Dynamic tensile strength weakening effect of pretension stressed red sandstone under impact load冲击载荷下张拉预应力红砂岩的动态张拉强度弱化效应

Tension failure of deep surrounding rock is a very common failure mode, which is closely related to the couple of static pre-stress and impact load. Thus, the dynamic tensile strength of pretension stressed Brazilian disc (BD) specimens subjected to the impact load was measured at the couple different pretension levels and loading rates with the modified split Hopkinson pressure bar (SHPB) system. Six groups of Linyi sandstone BD specimen were impacted with the loading rates from 400 to 1200 GPa/s under the pretension of 0, 0.48, 1.44, 2.39, 3.45 and 4.30 MPa. The test results reveal the dynamic tensile strength has a very significant linear positive correlation with the loading rate, wherein increases gradually with the loading rate increase, reflecting the obvious rate dependency. The dynamic tensile strength decreased significantly with pretension stress level increase at the same loading rate, showing an obvious dynamic tensile strength weakening effect. Besides, the mechanism of the dynamic tensile strength weakening effect is summarized, wherein the pretension stress level dominates and determines the dynamic tensile strength weakening level, and the impact load induces the appearance of the strength weakening effect.