Crack evolution behavior of rocks under confining pressures and its propagation model before peak stress

Abstract

The understanding of crack propagation characteristics and law of rocks during the loading process is of great significance for the exploitation and support of rock engineering. In this study, the crack propagation behavior of rocks in triaxial compression tests was investigated in detail. The main conclusions were as follows: 1) According to the evolution characteristics of crack axial strain, the differential stress-strain curve of rocks under triaxial compressive condition can be divided into three phases which are linear elastic phase, crack propagation phase, post peak phase, respectively; 2) The proposed models are applied to comparison with the test data of rocks under triaxial compressive condition and different temperatures. The theoretical data calculated by the models are in good agreement with the laboratory data, indicating that the proposed model can be applied to describing the crack propagation behavior and the nonlinear properties of rocks under triaxial compressive condition; 3) The inelastic compliance and crack initiation strain in the proposed model have a decrease trend with the increase of confining pressure and temperature. Peak crack axial strain increases nonlinearly with the inelastic compliance and the increase rate increases gradually. Crack initiation strain has a linear relation with peak crack axial strain.