Collapse mechanism of stratum induced by subsurface excavation for a shallow buried tunnel in water-rich region

The collapse of stratum induced by subsurface excavation for a shallow tunnel in water-rich region is common in urban tunnel engineering. Although scholars have conducted numerous research on the stability of the soil mass above shallow-buried tunnel roof, the collapse characteristics of the soil mass induced by shallow-buried tunnel construction in water-rich strata have not been well investigated. In this work, a new three-dimensional collapse mechanism of the stratum above shallow-buried tunnel roof is generated “point by point” based on the spatial discretization technique for the first time. A scaled model test is designed to verify the validity of the constructed collapse mechanism. By introducing the pore water pressure which is obtained from numerical simulation as an external force into the virtual work equation, the safety factor of the stratum is derived from the upper bound theorem of limit analysis. Finally, a comparison between the theoretical solutions and numerical solutions have been conducted to prove the effectiveness of the proposed method