基坑开挖引起的周边土体三维位移场的简化分析

虽然不少经验方法可以用来计算基坑开挖引起的地表沉降以及围护墙水平位移，但是目前基坑开挖引起的地表以下土体位移场的预测缺乏简单的计算方法，而主要依赖于有限单元法。有限元分析中如何选用合理的参数来准确计算开挖引起的土体位移一直是个难题。在有限单元法的基础上，考虑土体小应变特性，基于芝加哥地区实际基坑工程的实测数据，通过反分析方法确定了能够准确计算基坑开挖引起的土体位移的合理计算参数。利用这些参数较为准确地计算了基坑开挖引起的土体位移，总结了基坑周边土体三维位移场的衰减规律，并由统一表达式来表示，同时结合围护墙水平变形与墙后地表沉降的经验公式，通过二次拟合提出了基坑周边土体三维位移场的简化计算方法。通过与有限元计算结果以及实测结果的对比，验证了该方法的合理性。

Simplified method for analysis of soil movement induced by excavations

At present, the prediction of the free-field soil movement caused by the excavation of foundation pits, which mainly depends on the finite element method, lacks simple methods. Usually, the accuracy of the prediction for soil movement induced by excavations through FEM depends on soil models and the selection of parameters for the corresponding soil model. However it is hard to identify reasonable parameters for soil models in FEM to calculate the soil movement accurately in practice. Considering the small strain behavior of the soil, HSS model, which can be used to calculate the soil movement induced by the excavation accurately, is employed in FEM. The soil parameters for HSS model are identified based on the inverse analysis coupled with FEM. Based on the relatively accurate soil movements calculated by FEM with those parameters, the attenuation laws of the soil movement behind the wall are generalized. Coupled with the empirical methods to calculate the wall movement and ground settlement induced by the excavation, a simplified method to calculate the soil movement induced by excavation is developed. It is verified through comparisons with FEM and the measured results. It can be concluded that the proposed method is reasonable to calculate the soil movement induced by excavations, and it is a useful tool for the design of excavations.