ABSTRACT
During last sixty years several kilometres of tunnels have been constructed in Himalaya in connection with hydropower projects. Most of these projects have faced problems related to excessive support pressures, occurrences of clay pockets, seepage water and hazards associated with Himalayan tectonics like mountain-stresses, abnormal rock loads and geothermal gradients etc. It is therefore necessary to evaluate support pressures and requirements judiciously. The present paper describes rock mass characterization and evaluation of support pressure for head race tunnel of Nathpa Jhakri power project in Himalaya.
