Sealant behavior of gasketed segmental joints in shield tunnels: An experimental and numerical study

Segmental joints are vulnerable parts of the lining structure in precast shield tunnels, both from the structural (lower stiffness compared to main segments) and non-structural (potential water leakage points) perspectives. Previous works have focused on the structural behavior of segmental joints rather than the sealant behavior. This paper presents a combined experimental and computational study to investigate the sealant and mechanical behavior of the gasketed joints used for a tunnel prototype, i.e., Nanjing Weisan Road Tunnel, which was recently built using a tunnel-boring machine below the Yangtze River, whose 72-m water table head is the highest in China. A total of 7 gasket profiles were tested using a testing apparatus developed in-house. The objective of the joint waterproof tests was to quantify the water leakage pressure (or joint waterproof capacity) versus the joint opening relationships under various joint offset scenarios. The objective of the gasket-in-groove mechanical tests was to quantify the force versus deformation relationships. Finite element models of the gaskets were developed and verified against the test results. A supplementary parametric study was conducted to investigate the effect of joint opening, joint offset and gasket hardness on the detailed distribution of contact stress of the gasket interface. Combining the experimentally recorded and the numerically computed data presented in this paper, a simplified design formula that quantifies the relationship between the contact stress of the gasket and the water pressure was proposed, and its rationality was validated against the available test data in the literature.