A Tunnel is a tube hollowed through soil or

stone.

Constructing a tunnel is one of the most

complex challenges in the field of civil

engineering.

There are many different ways to excavate

a tunnel, including manual labour,

explosives, rapid heating and cooling,

tunnelling machinery or a combination of

these methods.

There are three broad categories of

tunnels:

A. MINING Tunnels.

B. PUBLIC WORKS Tunnels.

C. TRANSPORTATION Tunnels.

1. Mine tunnels are used during

ore extraction, enabling

labourers or equipment to

access mineral and metal

deposits deep inside

the earth.

2. They cost less to build.

3. Mine tunnels are not as safe

as tunnels designed for

permanent occupation.

1. Public works tunnels carry water, sewage

or gas lines across great distances.

2. The earliest tunnels were used to transport

water to, and sewage away from, heavily

populated regions.

3. Engineers used an extensive network of

tunnels to help carry water from mountain

springs to cities and villages

1. Before there were trains and cars, there

were transportation tunnels such as canals.

2. Canals are artificial waterways used for

travel, shipping or irrigation purpose.

3. Trains and cars had replaced canals as the

primary form of transportation, leading to

the construction of bigger, longer tunnels.

Shield Tunnelling Method

CUT and COVER Tunnelling Method

Classical Method

Drill and Blast

Tunnel Boring Machines

Tunnel Jacking

This method involves the use of shield

machine to drive the tunnels below

the ground.

This construction method causes

minimal disruption to traffic and the

environment because all the work

takes place below ground and the

ground level environment is

unaffected.

This construction method, whereby the site is fully excavated, the structure built and then covered over, uses diaphragm walls as temporary retaining walls within the site area.

Step one : Construction of diaphragm walls, pin piles, and decking.

Step two : Excavation within the diaphragm walls, installing struts as work progresses.

Step three : Construction of permanent floor slabs and walls.

Step four : Fitting out the internal structures, backfilling, and reinstating the surface structures.

Tunnel engineers, like bridge engineers, must be concerned with an area of physics known as statics.

Statics describes how the following forces interact to produce equilibrium on structures such as tunnels.

Tension, which expands, or pulls on, material.

Compression, which shortens, or squeezes material.

Shearing, which causes parts of a material to slide past one another in opposite directions.

Torsion, which twists a material.

The tunnel must oppose these forces with strong materials, such as masonry, steel, iron and concrete.

In order to remain static, tunnels must be able to withstand the loads placed on them.

Dead load refers to the weight of the structure itself .

Live load refers to the weight of the vehicles and people that move through the tunnel.

Reduction of harmful effects during

construction.

Preservation of the forested land.

Avoidance of harmful effects in residential

areas (Noise pollution).

Limitation of harmful effects on historic

monuments.

Reduction of greenhouse gas emissions.

Traffic congestion control.