Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

Rock stress measurements are performed by the calcite strain gauge (CSG), the differential strain curve analysis (DSCA) and the compact conical-ended borehole overcoring (CCBO) in order to measure and to estimate the state of stress with respect to the Torigata limstone open pit mine of Kochi prefecture in Japan. And also the back analysis in terms of the regional stress field is adopted to afford the basic data for estimation of rock slope stability on this mine. CSG technique is to measure paleostress, and DSCA and CCBO techniques are to clarify present-stress. The maximum principal strain measured by CSG was oriented to NW-SE with a low inclination. This direction is in agreement with the maximum principal direction of discontinuities developed near mine. The state of stress by DSCA was indicated NW-SE which is the same with that by CSG. It means that this is not the directions of microcracks generated by in-situ stress, but is accordance with those generated in the process of stress relief of paleostress. In the state of present-stress, the maximum principal stress was to NE-SW which was estimated by the back analysis using the 3-D finite element method based on the results of rock stress measured by CCBO, and is different from that by above two methods. It is suggested that the state of stress in study area might be changed NW-SE of the past into NE-SW of a present-day, moreover, is strongly affected by the Philippine sea plate, one of the tectonic plates acting on the Japanese Islands.