Hybrid finite-discrete element simulator based on GPGPU-parallelized computation for modelling crack initiation and coalescence in sandy mudstone with prefabricated cross-flaws under uniaxial compression

Discrete element method or extended finite element method is often adopted to simulate crack initiation, propagation, and coalescence. However, the transition of rock from continuous medium to the discontinuous medium cannot be simulated. Moreover, previous studies on propagation and coalescence of prefabricated flaws often focus on single or multiple parallel prefabricated flaws. In reality, the fractures in rock mass usually exist in the form of cross flaws. To solve the inconsistency, the uniaxial compression of rock samples with prefabricated crossflaws is modelled in this study through the GPGPU-parallelized Y-HFDEM IDE, and the modelling results are compared with those from laboratory experiments. The effects of four geometric parameters of the prefabricated cross-flaws on the crack initiation, propagation, and coalescence process are explored: (1) the joint continuity parameter k, (2) the angle ? between the axial load direction and the dip direction of the primary flaw, (3) the angle ? between the direction of the rock bridge and the dip direction of the primary flaw, and (4) the angle ? between primary and secondary flaws. It is found that numerical simulation results are in good agreement with those of laboratory experiments in terms of not only the qualitative crack initiation, propagation, and coalescence processes but also the quantitative crack initiation locations and stress, crack propagation mechanism, and coalescence locations. It is concluded that the presence of the prefabricated cross flaws promotes the rock samples fracture more seriously during uniaxial loading. Moreover, two new crack coalescence mechanisms that have not been reported in previous studies are observed through numerical simulations and laboratory experiments. Thus, compared with laboratory experiments, the GPGPU-parallelized Y-HFDEM IDE provides another cheaper but more flexible and robust tool for the study on the crack initiation, propagation, and coalescence process in rocks with prefabricated flaws.