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

Kuji, Masayoshi*; Asai, Hideaki*; Hashizume, Shigeru; Horiuchi, Yasuharu; Sato, Toshinori  ; Matsui, Hiroya 

Rock mass classifications are used for design and construction of underground structures. However, the classification methods commonly used in Japan are qualitative and inadequate for estimating the actual mechanical properties of a rock mass based on site specific geological features. Considering the design, construction and safe operation of large underground facilities, 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 JGS standard was proposed and applied to the sedimentary formations and the granite at MIU. The results were compared with the rock mass classification system developed by CRIEPI and commonly used in JAPAN. Then the applicability of the new rock mass classification could be evaluated.