基于颗粒流数值方法的岩石压剪破坏细观特征研究

压剪破坏是影响岩体工程安全的主要因素,基于颗粒流程序的伺服控制原理,采用等效晶质模型模拟了粉砂质板岩的压剪破坏过程,通过与室内试验对比验证了其适用性,并从细观角度揭示了岩石在压剪过程中的破坏机理。结果表明:裂纹增长速率与试件压剪过程中经历的弹性、塑性和破坏3个阶段具有相关性;张拉、剪切裂纹呈同步增长趋势,但峰后张拉裂纹增长速率快于剪切裂纹,即试件峰后以张拉破坏为主;随剪切角增大,由沿晶和穿晶断裂向以沿晶断裂为主转变,裂纹数量减小且扩展方向向断裂面集中;穿晶断裂的扩展更容易导致局部失稳,即在宏观上表现为塑性阶段;穿晶裂纹主要沿断裂面扩展、贯通,一定程度上可以抑制断裂面附近较大破裂块体的产生。

Meso-characteristic research on the rock of compression and shear failure based on the particle flow numerical method

Based on the servo principle of particle flow code( PFC2D),this paper has proposed a loading method for the numerical simulation of the variable-angle shear test. At the same time,this paper has also observed and analyzed the rupture surface fracture features of the silt slate as a result of compression and shear failure by means of the electronic microscopy scanning. In addition,we have also analyzed the mineral composition of the silt slate of the rock layers with the X-ray irradiation,so that we can construct an equivalent crystalline model,which proves to be in conformation of its microstructure features. Thus,we have successfully simulated the compression and shear failure process of the silt slate through the model,by verifying the model and comparing it with the laboratory tests. And,so,it can be seen that,compression and shear failure should be taken as the chief factors affecting the safety of the rock mass engineering research circle. And,finally,according to the fracture and propagation particularities of the cracks,this paper has revealed the intrinsic mechanism of the macroscopic compression and shear failure of the rocks from the mesoscopic viewpoint. The study also indicates that: in the process of compression and shear failure,the crack growth of the specimens may experience a stable growth process,a fast growing period and the fastest growth after the peak growth period,which should be correlated with the 3 stages of elasticity,plasticity and failure in compression and shear process of the specimens;whereas the tensile and shear cracks show a synchronous growth trend. Nevertheless, the growth rate of the post-peak tension crack is faster than that of shear crack,namely,the tensile failure has to be dominant after the peak growth. And,after the compression and shear failure,the cracks on the fracture surface of the equivalent crystalline model tends to reveal a combination trend of the transgranular fracture and intergranular fracture. And,then,with the increase of the shear angle,the transition trend from the intergranular and transgranular fractures to the intergranular fracture ought to be dominant,however,on the contrary,while the number of cracks decrease gradually,the direction of the crack propagation tends to be focused on the fracture surface. In addition,the friction induced by the normal stress on the fracture surface tends to play a positive role in the transgranular failure,though the growth and propagation of the transgranular fracture are more likely to cause the local instability, namely, into the macro-plastic stage.Hence,the transgranular cracks can mainly appear and propagate along the fracture surface and then tends to be intersected with the intergranular cracks,such a combination may in turn lead to the prohibition of the appearance of large fracture blocks near the shear surface to a certain extent.