Application of differential strain curve analysis to the Toki Granite for stress determination at the Mizunami Underground Research Laboratory, Japan

Sanada, Hiroyuki; Hikima, Ryoichi; Tanno, Takeo; Matsui, Hiroya ; Sato, Toshinori  

In this paper, application of DSCA to the Toki Granite in the region around the MIU is described. The purpose of this study is to confirm the reliability of DSCA in characterising crystalline rocks and to understand stress conditions around the MIU. For verification of in situ stress measurement results obtained in this study, they were compared to in situ stress measurement results from hydraulic fracturing studies and regional stresses estimated from stress indicators such as triangulation etc. in the Tono region of Central Japan. Based on the comparisons carried out in this study acquired by DSCA, the maximum principal stress direction in the MIU area was estimated to vary from N to W, which corresponded with stress indicators. Principal stress ratios decreased with depth in the region, with the exception of stresses in a fault zone.