Simulation And Optimization Of Deep Foundation Pit Excavation And Dynamic Prediction Of Construction

In recent years, with the development of our national economy, the scale and depth of the deep foundation pit engineering reached a new record. As an important part of the excavation of deep foundation pit project, it's difficult to research because it involvses so many factors. Although China has successfully completed the design and construction of some large foundation pit projects, but due to the lack of theoretical knowledge and engineering experience, foundation pit accidents still occur frequently, the accident rate accounted to more than 1/4 of the total excavation of foundation pit projects. In a manner of speaking, the excavation stage is the most important point to control the deformation of foundation pit and pit accident. Therefore, using the numerical simulation of computer technology to analyse the process of foundation pit excavation has important engineering significance. At the same time, using information technology combined with the on-site data to back analyse the calculate parameters accurately and predict the foundation pit construction process in a dynamic way which can greatly reduce the accident rate during the construction of foundation pit and save the economic cost.This thesis combines the deep foundation pit project of HengDa center in Hefei, using MIDAS-GTS finite element software to make umerical simulation analysis of feasible schemes of foundation pit excavation and to select the best scheme. At the same time using back analysis method and the BP neural network to inverse the soil mechanical parameters, so the deformation characteristics of foundation pit in the next construction stage can be forecasted and the guiding opinion of the construction can be given. There is a number of work for this paper:(1) This thesis summarizes several common ways to excavate the deep foundation pit project, introduces the advantages and disadvantages and applicability of different excavation methods, and puts forward the preliminary design process of foundation pit excavation scheme, discussed the factors which can influenced the feasibility of foundation pit excavation scheme.(2) This thesis based on the background of practical engineering, according to the field conditions of the actual project site, proposed three feasible construction schemes to excavate the foundation pit.(3) The thesis combined with the practical engineering case, using MIDAS-GTS finite element analysis software to make numerical simulation analysis of three feasible excavation schemes.(4) This thesis tracking the construction, according to the construction data which measured in the site, using back analysis method to inverse the key mechanical parameters of excavation stage, then using the parameters which inversed by back analysis method to predict the deformation and stability of the next construction stage of foundation pit while propose the guidance of construction.(5) This thesis makes research in accordance with the influence of the excavation of foundation pit in the "pit in pit", before the excavation, using the data which measured by construction site to inverse the key mechanical parameters, then using the positive analysis method to simulate the influence of pit deformation of support system when excavating the “pit in pit”.