苏州地铁车站基坑多支点咬合桩插入比分析

Analysis of ratio of embedded depth of multi-pivot secant piles to excavation depth in Suzhou subway stations

以苏州地铁一号线南施街站咬合桩支护结构为例,运用深基坑支护结构分析软件,对插入比与基坑变形、支护结构内力的关系进行了分析.结果表明,咬合桩的最大侧移并非随插入比的增加而无限制地减小,当插入比达到一定值后,继续增加插入比几乎不能减小咬合桩的最大侧移;插入比对最大坑外地表沉降、最大支撑轴力、咬合桩桩身最大弯矩和最大剪力的影响与此类似.因此,在满足抗渗流稳定性验算的条件下,苏州地铁车站基坑多支点咬合桩的插入比建议取为0.7～0.8,这样既能保证基坑的稳定和支护结构的安全,又能减少工程量,降低工程造价,且优化后的咬合桩支护结构仍具有较大的安全储备.该研究可为后续地铁线路及城市高层建筑的基坑设计提供借鉴.

Taking a foundation pit of Nanshijie station in Suzhou subway as an example, the rela- tionship between the ratio of the embedded depth of the secant pile to the excavation depth and the deformation of the foundation pit and the internal forces of the retaining structure is analyzed to de-termine the suitable embedded depth by deep excavation design software. The results show that the maximum lateral displacement of the secant pile wall does not reduce monotonously with the increase in the ratio of the embedded depth to the excavation depth, and it is little affected by the increase in the ratio of the embedded depth to the excavation depth when the ratio reaches a certain value. Thesimilar regularity can be found in the influence of the ratio of the embedded depth to the excavationdepth on the maximum ground surface settlement, the maximum axial force of each support, the maximum bending moment and shear force of the secant pile wall. Therefore, it is considered to beoptimum when the ratio of the embedded depth of the secant pile to the excavation depth in Suzhou subway stations is between 0. 7 and 0. 8 after checking computations of stability of resistance to pene- trability. This reference range can not only guarantee the stability of the foundation pits and the secu-rity of the retaining structures, but also reduce the engineering quantity and the construction costs. And the suggested values still have large safety reserve. This study provides a reference for the de- sign of the foundation pits of other subway lines and urban high-rise buildings.