Abstract: Since underground water-sealed caverns are mostly of large span, high sidewall, with no lining or less lining, the building rock are mostly granite and granitic gneiss of good quality. The existing rock mass classification could not well distinguish the levels of rock quality. Having determined the main factors affecting rock mass quality, we proposed a rock mass classification system of Underground Water-sealed Caverns Quality (UWCQ). The RQD (rock quality designation), spatial distribution and roughness of joints, groundwater, geostress and pressure were taken into consideration in the system. The system was applied to evaluate the rock mass quality of Huangdao underground water-sealed caverns. Results show that the UWCQ system is feasible and could meet the engineering requirements. It’s of engineering significance for the excavation, support, and safety evaluation of underground water-sealed caverns.

Key words:  rock mass classification, UWCQ system, underground water-sealed caverns