Joint waterproofing configuration and performance of prefabricated utility tunnels under U‑shield dynamic thrusting

To address the issue of waterproof failure at the joints of ultra-long, shallow-buried prefabricated utility tunnels under dynamic thrusting conditions in U-shaped shield integrated construction, a novel dual-ear horseshoe-shaped rubber gasket configuration is proposed and compared with the conventional horseshoe-shaped cross-section. Through numerical simulation, laboratory tests, and field monitoring, the deformation coordination mechanism, stress distribution, and waterproof performance of the gasket under dynamic compression are systematically investigated. Numerical analysis shows that the conventional horseshoe-shaped cross-section exhibits stress concentration at the cavity edges with a single load-transfer path, whereas the dual-ear horseshoe-shaped cross-section reconfigures the load-transfer path, enabling a stable transition from ear-priority contact to full cross-sectional cooperative load bearing under eccentric loading and minor alignment deviations. Within the compression range of 20.0–22.5 mm (compression ratio of approximately 40%–45%), the dual-ear horseshoe-shaped gasket demonstrates stable mechanical response and good waterproof performance, maintaining stable pressure holding under a water pressure of 0.20 MPa with a considerable safety margin. Field application confirms that this optimal compression range is achievable under actual construction conditions, and the gasket compression state and waterproof performance remain stable overall. The findings provide a practical technical reference for joint waterproofing design and construction control in U-shaped shield construction.