循环剪切荷载作用下岩石节理宏细观力学特性研究

Research of Macro and Micro Mechanical Characteristics of Rock Joints under Cyclic Shear Loading

借助颗粒流程序(PFC)建立了含有起伏节理的岩样模型,开展了4种法向应力下的循环剪切数值试验。根据试验结果,从宏观方面讨论了剪切应力-位移曲线在4个阶段的峰值应力变化特征。基于PFC软件内嵌的fish语言,编制了裂纹扩展过程监测模块,从细观角度描述了节理试样在循环剪切过程中裂纹扩展规律和破坏模式。经分析发现,裂纹主要集中在节理凸起处,节理起伏度和法向应力对试样的破坏模式有着重要影响。通过追踪微裂纹的数量对试样破坏规律进行量化分析,结果与裂纹示意图中得到的规律保持一致。循环剪切过程中,裂纹扩展相对于剪切应力增长来说,有滞后效应且对其有抑制作用,很好地揭示了节理试样在抵抗剪切荷载时的力学机制。

With the help of particle flow code(PFC),a rock sample model with undulating joints was established,and cyclic shear numerical tests under four normal stresses were carried out.According to the test results,the peak stress variation characteristics of the shear stress-shear displacement curve in four stages are discussed from the macroscopic aspect.Based on the fish language embedded in PFC software,a crack propagation process monitoring module was developed to describe the crack propagation law and failure mode of joint specimens during cyclic shear from a microscopic perspective.Through analysis,it is found that the cracks are mainly concentrated in the joint protrusions,resulting in different degrees of joint failure.The joint undulation and normal stress have an important influence on the failure mode of the sample.The failure law of the sample was quantitatively analyzed by tracking the number of microcracks,and the results were consistent with the law obtained in the crack schematic diagram.In the process of cyclic shear,the crack propagation has a hysteresis effect and an inhibitory effect on the shear stress growth,which well reveals the mechanical mechanism of the joint specimen in resisting shear load.