卸荷作用下砂岩力学特性及能量演化规律研究OA

Laboratory experiments were conducted to investigate the mechanical properties and energy evolution laws of rocks under unloading conditions.The results indicate that:Unloading damage has obvious influence on the reloading peak strength of rock samples,with the peak strength demonstrating a nonlinear decreasing trend as the unloading magnitude increases.During unloading tests,the deformation modulus of rock specimens exhibited a nonlinear reduction trend with increasing unloading magnitude,and the reduction amplitude demonstrated a positive correlation with the initial confining pressure.As the degree of unloading damage intensified,the failure mode transitioned from shear-compression to tensile-shear during reloading-induced rupture.Compared with triaxial loading conditions,the cohesion of unloaded rock specimens was reduced by 21.2％,while the internal friction angle increased by 16.2％.The shear strength parameters of specimens subjected to unloading-reloading exhibited intermediate values between the aforementioned two conditions.During the unloading process,the elastic energy,dissipated energy,and energy storage limit exhibited synchronous increases with the initial confining pressure,while the proportion of dissipated energy demonstrated a positive correlation with the unloading magnitude.The unloading damage variable is defined as the ratio of dissipated energy under specific unloading magnitudes to the dissipated energy at unloading-induced failure,serving as a quantitative indicator of rock damage evolution during unloading processes.Experimental observations reveal that the rock damage degree exhibits a monotonic increase with escalating unloading magnitudes.