Deformation Prediction And Deformation Control Research Of Retaining Structure Under Foundation Excavation

In recent years,with the acceleration of urbanization and the continuous improvement of urban infrastructure,foundation pit engineering,as an indispensable part of urban construction,has received more and more attention and importance.During the construction of foundation pit project,the deformation of the retaining structure is a very critical issue.The unreasonable design of the retaining structure leads to the excessive deformation of the retaining structure and the surrounding environment,which is directly related to the safety and construction quality of the project.The existing methods for predicting the deformation of the retaining structure often use finite element simulation and empirical formula calculation,which can not consider the influence of deformation due to the change of construction parameters during the construction process.Most of the existing foundation pit retaining research results are about symmetrical foundation pits,while many factors such as soil conditions restrictions,the presence of a basement on one side,etc.will lead to the excavation of the foundation pit under asymmetrical situation.In this case,if the design of the retaining structure is only designed according to the deeper side of the force,the shallow side of the retaining structure will be underutilized,resulting in the waste of human and material resources.Therefore,it is important to investigate the deformation prediction method of retaining structure and the deformation control theory of asymmetric excavation pit.For this research area,the following work is carried out in this paper:(1)Relying on the actual measurement data of the foundation pit project of Yuhang high-speed railway station,the change law of the top deformation of the retaining structure caused by symmetric excavation of the foundation pit,horizontal displacement of the enclosure structure,surface settlement around the foundation pit and horizontal displacement of the enclosure structure during asymmetric excavation of the foundation pit were studied.And the main stages of deformation and the causes of deformation were summarized.(2)Support vector machine model and multiple layer perceptron model in artificial neural network were introduced to predict the maximum horizontal displacement of the retaining structure triggered by foundation excavation,and the prediction effects of the two models were compared.Two improved recurrent neural network models,LSTM and GRU,were introduced to predict the horizontal displacement of the retaining structure at different stages of foundation excavation,and the differences between these two models and the traditional artificial neural network models were compared in terms of prediction effects.(3)Based on the equivalent beam method and common deformation method,the calculation formula of the length of the retaining structure during asymmetric excavation is derived by correcting the earth pressure acting on the enclosure structure according to the change of the displacement of the enclosure structure.And the validity of the calculation formula is verified by finite element simulation,anti-bulge stability verification and earth pressure distribution analysis,and the influence of the excavation depth on the insertion ratio of the enclosure structure on the deep and shallow side of the asymmetric excavation is further analyzed.