16.Which one of the following is considered to be an advantage of the heading and benching method of tunnel construction?

17.American method of tunneling i) is suitable for large sized tunnels ii) is no,' suitable for railway or highway tunnel's iii) requires heavy timbers Of these statements

18.If 'N' is the number of shafts used, then the total number of feces available for attacking the excavation and construction in tunnels are

19.Which one of the following tunneling methods is used for laying under ground sewers ?

20.A good blast with a good yield is obtained if the cut hole is