Experimental study on the mechanical properties and energy dissipation of granite during the fracturing process

The conventional triaxial and cyclic loading-unloading tests with acoustic emission monitoring at different confining pressures were conducted to investigate the fracture process and failure characteristics of granite under confining pressure. This study compares the evolution of mechanical parameters，acoustic emission characteristics，energy dissipation patterns，and the effects of confining pressure under two stress paths. The results indicate that：(1) under both stress paths，peak strength，residual strength，axial peak strain，elastic modulus，and Poisson's ratio increase with the confining pressure. The elastic modulus during cyclic loading-unloading is lower than that observed in conventional triaxial tests，while the Poisson's ratio is higher. (2) The ringing ratio in conventional triaxial tests correlates well with the crack propagation stage of the rock samples，whereas the acoustic emission activity during cyclic loading-unloading exhibits a clear Kaiser effect，with a higher peak ringing ratio compared to conventional triaxial tests. (3) As axial strain increases，the input energy，dissipated energy，and elastic energy for cyclic loading-unloading initially increase and then decrease，while for conventional triaxial tests，both input and dissipated energies gradually increase，and the elastic energy follows a similar trend. (4) Under both stress paths，input energy，dissipated energy，and elastic energy increase with confining pressure，with both paths exhibiting similar input energy levels. However，the dissipated energy in conventional triaxial tests is greater，while the residual elastic energy in cyclic loading-unloading is higher. The failure patterns revealed in this study provide significant insights for the stability analysis of deep underground engineering，the degradation patterns of rock parameters，and disaster prevention and control strategies.