Influence of Pile Foundation Construction on Existing Tunnels in a Metro Protection Area: Field Test and Numerical Simulation

On the basis of the Fengqi Chaoming project in Hangzhou City, Zhejiang Province, China, this paper investigates the influence of pile foundation construction on the existing tunnels in a metro protection area to ensure the stability and safety of the pile foundation construction in the area of Hangzhou Metro Line 2 through in situ pile tests and numerical simulations. The test results show that the pile foundation construction has a certain influence on the existing metro tunnels, and the degree of influence gradually decreases as the distance between the pile foundation and the metro tunnel increases. The corresponding impact level for the pile foundation at 12 m from the tunnel is 1.06 mm, and that for the pile foundation at 4.9 m from the tunnel is 1.18 mm. Different types of pile foundations also lead to different degrees of influence. The maximum settlement corresponding to triaxial cement mixing piles is 1.89 mm, while the hard-method occlusal piles is 1.18 mm. The monitoring point of the metro tunnel with the smallest distance from the pile foundation experiences the largest deformation, but several sets of deformation data meet the requirements of the deformation control index, indicating that the pile foundation construction is safe and controllable.