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根据基坑开挖深度、地层条件的不同,对北京市轨道交通80个明挖顺作法基坑工程实测结果进行统计分析,研究确定北京砂卵石和黏性土地区深基坑开挖引起的桩体变形规律。研究表明:1围护桩顶和桩体均存在向基坑内和基坑外两个方向的水平位移,水平位移实测结果分布形态均近似符合正态分布。2围护桩整体最大变形均以桩体变形为主,桩向基坑内水平位移平均值约为0.05%H~0.12%H,向基坑外水平位移平均值约为0.02%H~0.07%H。3插入比、长宽比、基坑系统刚度等对桩的最大水平位移有一定的影响。4桩向基坑内水平位移最大值主要出现在0.26H~0.45H处,向基坑外水平位移最大值主要出现在0.18H~0.20H处。研究成果可对未来北京及其他地区城市轨道交通基坑工程变形大小及安全性的预测和评估,指导基坑工程设计与施工工作,对防止基坑事故的发生具有重要意义。
According to the different excavation depth and stratum conditions, the statistical analysis is made on the actual measured results of 80 excavation and foundation pit excavation works in Beijing Metro. Body deformation rules. The results show that: 1 Both the top and the pile body of retaining wall have horizontal displacement to both inside and outside of the foundation pit, and the distribution of the measured results of horizontal displacement all approximate the normal distribution. 2 The maximum deformation of the whole retaining pile is mainly the deformation of piles. The average horizontal displacement of piles to the foundation pit is about 0.05% H ~ 0.12% H, and the horizontal displacement outside the foundation pit is about 0.02% H ~ 0.07% H . 3 insertion ratio, aspect ratio, stiffness of foundation pit system and so on have a certain impact on the maximum horizontal displacement of piles. The maximum horizontal displacement of piles to the foundation pit mainly appears at 0.26H ~ 0.45H, and the maximum horizontal displacement outside the foundation pit mainly appears at 0.18H ~ 0.20H. The research results can predict and evaluate the size and safety of urban rail transit pit excavation in Beijing and other regions in the future and guide the design and construction of the foundation pit engineering, which is of great significance in preventing the occurrence of foundation pit accidents.