Analytical model for the sealant performance of tunnel gasketed joints based on multi-scale contact and percolation theories

The localised leakage in shield tunnels that mainly occurs at segment joints may induce other defects, which threatens operational safety. To obtain a universal solution for the sealant performance of gasketed joints, we proposed a novel analytical model based on the multiscale contact and percolation theories, in which the obtained percolation pressure and interfacial separation can be utilized to derive the critical water leakage pressure and leakage rate. The evolutionary process of leakage was divided into three stages (i.e., the percolation, leakage and breakdown), which explicitly reveal the progressive hydraulic deterioration of gasketed joints. The gaskets still own partial waterproof capacity until the end of the leakage stage due to the remaining contact pressure at surface asperities. The proposed model was first verified by several sets of experimental data, based on which the determination of three key model parameters (i.e., self-sealing slope, sealing coefficient, and expel pressure) were discussed in detail. The parametric study indicates that the waterproof capacity is significantly affected by the joint opening, offset, and the surface roughness of the gaskets. The variation in waterproof capacity with joint opening is mainly due to the nonlinearity of the gasket's modulus and self-sealing slope. The increase in joint offset can result in a lower waterproof capacity as well as a larger leakage rate. Gasket's surface roughness affects the percolation pressure and interfacial separation, which contributes to the long-term sealant performance.