Stability Analysis of Metro Shield Construction in Sandy Soil Strata under Tidal Forces in Coastal Areas

The tidal effect on coastal areas is one of the main factors affecting groundwater. The groundwater including the unconfined aquifer layer and confined underground water layer is the main hazard source in the construction of a shield tunnel in the sandy soil area of a subway. It is necessary to study the influence of shield tunneling on land subsidence when the tides affect the underground diving position in the coastal area. In this article, the surface deformation of a simulated shield tunnel at different water levels and different tunneling lengths in sandy soil environment is measured through a model test, and the relationship between land subsidence, tunnel deformation, and water level change is analyzed. The results show that the change in groundwater level caused by tide will directly affect the floating or subsidence of the shield tunnel. Finite element simulation analysis during the process is carried out, and the influence of rising underground water level on the structure of the shield tunnel in terms of displacement and deformation is studied in detail, revealing the influence law of rising underground water level on the shield tunnel structure. The numerical results are well validated with the experimental results. Therefore, the influence of tide should be considered in the construction of an inshore shield tunnel, and the construction time window should be selected reasonably according to the tidal law.