ABSTRACT
Tunnels, like any other structure require proper maintenance, which calls for periodical structured inspection and follow up action. Unlike any other over ground structure, tunnels are subjected to the stresses caused by the passing loads, have to withstand the forces exerted by the surrounding ground and overburden. While the older tunnels were generally bored through rocks and geologically more stable and settled soils, many of the newly constructed and under construction tunnels are through challenging geological conditions. Thus their maintenance throws up more challenges.
