Tunnels are dug in sorts of materials fluctuating from delicate mud to hard shake. The technique for burrow development relies upon such factors as the ground conditions, the ground water conditions, the length and distance across of the passage drive, the profundity of the passage, the coordination of supporting the passage removal, the last utilize and state of the passage and proper hazard administration.
There are three fundamental kinds of tunnel construction in common use:
· Cut-and-cover tunnel (constructed in a shallow trench and then covered over)
· Bored tunnel, constructed in situ, without removing the ground above. They are usually of circular or horseshoe cross-section.
· Immersed tube tunnel, sunk into a body of water and laid on or buried just under its bed.