Study of the Leakage Mechanism of a Utility Tunnel Waterstop Based on a Fluid–Solid Coupled Method

To explore the leakage mechanism of waterstops in deformation joints in utility tunnels, this paper carried out indoor model tests. By testing the apparent resistivity around a deformation joint, the waterproofing performance of a waterstop under different water pressures was obtained. Based on the coupled Eulerian–Lagrangian (CEL) method, a numerical model was established to simulate the dynamic leakage process of the gap between the waterstop and the concrete. The interaction between the water flowing into the gap and the waterstop was analyzed. The influence of different water pressures and different waterstop materials on the waterproofing performance of the waterstop was studied. Based on the fluid flow model of the sealing gap of the rough surface, the leakage rate of the gap flow between the waterstop and the concrete structure was calculated quantitatively. The results of the study show that the leakage mechanism of the waterstop is divided into extrusion deformation, opening flow, and gap leakage, and that the softer the material or the higher the roughness, the higher is the leakage rate of the waterstop. Comparing the results of indoor tests, numerical simulations, and theoretical calculations showed that the roughness of the rubber surface has a significant influence on the waterproofing performance of the waterstop. The calculated results followed the same trend as the test results, verifying the applicability and accuracy of the method described in this paper in predicting the leakage rate of waterstops in utility tunnels and providing an evaluation method for the study of the long-term waterproofing performance of waterstops.