深基坑施工围护结构变形的时间特性研究

软土地区深基坑工程施工过程中,时有发生超挖未能及时加撑的现象,由于土的蠕变特性,导致围护结构变形急剧增大。通过弹粘塑性本构模型的二次开发,对软土地区深基坑施工过程中的及时支撑和超挖两种情况进行数值模拟,分析深基坑围护结构变形随时间的变化规律及深基坑的安全性状。结果表明:在每一个工况下,若能及时加撑,深基坑将一直处于安全可控状态;在超挖3m的情况下,围护结构变形特点与及时支撑类似,但达到稳定的时间与变形总量更大;在超挖6m的情况下,围护结构变形特点与上述两者迥异,较短时间之内,深基坑可能会由于变形过大而破坏。

Analysis on Deformation Temporal Characteristics of Retaining Structures in Deep Foundation Pit

During the excavation of foundation pit in soft soil area, the phenomena of over-excavation and not timely support setting occur frequently, and the characteristics of soft-soil creep lead to the sharp increase of deformation of retaining structures. With the secondary development of the elastic-viscose-plastic constructive model, the conditions of normal construction and over-excavation of foundation pit in soft clay area were simulated; the change of retaining structures with time and safety state of foundation pit were analyzed. The research result shows that the foundation pit would be in a safety state if the support was set in time in different construction step. In the case of 3m overbreak, the deformation characteristics of enclosure is similar to that for the case of supporting in time, but there would be more time and deformation for reaching stability. In the case of 6m overbreak, the deformation characteristics are different from both above, and the foundation pit will be fractured because of big distortion.