Effect of Shield-Tunnel Excavation on Adjacent-Pile Foundation Based on Modified Cam-Clay Model

To ensure the safety of shield tunneling near pile foundation and reduce the disturbance of this phenomenon in an urban metro in the loess area of China, a three-dimensional finite-element analysis model of shield-tunneling construction is established based on ABAQUS numerical simulation software and modified Cam-clay model. The deformation and ground settlement of adjacent-pile foundation during shield tunneling are analyzed. The law of descent is calculated and analyzed. Results show that the influence of tunnel shield on adjacent-pile foundation is primarily manifested in the X-direction displacement of the buried depth of the tunnel. During the shield-excavation process, the X-direction displacement of the pile increases gradually with decreased distance between the excavation face and the pile. When the distance between the pile axis and the excavation face of the tunnel is approximately[-0.5D, +0.5D], the displacement is the largest; when D continues to increase, the X-direction displacement is the largest. The displacement also continues to increase and eventually stabilizes. By obtaining the deformation curve of ground settlement, we find that the ground deformation is the largest above the tunnel axis and gradually decreases to both sides, whereas the pile cap is affected by uneven settlement. In the actual excavation of the tunnel project, strengthening the monitoring of the uneven settlement of the cap is necessary to take timely control measures.