Large deformations of strata caused by shallow tunnel excavation in urban reclamation areas pose a serious threat to geological safety. In this paper, geo-mechanical model tests and numerical simulations were conducted to investigate the large deformation characteristics based on the Haicang tunnel in Xiamen, China. First, the tunnel excavation process using the double side drift method was simulated to reveal the large deformation characteristics and influencing factors. Then, geo-mechanical model tests were conducted to further investigate the deformation characteristics, stress release patterns and pore water pressure evolution. The results show that groundwater and the thickness of the backfill soil are the primary factors affecting the deformation behavior. Meanwhile, the stress release and pore water pressure dissipation resulting from the core construction procedure are direct causes of large deformation. The research results can serve as a reference for the prevention and control of large deformation in shallow buried tunnel construction.

Tunnels offer myriad benefits for modern countries, and understanding their behavior under loads is critical. This paper analyzes and evaluates the damage to buried horseshoe tunnels under soil pressure and traffic loading. To achieve this, a numerical model of this type of tunnel is first created using ABAQUS software. Then, fracture mechanics theory is applied to investigate the fracture and damage of the horseshoe tunnel. The numerical analysis is based on the damage plasticity model of concrete, which describes the inelastic behavior of concrete in tension and compression. In addition, the reinforcing steel is modeled using the bilinear plasticity model. Damage contours, stress contours, and maximum displacements illustrate how and where traffic loading alters the response of the horseshoe tunnel. Based on the results, the fracture mechanism proceeded as follows: initially, damage started at the center of the tunnel bottom, followed by the formation of damage and micro-cracks at the corners of the tunnel. Eventually, the damage reached the top of the concrete arch with increasing loading. Therefore, in the design of this tunnel, these critical areas should be reinforced more to prevent cracking.

In order to explore the dynamic behavior and damage mode of shallow buried tunnel induced by underwater explosions (UWEPs), a fully coupled numerical model of a shallow buried tunnel based on Arbitrary Lagrangian and Eulerian (ALE) method was established. The strain rate effects of concrete and steel bar under explosion load, the explosion wave propagation, the interaction between fluids and solids, and the nonlinear response of the structure were considered. The reliability of the numerical method was verified by comparing the experimental and analytical results. The damage process and damage mechanism of submerged shallow buried tunnel due to UWEPs were investigated. The effects of saturated soil covering, explosive weight, buried depth and water depth on the dynamic behavior and damage mode of the tunnel were discussed. Finally, the dimensional analysis was used to obtain the functional relationship between the peak displacement, charge weight, buried depth and water depth. The results show that the saturated soil covering can effectively reduce the impact of explosion load on the tunnel. Increasing the buried depth can mitigate the blast effects on the structure, and the failure modes switch from local damage to global failure. The response of the tunnel increases with the increasing water depth, but the influence of water depth decreases gradually. The damage modes of shallow buried tunnel can be classified into local punching or spalling damage, global bending failure accompanied by spalling damage, and global bending failure.