hiu send the request as mentioned

A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.Tunnel engineering makes possible many vital underwater and underground facilities. the constructors and users of these facilities are to be protected from the extreme environments and as a result, special construction methods are to be adopted while the construction of tunnels.most often high pressures and extreme conditions have to be withstood by the tunnels.
The kind of soil and/or rock through which they will pass, the depth, the obstructions to be encountered along the route etc are the factors that determint the method of construction of the tunnel. The different methods are:
-cut-and-cover construction,
-drill and blast,
-tunnel boring machine (TBM),
-immersion of prefabricated tunnels,
-sequential excavation methods (SEM).

Metods such as ground freezing and tunnel jacking are used less frequently as they are complex. Internal space, design life, and similar requirements of the tunnel must be defined at first. The design loading conditions
must then be established for the tunnels and this includes the acceptable conditions if the tunnels is under the extreme conditions.

get the report here:
http://scribddoc/23609526/20-TUNNEL-ENGINEERING