Analytical solution for steady seepage into a circular deep-buried mountain tunnel with grouted zone in anisotropic strata

Due to the existence of a large number of discontinuous fractures and interfaces in tunnel surrounding rocks, the groundwater inflow into tunnel generally presents significant anisotropy. Therefore, it is of great significance to consider the anisotropic permeability when dealing with water gushing-induced engineering accidents in water-rich mountain tunnels with large burial depth. In this study, based on the complex variable method and the seepage flow theory, a theoretical model of water inflow into a deep-buried circular tunnel in a fully saturated, anisotropic and semi-infinite aquifer is developed. The influence of grouted zone, initial support and secondary lining is fully considered. By comparison to the existing analytical methods and numerical results, the reliability of this proposed analytical solution is well validated. It is indicated from the parametric study that the groundwater inflow into tunnel presents an upward trend with an increasing value of the strata permeability in the vertical direction. Moreover, the water inflow rate and the total water head decrease with the growth of the thickness of grouting circle. It is suggested that reasonable grouting thickness and permeability should be controlled to enhance the grouting effect. This study provides a practical method for estimating the water inflow into a deep-buried, grouted and lined mountain tunnel considering the anisotropic strata permeability.