A study on rock mass crack propagation and coalescence simulation based on improved numerical manifold method (NMM)

As an emerging numerical calculation method, the numerical manifold method (NMM) has incomparable advantage in solving continuous and discontinuous deformation problems in a unified framework. In this study, an improved numerical manifold method was deployed to solve the crack propagation and coalescence problem with cracking friction effect in fractured rock mass. Firstly, based on the basic theory of NMM, the structural surface roughness JRC coefficient was introduced into the friction matrix, and the numerical manifold matrix derivation of the friction matrix is embedded into the original software package, which enhanced the NMM calculation program module. A new method of numerical manifold displacement method for solving crack propagation problem is proposed. The calculation formula of stress intensity factor in crack propagation process are given, and the program module used to simulate crack propagation process was developed. Furthermore, two case study was introduced to verify the reliability and applicability of the calculation package. Through comparison of the experiment result with the numerical solution of a rectangle flawed red sandstone specimen with prefabricated hole and fissure, it could be certified that the improved method can acquired the accuracy to an extent, and also enhanced the effectiveness of the proposed method for fracture propagation and coalescence behavior under complex geometry.