关键词: 临近既有隧道;深基坑开挖;隧道变形;敏感性分析;宁波市;

Abstract: After excavation, the foundation rebounds due to stress unloading, which leads to the deformation of tunnels near the deep foundation. The deformation of the tunnel is not only related to the degree of excavation unloading, but also related to the location of the tunnel. Based on a shield tunnel project of Ningbo Metro Line 1, the influence of soft soil foundation excavation on the segment deformation of adjacent existing shield tunnel is investigated by using the small strain hardening model and two-dimensional finite element numerical method. Single factor analysis and multiple factor analysis methods are used to analyze the effect of different influencing factors, namely, excavation width, excavation depth, buried depth of tunnel, and the distance between tunnel and foundation, on the vertical and horizontal displacements of tunnel segments. The results show that: ①Under the influence of deep excavation, the vertical displacement and horizontal displacement of the existing tunnel segment increase gradually with the increase of the excavation depth. The tunnel segment displacements include vertical settlement and horizontal movement toward the foundation. The deformation of tunnel segment generally shows a ‘horizontal duck egg’ shape. ②The excavation depth, distance between the tunnel and the foundation, and the excavation width are important factors affecting the settlement and horizontal displacement of the tunnel, while the influence of the buried depth of the tunnel is relatively small.

Key words: adjacent existing tunnel; excavation of deep foundation pit; tunnel deformation; sensitivity analysis; Ningbo City