地圧計測のための原位置水圧破砕実験
異方性岩石における水圧破砕に関する実験的研究 (第5報)
1987 年 103 巻 1187 号 p. 1-8
詳細
1987 年 103 巻 1187 号 p. 1-8
The purpose of this report is to discuss the application of the suggested methods for stress determination and pressurizing cycle on hydraulic fracturing to in-situ stress measurement (presented in 4th report). In-situ hydraulic fracturing tests were conducted for four vertical and inclined boreholes. The test site is located at about 600 meters deep level from the surface in Toyoha mine and a rock is green massive dacite.
The stress conditions were determined at the site by selected re-opening and shut-in pressures with high reproducibility. The difference of stress conditions shows that the pressure data used to stress evaluation must be selected by means of repressurizing tests. The comparison of primary and secondary pressure histories show that the tensile strength of dacite at the test site is about 38kgf/cm2 and the energy to extend hydro-fracture is smaller than 60J/m2. The comparison of hydro-fracture impression and fracture form which is imagined on the basis of stress distribution and weakness plane on the borehole wall suggests that the direction of fracture may be influenced by not only the direction of borehole axis and stress condition but also rock anisotropy (Fig. 20).
The suggested method to determine in-situ stress in anisotropic rocks is proved to be apropriate by the experimental study in this report.
