Fracture growth of Brazilian disk with open/closed cracks

Many rock mass hazards and instabilities are tightly associated with the initiation,propagation and penetration of joints and faults. The study of crack propagation mechanism and analytical methods have profound meanings for the prevention of catastrophes. Numerical simulation is favored by researchers,as an effective rock failure analysis method. However,current simulation methods will encounter the unrealistic issues of zigzag propagation path,grid dependence,and limited propagation length when analyzing complex fracturing such as the compression-shear closed. To solve this,the present study explores the effects of various fault types(open,closed,filled),contact friction,fault inclination and other physical and mechanical parameters on both the fracture propagation characteristics and the fracture mechanism by taking Brazilian disc as the basic research object. First,based on the theory of rock fracture mechanics and the stress field at the crack tip,the maximum tangential stress criterion(MTS) is used to study the propagation process of open and closed faluts,and the potential reasons why zigzag propagation path occurs are analyzed. And the issues of traditional methods are discussed in fast and effective simulation of fracture propagation path. Second,a fracture simulation method of rock mass based on fracture localization theory for quasi-brittle material is established,which avoids inaccurate calculation of fracture parameters and significantly improves the operability and accuracy of calculation. In addition,the fracture propagation length is not limited by the grid size by an automatic re-meshing method in the fracture tip,which addresses the grid dependence. Finally,the contact status of the contact surface in the whole fracture process and the mechanical mechanism of fracture propagation are obtained by analyzing the mechanical properties,fracture initiation angle and fracture propagation path. The proposed method boosts the efficiency and accuracy of rock failure process simulation,remedies the insufficient studies on closed crack propagations under compression and shear stress,thereby achieving detailed simulation of fracturing path.