模擬地下環境下における花こう岩の環境強度評価と地下き裂設計への応用

抄録

Environment sensitive fracture is one of the important phenomenon in designing fractures for geothermal energy extraction. Material degradation and environment assisted cracking, stress corrosion cracking (SCC) under constant applied load and corrosion fatigue (CF) under alternating load were investigated in a pressurized high temperature water environment. The test results obtained were applied to two kinds of rock mass according to the permeability, that is, impermeable rock mass and permeable rock mass. In the case of a permeable rock mass, material degradation caused by permeation can reduce maximum pressure for hydraulic fracturing. Crack propagation due to degradation as well as due to SCC and /or CF during long-term service performance is found to be of importance for predicting the stability over the lifetime of the geothermal reservoir. In the case of an impermeable rock mass, conventional fracture mechanics can provide a safe evaluation.