Study On Dynamic Prediction And Safety Evaluation Of Deep Foundation Pit Deformation

With the advancement of urbanization in China,the population continues to gather to the city,and the high-rise buildings and underground space is more and more,resulting in a large number of deep foundation pit engineering.The deformation prediction and safety evaluation of deep foundation pit is one of the most important tasks in the field of construction design.It is of great significance to predict the pit foundation sort time deformation and long-term long term trends accurately,and to evaluate its safety state scientifically and reasonably.Deformation prediction and safety evaluation of foundation pit is a comprehensive problem involving many subjects such as hydrology,rock and soil,engineering mechanics and so on,The change of any kind of factors may affect the final prediction result,so it is difficult to express the deformation mechanism of the foundation pit,but the monitoring data can directly reflect the results of the comprehensive action.So,it is feasible to determine the current and future trends of the deformation and safety of foundation pit by analyzing the data.The conventional modeling method cannot quickly and accurately predict and quantitatively analyze the safety status of the foundation pit during construction.In this paper,based on the analysis of existing literatures,this paper takes the deep foundation pit engineering of Shanghai Jiangqiao Hotel as the object of study,and takes the deformation monitoring data of foundation pit as the research object.In view of the above problems:(1)This paper summarizes the research progress of deformation prediction and safety evaluation of deep foundation pit at home and abroad,and analyzes the advantages and disadvantages of the existing conventional forecasting model and safety evaluation method in engineering practice.The mechanism of the deformation of the deep foundation pit itself and the surrounding surface and building is discussed.(2)Based on the deep foundation pit engineering of Jiangqiao Hotel in Shanghai,this paper briefly introduces the monitoring network layout and monitoring content of foundation pit project.A representative deformation monitoring point is selected.Elman dynamic neural network and support vector machine(SVM)are used to predict the displacement of the monitoring points by using the trained network model.Combined with historical monitoring data to analyze its long-term deformation trend,and quantitative analysis of the accuracy of the forecast results.(3)For the project only rely on monitoring data and monitoring the warning value cannot be clear to determine the safety of the foundation of the problem.Firstly,the correlation between the probability of occurrence of foundation pit and the monitoring data is summarized statistically.A safety evaluation grade and index system based on the monitoring data is used to evaluate the safety status of foundation pit.The system can convert the monitoring data into the risk value.According to the corresponding evaluation criteria,the safety state of the foundation pit can be quantitatively divided into five grades,which makes the safety state of the foundation pit more clear and clear.(4)Through the comparative analysis,the model predictions are consistent with the laws reflected in the measured results.The safety evaluation results are in accordance with the actual monitoring situation.This shows that the research results of this paper are reasonable and credible and have some reference value for the optimal design and construction of similar projects.