tunnel to the entrance, at the same time avoiding collapse of the roof and danger from noxious and inflammable gases. Perhaps caves presented the early workers with temptations to proceed further into the ground, at first just to enlarge the caves and crevices, and then to explore more deeply along the more easily removed layers of rock. Early tools Before the coming of tools and machinery bare hands must have served for the softer soils, followed by the use of crude digging tools fashioned from animal bones, antlers, and suitable pieces of wood. Modern experiments with these early tools for loosening the soil prove them to be surprisingly efficient. The material thus loosened could then be taken to the entrance by hand, perhaps conveyed in primitive baskets. Some of the details can be only conjecture, for little remains but worn pieces of bone from which to make inspired guesses. We are heavily dependent upon the archaeologist for information about those early efforts. The primitive tunnellers could not cope with hard rock, so work was necessarily restricted. One can imagine, and admire, the persistence of the early workmen scraping away with their primitive tools at the face of the softer rock; but tools of bone could make no impression on hard stuff like granite. Such penetration had to await the arrival of more advanced materials and more sophisticated methods. Stone age tools Some tools made from pieces of stone, broken from larger rocks made excavating easier, but when men found how to smelt ore to produce metals like copper and iron there was an immense enlargement of their technical horizons. Here were materials much harder than bone, much more resistant to wear, longer- lasting in the severe and laborious work of digging.

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Iron age The iron age opened up opportunities for tackling some of the harder rocks, though it was still difficult work, painfully slow; and the hardest rock defied the even those early iron tools. Iron was produced by smelting the iron ore, and the result was a crude cast iron at first. Shaping the tools was achieved by casting, pouring the molten metal into moulds of the required shape. To produce a sharp cutting edge demanded long hours whetting the edge on some abrasive stone. In those early days when life was lived slowly time was more plentiful, labour was not costly, and there was probably no strong drive for rapid results. Steel Tools When methods were invented to take much of the carbon from the cast iron, steel was produced. Steel made better tools because, unlike iron, it could be heat-treated to alter the internal structure. Steel changes its properties when subjected to high temperatures and then cooled under controlled conditions. The shape of a steel chisel can be produced fairly easily while in a soft state. Then it can be hardened by heating and quenching. After re-heating, and then quenching at a lower temperature the hardness can be tempered, so modifying the properties to reduce the otherwise brittle nature of the material. The temperatures of this heat treatment determine the hardness and toughness of the finished product, though the carbon content of the steel controls the effects. The cutting edge can be formed by grinding away the metal, using hard stone. 35

Tunnel Watching The angle of the edge depends upon the use to which the chisel is to be put. These methods have been developed to a high degree of efficiency, and are still in use.

Carbide and Diamond tools Still, even the best of the earlier steels could not manage the more impenetrable materials; modern alloy steels did not appear till comparatively recently, and carbidetipped cutting tools even later. Diamond-coated abrasive wheels form another comparatively recent product. With their arrival there was a big step forward in speed of cutting and the capacity to cut the hardest rock. When dealing with smaller intrusions of materials like granite these can be removed by first digging round them to clear away the surrounding softer material, and then hauling them out; but this will not do when, as is more usual, layers of considerable extent lie in the path of the tunneller and are unavoidable. Sometimes a hole must be cut right through the rock itself. Modern methods employ carbide-tipped cutting tools, driven by powerful machinery. For a tunnel of circular cross-section the huge rotating cutter heads of up-to-date equipment make an impressive sight as they bite into the resistant face. The power requirements make heavy demands upon the plant, and the process is noisy. Health and Safety at Work regulations demand, among other things, ear protection for the workers at the face, as well as protective headgear. Tunnel-watchers are unlikely to see these processes close up, for the work-face is a hazardous place to be, but they may have an opportunity to see film and video-recordings of this impressive and fascinating work. The bore produced by these modern machines has a fairly smooth surface, requiring little work with regard to lining. In some cases only cosmetic work is needed. They are, 36

Tunnel Watching of course, expensive to produce and to operate, but produce overall economies that cannot be ignored.

