分层降水开挖对超大平面深基坑坑底回弹及桩基的影响

Influence of Layered Dewatering and Excavation on Pile Foundation and Base Rebound in a Super-large Deep Foundation Pit

基坑回弹既破坏先期实施结构,也影响工后沉降本文基于经典土体压缩及回弹理论,考虑土体应力路径变化,建立了考虑基坑分层降水开挖的坑底回弹理论模型,研究了超大平面深基坑中分层降水开挖对坑底回弹的影响,并基于有限元分析了桩土地基分层降水开挖时坑底回弹及桩身轴力分布。结果表明,坑底回弹与土体应力路径有关,基坑降水开挖分层越多坑底回弹越大;桩土地基中降水开挖分层越多,桩身受拉状态越久,但最终桩身应力分布与分层数无关。

The rebound of foundation pit not only destroys the structure stability during construction,but also affects the settlement after construction.In this paper,a theoretical model of foundation pit rebound considering of the layered dewatering excavation has been established.This model is based on the classic soil compression and rebound theory and takes into account changes in soil stress paths.The model is then used to study the influence of layered dewatering excavation on base rebound in a super-large deep foundation pit.The pit rebound deformation and pile axial force distribution during layered dewatering and excavation are analyzed using finite element method.The results show that the rebound at the bottom of the pit is related to the soil stress paths,and the rebound deformation increases with the number of dewatering and excavation layers of the foundation pit.The more layers,the greater the rebound deformation and the longer the pile remains in tensile state.However,the final stress distribution of pile is independent of the number of layers.