Study on the Anti-Seepage Characteristics of Joint Sealing Materials for Segments of Shield-Driven Water Conveyance Tunnels

Aiming at the challenges of lining cracking and water seepage in water conveyance tunnels under high internal water pressure, joint waterproofing is the key to improving the structural anti-seepage performance. This paper investigates the mechanical and anti-seepage properties of joint sealing materials, as well as the stress-deformation characteristics of the anti-seepage structure. Uniaxial tensile tests, bond tensile tests, and interfacial shear tests were conducted on three types of sealants—polysulfide, polyurethane, and polyurea—to systematically obtain the fundamental mechanical parameters. The results show that polyurea has the highest ductility, polysulfide exhibits the highest tensile strength (1.27 MPa), and polyurethane presents balanced performance. The interfacial shear strength between polysulfide and concrete reaches 0.5 MPa, demonstrating outstanding bonding performance. Based on the cohesive zone model, a numerical model of the joint sealing system was established to analyze the evolution of stress and deformation under two working conditions: inner-side water seepage and double-sided (inner and outer) water seepage. The results indicate that water pressure induces stress peaks at the contact interface between the sealing material and the segment. The stress peak under internal water pressure alone is significantly higher than that under combined internal and external water pressures. Comprehensive comparison shows that polysulfide sealant offers better stability in resisting internal water pressure and controlling deformation. The selection of sealant type in engineering should consider the stress characteristics, deformation requirements, and construction conditions of different structural locations.