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From gunpowder to Semtex Explosive methods for breaking up granite, using modern explosives, are relatively cheap. The earlier materials were gunpowder, dynamite, and TNT. Nowadays plastic explosives are available, safe to handle, and easily moulded to be placed where required. Powerful substances like Semtex have been developed, and chemists do not believe that that is the end of the line. An explosive material set off in the open air, in unconfined space, does not in general produce very spectacular results, for the sudden increase in volume is readily accommodated by the surrounding air yielding elastically and comfortably to the rise in pressure. To be truly effective an explosive device needs to be confined. Securing a confined space Explosives have to be handled with great care, though they are usually harmless until detonated. So the aim of the user is to place the explosive material in a confined space, with a detonating device beside it. At present this is commonly achieved by drilling a deep hole in the rock face with some form of percussion drill, and stuffing the explosive into the far end of the hole, ramming it home. The detonator with wires attached follows, and then the hole can be plugged. The wires, in the form of a length of electric cable, lead from the hole to some point far enough away to ensure the safety of the operators. It can then be connected to the 38

Tunnel Watching terminals of a small generator. Inside the generator box is a small dynamo with a drive connected to a plunger on top of the box. Producing the spark When the plunger is depressed the generator provides an electric current which travels along the wires to the detonator, producing a spark at the business end. This spark sets off the detonator, and hence the explosive material. The sudden rise in pressure creates enormous stresses in the surrounding rock. Admirers of Hollywood's Westerns will be familiar with this process. In experienced hands there is no danger attached to the method, but it is not work for the beginner. Horse power Methods of breaking up hard rock have changed a great deal over the years. Further, the speed of penetration has increased. What some of the earlier tunnellers achieved with their primitive methods is a matter for humble admiration. Following upon the wide use of manpower, and before the arrival of the internal combustion engine, the principal source of power was the horse. The removal of broken rock was carried out with horse-drawn wooden carts. These often had tilting frames, so that at the point of discharge the rear part of the cart could be up- ended, and the pieces of rock would slide off onto the ground. The frame would then be returned to the horizontal and locked into position ready to be taken back to the face for re- loading. They were sturdily constructed, and faced harsh conditions. There would be a constant coming and going of these carts, of which large numbers were used. Early working conditions Conditions of work were not attractive, for horse or man, though the noise levels then were less than they often are today. The horse was a common supplier of motive power at one time, and it was natural to use them underground. The work force got used to the overall dust and smell, and the general garb was corduroy trousers strapped at the knee, reputedly to prevent rats running up the trouser legs, but more likely to hitch the bottom of the trousers clear of the general muck. Pictures of old workings show not only this but the then modish wearing of top hats by those higher in the chain of command. The three principal types of hat, flat cloth, bowler and topper, were more-or-less badges of rank. Where large numbers of horses were used provision had to be made for feeding and stabling, grooming and veterinary attention, and this would often require the services of a large number of specialists. All signs of these conditions have long since vanished, 39

Tunnel Watching and the modern tunneller, dressed in protective clothing, relies upon conveyor belts or power- driven wagons. Use of Conveyor belts The conveyor belt is a very tough wide ribbon running over rollers, some of which are driven, and some idling. The rollers are so shaped as to form the belt into a shallow trough, and the speed can be adjusted to maintain full and steady flow of the material from the working face to the outside world. Effective maintenance of the conveyor belt is very important, for a breakdown can be a serious matter, leading to expensive delays in the work. If due precautions are not taken a conveyor belt can be a very dangerous piece of equipment, too, so the Safety Officer has this well up on his list. A belt can handle gentle curves and modest gradients, even steep gradients at a pinch, and is widely used. At the discharge point the belt can run back under the rollers on its return journey to the working face. The material discharged from the belt can be directed into a hopper, whence it is fed into lorries or onto other belts to take the rocks away from the tunnel entrance. Disposing of waste The waste may be used to fill in depressions outside, or to form embankments where needed, depending upon the type of material. Some types of rock are sought after for other purposes and may be sold to other contractors. In one sense the whole project can be regarded as a form of mining, though in most cases the material removed has little commercial value, unlike a dedicated mine which seeks to remove valuable minerals. The methods of dealing with unwanted water are usually straightforward. Modern pumping equipment of various sizes can be hired for the duration of the work or only at times when the need arises. Disposing of water Powerful pumps can remove great quantities of water rapidly, and the discharge is taken by pipes to points beyond the excavation. Mining concerns have much experience of this work and there are many competent firms who can supply the necessary equipment tailored for the job, given the conditions to be met. Calculations Previous to the discovery of the potential of the micro-chip the chief calculating tool of the engineer was the slide rule. A good understanding of this cunning little gadget made even complex calculations quick and easy. There were standard ones for use in the drawing office, and half-size ones frequently seen protruding from the breast 40

