Risk Assessment of Metro Tunnels in Submerged Sand Due to Nearby Excavation and Building Construction

New construction activities neighboring the existing structures are always challenging and even more complicated in the presence of an underground structure. In the present study, the potential risk of neighboring basement excavation and building construction on an existing tunnel was investigated. Twelve large-scale model tests were conducted by varying the number of basements and floors, groundwater table level, and the horizontal distance from the tunnel. Experimental observations showed that the crown and invert of the tunnel experienced tension in the unloading or excavation phase while loading or building construction, which resulted in compression at these locations. At the spring level, loading caused tension, while unloading caused compression. Observations from subsequent finite element analyses were in good agreement with the experimental results. As the water table was raised from invert level to ground level, the strain was observed to increase by more than 10%; when the horizontal distance from the tunnel was increased and the number of basements was reduced, the strain was observed to decrease by about 20%. The rankings based on statistical analysis showed that the horizontal distance between the tunnel and the building has the maximum impact on the tunnel among all the parameters.