Compression-shear fracture and energy evolution in rock-like materials under hydraulic-mechanical coupling effect

The mechanical behavior of fractured rock masses under the operation of hydraulic-mechanical coupling is of enormous practical relevance, and the failure process gives theoretical support for disaster avoidance and mitigation of high hydraulic pressure catastrophes in deep mines. In this study, conventional triaxial compression tests of rock-like materials with single-fissure are carried out under different confining pressures and hydraulic pressures, and a compression-shear fracture criterion is also derived. According to the experimental findings, the peak strength, residual strength, and elastic modulus all degrade with the hydraulic pressure and increase with confining pressure, the mechanical characteristics are at their lowest at the fracture angle of 45°. Meanwhile, the critical hydraulic pressure and initial fracture strength of a single fracture rock mass are established for pure tensile failure, pure shear failure, and compression-shear combinations failure. The link between the stress intensity factor, compression-shear coefficient, hydraulic pressure, confining pressure, and crack angle is also examined in the Zhou qunli compression-shear fracture theory. Finally, based on the energy release theory, the presence of hydraulic pressure intensifies the internal microfracture sprouting and external macrofracture initiation, expansion and penetration of the specimen, which leads to the transformation of elastic release energy to dissipation energy, whereas the confining pressure behaves in the opposite way.