Study on water inflow and pressure distribution in the underwater tunnel connection part under composite construction method
摘要
The seepage field of underwater tunnels at the connection between different construction method parts is rarely reported and is characterized by significant longitudinal seepage. This study employed numerical simulation to establish a refined multi-part tunnel model (shield, connection, and mining parts) that incorporates drainage and waterproofing systems. The longitudinal and circumferential distributions of water pressure were investigated, and the effects of various factors on water pressure and water inflow were analyzed. Model accuracy was validated against physical tests. Results show that, longitudinally, the distribution of water pressure in each tunnel part is governed by the drainage mode. Near the connection interfaces, complex variations occur: water pressure at the crown changes abruptly, while the sidewall exhibits a marked gradient due to longitudinal drainage pipes positioned along the sidewall. In contrast, the magnitude of water pressure at the invert is controlled by cross-sectional size due to the absence of the drainage pipes. Circumferentially, water pressure increases from vault to invert except near longitudinal drainage pipes. Variations in permeability coefficients of surrounding rock kr, grouting ring kg, and initial support kc, as well as drainage pipe spacing dp, have a greater impact on water pressure in the connection and mining parts compared to the shield part, while water level height hw has the opposite effect. Tunnel inflow rises with increasing kr, kg, kc, and hw, but decreases with larger dp. The discrepancy between numerical and model tests is below 9%, confirming the reliability of the simulations.