Transportation Tunnels

S. Ponnuswamy, D. Johnson Victor

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781315349305
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

Transportation Tunnels, 2nd Edition provides a comprehensive text on tunneling and tunnel engineering applicable in general to all types of tunnels, with more detailed information on highway and railway tunnels. While the First Edition of the book was confined to deal with railway and highway tunnels, the Second Edition is also extensively considering the latest trends in use of tunnels in different other fields. The book has been revised to provide coverage of water conveyance, navigation and material conveyance tunnels also and deals with these subjects in more detail.
It covers all aspects of investigation, design, construction, monitoring and maintenance of tunnels. Special emphasis has been laid on the geotechnical investigations, interpretation of findings and relating the same to the design as well as the construction of tunnels. The book reflects the advancements in the knowledge of ground behaviour and rock mechanics and also in construction technology, including use of TBM in the last two decades.
It covers in sufficient detail the basic requirements of tunnel profile, the geometric parameters, clearance requirements, aerodynamics, and cost economics in fixing alignments with different design parameters like curvature, gradient and operational requirements. It discusses in detail alternative forms of the cross section / profile and illustrates design methodology with examples.
The different methodologies that have been used in the past using timber or steel supports by stage wise expansion of cross sections and modern methodologies used for boring full profile using new tunneling methods and Tunnel Boring Machines are also comprehensively discussed.
Requirements of tunnels in respect of ventilation, lighting and drainage are adequately covered. Separate chapters have been included on 'Instrumentation' and 'Tunnel Inspection and Maintenance'.
The expanded text on the use and advantages of methodologies and equipment for dealing with various aspects of construction of tunnels is based on observations through site visits, discussions with, and experiences of people as recorded on large number of tunneling works which have been taken up recently for railways, highways and urban transport subway projects.
The book can serve as a textbook for undergraduate and graduate students and as a reference book for practicing engineers.

CHAPTER
1
Introduction

1.1 GENERAL

Tunnels are artificial passages built underground to facilitate transportation or conveyance of people, materials, water, sewage, other fluids and gas in pipes, electric power etc., across obstructions like hills, rivers and other obstructions like buildings, industrial structures and other communication lines like major roads and rail tracks. An alternative definition of tunnels refers to underground structures which apart from serving the above noted purposes are built using special underground excavation methods without disturbing the surface. Even underground garages and power houses are treated as tunnels.

Tunnels have been built from time immemorial for various purposes, such as defence, assault/ escape and normal traffic across fortifications and water bodies. The earliest known tunnel was constructed about 4000 years ago by Queen Semiramis in ancient Babylon under the Euphrates River to connect her palace and the temple of love¹. The tunnel was 1 km long and was of section 3.6 m × 4.5 m. It was constructed using the "cut-and cover" method with brickwork in bituminous mortar and vaulted roof. In Indian history, references are available to tunnels connecting forts and points of escape and private passages for the royalty from the palaces to river fronts and temples. (One such has been reported to have existed near River Godavari at Rajahmundry).

Current-day vehicular tunnels may be built for highways or railways and may be unidirectional or dual-directional. Often tunnels reduce distances. For example, the Banihal (Jawahar Road) tunnel joining the Kashmir valley with the rest of the country has reduced the road distance by 18 km, besides facilitating year-round communication. The world's second largest tunnel is the under Sea, Channel Tunnel linking Great Britain and France by rail. Considered an engineering marvel of the twentieth century, the tunnel is 50.5 km long and lies 50 m below the seabed for most of its length.

1.2 CLASSIFICATION

Tunnels can be broadly divided into two categories: (a) transportation tunnels and (b) conveyance tunnels. Some define (a) as traffic tunnels and define transportation tunnels to include tunnels used for conveyance of water to Hydro electric Power plants, water supply tunnels, sewage tunnels and tunnels used in industrial plants for conveyance of materials like those housing conveyors etc..

Transportation tunnels can be further classified as: (a) railway tunnels, (b) highway tunnels, (c) pedestrian tunnels, (d) navigation tunnels and (e) subway tunnels.

