循环冲击对围压作用下砂岩特征的影响

Effect of cyclic impact on sandstone characteristics under confining pressures

利用带围压装置的分离式霍普金森压杆系统对砂岩试样进行不同围压下的循环冲击试验,探讨了冲击应变波的波形特征,并对围压与应力应变、损伤因子等物理量间的关系进行了分析.结果表明:透射波在砂岩试件中传播时存在明显的非线性,并可计算得到砂岩中冲击波的形成距离;砂岩在无围压作用下发生脆性破坏,有围压时表现出明显的弹塑性特征.当围压一定时,应力-应变曲线的上升段斜率随冲击次数增加而减小;当围压增大时,不同冲击次数下的应力-应变曲线差异减小;砂岩损伤因子随平均应变率增大呈幂函数增长,且二者均随围压增加呈现出良好的规律性.

Based on the split Hopkinson pressure bar system with a confining pressure device,the cyclic impact tests on sandstone specimens under different confining pressures were carried out.The waveform characteristics of strain waves were analyzed,as well as the relationship among confining pressures, stress, strain and damage factors. It is demonstrates that the sandstone behaves nonlinear response under impact loads.The shockwave distance of the explored sandstone is calculated.Furthermore,sandstone behaves brittle failure when loaded without confining, but it shows evident elastic-plastic characteristic under confining pressures. When the confining pressure is constant, the slope of the stress-strain curve decreases with the increase of impact number.And a higher confining pressure makes smaller the difference in the stress-strain curves of different impact numbers.A power function relationship exists between damage factor and average strain rate,and both of them change regularly with confining pressures.