STUDY OF TUNNELS

By- SHAIKH ADIL

Seminar on-

WHAT IS TUNNEL?

It is an underground or underwater passageway, dug through the surrounding soil/earth/rock

A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal.

Secret tunnels are built for military purposes.

Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human-made barriers safely.

REASONS TO BUILD A TUNNEL

When the lane encounters an obstacle such as a mountain to avoid bypassing the obstacle

Built sometimes to overcome a water obstacle as a replacement for building a bridge above it.

Built to connect between military posts so the movement between them will not be visible for the enemy

Sometimes built for infrastructure like electricity cables, water, communication and sewerage to avoid damage and disruption above ground

HISTORY

the first tunneling was done by prehistoric people seeking to enlarge their caves.

First tunnel in Babylonia was a brick-lined pedestrian passage some 3,000 feet (900 meters) long was built about 2180 to 2160 B.C. under the Euphrates River to connect the royal palace with the temple

the largest tunnel in ancient times was a 4,800-foot-long, 25-foot-wide, 30-foot-high road tunnel (the Pausilippo) between Naples and Pozzuoli, executed in 36 B.C.

In 1681 gunpowder was first used for blasting the tunnels

First time the ventilation system for tunnel was developed in 1927 in Holland tunnel

In 1952 James.S.Robbins comes up with a good idea and designs the modern tunnel-boring machine

In 1988 Japan's 33-mile-long Seikan Tunnel, the world's longest and deepest railway tunnel (787 feet below sea level), connects the islands of Honshu and Hokkaido

In 1994 after 192 years of planning and six years of building, the Channel Tunnel runs under the English Channel

TUNNELING METHODS

depends on ground conditions, the ground water conditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and shape of the tunnel and appropriate risk.

COMMONLY USED METHODS1. CUT AND COVER

TUNNELING

2. DRILL AND BLAST

3. BORED TUNNELING Done by Tunnel Boring Machine (TBM)

It is often used for excavating long tunnels

4. SEQUENTIAL EXCAVATION METHOD Also known as the New Austrian Tunneling

Method (NATM). The excavation location of a proposed tunnel is

divided into segments first. The segments are then mined sequentially

with supports

PARTS OF TUNNELS

TUNNEL LININGS

These are the permanent or temporary support for keeping tunnel from collapse and provide safe.

Tunnel linings are grouped into three main forms some or all of which may be used in the construction of a tunnel:

1. Temporary ground support

2. Primary lining

3. Secondary lining

DESIGN CONSIDERATIONS Water Constructability Tunnel usage

COMMON TYPES OF LINING USED IN TUNNELS

1. Natural support in rock

When the tunnel is being bored through good quality rock

2. ROCK REINFORCEMENT Steel bolts are frequently set in holes drilled

into the rock to assist in supporting the entire roof or individual rock slabs that tend to fall into a tunnel

3. SHOTCRETE

Pneumatically applied mortar and concrete are increasingly being used for the support of underground excavations

4. WIRE MESH

Wire mesh is used to support small pieces of loose rock or as reinforcement for shotcrete.

Two types of wire mesh are commonly used in underground excavations:

1. Chain-link mesh:- commonly used for fencing

2. Weld mesh:- commonly used for reinforcing shotcrete

5. IN SITU CONCRETING

The process of placing concrete in situ was incompatible with timber supports.

The first uses of concrete were for tunnels in good rock and it was only with the introduction of steel supports that concrete became the norm for a tunnel lining material.

In-situ forms used for lining tunnels are, with few exceptions, of the travelling type, constructed of steel.

6. PRECAST CONCRETE SEGMENTS•Most commonly used method•Economical

VENTILATION IN TUNNELSVentilation is required because of : 1) Dust and gas caused by drilling,

blasting, loading of excavated materials and Shotcreting

2) Exhaust gas and smoke discharged by diesel

3) Poison gas made from explosive or organic solvent

4) Poison gas, flammable gas or oxygen shortage gas in ground

5) High temperature and high humidity

VENTILATION DURING CONSTRUCTION

During construction it is necessary to ventilate a tunnel for various reasons:

To furnish fresh air for the workers To remove the dust caused by drilling,

blasting, mucking, diesel engines, and other operations

To remove obnoxious gases and fumes produced by explosives

 SEISMIC DESIGN CONSIDERATIONS

Underground structures constitute crucial components of the transportation networks

Underground structures are constrained by the surrounding medium

Compared to surface structures, which are generally unsupported above their foundations, the underground structures can be considered to display significantly greater degrees of redundancy thanks to the support from the ground6

SEISMIC DESIGN V\S CONVENTIONAL DESIGN

Seismic loads cannot be calculated accurately. Seismic loads are derived with a high degree of

uncertainty, unlike dead loads, live loads, or other effects such as temperature changes.

