Determination of regional stress state for estimating local stress state (Contract research)

Mizuta, Yoshiaki*; Kaneko, Katsuhiko*; Matsuki, Koji*; Sugawara, Katsuhiko*; Sudo, Shigeaki*; Hirano, Toru; Tanno, Takeo; Matsui, Hiroya 

The best way to know the initial stress clearly is to measure it in the location where a tunnel will be excavated. However, it is difficult to measure a large number of the initial stresses, budgetary considerations notwithstanding, because of the large scale of underground structures like a radioactive waste disposal facility. Therefore we developed a method for determination of initial stress for arbitrary points from limited results of initial stress measurements. This report is a summary of the contract work about this development. At first, we made local scale numerical models of the Tono area. Using these models, we determined the regional stress state from limited initial stress measurements results. Then we applied the regional stress state to boundary conditions of other numerical models and estimated initial stress at arbitrary points. The result is an estimated initial stress that matched the original stress measurement results from the first analytical results.