Experimental study on the failure risk of existing metro station under unilateral large-scale excavation

Large-scale unilateral deep excavation makes the existing metro stations have a significant risk of potential slippage and overturn. To quantitatively assess the structural risk, this study reveals the deformation, earth pressure, and wall strain evolution process of the station structure under different unilateral excavation widths and depths through physical model tests. Notably, based on the lateral deformation of maximum risk and its safety warning level, the risk warning zoning of metro station under unilateral excavation in soft soil strata is proposed. Research results indicate that when the excavation depth is greater than 2/3 of the station height, the metro station has an obvious tilt angle towards the excavation side. According to the safety threshold, excavation widths of 0.5-1 times the station width will trigger lateral deformation warnings for the existing station. Moreover, the inclination of the metro structure makes the pressure release and a decrease in the bearing capacity of shallow strata behind the station, which causes the collapse of adjacent pavements or high-rise buildings to aggravate the engineering risk. Finally, the proposed warning zoning method, when applied in engineering, can predict the construction risk level based on the actual excavation scale, and then targeted strategies are implemented to effectively reduce potential hazards.