以武汉凯德广场古田项目深基坑工程为例,通过多级支护结构的使用,减少了大面积设置内支撑,有效地解决了传统桩撑支护造价高、工期长、拆除支撑产生的固体废弃物易造成环境污染等多方面的问题,取得了较好的社会经济效益。使用有限元方法对双排桩与单排桩组合多级支护结构深基坑的变形特性和稳定性进行了深入的研究。结果表明:基坑整体稳定性和破坏形式与2级支护间距有较大关联,与留土高度关系不大;随着2级支护间距的增大,第1、第2级支护最大水平位移均减小,基坑整体稳定性提高;随着留土高度的增大,第1级支护最大水平位移减小,而第2级支护最大水平位移增大,基坑整体稳定性基本不变。最后提出了整体式破坏、关联式破坏和分离式破坏分别对应的2级支护间距范围,可为基坑设计计算提供借鉴。

Traditional pile-bracing retaining structure is featured with many disadvantages such as high cost, long construction period, and large amount of solid waste produced by the demolishing of inner retaining structure. By adopting multi-level retaining structure composed of double-row pile and single-row pile, the above mentioned problems are effectively solved, and good social and economic benefits are achieved. The deep foundation pit of Capital Land’s Gutian project in Wuhan is taken as engineering background. Furthermore, the deformation and stability of the multi-level retaining structure are studied through finite element numerical simulation. Results conclude that the safety factor of stability and failure pattern have great correlation with the spacing between the two-level retaining piles, but have almost no concern with the height of earth berm. With the increasing of spacing between the two-level retaining piles, the maximum horizontal displacement of the first and second supporting piles both decreased, while the stability of foundation pit increased. With the increasing of height of earth berm, the maximum horizontal displacement of first-level retaining decreased whereas the second-level retaining increased, and the stability of foundation pit barely changed. Finally, the ranges of spacing between the two-level retaining piles corresponding to integral destruction, relational damage and separated damage, respectively, are given for reference for foundation pit design and calculation.