Deformation of metro station excavation and its influence on nearby pile foundations of bridge
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摘要: 采用三维显式有限差分数值模拟研究了上海软土地区某下穿城市高架桥梁并紧邻其下部桩基的地铁车站深基坑的变形及其对桥梁桩基的影响。基于FLAC3D建立考虑土体、基坑围护结构及桥梁桩基相互作用的三维整体计算模型，采用修正剑桥模型描述土体的变形特性，并根据实际施工工况划分不同的计算模拟步骤。基坑围护结构侧向变形计算值与现场实测值基本吻合，表明采用三维数值模型预测现场无法实施监测的承台下部桩基的变形是可行的。参数分析及现场实测数据与上海软土地区其他地铁车站深基坑实测数据的对比表明，本工程所采用的基坑支护结构方案调整、坑内地基加固及局部中板逆作等技术措施，不但有效控制基坑自身的变形，也有效保护桥梁桩基及上部结构的安全。Abstract: A three-dimensional explicit finite difference simulation is carried out to investigate the deformation of a metro station excavation and its influence on the nearby embedded pile foundations in combination with an underground metro station project in Shanghai soft soil deposits, which is under-crossing an urban elevated bridge and adjacent to its pile foundations. The numerical model, taking account of the interaction among the soil, retaining structures and nearby pile foundations, is established based on the geotechnical program FLAC3D, and the modified Cam-clay constitutive model is adopted to describe the deformation behavior of the soil. The computed lateral displacement curves of the retaining wall agree well with those of the in-situ measurements. This indicates that it is feasible to use the numerical model to predict the performance of the embedded piles underlying the abutment, which can not be monitored at the site. The parametric analysis and the comparison with the other relevant excavation projects show that the adopted countermeasures, which include adjustment of retaining structure scheme, inside ground reclamation and pre-installation of local concrete slab, not only restrict the deformation of the excavation itself effectively, but also protect the safety of the pile foundations as well as the upper bridge appropriately.
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Keywords:
- soft soil /
- excavation /
- pile foundation /
- jet grouting /
- cutoff curtain /
- deformation control
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