ABSTRACT
Lining is provided inside the tunnel section with masonry or concrete and /or by shotcreting to provide support to the cavity against thrust from surrounding ground. The internal dimensions and shapes of tunnel after lining should be in conformity with the minimum section required for the tunnel. Conveyance tunnels, such as water and sewage tunnels, have to be necessarily lined in order to give a smooth surface for the flow of water, to prevent any leakage/seepage and also to serve any structural purpose that may be needed for withstanding inside/outside pressures. Traffic tunnel bored through hard rock which can stand on its own need not be lined unless it is intended to have a pleasing and smooth surface inside for the purpose of aesthetics and cleanliness.
