Research On Deformation Based On Orthogonal Test And Prediction Of Deep Foundation Pit

With the continuous development of the city,urban land is becoming more and more tense,the scale of foundation pit is becoming larger and larger.The foundation pit excavation will inevitably lead to the overall deformation of the foundation pit.How to control the deformation,ensure the safety of the foundation pit and reduce the influence on the surrounding environment become the most important.The deformation of foundation pit is influenced by many factors.Most of the existing research results are used to analyze the influence of various factors on the deformation of foundation pit separately,and the deformation rules of foundation pit under multiple factors are not analyzed.At the same time,due to the importance of deep foundation pit engineering,the research on the influence factors of the deformation of deep foundation pit should be strengthened.Neural network can better simulate the nonlinear deformation of foundation pit,so it is often used to predict the deformation of foundation pit by neural network.However,most of the existing research results adopt the early deformation data to predict the later deformation,and have high requirements for the continuity of the construction.Based on the study of the influence factors of foundation pit deformation,this article discusses the neural network deep foundation pit excavation modeling method.It can better reflect the complexity of the construction process of foundation pit excavation.This article focuses on the study:(1)Based on the engineering example of a deep foundation pit under construction,according to the deformation monitoring results of foundation pit engineering,the monitoring data of diaphragm wall horizontal displacement and pit subsidence in foundation pit excavation are analyzed,and the deformation form and rule of foundation pit during excavation are revealed.(2)With the help of FLAC-3D finite difference software,the whole process of excavation of foundation pit is numerically simulated,and the deformation law of foundation pit in the process of excavation is analyzed.The horizontal displacement of the diaphragm wall first appears "inverted triangle" and then "arch".The maximum settlement outside the pit appears at a distance from the foundation pit,and the curve shows a "groove" distribution.Although there is a deviation between the simulation results and the monitoring results,the variation of the model is basically consistent,which verifies the reliability of the model.With the help of orthogonal test and numerical simulation model,the deformation law and action mode of foundation pit excavation under multiple factor adjustment are compared synthetically.The SPSS software is used to analyze the linear expression for the influence of the supporting stiffness and the thickness of the diaphragm wall on the horizontal displacement of the diaphragm wall and the surrounding settlement of the foundation pit.When the ground settlement is taken as the reference value,the order of influence is as follows:the elastic modulus of soil,the thickness of diaphragm wall,the cohesive force of soil,the supporting stiffness and the internal friction angle of soil.When the horizontal displacement of the diaphragm wall is taken as the reference value,the order of influence is as follows:the elastic modulus of soil,the thickness of the diaphragm wall,the supporting stiffness,the internal friction angle of the soil,and the cohesive force of soil.(3)The BP network construction modeling methods based on equal interval,monitor time and influence factors are discussed respectively.Based on the analysis of influence factors of foundation pit deformation,the factors affecting the prediction model are selected as follows:the elastic modulus of soil,the cohesive force of soil,soil unit weight,excavation depth and number of inner supporting layers.With the help of monitoring data,the accuracy and feasibility of the prediction model are verified,and some suggestions are provided for the design of similar foundation pit engineering and the deformation control in the construction process.