Study of the long-term behavior of segmented tunnels in cohesive soil based on the circumferential joint opening

Abstract

Aging tunnels in cohesive soils can show signs of an increase in lining loads and long-term ground surface settlement as the consolidation of soil around the tunnel continues. In this study, a model is proposed to study the long-term behavior of tunnels based on the amount of circumferential joint opening between ring to ring and drainage condition of the tunnel lining. The model is applicable for studying the long-term behavior of tunnels excavated in low-permeability soil using coupled soil–water numerical analyses. First, the initial drainage condition of the tunnel is decided based on the locations with the current maximum water flow. Then, the water leakage criteria through the joint opening and drainage conditions along the tunnel are determined. The proposed model is validated using measured data from an old tunnel experiencing long-term lining deformation and ground settlement. Using a coupled soil–water numerical model, the proposed approach is employed to study the behavior of the tunnel further. Results show that the proposed approach can provide accurate estimates of ground movement, lining deformation, development of lining loads, and pore water pressure generation and dissipation over the long term for tunnel linings with drainage along circumferential joints.