Optimization and monitoring verification of drainage control strategy of high-pressure water-rich karst tunnel: a case study of Dejiang Tunnel

The design of waterproofing and drainage is crucial in tunnel construction within high-pressure water-rich karst regions. Improper groundwater treatment can damage the ecology and compromise tunnel structural safety. Currently, the fully drained or fully waterproofed strategies are widely used in high-pressure, water-rich karst tunnels. However, these methods either disrupt the balance of water resources or cause the lining to bear full head pressure. Thus, this study proposes the principle of mainly waterproofed with limited drained strategy. Using the deep-buried water-rich mountain tunnel as a case study, the three aforementioned drainage designs were implemented. Through numerical analysis of FLAC3D, the distribution rules of seepage, displacement and stress field of the lining structure under different drainage conditions are obtained. Results indicate that mainly waterproofed with limited drained strategy maximizes groundwater resource protection, enhances surrounding rock waterproofing, and distributes water pressure on the lining structure. Additionally, it was found that the permeability coefficient and thickness of the grouting ring influence the water blocking and reinforcement effects. Finally, during the Dejiang Tunnel construction, implementing mainly waterproofed with limited drained strategy altered the lining’s water pressure values. This paper can provide a reference for the design, construction and remediation measures of high-pressure water-rich karst tunnels.