Numerical Implementation Of A Bounding Surface Model For Clay And Its Preliminary Application

In recent years,due to the increase of building density and the rapid development of rail transit construction in urban area,the surrounding environment of deep excavation becomes more and more complex,and it makes the deformation control become the key to the deep excavation in a complex environment.The traditional analytical method and the related specification method are increasingly unable to meet the requirement of the deformation analysis.Numerical analysis of excavation engineering has become an important method in a sensitive environment,and the key of numerical analysis is to choose the appropriate soil constitutive model and parameters.In this background,the main researches of this article include:(1)First of all,a wide applicability and relatively simple bounding surface model for clay was raised and introduced.And then the numerical implementation of this model in ABAQUS was completed through the UMAT secondary development platform of ABAQUS finite element analysis software.(2)The correctness of the numerical implementation about the model in this paper was confirmed through a series of simulation tests including the units drainage shear test and undrained shear test and one-dimensional consolidation settlement test.And it laid the foundation for further the analysis of complex geotechnical engineering of this model.(3)A three-dimensional analysis model about excavation engineering was established with the help of ABAQUS.And contact surface was adopted to simulate the contact action between soil and the diaphragm wall.For clay layer,the Mohr-coulomb model,modified cam-clay model and the model in this paper are used to simulate the excavation of foundation pit respectively,after then the results of three models of excavation deformation were fully analyzed.The major parameters of the model in this paper about the influences on the deformation of excavation was further analyzed.The unit verification and one-dimensional consolidation simulation showed that the numerical realization of this model in ABAQUS had good accuracy and stability.The excavation analysis of the foundation pit showed that the settlement of ground was better described if the contact surface between soil and wall was setted.The mohr-coulomb model adopted the same loading and unloading modulus,so it led to large rebounces in the bottom of the excavation surface,which made small horizontal deformation of continuous wall and the soil after the wall,and big uplift of the soil after the wall;the modified cam-clay model was improved,and the model in this paper further considered the anisotropy of the soil,and the result was more conservative.The boundary structure parameters of this model had a large effect on the surface settlement after the wall.All relevant conclusions can provide references for the application of this model in excavation engineering.