stress measurement in the Mizunami Underground Research Laboratory, Japan

Sato, Toshinori  ; Tanno, Takeo; Hikima, Ryoichi*; Sanada, Hiroyuki; Kato, Harumi*

Japan Atomic Energy Agency is operating underground research laboratory projects in order to establish a firm scientific basis for safe geological disposal of HLW. One of these is the Mizunami Underground Research Laboratory (MIU) project focused on crystalline rock. Rock mechanical studies, including stress measurements, are being conducted as part of the projects. This paper describes the current status of in situ stress studies conducted in the MIU. Applicability of high-compliance system for hydraulic fracturing was evaluated and the maximum stress values were revised. Core disking was observed with groundwater flow in galleries at the depth of GL.-200m, during the Compact Conical-ended Borehole Overcoring (CCBO) test was adopted. To simultaneously estimate regional stress fields and the elastic modulus of rock mass from in situ stress measurements, back analysis methods based on three-dimensional finite element analysis and the boundary element method were developed.