Support pressures in powerhouse cavern in weak rocks - A case study

An underground powerhouse chamber at chibro was constructed about two decades ago in dolomitic-lime stone of lower Himalayan region. Long-term instrumentation was planned during construction to check the safety and adequacy of the support system and to monitor the post construction behaviour of the excavation. The present paper essentially deals with the analysis of ten year data. The observed roof support pressure has been compared with the support pressures estimated from different empirical theories. The time-dependent effect has been noticed significantly where the rock mass is saturated due to seepage problem and near thick plastic shear zone.