Analysis of Water Seepage Mechanism and Study on Mechanical Properties of Highway Tunnel Based on Fluid-Structure Coupling

Shaoguan was hit by a extremely heavy rainstorm, and the mountain water catchment of Dabaoshan Tunnel in the southern section of Beijing Hong Kong Macao Expressway in Guangdong increased sharply. Due to the rapid rise of groundwater level, water and mud gushed at ZK141+227 of Dabaoshan, and serious water seepage occurred in other areas, bringing soil into the tunnel, which seriously hindered the safe passage of the tunnel. According to the on-site investigation of water and mud gushing, it was found that there were branches sandwiched in the mud gushing out, and at the same time, it was found that there was water leakage at the foot of some walls where drainage holes were added. Based on the fluid structure coupling mechanism, the seepage mechanism of highway tunnels was deeply explored, and the mechanical properties of tunnels under seepage were analyzed through experimental data and numerical simulation. The experimental results show that under the action of seepage, the stress distribution of the tunnel lining changes, and the phenomenon of local stress concentration is obvious. When the seepage pressure reaches 3.5 MPa, cracks appear in the tunnel lining, with a total of 5 cracks. The distribution of cracks is closely related to the seepage field. The numerical simulation further reveals the interaction mechanism between the seepage field and the tunnel structure, confirming the influence of the seepage field on the stability of the tunnel lining. When the seepage pressure increases to 4.0 MPa, the displacement change rate of the tunnel lining reaches 0.3 mm/m, and the maximum lining stress is 15.7 MPa. The purpose of this study is to propose a maintenance plan for highway tunnels to improve their safety. Consider the impact of seepage on tunnel structure and adopt effective waterproofing and drainage design. Further research on the seepage mechanism and tunnel mechanical properties is recommended to provide more reliable theoretical support for engineering applications.