Study on the influence of seepage control measures on external water pressure of deep buried hydraulic tunnel lining

The external water pressure of tunnel lining is closely related to seepage control measures such as anti-seepage grouting and drainage holes. The commonly used analytical formulas for external water pressure of lining cannot directly take into account the influence of drainage holes. The analytical solution to the seepage field of deep buried tunnel was carried out by using the vertical well method and parallel plate cubic law. Combining numerical calculation and analytical analysis, a new analytical formula for calculating the external water pressure of tunnel lining including the geometric parameters of drainage holes was proposed. The influence of different grouting rings and drainage hole parameters on the external water pressure of the lining was analyzed. The results show that decreasing the permeability of grouting circle can better reduce the external water pressure of lining compared to increasing its thickness, and drainage holes can effectively reduce the external water pressure of lining. As the number and depth of drainage holes increase and the spacing decreases, the external water pressure of lining decreases significantly. The diameter of the drainage holes is not the main influencing factor. Compared with numerical solutions, it can be seen that the proposed analytical formula can easily calculate the external water pressure of lining based on parameters such as the depth, diameter, and spacing of the drainage holes. The research results can provide reference for the design of anti-seepage and drainage schemes of lining for deep buried hydraulic tunnels in water-rich formation.