临海深厚软土地区地铁深基坑开挖变形规律研究

Deformation Law of Metro Deep Foundation Pit Excavation in Deep Soft Soil Area Near Sea

广州地铁4号线某车站基坑位于珠江三角洲冲(淤)积平原,上覆第四系海陆交互相、冲洪积相地层,软土层厚度巨大,下伏基岩主要为燕山期侵入花岗混合岩,基岩面埋藏较深,难以作为持力层,整体工程地质条件较差.为研究临海深厚软土地区深基坑开挖的变形规律及机理,采用有限元法对深基坑开挖工序及支护过程进行数值模拟.结果表明,该地铁深基坑开挖引起的地面沉降最大值为22.95 mm,坑底土体隆起最大值为29.65 mm,围护结构水平方向位移最大值为34.83 mm,桩顶竖向位移最大值为4.14 mm,变形量均处于基坑工程变形控制范围内.此外,利用基坑支护设计软件进行整体稳定验算及抗隆起验算,进一步证明该基坑在施工过程中处于稳定状态,所采用的支护措施有效.

The foundation pit of a station in Guangzhou Metro Line 4 is located in the alluvial plain of the Pearl River Delta.The soft soil layer is of great thickness,and the underlying bedrock is mainly intrusive granite-mixed rock of Yanshanian period.The bedrock surface buried deep,is difficult to be used as a bearing layer.In order to study the deformation law and mechanism of deep foundation pit excavation in deep soft soil area near sea,the excavation process and supporting process of deep foundation pit are simulated numerically by using finite element method.The results show that the maximum ground settlement caused by deep foundation pit excavation of a metro is 22.95 mm;the maximum heave value of the bottom soil is 29.65 mm;the maximum displacement of the retaining structure horizontal is 34.83 mm;the maximum vertical displacement of the pile head is 4.14 mm,and the deformations are within the control range of foundation pit engineering.In addition,the foundation pit support design software is used to check the overall stability and heave resistant calculation,which further proves that the foundation pit is in a stable state during the construction process and the supporting measures adopted are effective.