不同应变速率下非贯通裂隙介质的力学特性研究

Mechanical properties of fractured media containing intermittent fractures at different strain rates

针对地震、爆破等动力荷载作用下节理裂隙岩体的稳定性问题,采用含2条、3条闭合非贯通裂隙的类砂岩模型试样,对应变速率为1.7×10-5s-1、1.7×10-3s-1、1.7×10-1s-1条件下的含裂隙试样进行了单轴加载试验。结果表明:裂隙试样的变形与内部裂隙的贯通过程紧密相关,且呈现显著的局部化渐进破坏特征;随着应变速率的增加,裂隙试样应力-应变曲线斜率显著增加,裂隙试样与无裂隙试样弹模差别减小;不同应变速率下裂隙试样强度明显受控于裂隙的空间位置,且共面非贯通裂隙试样在倾角为35°左右时峰值强度呈现最低值,这与贯通裂隙试样在60°左右时强度出现最小值不同;不同应变速率下含3条预制裂隙试样破坏时的强度与预制裂隙间的贯通模式有关,且与发生相同贯通模式时的含2条预制裂隙试样峰值强度基本相同;裂隙试样峰值强度随应变速率的增加而增加,且含3条裂隙试样强度增幅较含2条裂隙试样、无裂隙试样明显,即随着应变速率的提高,含裂隙试样的弱化作用降低。

Aimed at the dynamic stability of fractured rock mass under earthquake and explosion loading, the mechanical properties of the fractured specimens were studied under uni-axial loading with strain rates 1.7 ×10^-5s^-1, 1.7×10^-3 s^-1, 1.7×10^-1s^-1. The specimens used in this study were made of sandstone-like modeling material and contained two or three intermittent fractures with different geometric distributions. It was shown that the deformation properties of the specimens were correlative with the process of fractures coalescence, and presented localized and progressive damage. With the strain rate increasing, the moduli of specimens increased and the differences between fractured and non-fractured specimens diminished. The peak strengths were primarily dominated by its geometry, and the minimum for the specimens containing co-planar fractures appeaed at 35° inclination angle which was different with that for the specimens containing continuous fractures whose minimum appeared at about 60° . The peak strengths for specimens with three fractures depended on the coalescence modes, and its strengths were close to those for specimens with two-fractures whose were similar to coalescence modes. Moreover, the peak strengths increased with the strain rates, and the extent of strength increment for specimens with three fractures was more obvious than that for speeimens with two fractures and non-fractured specimens. Thus the conclusion that the weaken effect of the fractures might be lowered with the strain rate increasing could be obtained.