Prediction Of Deep Foundation Pit Deformation Based On MSD Method

With the continuous advancement of urbanization,the infrastructure of urban has entered a new period of rapid development,the design and construction of deep foundation pits are inseparable.During the construction process of the foundation pit,it failed to predict the foundation pit deformation in time.As a result,the foundation pit deformation is too large and unstable accidents can be seen everywhere.Therefore,it is especially important to study the deformation prediction of deep foundation pits.A new prediction method of foundation pit deformation is introduced in the dissertation,MSD theory,which was first proposed by Bolton(1987).This method is a theoretical method for calculating the deformation of foundation pit based on the law of conservation of energy.The purpose is to solve the problem of the deformation of the retaining structure and the settlement of the surface during the construction of the foundation pit.This theory is based on a large amount of experimental data,and it is obtained a function that shows the relationship between the coefficient of mobilized shear strength and mobilized shear strain.According to lots of field data,the relationship between the mobilized shear strain and the maximum deformation displacement of the retaining structure is obtained.It also provides the basis for the calculation of foundation pit deformation.The MSD theory is introduced,which includes the applicable soil conditions,support structure,failure type,deformation mechanism and the principle of energy conservation.However,this theory does not consider the bending strain energy of envelope structure in the conservation of energy,the theory is improved in this paper.The bending strain energy of the retaining structure is considered in the calculation of foundation pit deformation displacement.FLAC3 D software is used to simulate the actual working stages of the project and the stability of foundation pits is analyzed from the three aspects of horizontal displacement,ground settlement,and the retaining structure deep horizontal displacement,get the following conclusions:(1)The MSD theory is introduced in detail.In terms of energy conservation calculation,the calculation formula of wall bending strain energy is derived,and the theoretical system of MSD method is improved.(2)The comparison between the calculated values of MSD method and the numerical simulation values shows that the results are similar,and the usability of MSD method is verified.(3)There are comparison with the numerical values of foundation pit,MSD method to calculate values,foundation pit monitoring values,and the result shows that there are a bit differences between the three,but the values have the same changing trend.Within the scope of engineering deviation,so it proves that the applicability and effectiveness of MSD method to predict the deformation of foundation pit.