Numerical simulation and simplified analytical method to evaluate the displacement of adjacent tunnels caused by excavation

摘要

? 2022Due to the limited space of congested urban environment, increasing number of excavation projects close to an existing subway tunnel were constructed. However, a sufficient understanding of the behavior of adjacent tunnels which is caused by the excavations supported by the bored piles and the inclined steel struts is still lacking. In this paper, the finite element models were established to obtain a better understanding of the displacement for adjacent tunnels caused by excavation, in which the excavation was supported by bored piles and inclined steel struts. The difference between the numerical results and the measurements is in the range of 6.5% ～ 31.4%, which validate the numerical model in some reasonable accuracy. Based on the finite element models, the effect of excavation geometry and the relative location between the tunnel and excavation on the lateral and vertical displacement of adjacent tunnel were investigated. It is found that the displacement of the tunnel mainly developed during excavation and the pouring of the floor slabs, which approaching to steady values after the construction of inclined steel struts. The factors including the width and the excavation depth, the distance between the bottom of the excavation and the top of the tunnel, and the distance between the centerline of the tunnel and the excavation significantly affect the displacement of the adjacent tunnel. While the maximum vertical and lateral displacement of the tunnel is in the range of 2.0 mm to 12.6 mm and in the range of 2.6 mm to 19.2 mm, respectively. Based on the numerical simulations, a simplified analytical method is proposed to provide a rapid predication of the maximum vertical displacement of existing adjacent tunnels caused by excavation and which was validated by three field cases.