Rebound Mechanism Of Foundation Piles In Deep Foundation Pit Excavation And Its Effect On Uneven Settlement Of Buildings

With the continuous development of modern cities,China's urbanization is accelerating,and the population of major cities is increasing.With the increasing development of underground space in cities,the wider and deeper foundation pit projects are also increasing.Faced with many problems,such as how to effectively control the deformation of foundation pit and its supporting structure,how to control the rebound deformation of foundation pile and the uneven settlement in the later loading process,and how to achieve reasonable cost under the premise of ensuring safety.Based on the measured data of the deep foundation pit of Ren Heng Plaza Phase IV in Nankai District of Tianjin City,this paper establishes a three-dimensional finite element model to simulate the process of foundation pit excavation and loading,and explores the mechanism of pile rebound and uneven settlement of buildings during the process of deep foundation pit excavation.In addition,the relevant prevention and control measures of uneven settlement of pile groups during loading process are put forward,which has certain guiding significance for engineering design.This paper monitors the deep foundation pit engineering,collects the data of pile foundation and supporting structure,uses ABAQUS software to carry out finite element simulation,and compares it with the measured results.The influence of rebound of foundation pit on the force and stiffness of foundation pile is studied.The existing calculation models are optimized,and the concrete damage model and other constitutive models are used to simulate and analyze.Using the validated finite element model,the plastic development zone of the pile body during excavation is explored.Finally,the relevant factors affecting the rebound value are discussed,and the rebound influence zone is divided.The results show that under the condition of deep foundation pit excavation,the concrete of pile body will crack and the plastic zone will develop,which has a great influence on the vertical stiffness of pile body.For piles with the same location,different length and different location,there are great differences in axial force,rebound,side friction and other aspects,and the uneven settlement of pile foundation after loading in later period is larger.In this paper,the phenomenon of uneven settlement of pile and superstructure is studied because the rebound degree of foundation pit is different in different positions,and then in the later loading process.The results show that the uneven settlement of pile groups is greatly affected by the degree of rebound at different locations,and the proportion of uneven settlement is 50% higher than that of non-excavated foundation pits.The uneven settlement of pile groups can be reduced by using different length of engineering piles at different locations,controlling the spacing of piles and changing the pile arrangement.