中文摘要：

通过对宽大型软土基坑坑底隆起特性及形成机理分析,将坑底土体划分成强作用区、弱作用区和自由变形区,提出综合考虑基坑开挖深度、围护结构插入比和土体性质的强、弱作用区边界计算方法;根据基坑开挖宽度不同时,坑底隆起作用区的变化情况,提出考虑坑底隆起宽度效应的基坑分类方法：将基坑划分为超大尺度基坑、大尺度基坑、小尺度基坑和沟槽类基坑4类,并明确各类基坑的宽度范围。最后结合上海某软土基坑工程实例,采用有限元法数值分析对本文提出的理论分类方法的正确性进行了验证。

英文摘要：

Through analyzing characteristics and forming mechanism of basal heave of the wide excavation in soft soil, by dividing basal soil mass into strong interacting region, weak interacting region and free deformation region, this paper puts forward a computing method of boundary length for different heave areas considering the excavation depth, embedment depth and soil properties. Then the foundation pits classification method considering the width effect is presented. In terms of transformation of each region in the process of excavation width change, excavation can be classified into extra-large scale excavation, large scale excavation, small scale excavation and trenches, whose width area of different foundation pits is given. The validity of this classification system is verified by FEM method combined with an excavation project in Shanghai.