22. The length of the needle beam used in needle beam method of tunnelling is usually
A. 2 m to 4 m
B. 2.5 m to 6 m
C. 4 m to 7 m
D. 5 m to 6 m.
23. Which one of the following statements is not correct with regard to heading and henching method of tunnelling.
A. Driving of tunnel is done in two portions of its section
B. Driving the top portion is done in advance of the bottom portion.
C. After driving the top portion 3 m to 3.5 m holes are drilled into the head and bench.
D. Firing of headholes is done just before the bench holes are fired:
24. WhiCh one of the following statements is not correct for heading and benching method of tunnelling ?
A. Drilling and mucking can be done simultaneously
B. Benching provides a plateform for working on heading
C. Removal of muck from the heading is very easy
D. None of these.
25. The following operations are required for tunnelling in rockYAerrain? 1. Renmving the foul gases 2. Marking the tunnel profile 3. Setting up and drilling 4. Checking misfire 5. Mucking The correct sequence is :
26. Pick up the correct statement regarding drilling a tunnel from the following :
A. Holes are drilled by pneumatically operated rock drills
B. One drill is required for each 4 to 5 m2 force area
C. The diameter of the bore hole at the deepest point should be 6 mm more than the diameter of the cartridge
D. All of the above.
27. The most commonly adopted pattern of cut holes is :
A. horizontal wedge cut
B. pyramid cut
C. fan cut
D. All the above.
28. The cut of a tunnel face is shown in Fig. 24.2. This is called
A. Michigan cut
B. Burn cut
C. Fan cut
D. Horizontal cut.
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