Water control of water-rich deeply buried tunnel: an analytical model of a combined scheme

Water inflow often occurs in water-rich deeply buried tunnels during tunnel construction. The water control scheme combining grouting with external pilot heading drainage is considered one of the most effective ways to control water inflow into a tunnel. In this study, a steady seepage model incorporating tunnel grouting and pilot heading drainage has been developed. The model has been solved by the conformal mapping and superposition method. The analytical solution has been verified by the results of a numerical simulation and the parameter analyses have been performed. The results indicate that: (1) the developed analytical model can obtain the results by solving several linear equations, and the analytical results agree well with the numerical simulation results. (2) To limit the tunnel water inflow within the allowable range, the permeability coefficient and the thickness of the grouting circle can be significantly reduced after pilot heading drainage. (3) The pilot heading drainage volume has a significant negative relationship with the tunnel water inflow. The influence of double pilot headings drainage on the tunnel water inflow is a linear superposition of the impact of single pilot heading drainage. (4) Double pilot headings drainage can make the water inflow around the tunnel more uniform. (5) The relative position of pilot heading and tunnel has little effect on tunnel water inflow.