地铁盾构隧道下穿城市公园地基加固宽度分析

Analysis on Reinforcement Width of Subway Shield Tunnel Underpassing City Park

为改变居住环境和生态环境,往往公园等大型公共用地的规划是动态变化的,例如公园内假山等景观的建造或拆除。对于地铁盾构隧道下穿该区域来说,运营阶段上覆荷载的改变,会使得结构横断面变形过大。后续的建设规划同地铁盾构隧道结构安全性之间存在矛盾。为解决这一矛盾,需要在地铁盾构隧道建设期进行地基加固。通过工程调研,分析了上海地铁盾构隧道在上覆荷载发生变化时,横断面变形现状;采用ABAQUS三维有限元,选取某典型软土地区深厚淤泥质土层断面,研究了盾构隧道下穿公园区域内假山建造和穿越土层性质对地基加固宽度的影响。结果表明:地基加固需分段考虑且山体高度不能超过3.5 m。隧道全断面穿越淤泥土层,山体高度小于3.5 m时,拱腰两侧加固3 m较为合适;穿越淤泥质粉细砂层,该宽度可减小至1 m;穿越粉质黏土层,拱腰两侧可无加固宽度。

To improve the living and ecological environment, the planning of large-scale public land such as parks is often dynamic, including the construction or demolition of landscapes like rockery in the park. For subway shield tunnel under the area, the overburden changes during the operation phase will make the structure cross-section deformation too large. Therefore, there is a conflict between the follow-up construction plan and the structural safety of subway shield tunnel. To solve this problem, it is necessary to reinforce the foundation in the construction period of subway shield tunnels. Through engineering investigation, the deformation of the cross-section of the shield tunnel in Shanghai Subway was analyzed. The ABAQUS three-dimensional finite element method was adopted to analyze the section of the deep silty soil in some typical soft soil area which was influenced by construction and crossing of soil layers on consolidation width of foundation in park area. The research results show that the foundation reinforcement should be considered in sections and the height of the mountain should not exceed 3.5 m. The 3-meter-wide reinforcement for both arch sides is appropriate; through silty fine sand layer, the width can be reduced to 1 m; through the silty clay layer, both arch sides do not need reinforcement.