冲击荷载下轴压对峰后破裂砂岩力学特性的影响

针对深部工程围岩常处于峰后破裂状态且遭受动力扰动影响的特点,利用动静组合加载SHPB实验装置对经静态压缩制备的峰后破裂砂岩进行冲击压缩试验,开展一维动静组合加载下破裂岩石的力学特性研究。试验中预先设置轴向静载为8,24和48 MPa三个系列,然后进行不同应变率下冲击加载,研究轴向静载对峰后破裂砂岩动力学特性的影响。对比完整砂岩试验结果表明:轴向静载8 MPa和相近应变率条件下,峰后破裂砂岩组合强度与冲击强度均低于完整砂岩组合强度与冲击强度,两者变形模量相差不大,但峰后破裂砂岩单位体积吸收能大于完整砂岩单位体积吸收能。轴向静载相同时,峰后破裂砂岩组合强度与冲击强度均随着应变率的增大而增大;轴向静载不同时,峰后破裂砂岩组合强度随着轴向荷载的增大而增大,而冲击强度随着轴向静载的增大先增大后减小。随着轴向静载的增大,峰后破裂砂岩单位体积吸收能也随之增大。动静组合加载下峰后破裂砂岩呈剪切破坏模式,且原始裂纹影响破裂面的扩展方向。

Effect of axial static stress on mechanical properties of post-peak cracked sandstone under impact loading

The surrounding rock mass in deep engineering is always in the post-peak state and suffers the influence of dynamic disturbance.The impact compression experiments on post-peak cracked sandstone samples were carried out to investigate the dynamic mechanical properties of cracked rock under one-dimensional coupled static and dynamic loads by using modified split Hopkinson pressure bar (SHPB) apparatus.The axial pre-compression stress was respectively set as 8,24 and 48 MPa,and the impact loading was carried on to investigate the effect of axial static stress on the mechanical properties of post-peak cracked sandstone under different strain rates.Compared with intact sandstone results,the results show that under the axial static stress of 8 MPa and the similar strain-rate,both the combined strength and the impact strength of post-peak cracked sandstone are lower than that of intact sandstone,and the deformation modulus is essentially the same,but the absorbed energy per volume of post-peak cracked sandstone is higher than that of intact sandstone.Under the same axial static stress,both the combined strength and the impact strength of post-peak cracked sandstone increase with the strain rate increasing.Under the different axial static stresses,the combined strength increases with the axial static load increasing,while the impact strength increases first and then decreases.Axial static stress has an effect on the absorbed energy per volume of post-peak cracked sandstone,and the absorbed energy per volume increases with the increase of axial static stress.The post-peak cracked sandstone is shear failure subjected to the coupled static and dynamic loads,and the original crack influences on the crack propagation direction during the process of impact failure.