深厚富水砂层排桩挡墙深基坑施工变形特性研究

Deformation characteristics of foundation pit excavation of row-pile supporting in deep water-rich sandy stratum

深厚富水砂层深基坑施工风险高、技术难度大、结构受力复杂。以某城市地铁深基坑工程为依托,通过现场测试和数值模拟方法,研究了深厚富水砂层排桩挡墙深基坑施工变形特性。研究结果表明:排桩挡墙水平位移分布曲线随开挖深度按斜线形-弓形-倒V形路径演变;排桩挡墙最大水平位移及其位置与开挖深度的关系可用线性函数描述,最大水平位移Ux,max约为(0.03%~0.15%)he(he为开挖深度),最大水平位移位置Hx,max约为(0.4~1.0)he;地表竖向位移随时间近似呈倒S形曲线分布,地表竖向位移沿横向水平距离呈凹槽形分布,沉降槽宽度约为(1.0~2.0)he,最大地表竖向位移位置距基坑边沿水平距离约为(0.30~0.50)he;保证止水帷幕施工质量及其防渗效果、重视并充分发挥基坑施工监测的预判和反馈作用有利于深厚富水砂层深基坑施工安全。研究成果可为富水砂层地区深基坑支护结构设计和施工变形控制提供参考。

Deep foundation pit construction has the characteristics of high risky, great difficulty and complex structure stress in deep water-rich sandy stratum. Based on the foundation pit of a subway station, the deformation characteristics of a row-pile supporting foundation pit induced by deep excavation in deep water-rich sandy stratum are studied by field monitoring and numerical simulation method. The research results show that the horizontal displacement distribution curve of retaining wall develops from a "oblique line" shape to that of a "bow" and "inverted-V" with excavation depth. The maximum horizontal displacement of retaining wall and its location with excavation depth could be described by linear function. The maximum horizontal displacement Ux,max is about(0.03%~0.15%)he(he is excavation depth), and the location of maximum horizontal displacement Hx,max is about(0.4~1.0)he. The distribution curve of ground vertical displacement behaves as a inverted-S with time, and the ground vertical displacement behaves as a groove shaped curve with an increase of transverse horizontal distance during the construction. The width of settlement trough is about(1.0~2.0)he, and the location of maximum ground vertical displacement is about(0.30~0.50)he away from the edge of foundation pit. The control measures such as ensuring construction quality and anti-seepage effect of waterproof curtain, attention to the prediction and feedback function of construction monitoring are proposed to ensure the construction safety of foundation pit in water-rich sandy stratum. The conclusion could be referenced for the supporting structure design and construction deformation control of deep foundation pit in water-rich sandy region.