Water pressure relief treatment for protecting the initial support of inclined shafts at high water pressures

The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount. This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method. Field monitoring was conducted to assess the load and deformation of the initial support structure, and on-site investigations identified the distribution of cracked areas. In addition, numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure, which were then compared with field observations for validation. The variations in the lateral pressure coefficient and water pressure were evaluated. The results revealed that damage was primarily concentrated in the shoulder, spring line, and knee areas, with the bending moment at the knee increasing by up to 66.9%. The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support. Post-treatment analysis indicated significant reductions in axial force and bending moment, enhancing structural stability. These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulic-pressure railroad tunnels.