The threat of seepage to the stability of underground structure has always been remarked by a number of experts, and there engineering subjects collapsed because of the effect of seepage force. Some pursuers on the seepage have got invaluable results to solve the problems developed by the seepage force. In this paper, the author has reviewed the analytical solutions of the inflow, the hydraulic gradient and the seepage force have been obtained, and then described the importance of seepage to the stability of tunnel; the numerical analysis by Midas GTS has been also used to simulate the seepage, and illustrated the distribution of seepage rate around the tunnel circumference, and analyzed the effect of the tunnel depth, the space and the relative location on the distribution and the maximum values of seepage rate along the tunnel circumference. Finally, based on the Darcy’s law the most instable location induced by the seepage force along the tunnel circumference has been represented for the single tunnel and the twin-tunnel, and the application range of the analytical expression has been also discussed, which will be advantage to the tunnel construction and reinforcement.
The seepage property of groundwater will affect the stability of tunnel directly. The above analyses have illuminated that the effect of the seepage force cannot be ignored, and we should regard the behavior of the seepage force to the stability of tunnel. In order to analyze the distribution properties of seepage flow along tunnel circumference, and then further understand the properties of seepage force, this paper has used the analytical solution and the numerical method to study the effect of the different depth, space and relative position between two tunnels on the seepage rate, which has represented the dangerous location induced by the effect of the seepage.