Tunnel Engineering

Shubham d. dabhade

Contents Tunnel Alignment

Tunnel Lining

Tunnel Lighting

Tunnel Alignment

Selection of Route for tunnels depends on following factors:Natural features, topography &

convenience for entrance and exitEase of securing the right way of tunnels

from its ownersFor sewer tunnels its better to locate

them under local streets where there is little development

Tunnel Alignment

For economy and ease of construction generally a straight alignment is preferred

Ground Conditions – which can be determined by geological investigations, to find the ground which may be tunneled most economically.

New Austrian Tunnelling Method (NATM)

Tunnel LiningLining of tunnel suggests the temporary

or permanent support to the tunnel roof and walls.

While construction tunnels are provided with temporary lining which is replaced by permanent lining after construction.

Purpose of LiningSaves rock from air slakeFor water tunnels, lining gives smooth

surface reducing turbulence.Adds to the structural strength.Gives correct Shape to tunnel.Withstands soil pressures in soft soils.Supports loosened rock pieces during

blasting.Prevents water percolation.

Types of LiningTimber LiningIron LiningCast-Steel LiningPressed Steel Liner PlatesBrick LiningStone Masonry LiningConcrete and R.C.C. Lining

Ex.-Concrete or R.C.C. LiningIt is most commonly used now-a-days.Thickness of the concrete lining

depends on:Condition of the groundSize and shape of cross sectionRelative horizontal and vertical

pressures on liningConstruction conditionsInternal pressure (Water tunnels)Ultimate use of the tunnel.

Concrete or R.C.C. Lining

Concrete or R.C.C. LiningAdvantages:

Concrete being plastic allows packing between forms and ground.

It is water tight.It provides smooth surface.Its thickness can be controlled

easily.Reinforcement of steel is easy for

increasing strength.

Tunnel LightingTunnels require lighting while construction

and also after construction.

A light intensity of 260 lumens is said to be satisfactory.

For lighting Oils, Coals, Acetylene gas were used formerly, but nowadays electric lighting is most preferred.

Need of LightingOperation and Equipments StationSwitches, turnouts and passing tracksDrilling and Mucking ZonesOn Drill CarriagesUnderground material supply and storage

pointsAt all obstructionsComplete lighting after construction for

utility of vehicles, etc.

Electric LightingIt is most commonly used for lighting in tunnels and also is a most perfect source.

Advantages:Furnish Steady and bright lightDoes not consume oxygenNo offensive gases are given offEasy for wiring and extensionLamps may be easily adjusted for intensity desired.

Thank You