Experimental and Numerical Investigation on the Effects of Foundation Pit Excavation on Adjacent Tunnels in Soft Soil

Zi-Tian Yu,Heng-Yu Wang,Wenjun Wang,Dao-Sheng Ling,Yong-Hao Qu,Xue-Dong Zhang,Can Wang,Wangcheng Zhang

doi:10.1155/2021/5587857

Abstract

Excavations near an existing tunnel are often encountered in underground construction. The influence of the excavation on the adjacent tunnels is not yet fully understood. This study presented a centrifugal model test about excavation next to existing tunnels in soft soil foundation. The bending moment of diaphragm wall, surface settlement, tunnel deformation, and earth pressure around the tunnel were mainly studied. The influence of tunnel location is further studied by numerical simulation. During the stabilization stage of foundation pit, the diaphragm walls present convex deformation towards foundation pit, and the surface settlement outside the diaphragm wall appears to be the concave groove type. During the overexcavation stage, the diaphragm walls are almost damaged, and the shear bands are nearly tangent to the tunnels. The displacement of the tunnels and the surface settlement rapidly increase. The deformation of the diaphragm wall and the surface settlement are limited by the existing tunnel. The numerical results indicate that the change of tunnel location has little effect on the retaining wall but an obvious effect on the tunnel itself.

Highlights

With the rapid development of the construction of coastal cities, the excavation of foundation pit is often close to the existing tunnels. e foundation pit excavation in coastal soft soil can lead to soil unloading. en additional stress and deformation to the adjacent existing subway tunnels may be formed due to the change of the stress field and soil displacement [1]
Zheng and Wei [3] carried out a numerical parametric study to investigate tunnel deformation and stress redistribution around the tunnel due to basement excavation. ey found that the tunnel deformation mode is influenced by the distance between the tunnel and the diaphragm wall
Results and Discussion e following results of the centrifugal model test are converted into the corresponding values of the prototype for convenience

Summary

Introduction

With the rapid development of the construction of coastal cities, the excavation of foundation pit is often close to the existing tunnels. e foundation pit excavation in coastal soft soil can lead to soil unloading. en additional stress and deformation to the adjacent existing subway tunnels may be formed due to the change of the stress field and soil displacement [1]. A centrifugal model test in soft soil foundation was conducted to evaluate the influences of the excavation on the existing tunnel, nearby ground, and diaphragm wall. Six laser displacement meters were arranged at 0.5He, He, and 2He away from the diaphragm wall, respectively, to monitor the ground surface settlement (He is the excavation depth of the foundation pit).

Results

Conclusion