Tunnel Watching pocket of the engineer. For specially precise calculations some very large ones were made, standing in a holder on the desk. They are all museum pieces now, and few modern engineers know how to use them. Then came the mechanical calculators, with numbered wheels, and handles for operating them, though they didn't last long, and are to be found only as mechanical curiosities in museums nowadays. Cumbersome and heavy, they were not suitable for the breast pocket, not portable instruments. Their place has been taken by the electronic computer, which has shrunk in size since the first models appeared.

Computers and tunnelling The development of the computer has been a welcome addition to the engineer's tool kit. It can be used not only for calculations, but to control machinery, and to enable work to be carried out in places too dangerous for the well-being of humans. It is well suited to the task of optimising conditions and setting up control schemes to get the best out of available equipment and personnel. Programming the work is facilitated by specialised computer applications now available. Problems of logistics are eminently suited to the unwearying precision of the electronic marvel, and it does save a great deal of paper. Unfortunately in the opinions of some, means have been found to make up for this by inventing new needs for piles of paper, contributing little to the success of the venture. As in other fields, special computer programs have been developed and are constantly being improved, to lighten the load of planners and controllers. For many modern engineers the task of carrying out a major tunnelling contract without computers would be daunting, to say the least. Carrying the load Turning now to the physical aspect of the work, it is often necessary to handle heavy loads, much beyond the capacity of a man, even with some form of crane. The workmen of earlier ages were compelled to use impressive numbers of men to do jobs which nowadays are easy for a competent robot or automaton.

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Tunnel Watching Robotic equipment The introduction of robots can lead to unemployment in some fields, but an increased demand for workers elsewhere. A smaller requirement for labourers has been offset by an increasing demand for staff to manufacture and operate computers and robotic equipment. The principal development is the robotic arm. This is an extending and highly manoeuvrable linkage that can reach into any spot within a defined space and there perform operations, obeying precisely commands from a human or electronic master. Such arms are widely used in factories manufacturing motor- vehicles, where they perform with speed fairly complicated operations on the assembly lines. The advantages of their application underground were soon recognised, and they now play an increasing role in many civil engineering undertakings, as they do elsewhere.

Moving the earth Modern earth-moving machinery has come a long way since the first crude diggers appeared. With their special attachments they can dig, scrape, and shovel up heavy loads of rock. Highly mobile, a modern machine requires only one skilled driver to carry out, rapidly and accurately, earth-moving jobs that at one time involved hundreds of navvies. They are highly adaptable, with usually a diesel engine as the power source, and hydraulic rams to operate the appliances. Even now they have not reached the limit of development. Dealing with spoil outside of the tunnel a good operator can deposit and grade the heaps to the best advantage. The machines are rugged and reliable, and can work for long periods between scheduled maintenance action, in hostile environments. Any tunnel-watcher with the time to spare will find much interest in looking (from a safe distance!) at these machines at work when a tunnel is being constructed, or at any other site.

