非均匀岩石裂纹扩展机制的数值分析

应用东北大学开发的RFPA2D软件,通过数值手段对预制裂纹的非均匀岩石单轴加载条件下的裂纹扩展模式进行了研究,结果表明:非均质度越差,材料的破坏峰值强度越低;裂纹扩展模式受岩石均质度制约,当岩石的均质度较低时,裂纹扩展表面粗糙,且呈现断断续续方式扩展,并且在扩展中出现跳跃方式,与均质岩体有本质区别;均质岩体AE分布集中于裂纹尖端,而非均质岩体裂纹呈弥散分布,并最终逐渐集中而形成裂纹.

Numerical Studies of Influence of Heterogeneity on Rock Failure With Pre-existing Crack in Uniaxial Compression

Fractures in the forms of joints and microcracks are commonly found in natural rocks,and the heterogeneity of rock is an inevitable and difficult problem to the researchers when they use the rock fracture mechanics,because it has a great influence on the initiation,propagation and coalescence of crack which lead to the eventually failure of rock mass.Therefore,it is important to examine how the crack behaves in rock of different heterogeneity.To overcome the difficulties in analytical model studies,a numerical code,RFPA~2D(Rock Failure Process Analysis),developed by CRISR,Northeastern University,China,is used to evaluate the effect of the heterogeneity on the fracture processes and strength characterization of brittle rock containing the single pre-existing crack under uniaxial compression loadings.The numerical simulation reproduces the evolution of the stress and strain fields in crack propagation process,the mode of acoustic emission related to the heterogeneity of rock and the phenomenon of rock bridge related to discontinuous failure.It is shown that the lower the value of the homogeneity index,the bigger influence of local variation on the propagation process of the pre-existing crack,and microfractures the more randomly distributed throughout the specimen.Studying the details of macrofracture formation in relatively homogeneous specimens,it is interesting to find that there exists a'constant jump'propagation pattern of the wing crack,which is responsible for the formation of the rock bridge.The numerical results also demonstrate that the stress-strain relation and strength characterization depends strongly on the heterogeneity of the specimen,the shape of the heterogeneous rock has a gentler post-peak behavior,while the more homogeneous specimen has a higher strength,and accordingly,the curve becomes more linear and the strength loss is also shaper.