Conveyance tunnels serve to convey liquids and may include: (i) hydroelectric power station tunnels, (ii) water supply tunnels, (iii) tunnels for the intake and conduit of public utilities, (v) sewer tunnels and (v) tunnels in industrial plants, such as conveyor-belt tunnels.

We can also include under (i) above tunnels which have been driven for purposes of diversion of water during construction of dams. The earliest example of this use in India is the Periyar tunnel, which has been used as a permanent means for diverting water from the western slopes of the Western Ghats to the East. A recent major example of such conveyance tunnel is that used for temporary diversion in connection with the Bhakra dam construction.

1.3 TRAFFIC/VEHICULAR TUNNELS

1.3.1 Major Transportation Tunnels.

Railway and highway tunnels are similar in nature and normally refer to surface-to-surface route tunnels, i.e., those provided for the purpose of crossing hills and mountains as distinct from subway tunnels (also known as tubes) used for underground railway in cities. Typical examples of a few remarkable railway and highway tunnels² are given in Table 1.1.

Table 1.1 Selected Railway and Highway Tunnels

Tunnels are warranted in the context of transportation for the following purposes:

(a) to avoid a long circuitous route around a mountain or spur;

(b) to avoid slips of slides of open cuts in soft strata;

(c) to avoid steep gradients in hilly terrain;

(d) to avoid crossing precipitous ridges or high peaks or zones likely to be under snow for a major part of the year;

(e) to avoid acquisition of valuable property or to avoid interfering or damaging a heritage structure.

However, tunnels are attendant with some disadvantages, such as:

(a) high initial cost;

(b) long construction period;

(c) specialised work, needing special equipment and highly skilled labour.

From the point of view of economics, a tunnel is preferred when depth of cutting through hard solid exceeds 18 to 20 meters.

Amongst transportation tunnels, railway tunnels are more numerous. Most have been constructed under water also, e.g., tunnel of New Tokaido line connecting two islands across the sea channel and the Channel Tunnel connecting France and England.

Subaqueous tunnels require fairly heavy approach gradient, take longer to construct and involve more personal risk to the workers. Maintenance costs are also higher, especially in seismic zones.

1.3.2 Subway Tunnels

Urban underground railways are mostly in the form of tunnels, otherwise known as tubes (after the shape used in boring). The earliest constructed was that provided for the London Tube, the first section of which was commissioned in 1863. The special requirement of underground and subaqueous railway tunnels, which distinguish them from the other railway tunnels, are:

(a) Increased safety requirements due to high density and high speed of traffic and likely disastrous consequences of any derailment/ accident;

(b) Careful water sealing;

(c) High standard of cleanliness

(d) Ventilation with or without air conditioning, with duplicate power supply facilities;

(e) Full length needs to be provided good illumination and communication facilities for help in inspection/maintenance operations and for emergency evacuation of commuters.

(f) Availability of fire emergency facilities over full length and adherence to National Fire Hazard regulations.

1.3.3 Highway Tunnels

These are similar to railway tunnels except that due to the steeper permissible ruling gradient they may be shorter and require fewer spiral alignments. In cross-section they are now comparatively less in height and wider.

The additional factors to be considered in design and construction of highway tunnels are:

(i) Size: They have to be wider to accommodate the number of lanes of roadway to be carried. Hence, their width-height ratio is more than that of railway tunnels.

(ii) Shape: In view of the greater width required and also the need to carry additional services, a circular shape more often fits in better, with services carried through ducts provided in the lower half of circle.

(iii) Geometry: The curvature has to take into account the higher speeds of vehicles (which cannot be externally controlled) and also the need for a good view of each other by opposing traffic lane users.

(iv) Ventilation: Artificial ventilation (by induced draft through ducts) becomes a 'must' in view of harmful fumes and gases emitted by cars, buses and trucks.

(v) Lighting: Artificial lighting also is necessary for proper viewing inside by various types of users.

(vi) Drainage: Since the road surface and pavements have to be kept dry and non-slippery, no dripping from roof or sides can be allowed. Lining has to be waterproof and effective side drains to lead out seepage and other water become necessary.