Any specified seismic effect has a risk associated with it.

Seismic motions are transient and reversing (i.e., cyclic). The frequency or rate of these cyclic actions is generally very high, ranging from less than one Hz to greater than ten Hz.

Seismic loads are superimposed on other permanent or frequently occurring loads.

GENERAL EFFECTS OF EARTHQUAKE

1. Ground shaking Ground shaking refers to the vibration of the

ground produced by seismic waves propagating through the earth’s crust

It composed of two different types of seismic waves

1. Body waves travel within the earth’s material. They may be either longitudinal P waves or transverse shear S waves and they can travel in any direction in the ground.

2. Surface waves travel along the earth’s surface. They may be either Rayleigh waves or Love waves.

GROUND FAILURE Ground failure broadly includes various

types of ground instability Such as faulting, landslides, liquefaction,

and tectonic uplift and subsidence. Each of these hazards maybe potentially

catastrophic to tunnel structures, although the damages are usually localized.

Design of a tunnel structure against ground instability problems is often possible, although the cost may be high.

TYPES OF DEFORMATIONS.

1. AXIAL AND CURVATURE DEFORMATIONS

1. OVALING (FOR CIRCULAR TUNNELS) AND RACKING (FOR RECTANGULAR TUNNELS SUCH AS CUT-AND-COVER TUNNELS

CRACK DISTRIBUTIONALONG THETUNNEL LINING DURING EARTHQUAKE

CASE STUDY

The Gotthard Base Tunnel is a railway tunnel in the heart of the Swiss Alps

route length-57 km total of 151.84 km of tunnels world's longest rail tunnel. Detailed preliminary investigation took place in

1986. It came to know that there are total of 90

geologic problem zones at site. most difficult zone for the tunnellers on the Piora

Basin stretch - a funnel-shaped formation filled with sugar grained dolomite and water

A thick jet of water mixed with dolomite shot out of the mountain and flooded the road.

A series of 19 inclined drills were made finally giving the engineers the all

clear. They hit on hard rock with no water pressure.

geology is very important while designing a tunnel. The method adopted for tunneling is based on the type of rock and geological conditions. tunnels are safer to the earthquake from the other on ground structures.necessary to consider the seismic design of tunnel, ventilation of tunnel is very important in tunnel during the construction and after the construction,

CONCLUSION

REFERENCES IS 15026 (2002): Tunneling Methods in Rock Masses -Guidelines [CED 48:

Rock Mechanics]

HossamToma,Tunnel Lining Methods: Selection of an efficient method, International Journal of Advanced Technology in Civil Engineering, pp 14-20

Bickel. (1995). Tunnel engineering handbook, 2nd edition. CBS Publishers.

Seismic Design of Tunnels, “A Simple State-of-the-Art Design Approach”1991 William Barclay Parsons Fellowship, Parsons Brinckerhoff, Monograph 7

Design features of Jammu-Udhampur-Srinagar-Baramulla Rail Link Project (v.k.duggal dyce/con./n.rly,d.k.pandey sr den/lko/n.rly)

Kawashima K., (2000), Seismic design of underground structures in soft ground: a review, Geotechnical Aspects of Underground Construction in Soft Ground, Kusakabe, Fujita & Miyazaki (eds). Balkema, Rotterdam, ISBN 90 5809 1066.

Wang J., (1993), Seismic Design of Tunnels: A Simple State-of-the-art Design Approach, Monograph 7, Parsons, Brinckerhoff, Quade and Douglas Inc., New York.

G. Lanzano, E. Bilotta, G. Russo. “Tunnels under seismic loading: a review of damage case histories and protection methods”.