Research On Stability Of Pile-concrete Internal Support Structure System

With the development of China’s economic construction,the utilization of urban space becomes more and more tense,and the number of foundation pit projects to meet the needs of urban construction is increasing day by day.At the same time,due to the deepening of the excavation depth of the foundation pit,the increase of the density of urban buildings,the underground pipeline layout of the encryption,the excavation of the foundation pit support difficulty is increasing.In this context,the foundation pit stability problem is more prominent,and the stability of the supporting structure system is an important part of the foundation pit stability.In this paper,the stability of the foundation pit is firstly divided into structural stability and normal use stability.The present situation of foundation pit stability research is summarized,and the foundation pit deformation mechanism and supporting structure theory are systematically analyzed.Based on the theory of structural stability,with laterally-braced compression rod as object,the critical stiffness of lateral support and the corresponding internal force is studied.Then,the stiffness and internal force of laterally-braced compression members are studied.The conclusion of the research above is applied to the stability of foundation pit support system,which provides the theory basis for the design of the connecting rod.Then,taking a practical excavation project as an example,the numerical simulation of excavation process is carried out by using the geotechnical finite element software MIDAS-GTS.This paper makes a comparative study of several factors affecting the stability of foundation pit,obtains the deformation law in the process of foundation pit excavation,and analyzes the influence of different values on the stability of foundation pit.Finally,based on the theory of orthogonal experimental design,the horizontal displacement of row piles,surface subsidence and bottom uplift were taken as the experimental indexes,and the elastic modulus,cohesion,internal friction angle,pile diameter and pile length were selected as factors.Through the range analysis and variance analysis of the test results,the order of the influence of each factor on the foundation pit stability is obtained,which can provide reference for the design and construction of similar foundation pit projects.