Influence of foundation pit excavation on deformation of subway tunnel below

Abstract

Aiming at the problem that the change of stress field caused by the excavation of a foundation pit in Zhengzhou drives the vertical and horizontal displacement and deformation of the subway tunnel which has been put into operation. In this paper, ABAQUS finite element software is used to conduct three-dimensional numerical simulation of foundation pit excavation, and the influence of the same foundation pit area but different length and width and the distance between the tunnel and the center of the foundation pit on the tunnel is discussed, and the size of the bending moment of the single tunnel under the foundation pit is analyzed during the excavation process. The results show that the excavation of the pit with four equal sides has the greatest effect on the vertical displacement of the tunnel below, which increases by 19.90% compared to the original pit shape displacement, and the vertical displacement of the tunnel increases by 14.58% compared to the original pit for the excavation of the pit with long sides parallel to the tunnel. When the horizontal distance of the tunnel from the center of the pit increases in sequence, the vertical displacement of the top of the tunnel will gradually decrease, and when the horizontal distance is 28m, the vertical displacement of the tunnel is 6.56mm. During the excavation of the pit, a pressure and tension area will appear in the tunnel section near the bottom of the enclosure structure, and this area will approach the center of the pit as the excavation depth deepens. The research results provide reference significance to the protection of the subway tunnel below the foundation pit during the excavation of the foundation pit under the geological conditions in Zhengzhou area, and accumulate experience for the construction of the project around the tunnel in Zhengzhou are