软土地基基坑开挖对坑底桩受力与位移影响的时效分析

深基坑开挖卸荷会对坑底工程桩的桩身受力和位移特性产生影响,同时在实际工程中,软土在开挖情况下具有较为明显的蠕变效应,但较少有人研究蠕变对坑底工程桩桩土相互作用的影响。采用两阶段分析方法,第一阶段基于H-K三参量模型推导出Mindlin的时域解,提出了一种用于计算基坑开挖卸荷引起的坑底土体竖向附加应力的计算方法,并进一步解得坑底土体竖向位移场的时域解。第二阶段通过建立桩身控制方程,利用有限差分法得到开挖卸荷后考虑坑底土体蠕变变形的单桩非线性分析方法。研究结果表明,得到的时域解能够较好地反映软土基坑开挖条件下考虑土体蠕变变形时坑底单桩的桩身轴力和位移特性发展趋势,为相关工程提供参考。

Time Effect Analysis of Foundation Pit Excavation on Pile axial force and Displacement in Soft Soil Foundation

The excavation unloading of deep foundation pit will affect the pile stress and displacement of pile in pit bottom engineering. At the same time, in practical engineering, soft soil has obvious creep effect under excavation, but few people study the influence of creep on pile-soil interaction in pit bottom engineering.A two-stage analysis method is used in the article, In the first stage, the time domain solution of Mindlin is derived based on the H-K three-parameter model, and a method for calculating the vertical additional stress of the bottom soil caused by excavation unloading is proposed, then the time domain solution of the vertical displacement field of the bottom soil is obtained. In the second stage, the nonlinear analysis method of vertical loaded single pile considering creep deformation of bottom soil after excavation unloading is obtained by establishing pile control equation and finite difference method. The results show that the obtained time domain solution can better reflect the change and development trend of axial force and displacement of single pile at the bottom of the pit under the condition of soft soil foundation pit excavation considering soil creep deformation, and provide reference for related projects.