Influence of Ground Loading on the Existing Shield Tunnel and Connected Shaft Structures

To explore the impact of ground load on existing shield tunnels and connected shaft structures, this study designed a testing device to identify the stress of shield tunnels and connected shaft structures under ground load. By controlling the location and magnitude of the load, we investigated the internal forces and deformations of the tunnels and shafts, as well as the displacement of the soil. Additionally, a three‐dimensional finite element model was established to reveal the internal forces and deformations of shield tunnels and connected shaft structures under uniform ground load, as well as the settlement of the soil. The finite element simulation results were highly consistent with the results of indoor model tests, demonstrating the consistency between these two methods. The results indicated that the internal forces and deformations of the shafts vary significantly with the magnitude of the surcharge load. When the surcharge is directly above the tunnel axis, the internal forces of the shafts decrease as the distance between the load and the shaft increases. Within the 2D eccentric range, the internal force changes caused by the load effect are significant, but outside the 3D eccentric range, the internal forces and bending moments of the shafts decrease significantly, and the magnitude of the changes is not obvious. Beyond the 2D range of the load area, the displacement of the soil decreases significantly, and the magnitude of the changes is not obvious. This reflects the significant impact of ground load on the shaft structure and highlights the tolerance of remote soil measurement points to load fluctuations. This study has strong reference significance for the excavation of vertical pipelines under shield tunnels.