Surrounding rock excavation of underground engineering such as tunnels is a typical unloading process.Based on the engineering practice of a tunnel under construction in Liaoning Province,the unloading test of surrounding rock(sandstone)was carried out under complex stress paths,and the deformation and damage mechanisms of the sample under different damage conditions(LD-weak damage,HD-strong damage)were analyzed.For the triaxial unloading condition,the axial strain E1 shows a trend of decreasing first and then increasing in LD state,while in HD state,ε1 shows a trend of gradually increasing when the unloading rate is small(v=0.01 MPa/s),and decreasing first and then increasing when the unloading rate is large(v＞0.01 MPa/s).For triaxial cyclic unloading condition,the radial strain ε3 increases negatively during unloading,the area of the hysteresis curve increases with the increase of the number of cycles,and the negative growth rate of ε3 increases rapidly when the stress is below the minimum stress of the previous cycle.In LD state,the strain response △ε1decreases with the increase of unloading rate;in HD state,the △ ε1 is large when the unloading rate is low,and then it fluctuates.The variation trends of△ ε1 and △ ε3 are different in LD state,△ ε3 increases gradually with the increase of cycling cycles,while △ ε1 has no obvious trend in the first 5 cycling cycles;in HD state,△ ε1 and △ ε3 increase gradually.The research results can provide a theoretical basis for revealing the excavation unloading damage mechanism of the surrounding rock in tunnels and other underground projects.
关键词
隧道围岩/砂岩/应力路径/循环卸围压/卸荷速率/应变响应
Key words
tunnel surrounding rock/sandstone/stress path/cyclic unloading of confining pressure/unloading rate/strain response
维普
万方数据