中文摘要：

利用动静组合加载试验装置,对具有不同轴压和围压的砂岩进行循环冲击试验,研究砂岩抵抗循环冲击载荷能力的变化特性,并重点讨论围压和轴压对砂岩动态疲劳力学特性的影响。围压分别设置为4,8,10和12 MPa四个系列,轴向静载荷分别设置为49,84,105和125 MPa四个系列,入射杆上的入射波大小相等,入射能大小为230 J。结果表明,相同围压下,总循环冲击次数随轴压的增大而减小;相同轴压下,随围压的增加,岩石承受的总循环冲击次数增加。随循环冲击次数的增加,岩石动态峰值应力、加载段的变形模量和弹性应变逐渐减小,动态峰值应变和残余应变逐渐增加。动态峰值应力和平均应变率具有良好的负线性关系;相同围压情况下,随轴压的递增,动态峰值应力和平均应变率拟合直线斜率的绝对值越来越大;相同轴压情况下,随着围压的增加,拟合直线斜率的绝对值越来越小。三维静应力情况下,减小轴压或增加围压有利于提高岩石抵抗外部循环冲击的能力。

英文摘要：

Cyclic impact tests on sandstone under different axial and confining pressures are conducted with a modified three-dimensional split Hopkinson pressure bar（SHPB）, in order to analyze the impact resistance of sandstone with cyclic impact number and to research the effect of axial and confining pressures on dynamic fatigue mechanical properties. Confining pressures are set as 4, 8, 10 and 12 MPa, and four levels of axial static stresses are 49, 84, 105 and 125 MPa, respectively. Incident waves in input bar are approximately constant, and incident energy is 230 J. The results show that total cyclic impact number will decrease with the increase in axial stress when the confining pressure is constant. The total cyclic impact number has an increasing trend with the increasing confining pressure when axial compression is constant. With the increasing cyclic impact number, dynamic peak stress, deformation modulus at loading stage and elastic strain decrease, whereas dynamic peak strain and residual strain increase. Rock dynamic peak stress has a good negative linear correlation with average strain rate. When the confining pressure is constant, the absolute values of linear-fitted slope of dynamic peak stress and average strain rate increase gradually with the increase in axial stress; and when the axial stress isconstant, the bigger the confining pressure is, the smaller the absolute values of linear-fitted slope is. Decreasing axial compression or increasing confining pressure is able to improve rock resistance to cyclic impact loads when the rock is under three-dimensional static stress.