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Tunnel Watching Lighting the way The change from scrabbling in the dark to working in the feeble glow of lighted wicks, and then rushlights, has been a slow one, gradually accelerating to the modern electric lighting systems. Work underground nowadays is carried out in conditions of lighting which would have astonished our forefathers. Electric cables can be run along to the working face, with lights at intervals all the way. Altogether, electricity has been a great boon, for the conveyance of power and light by cable is such a convenient arrangement. Where there is the least danger of inflammable gases being present special precautions must be taken to see that no dangerous sparking occurs. The Davey Lamp When flames were used to provide light this was a constant danger. The old miner's lamp, invented by Sir Humphrey Davey, took care of this by enclosing within a gauze the flame that was at that time used to provide light. It was a simple invention but effective. Nowadays they are collectors' items, polished and gleaming on peoples' sideboards. With the ready availability of electricity the safety lamp of that era is no longer required; but some people consider that for sheer beauty they leave the modern light standing. Lighting installations The lighting installation in the completed tunnel depends upon individual requirements. Most of the old tunnels had no permanent lighting at all. Modern constructions include good systems according to needs. Underground railway systems, for example, often have artificial lighting at the stations only.

The tunnel-watcher will find many variations from no lighting at all to full overhead and wall electrical systems, using fluorescent tubes and filament lamps. Roads underground are normally well lighted throughout, though the requirements for railways are not so demanding; and tunnels for conveyance of water are usually not lighted at all. 43

Tunnel Watching In many parts of the world, especially in remote areas, methods of construction may call for generating plant on site to supply current for lighting and machinery. Pneumatic and hydraulic systems are sometimes used, too. In a completed tunnel there is often nothing to indicate what methods were used in the construction, though informative publicity brochures are often available for the larger undertakings, it is often worth while to make local enquiries for information when there is interest in a particular tunnel. In some places they are, justifiably, very proud of their tunnels. Fibre optics Advances in the field of fibre optics have led to the use of this method of conveying information being used in the control and operation of machinery. The method depends upon the conversion of signals into modulated pulses of light being sent along lines of tiny diameter at virtually the speed of light. Tunnel brickwork The methods of lining depend upon what materials are to be used. For major works the old clay brick is no longer used. Each job required an immense number of bricks. For example, when the four-mile tunnel under the Severn was built in Britain, towards the end of the nineteenth century, over seventy-six million bricks were used. One can imagine the labour involved in making, transporting and placing that huge number of bricks. The method of lining with bricks is to support them with shuttering, or wooden forms, as they are laid, till the last brick is in place to key them all together, when the shuttering can be removed. Concrete linings

Modern lining methods employ concrete, which is bad for brick yards, but good for tunnellers. Whenever the chance arises, no serious tunnel-watcher should miss an opportunity of looking inside a modern tunnel. 44

Tunnel Watching This is easy in a road tunnel, where all is bright and clearly visible, but not so simple a matter on the railway. For that you need to get special permission, and you won't find that easy. Railway tunnels are dangerous places for a pedestrian, and usually dark, too. This applies equally to large sewer systems. Examining brickwork At the time of writing there is a splendid opportunity to look inside a disused tunnel at Wormit, in Fife, Scotland. Easy of access, rubbish has been permitted to accumulate inside, but one can walk through in daylight, and it is not very long. It has been allowed to fall into disrepair since it was last used, which is a pity. The tunnel watcher gains, for he or she can examine the brick construction of the interior, and see the provision made for workmen to take refuge from passing traffic. Following developments In this chapter it has not been possible to cover all the wonderful ideas that have developed over the years in the art of boring through the earth. Things sometimes move very fast, and there may be a lot of difference between what you see in an old tunnel and what happens now. Tunnels last a long time, and what you can now observe can cover centuries of development. Whenever a new tunnel is proposed, it is worth while to keep in touch with developments. One can sometimes follow the progress from the initial vague ideas through the various stages of growth in a series of committee meetings and their associated reports. The changes from the original suggestions to the final decisions can make fascinating reading. The reasons for the changes may be geological, technical, or political, but they all contribute towards the firming of the final settlement. A tunnel is a permanent structure, and much preliminary work is fully justified. You may feel that, unlike a building on the surface of the earth, it is a pity that so much effort should be largely buried; but for those who know something about tunnelling, what lies beneath the surface can have an abiding interest.

