Semi-analytical solution for water inflow into a tunnel in a fault-affected area with high water pressure

Abstract

This paper studies the water inflow problem when a tunnel is excavated in the area affected by a water-rich fault from an analytical perspective, and a seepage model considering the influence of the fault boundary is established. In the model, the inclined fault is equivalent to the vertical fault by regarding the volume of water inflow and the distribution of water head as the standard of measurement; then, the image superposition principle is used to transform the seepage problem with a finite boundary into a seepage model in semi-infinite space. In the process of solving the model, the stratum adopts a conformal mapping coordinate system, and the lining and grouting circle adopt the polar coordinate system, both of which are jointly solved. Then, the distribution formula of the water head in the stratum and the semi-analytical solution to water inflow are obtained, and the rationality of the semi-analytical solution is proven by degenerate checking, numerical simulation calculation and engineering case. Finally, the paper analyzes the sensitivity of the water inflow to various influencing factors and finds that the effect of the distance between the tunnel and the water table is less than that of the construction quality of the waterproof measures and more than that of the distance between the tunnel and the fault.