宁波轨道交通车站基坑变形特征统计分析

Statistical Analysis on Deformation Characteristics of Foundation Pit in Ningbo Rail Transit Station

重点对宁波轨道交通1号线一期工程13座地下2层车站基坑的墙体最大水平位移及墙后最大地表沉降进行研究,分析基坑墙体水平位移、墙后地表沉降的变化规律以及墙后地表沉降与墙体水平位移的关系。结果表明:受宁波软土流变特性影响,基坑墙体水平位移及墙后地表沉降均较大,其中墙体水平位移平均达0.46%H,墙后地表最大沉降平均值达0.7%H;墙后地表沉降呈现为"凹槽形",地表最大沉降位于(0.5~1.0)H范围内;墙后最大地表沉降与墙体最大水平位移比值的平均值为1.71。根据数据分析,提出坑底加固、基坑开挖重视"时空效应"、尽快施作垫层封闭基坑等建议。

This paper focuses on the study of the maximum horizontal displacement and the maximum surface settlement of the foundation pit for 13 underground stations with two layers in Line 1 of Ningbo rail transit. The horizontal displacement of foun- dation pit wall and the variation of the ground surface settlement behind the wall and the relationship between them are analyzed. The results show that the influence of rheological characteristics of Ningbo soft soil, foundation pit wall displacement and ground settlement level are larger; the horizontal displacement of the diaphragm wall reached an average of 0.46% H, while the maxi- mum vertical surface average value was 0. 7% H; the surface settlement behind the wall shows a ＂groove＂ form, and the maxi- mum surface settlement is located in the range of 0.5-I. OH; the average ratio of the maximum surface settlement behind the wall and the maximum horizontal displacement of the wall is 1.71. According to the data analysis, suggestions are put forward on the reinforcement of foundation pit excavation, emphasis on ＂space-time effect＂, and implementation of closed pit cushion as soon as possible.