Failure analysis of metro tunnel induced by land subsidence in Xi’an, China

Abstract

Land subsidence is a geological disaster distributed worldwide, and the large-scale exploitation of confined aquifers is the leading cause. Xi'an is a city with severe land subsidence among inland cities in China, which risks the construction and safe operation of large-scale urban metro projects. To reveal the deformation and failure mechanism of the built metro tunnel under land subsidence induced by groundwater overexploitation, a test device simulating land subsidence was developed and a physical model test was carried out. Combined with numerical simulation, the deformation and stress characteristics of the tunnel lining caused by land subsidence were analyzed. The results show that during land subsidence, the surrounding soil pressure at the top and bottom of the tunnel decreases in the influence area of land subsidence and increases outside. The longitudinal length of metro tunnel affected by land subsidence is 1.25 times the length of the major axis of land subsidence area. The deformation of the tunnel crossing land subsidence area shows a settlement in the middle and upward warping at both ends, and the longitudinal deformation was found to conform to the Gaussian distribution. The tunnel vault in the subsidence area is in compression, and the inverted arch is in tension. The deformation and failure of the tunnel in the land subsidence area are in tensile bending failure mode. The suggestions, including design principles and structural measures, are proposed to alleviate metro tunnel damage induced by land subsidence, providing a significant reference for structural design and safe operation of metro tunnels crossing land subsidence areas.