软土地区深基坑变形特性分析

Analysis of the deformation characteristics of deep excavations in soft clay

随着地下空间开发利用规模的加大,基坑工程向更深更大的方向发展。本文就杭州和上海软土地区46个成功深基坑的实测结果进行了研究和总结,分析了基坑开挖深度与最大侧移及其位置的关系,分析了当前基坑开挖深度和所采用支撑系统相对刚度之间的关系。由于抗隆起稳定安全度与基坑变形的关系密切,本文就实测数据进行分析并建立了抗隆起稳定安全系数与围护体最大侧移和墙后最大地面沉降与之间的关系。并对随深度增加后深基坑的变形控制标准提出自己的观点。通过实测数据的分析,有以下结论:随着基坑深度的增大,由于支撑系统的相对刚度迅速增长,使得最大相对侧移值并没有增大,最大侧移位置一般发生在开挖面附近,随基坑深度的增加有向上移动的趋势,抗隆起稳定安全度的提高对减小基坑的变形具有重要的作用,随着基坑深度的增加,基坑的变形在超出当前规范的控制标准时亦可实现基坑自身和周围环境的安全。

Excavations are becoming deeper and larger with the increasing scale of underground space exploitation. In this paper, 46 case histories of deep excavations in soft clays in Hangzhou city and Shanghai city are summarized and studied, the relationships between the excavation depth and the magnitude and location of the maximum lateral displacement, and the excavation depth and the relative stiffness of the supporting system are analyzed. As the heaveresistant stability is strongly related with the deformation of the excavation, the relationships between the safety factor of heave-resistant stability and the maximum lateral displacement and the maximum ground surface settlement are analyzed and established. Suggestions on the deformation control criterion for deep excavations are put forward. The conclusions include： 1） with the increase in the depth of excavation, the maximum relative lateral displacement tends to occur in the vicinity of the excavation face and the location tends to move upwards; 2） Increase in heave-resistant stability has important effect on decreasing the deformation, and the excavation as well as its surrounding environment may remain safe even when the deformation exceeds the control criterion prescribed in the current design code.