邻近边坡地铁车站基坑顺逆结合施工稳定性分析

Analysis on the stability of bias metro station pit excavated through the combination method of bottom-up and top-down technology

随着城市地铁线路穿越山地环境及交通干线的日益增多,车站基坑邻近边坡以及横跨交通干道作为两种典型的特殊施工环境变得愈发难以避免,而采用顺逆结合施工技术可有效缓解基坑工程与现有交通的矛盾.现有研究对于偏压环境下地铁车站基坑顺逆结合施工过程的系统分析相对欠缺,为分析偏压环境及顺逆结合施工方式对于基坑稳定性的影响,本文依托深圳轨道交通2号线莲塘口岸站工程,基于现场监测数据分及数值模拟方法对偏压环境下顺逆结合施工过程中地层及围护结构的稳定性情况进行了研究.结果显示,施工过程中基坑土体及围护结构均处于稳定状态,施工完成后地表沉降主要影响区分布在0~1.25H之间,次要影响区在1.25~2.0H之间,沉降最大值出现在0.25H区域附近(H为基坑开挖深度),相对于无偏压环境扩大了25%的沉降影响范围.边坡偏压的存在主要影响邻近边坡处围护桩变形,偏压侧拉锚作用可显著减小围护桩的水平变形,相对于无锚索情况可有效缩减10倍的围护桩水平变形.

With the increasing number of subway lines crossing the mountain and transport arteries,it becomes more difficult to avoid the situation of the station adjacent to side slope and the cross-city traffic artery.Through the combination method of bottom-up and top-down technology,contradiction between the foundation pit project and the existing traffic can be well relieved.There is a lack of systematic analysis on the construction process of the subway station foundation pit under the bias environment.Based on the project of Liantangkouan metro station of No.2 rail line in Shenzhen,deformation characteristics of stratum and supporting structures were analyzed through practical monitor data and numerical simulation method,to obtain the effect of bias pressure of high slope and the construction method.As the results shown,the foundation pit soil mass and the surrounding structure are in a stable state during the construction.Also,the main impact area of surface subsidence is distributed between 0~1.25H,when the secondary impact area is between 1.25~2.0H(“H”refers to the depth of excavated pit).The maximum settlement is distributed around 0.25H.The influence range of settlement is increased by 25%compared with the unbiased environment.Moreover,the existence of slope bias mainly affects the deformation of retaining piles near slope.The anchor tension plays an important role that the maximum horizontal deformation of the support piles can be reduced by approximately 10 times.