Failure modes and energy release characteristics of sandstone containing circular holes considering the influence of stiffness degradation

ZHAO Guangming; WU Xukun; LIU Chongyan; XU Wensong; ZHANG Qihang; HAN Guanghui

doi:10.13247/j.cnki.jcumt.20240532

Abstract：Due to the influence of excavation disturbances,the rock mass in roadways inevitably experiences damage,leading to a gradual degradation of its stiffness and strength.To investi-gate the influence of loading modes on the failure characteristics of roadways after stiffness degradation,a two-dimensional variable stiffness dynamic failure simulation test system was u-tilized.Biaxial compression loading tests were conducted on pre-damaged specimens containing circular holes to analyze the impact of loading system stiffness on the failure modes and energy release mechanisms of the damaged specimens under lateral constraints.This study focuses on the failure modes and energy release characteristics of sandstone containing circular holes,con-sidering the effects of stiffness degradation.The results show that the initial degree of damage significantly affects the bearing capacity and elastic modulus of the specimens,with degrada-tion ranges of 0.54％to 7.01％and 5.76％to 50.74％,respectively.Lateral constraints effec-tively inhibit crack propagation and reduce stress concentration caused by the holes,thereby enhancing the structural integrity and overall strength of the rock specimens.Pre-existing damage has a pronounced impact on the failure characteristics of roadways with circular holes.As the degree of damage increases,the time to failure decreases.Conversely,higher loading system stiffness and greater lateral constraint forces significantly extend the time to failure.Based on the principles of energy release and dissipation,the coupling relationship between stiffness degradation and accumulated elastic strain energy was established.It was found that an increase in the stiffness degradation coefficient leads to a reduction in elastic strain energy,with a nonlinear mathematical relationship existing between the two.Furthermore,lateral constraint force is positively correlated with the accumulation of elastic strain energy.The re-search results provide a theoretical basis for understanding the influence of stiffness degrada-tion on the failure mechanism of surrounding rock and the control of stability time-effective-ness.It is proposed that by adjusting the system stiffness and lateral restraint force,the bear-ing capacity and overall stiffness of the surrounding rock can be enhanced at different failure time stages,which can resist the adverse effects brought by damage to a certain extent.