三轴SHPB加载下砂岩力学特性和破坏模式的试验研究

利用改造的三轴SHPB动静组合加载实验装置，对均质砂岩进行了不同围压和不同应变率下的三轴冲击压缩试验，作为对比利用RMT-150C试验机也进行了部分准静态下的三轴压缩实验。根据实验结果，分析了围压对砂岩动态冲击性能的影响，并重点讨论了冲击过程中岩石的破坏模式。研究结果表明，在围压一定的情况下，岩石的动态压缩强度随应变率的提高而提高；在应变率相同的情况下，岩石的动态压缩强度和弹性模量会随着围压的增大而增大。岩石发生破坏的临界入射能，随着围压的增大而增大。岩石单位体积吸收能与应变率之间呈线性递增关系，而且递增的程度随着围压的增加而增加。三轴冲击加载下，应变率较低时岩石内部形成压剪破裂面但整体不失稳，应变率很大时岩石破碎形成锥形块体形式。

Tests for sandstone mechnical properties and failure model under triaxial SHPB loading

Dynamic triaxial compression tests of sandstone were conducted with a modified triaxial split Hopkinson pressure bar(SHPB) coupled static and dynamic loads.For the comparison,the quasi-static triaxial compression tests were also conducted with RMT-150C device.The influence of confining pressure on dynamic characteristics of sandstone and its failure model in impact tests were analyzed based on the experimental data.The results showed that the dynamic compression strength of sandstone increases with increase in strain rate when the confining pressure is a constant;when the strain rate is a constant,the dynamic compression strength and the elastic modulus of sandstone increases with increase in confining pressure;the critical incident energy for rock failure increases with increase in the confining pressure;there is a linear increasing relationship between the energy absorption per unit volume of rock and strain rate;under the triaxial dynamic impact,there are some compression-shear breaking surfaces inside rock and rock keeps stable when the strain rate is low,when the strain rate is high,rock failures and breaks into some cone-shaped blocks.