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Examples In level areas there is no incentive to go underground for transport; but in hilly country there are tunnels to be seen pretty well everywhere, as people build their roads, canals and rail systems to take the most direct routes. So in general the tunnel-watcher is more likely to find interesting examples in hilly or mountainous areas. It is also true that land is so highly priced in some places that even though tunnelling is expensive it may yet be worth consideration. This is especially true in large cities, where a direct route above ground might entail demolition of valuable properties. Occasionally, then, you may come across places where transport is taken under buildings and other roads and rail lines, even for comparatively short distances. In almost every part of the world there are examples of tunnelling to be seen and investigated. You might spot them when walking, cycling or motoring. The mouths or the ventilation shafts are the things to look for of course. Good large-scale maps of the country show the roads and railways, and often their underground parts are indicated by dotted lines. Where a dotted line joins a full line there will be a tunnel entrance. An odd hour poring over large-scale maps can produce some valuable information. Local guide-books sometimes mention tunnels in the vicinity, if they are deemed to be historic, or otherwise special. Accessibility Not all tunnel mouths are readily accessible, and in some cases you may need permission to approach them. However, when you can't get near them a good pair of binoculars or a telescope may help you to make out detail. Again, a telephoto lens on a camera can be useful to make records of interesting features. Although localities do not usually boast about their tunnels, reference books can provide much useful information. Famous or unusual tunnels are generally listed in encyclopedia-type books, and in this way you may find mention of some in your area. You may even find an excuse for going that way the next time you go touring. Compiling research Although it no longer exists, due to land erosion, there was at one time a small tunnel through the cliffs close to the sea at Sidmouth, Devon, on the south coast of England. It is reported that the line was intended to be a temporary one, to carry material to Sidmouth, but that when it was finished they found that the locomotive was too big to go in. Well, that may or may not be true. In any event, the hole was near to the cliff face, and when the cliff was eroded it collapsed and took with it what remained of the tunnel. The reader may find it interesting to consult the local records for further details. It is not unknown for a dedicated tunnel-watcher, compiling a record of what he or she has seen and visited, to make a special effort to go to some place where a particularly 46

Tunnel Watching fine or unusual specimen is to be seen. Sometimes local authorities may have records showing how certain problems were tackled when a tunnel was bored in the vicinity, and how the construction requirements sometimes created headaches for the authorities. Tunnels as tourist attractions In Britain and France, as well as their own country, the Romans left some wonderful water and sewerage systems which have been well-preserved in many places. Often these are open as a tourist attraction. There are some fine examples of underground hole-boring in places like Exeter in Devon, which are open to the public.

Channel Tunnel Among the longest tunnels are those such as the Channel Tunnel, a magnificent piece of engineering, about which much has been written for both the technical press and the general public. Inclined at both ends, it dips beneath the English Channel to cross under the water, joining Dover to Calais with a double bore. It cost an astronomical sum to construct, and at the present time is not finding it easy to meet the financial burden; but it has cut the time for travel between London and Paris remarkably. Until recently it was possible to see the equipment used to cut the bore, displayed not far from the mouth.

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Tunnel Watching This tunnel has been well documented, with books and papers covering every aspect of the work, all good reading material. It is among the most modern of underground achievements, and it is illuminating to compare the work with that for earlier penetrations in other parts of the world. More fascinating examples There are many other long tunnels, some dating back many years. An unusual undertaking was the 3-mile hole in Cheshire, England, built in the mid eighteeneighties. Round about that time there were some others of note, for example a couple in Yorkshire, Standedge no.2 and Standedge no.3, of similar length. Also, a little later, they built a 4-mile bore, the Hoosac at Massachusetts, in the USA. At that time longer and longer tunnels were being considered. After the turn of the century some over ten miles long were being dug, like the Simplon tunnel, taking rail traffic underground for over twelve miles. All this underground work took its toll in the lives of those engaged in the risky work. For example, it is reported that the Simplon tunnel claimed some sixty dead. Roads, too, have helped in making their mark. Going back to the twenty-first century BC we have records of the thousand- yard tunnel near Hillah, in what was then Mesopotamia, and is now Iraq. In that part of the world the earth is largely sedimentary, and the workers did a fine job. It sometimes appears that in those days, compared with modern times, more money and energy was spent on carrying out exciting works and less on conflicts to hurt people, though the cost must have been high in lives for such an undertaking as the Mesopotamian tunnel. For the conveyance of water it is probable that the West Delaware water supply is one of the most impressive for length, some 85 miles long. This was built in the late thirties and early forties. Others, not quite as long, had been bored in the late eighteen-eighties, for water, road and rail. Linings to carry water Water is often taken underground for canal-borne traffic and for the distribution of domestic supplies. Where this is done by tunnelling the lining is of special importance, lest waste occur. The water itself is not expensive, of course, since like all the good things in this world it is free. The costs arise from getting it ready for use and sending it to where it is wanted, so waste is to be avoided. Some of the larger sewers that deal with the effluents from cities are tunnelled, too. In following some of the parts of sewerage and canal systems you may find the lining of special interest. Most of the great canal systems built in Britain in the nineteenth century used bricks, by the million, for lining the bores through hills. 48

