| The formation,distribution,and complexity of the engineering properties of the rock formation are objective.The site survey does not fully and truly reflect the entire site’s stratigraphic structure and its engineering geology and hydrological conditions.During the construction of the foundation pit,the soil excavation will inevitably lead to displacement of the surrounding surface and deep soil,changes in groundwater level and changes in the nature of the formation,resulting in changes in physical and mechanical parameters of the soil.If the foundation pit support design and construction are only based on the parameters of the rock strata obtained from the engineering survey,it will not reflect the change process of the internal force adjustment and deformation development of the foundation pit supporting structure caused by the change of the stratum properties during the construction process.Reasonable pit design.Therefore,how to use informatization monitoring data to invert the dynamic changes of formation parameters and actual parameter values,thereby tracking and reviewing the safety of supporting structures and ensuring the stability and safety of the surrounding environment is a problem that needs to be solved in the foundation pit project.There are difficult problems.This paper aims at the change of geotechnical properties caused by the deformation of the foundation pit and pile support structure,the variation of groundwater level,the creep of support structure,and the surrounding additional load,which in turn leads to the objective fact that the safety of foundation pit supporting structure is reduced.A three-dimensional finite element model of Midas-GTS was established and a Matlab program was written to study the safety of the pile-anchor support structure in the foundation pit and the response law of the dynamic change of geotechnical parameters.At the same time,combined with the actual case of the foundation pit project of the Yishang Baishangcheng project,through the monitoring data of different stages of the foundation pit project,the calculation results of the back analysis program and the calculation results of the three-dimensional finite element analysis model,the three-dimensional finite element was revised.The model and optimization of the anti-analysis procedure will further predict the excavation deformation of the foundation pit in the later stage,and put forward prevention and control measures for the possible risks encountered by the pile anchor supporting the foundation pit.The main content of this article includes the following aspects:(1)Study and analyze the interaction mechanism between soil and supporting piles,soil and anchor rods,supporting piles and anchor rods.The commonly used deformation calculation methods for piles and anchored foundation pits are summarized as theoretical analysis methods,empirical estimation method,Numerical simulation method,determine the numerical simulation method as the analytical calculation method of this paper.(2)Introduce the basic theory of back analysis,select the direct method(positive and negative analysis method)in numerical method as the research method of this article;introduce the basic principles and operation flow of BP neural network algorithm and genetic algorithm;optimize the BP neural network using genetic algorithm The thresholds and weights of the algorithm get better GA-BP neural network algorithm;Matlab program to compile GA-BP neural network algorithm;(3)According to the actual situation of the project,define the assumptions,material parameters,and boundary conditions of the Midas-GTS model,select the MC model as the constitutive model of the soil,and establish a finite element model that meets the actual conditions of the project;(4)Uniform test design of soil parameters,analysis of the deformation displacement of the foundation pit under different soil layer parameters,simulation of the soil parameters in the uniform test,simulation deformation results calculated by the three-dimensional model,and actual monitoring results of the early construction of the foundation pit.The normalized processing results in the sample data of the GA-BP neural network algorithm.Based on this,the GA-BP neural network algorithm is optimized to complete the cycle of optimization,learning,training,and optimization,and the deformation displacement of the pile-anchor support structure in the foundation pit is established.Nonlinear mapping model with rock and soil parameters.(5)According to the GA-BP neural network algorithm program and Midas-GTS model after optimization of training,the inverse analysis of the soil parameters is carried out to predict the possible deformation during the further construction of the foundation pit and analyze the safety and reliability of the foundation pit.(6)Explain the risk that the foundation pit of the pile-anchor support may present in the construction process,analyze and discuss the reasons for the risk of the foundation pit of pile-anchor support from the four perspectives of survey,design,construction and management,and propose the risks accordingly.Control measures. |
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