基坑反压土时间效应影响的有限元分析

Finite Element Analysis of Time Effect Influence on Foundation Pit

由于软土具有较强的流变性,基坑变形除了考虑瞬时变形还有必要考虑蠕变变形,目前基坑考虑软土蠕变变形方面的研究较少。本文在基坑开挖反压土分析时考虑了其时间效应的影响,采用PLAXIS 3D有限元软件中的三维软土蠕变模型(SSC模型),并结合具体工程实例,计算了反压土对于围护结构变形和内力、土体应力和对环境的影响的时间效应,并考虑当反压土面积一定时,随着时间的发展,宽高比与围护结构变形和内力以及土体应力的变化存在一定比例关系。工程表明,缩短工期、控制反压土暴露时间、控制降水并且必要时可对反压土进行一定的加固,可减少反压土蠕变变形,增强反压土稳定和安全性,同时也增强了基坑的整体稳定性。

As the soft soil has a strong rheology character,the deformation of foundation is composed of two parts,namely,the instantaneous deformation and creep deformation. At present,the research on deformation of foundation pit considering deformation of soft soil creep is little. This paper considers the time effect on analysis of earth berm excavation. Using three-dimensional Soft Soil Creep model( SSC model) in PLAXIS 3D finite element software,combined with specific examples of projects,this paper calculates the time effect of earth berm on deformation and internal force of the building envelope,soil stress and environment. When the earth berm area is the same,with the development of time,the aspect ratio and deformation of retaining structure and internal forces as well as changes in soil stress has a certain proportional relationship. The projects show that shortening the construction period,controlling anti-compacted soil exposure time,controlling precipitation,if necessary,with certain earth berm reinforcement can enhance the stability and security of earth berm,and enhance the overall stability of foundation pit.