软土区超深箱式挡墙支护结构监测与仿真优化

Monitoring and Simulation Optimization of Ultra-deep Box Retaining Wall Supporting Structure in Soft Soil Area

摘要:

为了阐明新型超深箱式挡墙在软土区深基坑围护体系中的工作性状，以上海软土区某箱式挡墙基坑工程为依托，基于现场原位监测数据分析开展深基坑开挖全过程有限元数值仿真。箱体挡墙应力及测斜监测结果表明箱式挡墙支护结构刚度较大，向坑内滑移及倾覆趋势不明显。基于不同宽度的箱式挡墙的有限元数值仿真结果，评价其抗滑移、抗倾覆稳定性并验算承载能力，发现前、后墙和桩顶抗剪力对结构抗滑移稳定性的贡献最大，结构自重和后墙轴向拉应力对抗倾覆稳定性的贡献最大，而地基反力和前墙轴力对承载力的贡献最大。仿真优化结果表明：从抗滑移、抗倾覆和承载力等安全性方面考虑，箱式挡墙结构宽度取0.45倍基坑深度时，箱式挡墙支护结构的墙体、隔板、底板的承载力既得以充分发挥，满足规范要求，同时能提高构件利用率，节约工期，经济性更好。研究成果对后续软土区箱式挡墙支护基坑工程的设计和参数优化具有参考意义。

关键词:软土;箱式挡墙;监测;优化分析;有限元分析

Abstract:

In order to elucidate the working performance of the new ultra-deep box retaining wall in the deep foundation pit enclosure system in the soft soil area, relying on a box retaining wall foundation pit project in the soft soil area of Shanghai, the finite element numerical simulation of the whole process of deep foundation pit excavation is carried out according to the analysis of the in-situ monitoring data. The monitoring results of stress and slope measurement of box retaining wall show that the stiffness of the box retaining wall is large, and the tendency of sliding into the pit and overturning is not obvious. Based on the finite element numerical simulation results of box retaining walls with different widths, the stability against sliding and overturning is evaluated, and the bearing capacity is calculated. It is found that the shear resistance of front wall, rear wall and pile head contributes the most to the anti-sliding stability of the structure. The structural dead weight and the axial tensile stress of the rear wall contribute the most to the stability against overturning. And the foundation reaction and the axial force of the front wall contribute the most to the bearing capacity. The results of simulation and optimization show that considering the safety of sliding resistance, overturning resistance and bearing capacity, when the width of the box retaining wall structure is taken as 0.45 times of the depth of the foundation pit, the bearing capacity of the wall body, partition and base plate of the box retaining wall support structure can be given full play to meet the specification requirements, and at the same time, the utilization rate of components can be improved, the construction period can be saved and the economy can be better. The research results have a reference significance for the design and parameter optimization of the subsequent foundation pit engineering of box retaining wall in soft soil area.

Key words:soft soil;box retaining wall;monitoring;optimization analysis;finite element analysis