围压卸荷条件下砂岩损伤与动态破碎特性研究

为研究深部高应力岩体开挖卸荷对围岩的影响,运用自制的带轴向静压和围压装置的霍普金森压杆(SHPB)设备,开展不同速度围压卸荷试验。结合围压卸荷过程砂岩试样声发射特性及动态加载后试样破碎块度分维特性,分析围压卸荷速率对试样损伤的影响。试验结果表明:当卸荷速率在0.5～10 MPa/s范围内变化时,砂岩损伤、声发射能量及破碎分形维数随围压卸荷速率增大而增大;但当卸荷速率增大到200 MPa/s时,砂岩损伤、声发射能量及破碎分形维数反而减小。在一定范围内提高围压卸荷速率,有助于提高砂岩试样裂隙发育及损伤程度。

Research on Damage and Dynamic Fragmentation Characteristics of Sandstone under Unloading with Confining Pressers

In order to research influence of excavation unloading on surrounding rock of high stress rock mass,unloading confining pressure tests of sandstone were conducted with a modified triaxial split Hopkinson pressure bar(SHPB) coupled static and dynamic loads.Based on the unloading confining pressure tests with triaxial high stress under conditions of different unloading rates,the effects of unloading rate of confining pressure on rock damage were analyzed by acoustic emission and fractal dimension characteristics with the confining pressure unloading process.The results show that varies in the range of 0.5-10 MPa/s,the damage variable and acoustic emission energy and fractal dimension of sandstone gradually increase with the unloading rate,that when the unloading rate reaches 200 MPa/s,the damage variable and acoustic emission energy and fractal dimension decrease,and that within a certain range,the increase in the unloading rate contributes to the sandstone test sample's greater crack and damage growth degrees.