Water inrush is one of the most serious threats to the construction safety of karst tunnels. Numerical simulation is one of the important means of underground engineering research, which is of great significance for revealing the evolution process of water inrush. In this study, an improved peridynamic model is established to simulate the formation process of water inrush channels due to rock mass progressive failure in karst tunnels. The results show that the surrounding rock between the karst cave and the tunnel excavation area is gradually damaged under the integrative action of excavation disturbance and karst cave water pressure during tunnel excavation. The initiation, propagation, and coalescence of cracks in the surrounding rock are spontaneous, and the water inrush channels are finally formed by the cracks. Based on the improved peridynamics, a total of 21 simulations were performed to study the influence law of different factors on the evolution process of water inrush channels. The influencing factors mainly include water pressure and radius of karst cave, distance between karst cave and tunnel, elastic modulus, and tensile strength of rock mass. Through the analysis of the morphological difference of water inrush channels and the damage degree of the surrounding rock under different calculation conditions, the formation mechanism and evolution process of water inrush channels are revealed. The research methods and results can provide some guidance for disaster prevention and mitigation of karst tunnel water inrush.

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.