Abstract:Based on analysis of thermo-hydro-mechanical-chemical (THMC) coupling mechanism for brittle rock, THMC coupling indicator in terms of rock porosity was introduced to represent the influencing degree of THMC coupling field on stress field in order to establish THMC coupling fracture criterion. A novel real-time measurement method of permeability (related to porosity) was proposed to determine the THMC coupling indicator, and self-designed THMC coupling tests and scanning electron microscope tests were conducted on pre-cracked red sandstone specimens to study the macroscopic and microscopic fracture mechanism. Research results show that the higher the hydraulic pressure is, the smaller the crack initiation load is and the easier the Mode I fracture occurs. Test results are in good agreement with prediction results (crack initiation load and angle, and fracture mode), which can verify the effectiveness of the newly established THMC coupling fracture criterion. This new fracture criterion can be also further extended to predict THMC coupling fracture of multi-crack problem.

Key words: THMC coupling; fracture criterion; THMC coupling indicator; brittle rock