Interaction between tunnel supports and ground convergence—Consideration of seepage forces

Seepage forces can cause a significant threat to the safety of underwater tunnels because the seepage forces remain while the effective overburden pressure can be distributed by the arching effect during tunnel excavation. Although seepage forces are very influential in underwater tunnels and their support systems, the effects of seepage forces on the ground reaction curve of a tunnel reinforced with grouted bolts and grouting have yet to be clearly defined. Thus, in this paper, we first performed theoretical analyses on the ground reaction curve reinforced with grouted bolts and grouting by taking into consideration seepage forces under steady state, full drainage, and radial flow conditions. Secondly, we carried out mechanical–hydraulic coupled finite element numerical analyses for comparison with the theoretical analyses. The results show that the analytical solution is valid in a deep tunnel. Thirdly, we performed a parametric study of grouting reinforcement effects on the ground reaction curve considering seepage forces. The results show that the ground reaction curve with the consideration of seepage forces shows a greater radial displacement than that of a dry condition at the same internal pressure level because the seepage forces are applied to the tunnel section as an additional body force. The overall results suggest that the analytical solution of ground convergences considering the effect of seepage forces on tunnel supports presented in this study can be effectively used for the further realistic design of tunnels under groundwater.