Tunneling

-TUNNELING -

 INTRODUCTION:- 1) Excavation of tunnels are required for roads, railways, canals, power projects etc. 2) Geological conditions are the most important factor affecting it ( types of rock and structure).3) Difficulties most commonly meet with in tunneling such as roof collapse, cavity in of sides, occurrence of ground water.4) Therefore an accurate knowledge of geological condition along the alignment is necessary for proper designed construction of tunnel.

 GEOLOGICAL INVESTIGATION :- 1) The importance of geological investigation of the site.

a) In selecting the right alignment,

b) In selecting right kind of machine and equipment required for tunneling.

c) In making an estimate cost and time.

2) The geological investigation of site is very important if it is neglect it starts to serious effect.   

3) The correct geological procedure to investigation is surface survey first and then subsurface exploration.

4) Detailed ground water studies is essential to avoid the serious effect of ground water.

5) The final geological section will indicate the geological condition along the alignment and if any features likely to cause trouble are seen the alignment is changed to avoid them provided. There is scope for changing the alignment. Eg:-

1) Sundar rigar sutlag tunnel was realigned to avoid a fault.

2) Giri and Yamuna Hydro electric project tunnel.

Ex:- At muladam Nagar dist. The proposal for a tunnel outlet for river bank canal was given up when geological examination carried out shows that excavation lay in highly jointed C. B. having trouble to continues roof falls.

                 It is however not always possible to change the alignment to suit geological consideration. However the alignment most suitable from geological point of view was not found suitable from engineering point of view.

6) The design and cost of tunnel depends not only on the type of rock but also structure of rock.

7) The structural features of the rock through which if tunnel is passing. It is always play a major role in proper planning, excavation and successful working of tunnel.

Que :- Discuss the importance of geological investigation while deciding suitable site for a tunnel. Explain a different feature with neat sketches.

Que :- Discuss in details the significance of geological structure.