(vii) Lining: Even where structurally not needed, lining is necessary for purposes of aesthetics, better lighting (reflection) and to control seepage. Properly cambered road surface, footpath and drains have to be provided at the invert level also.

1.3.4 Navigation Tunnels

Water transport is a form used by the man since the early days using rivers and streams for the purpose. Canals had been primarily built for purpose of irrigation and as early as 16th century, they have been used for inland transportation, one of the earliest examples being a canal built parallel to River Exe in Devon (UK) for the purpose in 1564. Industrial development gave a boost to this form of transport, before the advent of railways in the eighteenth century. Taking them across mountains through tunnels was a natural corollary and Navigation tunnels came into being. Rapid development of canals for inland transport and tunnels where required grew rapidly. For quite some time, they competed with the railways also. Rapid growth of railways and roads, with advent of motorised vehicles capable of providing quicker transport and door to door service, edged canal form of transport from reckoning.

Navigation tunnels are similar to highway tunnels. They have to be comparatively wider to allow for maneuvering of boats and provide sufficient space between boats plying in opposite directions. The waterway has to be provided with raised walkways on either side for movement of people. The waterway portion has to be impervious to prevent loss of water. They will have gentle or no gradient to suit the flow of water.

1.4 CONVEYANCE TUNNELS

The conveyance tunnels cover those provided for water supply, sewerage and those provided for housing pipe lines for fluids or conveyor belts, as in case of mines, power houses etc.. They also include tunnels provided in industrial plants for local conveyance of materials and products in any of the forms mentioned above. This classification includes also tunnels provided for diversion of water permanently for feeding power houses or transferring from one valley to another for irrigation and other purposes.

1.5 RAILWAY TUNNELS

The earliest railway tunnels to be built for steam powered Railways seem to be the ones built in Derbyshire in United Kingdom in 1830, most of them being short ones. The longest one to be built then was the 'Wymington'tunnel, 1690 m long built in 1859. The most notable early railway tunnels known world over are the Simplon Tunnels I and II in Switzerland connecting Italy with Germany, the first one built in 1906 and the second one in 1922. They are single line tunnels. They have been supplemented recently by the World's longest rail tunnel (as in 2016) known as Gotthard Base Tunnel, comprising two parallel circular (8.83 m - 9.50 m dia.) sections. The work on them is reported to be just complete, and they are under trial. They are likely to be commissioned in June 2016. It is 57 km long running parallel to each other with interconnections at intervals. Two multi-purpose stations in between have been (each in a single encompassing tunnel). They are designed for operation of passenger trains which can be run at 250 kmph and freight trains hauling 3500 t each. They are expected to save over an hour in running time of high speed trains for passengers. Longest under water rail tunnel as on date if the 53.8 km long Seikan Tunnel in Japan connecting Honshu and Hokkaido islands. Of this length, 23.5 km is under sea bed, considered deepest in the world. The other notable under sea tunnel is the 50.5 km long Channel Tunnel (Chunnel) connecting France and United Kingdom, designed for high speed train operation also. It has the longest under-sea length of 37.9 km. Though talked of since 1802, its construction was started in 1988 and completed in 1994. It consists of two circular sections of 7.6 m dia each, with a smaller 3.0 m dia service tunnel running parallel in between, with multiple purpose of providing ventilation and emergency services etc.. It also served as a pilot tunnel to know the kind of soil to be bored through, in advance, helping the drilling of main tunnels. It is a joint venture project involving priv...

Table of contents

• Cover Page
• Title Page
• Copyright
• Foreword
• Preface to Second Edition
• Preface to First Edition
• Contents
• 1 Introduction
• 2 Route Selection and Preliminary Investigations
• 3 Tunnel Requirements
• 4 Design of Tunnels
• 5 Survey and Setting Out
• 6 Tunnelling Operations
• 7 Drilling, Blasting and Mucking
• 8 Metro Tunnels
• 9 Lining
• 10 Ventilation, Lighting and Drainage
• 11 Instrumentation in Tunnelling
• 12 Inspection and Maintenance of Tunnels
• Abbreviations
• Bibliography
• Index
• About the Authors