Analytical study on water inflow and pore water pressure of tunnels under drainage

The calculation of water inflow and pore water pressure of tunnels is always the focus of underground engineering. However, the effect of water inflow and pore water pressure of tunnels under drainage has not been well solved. The analytical analysis of shallow, deep and lined tunnels is carried out respectively. Then, the expressions for the key parameters (influencing distance, equivalent underground water level and equivalent underground water level of linings) are obtained by using the numerical method, and the analytical formulae for water inflow into tunnels are put forward. Finally, the distribution rules of pore water pressure are discussed. The results show that the water inflow into tunnels depends on the tunnel radius, the initial groundwater level and the relative permeability of the surrounding rock and linings, among which the relative permeability of the surrounding rock and linings plays a key role. The lining ring significantly changes the amount of water inflow and distribution of pore water pressure of tunnels. With the increase of the relative permeability, the fitting degree between the analytical solution and the numerical solution of pore water pressure increases gradually. Compared with traditional analytical solution and numerical solution, the proposed analytical formula more truly describes the seepage field characteristics of shallow, deep and lined tunnels, and the calculated results are more reasonable and accurate.