Study On Deformation Of Foundation Pit In Changchun Certain Area Based On Grey Prediction Method

The emergence of high-rise buildings can be traced back to 1980 s.The construction of high-rise and super high-rise buildings,to the air and underground development,is an important means to solve the shortage of land resources in China.The higher the height of the building,the greater the excavation depth of the corresponding foundation pit,so the emergence of a large number of high-rise,super-high-rise buildings,also makes more and more deep foundation pit engineering.Previously,for shallow foundation pits,slope excavation of the traditional technology can meet the requirements,but with more dense buildings,foundation pit surrounding underground facilities more complex,making this traditional technology can no longer meet the needs of modern urban construction.Excavation and support of deep foundation pit have been paid close attention to by all aspects.There are many types of retaining structures used in deep foundation pit support,and each retaining structure has its own characteristics,so their scope of application will be different.The selection of supporting structure is related to technical and economic factors,and should be considered from construction requirements,construction period,economic benefits,scheme feasibility and other aspects.And supporting structure selection should also consider supporting type,precipitation plan,excavation scheme and other supporting construction.As we all know,the frequent accidents of foundation pit engineering at home and abroad,on the one hand,is due to the imperfect investigation of the surrounding environment of the foundation pit before construction;on the other hand,the stability of the retaining structure itself is insufficient;on the other hand,it is also closely related to the construction quality,foundation pit monitoring.The above factors will not only prolong the construction period of the project,cause serious waste of human and material resources andfinancial resources,and even endanger the safety of buildings,the consequences are immeasurable.So it is necessary to design and optimize the supporting structure of deep foundation pit.Information construction is a very important means of construction,and deformation monitoring is an essential link in information construction.At the same time,the reliability of monitoring data also directly affects the accuracy of the numerical method to predict the deformation of foundation pit.Therefore,monitoring points should be arranged according to the actual site engineering situation and high precision monitoring instruments should be used as far as possible,and the development trend of deformation should be analyzed according to the monitoring data to prevent the occurrence of dangerous accidents.In this paper,deformation monitoring and theoretical analysis are carried out for deep foundation pit excavation,theoretical analysis is carried out by numerical simulation method,and deformation prediction is carried out based on grey system theory.The main work of the paper is as follows:1.According to the example of deep foundation pit engineering,a reasonable monitoring scheme is worked out,and the monitoring results are analyzed,and the deformation law of foundation pit is obtained.2.According to the engineering geological conditions of the site,GTS software is used to simulate the horizontal displacement variation law,and the comparison and analysis with the measured values show that the variation law is highly consistent,which verifies the accuracy of numerical simulation and the reliability of the measured data.3.This paper introduces the basic principle and modeling process of grey theory.Taking the original measured data of equal time interval as samples,GM9(1,1)model is established.The horizontal displacement of deep foundation pit support structure is predicted by grey system prediction method,and the predicted value is obtained.The predicted values are compared withthe measured values in the field,and a grey prediction system for accurately predicting the actual deformation is obtained.4.Based on the measured data,the gray system is used to predict the deformation of enclosure steel in a short period of time to guide construction.