围压卸载速度对岩石动力强度与破碎特性的影响

Effects of unloading rates of confining pressure on dynamic strength and fragmentation characteristics of rock under impact loads

利用带轴向静压和围压装置的霍普金森压杆设备,对砂岩在不同围压卸载条件下的动态力学性能进行试验研究,即保持轴压和冲击条件不变,改变围压卸载速度的动静组合冲击试验,着重研究了围压卸载速率对岩石动态强度及损伤的影响。实验结果表明:在仅改变围压卸载速度条件下,当卸载速度在0.5～10 MPa/s范围内变化时,砂岩动态抗压强度、能耗密度随围压卸载速度增大而降低;破坏块度分维数则呈现出随围压卸载速度增大而增大。但当卸载速度增大到200 MPa/s时,其动态抗压强度、能耗密度反而增加,而破坏块度分维数则降低。

By means of the improved SHPB with axial pre-pressure and confining pressure,experimental studies on the dynamic mechanical properties of sandstone under different unloading confining pressures are performed.In the experiments,the sandstone specimens are subjected to the static-dynamic coupling loads with fixed axial static pressure and impact energy and various rates of unloading confining pressure.The effects of unloading rates of confining pressure on rock dynamic strength and damage are investigated.The results show that when the unloading rates vary in the range of 0.5-10 MPa/s,the dynamic strength and energy density of sandstone gradually decrease,but the fractal dimension gradually increases.However,when the unloading rate reaches 200 MPa/s,the dynamic strength and energy density increase,and the fractal dimension decreases.