An FDM-DEM coupling method based on REV for stability analysis of tunnel surrounding rock

An FDM-REV-DEM interface coupling method was proposed based on the concept of the representative elementary volume (REV). The coupling method was applied to the Shantou Bay submarine tunnel of ShantouShanwei High-speed Railway. In the simulation, the REV equivalent mechanical parameters were used. The disturbed zone of tunnel excavation was solved by discrete element method (DEM), and the undisturbed zone was solved by finite difference method (FDM). The force, displacement, and other information were transmitted between the two zones through the wall unit. The tunnel excavation process was simulated by this method, and the simulation results were compared with those of FDM, DEM and field monitoring. The results show that the coupling method can not only accurately characterize the displacement and stress distribution of surrounding rock, but also reveal the crack propagation process and large deformation. Thus, the method has a higher degree of accuracy than the traditional continuum method. Meanwhile, the calculation efficiency is 7.56 times that of DEM, which greatly reduces the calculation time. This study provides a continuum-discontinuum coupling numerical method with high efficiency and high precision for engineering-scale tunnel excavation simulation.