Evaluation of applicability of a new quantitative rock mass classfication method at the Mizunami Underground Research Laboratory

Asai, Hideaki; Kuji, Masayoshi*; Horiuchi, Yasuharu; Matsui, Hiroya 

Considering the design, construction and safe operation of large underground facilities such as for the geological disposal of high-level radioactive waste, an important requirement is to utilize a rock mass classification method that can estimate site specific rock mechanical properties based on surface-based investigations and geological observations during excavation. For this study, a new quantitative rock mass classification method based on the Japanese Geotechnical Society standard was proposed and applied to the sedimentary formations and the granite at the Mizunami Underground Research Laboratory. The results were compared with the rock mass classification system developed by the Central Research Institute of Electric Power Industry and commonly used in Japan. Then the applicability of the new rock mass classification could be evaluated.