Tunnel Watching Bodies of information For details of the many tunnels in Britain, and some of those abroad which were built by British engineers, reference may be made to the Proceedings of the Institution of Civil Engineers, (Proc. I.C.E). There are similar bodies in other countries, too, with vast resources of learned papers going back over many years. For the layman some of this may prove hard going, but there is much in those technical papers which reveal the difficulties and successes of the older works. Modern undertakings are fully reported in technical journals, sometimes in popular magazines, too. The press, too, reports new work, often well illustrated. As you travel around you may find new interest in the varied examples of tunnels in all parts of the world. In particular, in areas where some materials are scarce, the use of others can be fascinating. Not all tunnels are the product of experienced engineers with modern machinery and up-to-date materials.

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Glossary Adit A horizontal or sloping passage that leads into underground workings, a mine entrance. Arch A form of structure to support a (frequently evenly distributed, though often a rolling) load. It is normally supported on two piers, each carrying a horizontal block, the impost, on which rests the springer. In a brick or stone arch the voussoirs are the tapered blocks that form the curved part of the arch. Sometimes decorative arch embellishments can be found at the mouths of tunnels, especially the older ones. Camber The rise in the centre of a road due to crosscurvature. This helps the road surface to shed water. Explosives An explosive material is one which under certain conditions produces a sudden increase in volume. If confined, the explosion is accompanied by a large increase in pressure, which can be applied to cause rupture of surrounding rock. Explosives include gunpowder, nitrate mixtures and compounds, and chlorate mixtures. Underground, mainly used to deal with hard rock. Modern explosive material is powerful yet safe to handle when proper precautions are taken. Strict regulations govern the storage and use of all explosive material. Gauge In railway construction, the gauge is the distance between the rails. Although this distance can be of any convenient amount, in practice most railways use an agreed standard, 4'8 ", (1435.1 mm). There are some who feel that the earlier broad gauge would have been a better choice, providing better stability and a more comfortable ride. On the other hand, a tunnel need not be so wide, and hence expensive to construct, when using the narrower gauge. Light railways for trucks and tubs often use lines laid together more closely. Igneous A term applied to rock which was originally formed by the solidification of molten material. The hardest rocks are found in this group. Examples are granite and lava. Intrados The concave side of an arch. The convex side is called the extrados. It can be regarded as the roof of an arched structure such as a tunnel. Metamorphic This word refers to rock which has suffered changes, usually in temperature and pressure, and covers a wide variety of material. Examples of metamorphic rock include slate, marble and quartzite. Parabola A curve considered by many to be the most beautiful in nature, this lovely shape can be seen by slicing through a cone parallel with the axis. It has many applications, and in the theory of structures is the shape of the diagram of bending effect on a beam uniformly loaded. If an arch is constructed in the form of a parabola, it is effectively free from bending tendency when sustaining an evenly distributed load. 50

Tunnel Watching Tunnels with paraboloidal inverts are thus well suited to sustaining the vertical load imposed from the rock above. Sedimentary This term refers to rock which has resulted from the deposition of material, often in the form of granules, sometimes from solutions of minerals. The deposited material is afterwards compressed into a solid by great pressure. The types most often encountered are sandstone, shale, and conglomerates. Sedimentary rocks commonly show banding or stratification, clearly seen in cliff faces. Soffit The underneath part of a structural component such as an arch. Tunnel An artificial passage below the surface of the earth. The word comes from the French word "tonnelle". Underground Anywhere below the surface of the earth. The word is used also to refer to railways which operate in tunnels in cities, as an abbreviation for '`underground railway", as distinct from "elevated railway", lines elevated above street level, as in Chicago.

