Correct Answer : Bents of steel
Explanation : The provision of soft strata must be done for withstanding the excavation. It can be provided by bents of wood, bents of steel, liner plates and poling, which are placed to retain material between the adjacent bents.
Correct Answer : Option (D) : 2N + 2
Correct Answer : Option (A) : Fire-setting
Explanation : Blasting is the conventional method which is adopted in case of rock tunneling. In the case of fire-setting, tunnel is heated with fire and then cooled with water. Rapid expansion and contraction weakens and rock and tends to break.
Correct Answer : Option (C) : Marking profile
Explanation : Rocky strata involve usage of blasting method for developing tunnels. The sequence contains marking profile, loading explosive, removing foul gases, checking, scaling, mucking and bolting.