Tunnel construction adjacent to the fault fracture zone is prone to water inrush disasters, which pose a serious threat to the safety of tunnel construction. To provide theoretical support for the early warning and prevention of water inrush disasters of the tunnel adjacent to the water-rich faults, a numerical analysis based on the three-dimensional discrete element method (DEM) was performed to study the evolution of the displacement and seepage fields of the water-resistant rock mass of a tunnel adjacent to a water-rich fault during the water inrush process by taking the Xianglushan tunnel as the research project. With reference to the obtained results, a grouting reinforcement scheme was developed, and its effectiveness was evaluated. The results indicated that as the tunnel face approached the water-rich fault fracture zone, the effect of water pressure gradually became obvious, and the displacement at the face continuously increased. When the tunnel face was excavated to the position 5 m from the fault, the displacement at the center of the face changed suddenly with a sudden increase in water pressure. The water-resistant rock mass ahead of the center of the face was damaged, and a water inrush disaster occurred in the tunnel. Numerical simulation results demonstrated the feasibility of the grouting reinforcement scheme. The assessment based on the borehole acoustic waves, borehole TV, geological radar detection, and convergence monitoring as well as the excavation results confirmed that the water inrush disasters in the 2# adit of Xianglushan tunnel adjacent to the water-rich fault were effectively prevented and controlled, which can provide a reference for the prevention and treatment of the frequent water inrush disasters in underground projects constructed in the water-rich fault area.

Strain rockburst is a severe failure phenomenon caused by the release of elastic strain energy in intact rocks under high-stress conditions. They frequently occur in deep tunnels, causing significant economic losses, casualties, and construction delays. Understanding the factors influencing this disaster is of significance for tunnel construction. This paper first proposes a novel three-dimensional (3D) discrete element numerical analysis method for rockburst numerical analysis considering the full stress state energy based on the bonded block model and the mechanics, brittleness, integrity, and energy storage of the surrounding rock. This numerical method is first validated via laboratory tests and engineering-scale applications and then is applied to study the effects of compressive and tensile strengths of rock mass, tunnel depth, and lateral pressure coefficient on strain rockburst. Meanwhile, sensitivity analyses of these influencing factors are conducted using numerical results and systematic analysis methods, and the influence degree of each factor on the rockburst tendency is explored and ranked. The results reveal that laboratory tests and actual engineering conditions are consistent with numerical simulation results, which validates the rationality and applicability of the novel rockburst analysis method proposed in this paper. With the increase in compressive strength, the stress concentration degree, energy accumulation level, maximum stress difference, and maximum elastic strain energy within the rock mass all increase, leading to a stronger rockburst tendency. Tunnel depth and the lateral stress coefficient are positively correlated with rockburst tendency. As the lateral pressure coefficient and tunnel depth increase, rockburst tendency exponentially increases, while the maximum stress difference and maximum elastic strain energy within the rock mass also increase. The influence degree of each factor is ranked from highest to lowest as follows: tensile strength, lateral pressure coefficient, compressive strength, and tunnel depth. The research results provide theoretical support and technical guidance for the effective prediction, prevention, and control of rock burst disasters in deep tunnels.

In order to ensure the safety of the tunnel approaching the fault and prevent water inrush disasters, and then take reasonable protective measures, a fault-tunnel-surrounding rock is established by using a three-dimensional (3D) discrete element numerical analysis method, which takes into account the fluid-structure coupling effect. Based on the method of control variables, the catastrophe information characteristics of displacement and water pressure of the surrounding rock of the tunnel face and the corresponding characteristics of changes before the occurrence of water inrush disasters were studied under different fault water pressures during the excavation of the tunnel approaching the water-rich fault. The results show that, during excavation at the same step, displacement and its magnitude in the surrounding rock escalate as fault water pressure increases. The maximum pressure of the water in the surrounding rock is also constantly increasing. As tunnel excavation progresses, at constant fault water pressure, longer excavation distances result in greater axial displacement of the surrounding rock mass and increased water pressure at corresponding positions within the surrounding rock, leading to higher magnitude increases. As excavation proceeds, the displacement and water pressure in the surrounding rock and the increase of its amplitude continue to increase. Pre-reinforcement grouting techniques and pipe umbrella support systems that are very effective protective measures can be determined by a comprehensive approach integrating advanced geological forecasting methods, real-time water pressure detection, and the analysis of stress-strain and seepage pressure field variations in the surrounding rock mass.