上海地区板式支护体系基坑变形预测简化计算方法

Simplified method of deformation prediction for excavations retained by embedded walls in Shanghai soft soil

基坑变形预测是分析基坑开挖对环境影响的核心内容之一。收集了上海地区65个常见的板式支护体系基坑工程案例,并对其进行了分类。对不同类型的板式支护体系基坑建立不同的基于土体HS-Small模型的平面应变有限元模型进行分析。根据室内土工试验结果与基于实测数据的参数反演分析,确定了上海软土地区典型土层土体的HS-Small模型计算参数。通过对108个有限元计算结果的分析及归一化,推导了能够综合考虑基坑系统刚度、基坑深度和基坑宽度的上海地区板式支护体系基坑围护结构最大侧移和地表最大沉降的简化计算公式,并且提出了基坑围护结构侧移曲线和地表沉降曲线,同时也给出了上海地区板式支护体系基坑变形的预测流程。采用本文给出的简化方法预测了上海地区的7个工程的变形并与实测结果进行了比较,结果表明该方法能较好地预测上海地区的板式支护体系基坑的变形。

Deformation prediction of excavations is one of the core contents in analyzing their effect on environment. 65 case histories of excavations retained by embedded walls in Shanghai are collected and divided into different groups. Plane strain finite element models are set up to simulate the construction procedures of excavations retained by embedded walls of different groups. The parameters of HS-Small model for Shanghai typical soil layers are got from laboratory tests and back analysis, The simplified calculation formulas considering system stiffness, excavation depth, excavation width for the maximum lateral deformation of embedded walls and the maximum ground surface settlement are deduced by normalizing 108 FEM results. The lateral deformation profile of embedded walls and the ground surface settlement profile behind the embedded walls are provided. The procedure of adopting the simplified analysis method is also illustrated. Comparison of the monitored deformations of 7 case histories and predicted deformations using the simplified analysis method reveals that the proposed simplified method is suitable for analyzing deformation of deep excavations in Shanghai.