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Bibliography These are some sources for further information, most of which are necessarily technical in content. The list does not pretend to be exhaustive, and many books have been published of a less technical nature. These often offer a gentle introduction to learning about tunnels, and can help to extend your knowledge. The sources are listed in alphabetical order by author. Although a few may seem a little out-of-date, they are all very informative. Since the publication of some of these, the use of metric units has been compulsory in a few places; miles feet and yards were commonly used by many engineers prior to that legislation, and most of the earlier books and papers used these units. Attewell, PB Soil Movements induced by tunnelling and their effects on pipelines .... PB Attewell, J Yeates, AR Selby 1986 Bardett, JV The Bentonite Tunnelling Machine, by JV Bardett, AR Biggart and RLTriggs 1973 Bender, Lionel. Eurotunnel 1990 Craig, RF Soil Mechanics pub. Chapman and Hall Dean, Frederick Ernest. Bridges and Tunnels, revised edition 1974 Department of the Environment, UK The Channel Tunnel 1973 Department of The Environment, UK Channel Tunnel Advisory Group. The Channel Tunnel and Alternative Crosschannel Services 1975 Golder Associates, Tunnelling Technology, an appraisal of the state of the art for application to transit systems 1976 Harding, Harold Tunnelling History and My Own Involvement 1981 Haining, Peter Eurotunnel; an illustrated history of the ChanneI Tunnel Scheme 1973 Parker, Albert D Planning and estimating underground construction 1970 Pastore, Arthur Ralph Dynamite Under The Alps: The Challenge of the Mont Blanc Tunnel 1967. Pursall, BR The Aerodynamics and Ventilation of Vehicle tunnels 1977 52

Tunnel Watching Rickard, Graham Tunnels 1988 Rigby, Sue Pocket Guide to Rocks, Minerals and Gemstones, pub. Mitchell Beasley Wahlshom, Ernest E Summary of the Engineering Geology of the Harold D Roberts Tunnel, Colorado 1979 Wamer, Lawrence A Geology of the Eastem Part of the Harold D. Roberts Tunnel, Colorado Lawrence A Warner and Chades S Robinson 1981 In addition to these the reader is recommended to dig around among the engineering shelves in the library where little nuggets of information can be found in books on civil engineering, geology, and other related subjects.

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Tunnel Watching Edmund W. Jupp The aim of the "Watching" series is to draw attention to some of the very interesting items around us, things that perhaps we don't notice as much as we might. The first was "Bridge Watching", and when this was put "on the Net" it produced, to the surprise of the author, such a pleasant flood of e-mail that another was written, called "Water Watching". This, too, was kindly received. So it was tempting to continue with the theme. Some people find pleasure in taking photographs and some like to sketch or paint, because tunnel mouths are often set in lovely countryside. A train emerging from a hole in the side of a hill makes a good picture, in any weather conditions, whether as a photograph or a painting. On the other hand some people like to just look, without recording the sight. Whichever may be your choice, I wish you happy tunnel watching. There are other reasons for tunnelling, such as providing an approach for men and materials, to get at something not otherwise accessible from the surface, escaping from a prison, robbing a bank, or following a seam of mineral deposits, perhaps to carry water or other liquids from one place to another. As you extend your knowledge during tunnel-watching sessions I wish you well. You may also be drawn to some of the literature on the subject, either easy introductory material like this or more technical treatment, leading you along fascinating lines of learning. Go forth and enjoy this free entertainment. Author Edmund W. Jupp (BSc (Eng), FIMech E) was born during the First World War in Sussex, England and received his early education at Brighton. After service in the 1939-45 war he worked in engineering and education, and travelled widely. He was appointed Principal of the Technical Institute in Guyana.

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