Fissures in rock masses offer sites for groundwater seepage and weaken the mechanical properties of rocks to a certain extent. Moreover, seepage water pressure exerts a direct influence on engineering construction and may even trigger engineering accidents. For three-dimensional fractured rock masses, the MATLAB program was independently programed based on the Monte Carlo method to build a three-dimensional fracture network model of the natural rock mass, realize visual reconstruction of three-dimensional fractures, and generate a three-dimensional fractured rock mass model based on the statistical data of fractures in the literature. Using the established three-dimensional fluid–structure coupling simulation method, the simulation of prefabricated directional hydraulic fracturing and the hydraulic fracture propagation law of naturally fractured rock masses with different inclination angles are performed. The results highlight several complex mechanical behaviors, such as shear and tension, in the hydraulic fracturing process of the fractured rock mass. The expansion mode of hydraulic fracture is mainly controlled by two factors: propagation induced by natural fractures and propagation controlled by the maximum principal stress. Therefore, establishing a three-dimensional fractured rock mass fluid–solid coupling peridynamics simulation method can provide an effective means of analyzing the damage and failure process of fractured rock masses under the stress-seepage coupling effect.

An FDM–DEM bridging domain coupling method considering blasting dynamic disturbance was proposed for the construction process of drilling and blasting tunnels. In the simulation, the disturbed rock mass was established by particles, and other elastic areas (less affected or not affected by blasting) were modeled using FDM grids. An equivalent application strategy of blasting dynamic loads in DEM was proposed. The blasting effect of group hole explosion was equivalently applied to the tunnel face. The accuracy and reliability of the coupling model were demonstrated by analyzing the distribution of velocity, displacement, and stress during the blasting loading and tunnel excavation process. The necessity of simulating tunnel blasting excavation was investigated by comparing the results of dynamic and static simulation. This study can provide an effective numerical simulation method for tunnel excavation at the engineering scale.

The discrete element method (DEM) cannot effectively account for macroscale problems because of its high computational cost and time-consuming nature, especially for fluid–solid coupling problems. Therefore, a spatially scaled-down model, which should be established based on a set of scaling laws, is commonly employed to study the behaviors of the macroscale prototype. In the present study, various basic scaling relationships proposed by previous researchers for a scaled-down model are summarized first, as well as their limitations when they are used for DEM-CFD simulation of fluid–solid coupling problems in saturated and cohesiveless granular soils. Then, a new set of scaling relationships is proposed using a governing equation approach. Finally, a DEM-CFD model is established as an example analysis to study the feasibility and accuracy of the new scaling relationship present in this study for simulating fluid–solid coupling problems in saturated and cohesiveless granular soils. The results are analyzed in comparison with other scaling relationships, and the results indicate that the new set of scaling relationships is more reasonable and accurate than others.