Question 161.   For initial surveys of tunnels, the following activities are involved : 1. Marking portal point with concrete pillars on the ground 2 Marking tunnel obligatory points on the topographical maps 3. Preliminary setting of the tunnel on the topographical Survey of India maps 3. Driving lines between the fixed obligatory points. The correct sequence of the activities is :

Question 162.  Which one of the following statements is not correct in respect of setting of an inclined tunnel :

Question 163. .  For B.G. single track railway, the height of the tunnel above top of rails should be

Question 164. .  For B.G. single track, the section of the tunnel must have a width

Question 165.   For transferring the'tunnel alignment through shafts, we adopt the following steps : 1. Hanging two or more plumb lines in the shaft 2. Determining the bearing of the plumb lines i.e. plumb plane 3. Suspending a 35 kg weight by each plumb line 4. Immersing the weights of both the plumb lines in the buckets containingi,vater. The correct sequence of steps is :

Question 166. .  For tunnels exceeding 300 m in length, the grade should be proded below

Question 167. . The difference of heights of the tunnels above rail tops of BG and MG tracks is kept

Question 168. . The advantages of providing a pair of tunnels as compared to only one large highway tunnel is :

Question 169. .  Which one of the following methods is generally adopted for tunnelling in firm ground

Question 170. .  For full face method, the excavation to be done is generally divided into