Development And Application Of Duncan-Chang Model Considering Residual Soil Anisotropy

Granite residual soil is the debris left by the granite after physical weathering and chemical weathering.It is widely distributed in China,especially in the southeast coastal zone.It is one of the engineering geological types of infrastructure construction in province of Fujian.Granite residual soil has special engineering properties different from sedimentary soil.Because it is not known about its nature,if it is treated with the knowledge and experience of sedimentary soil,it may cause engineering accidents or lead to an increase in project cost,so that the residual soil can be systematic.The research has important theoretical and engineering significance.Due to the different degrees of weathering,the granite residual soil has obvious differences in vertical and horizontal directions,mainly in the variation of particle gradation.The difference in particle gradation directly affects the physical and mechanical properties of the soil,that is,the heterogeneity and anisotropy of the residual soil.Anisotropy has an important influence on the soil stress-strain law under complex stress conditions.Most scholars have studied the classification of residual soil,mineral composition,chemical composition,disintegration,etc.,but little research has been done on the constitutive model of residual soil and the influence of primary anisotropy on the mechanical properties of soil.Therefore,this paper uses the indoor test method to study the anisotropic properties of the residual soil itself.The research contents and main research results are as follows:(1)Take the undisturbed soil from a high slope in Nanping area,conduct various physical property index tests on the undisturbed soil,and determine the basic physical properties of the residual soil in the area.The undisturbed soil was sampled in different directions,and the sampling directions were 0°,45°,and 90°,respectively.The samples with different sampling angles were obtained for the triaxial consolidation drainage test considering the anisotropy of the residual soil.The stress-strain curves of the three sampling directions were compared,and the effects of primary anisotropy on failure modes,shear strength indexes,and failure principal stress lines were analyzed.(2)Based on the above test,the Duncan-Chang model parameters of the residual soil are obtained,and the influence of anisotropy on each parameter is analyzed.Based on the UMAT subroutine secondary development platform of ABAQUS,the Duncan-Chang model was developed.The Duncan-Chang model subroutine and parameters were imported into ABAQUS to carry out numerical simulation analysis on the residual soil anisotropy test to verify the reliability of the subroutine.The accuracy of the parameters.(3)A two-dimensional finite element model is established for the sampled high slope,and the anisotropic Duncan-Chang parameters are introduced for numerical analysis.The analysis results are compared with the on-site monitoring values,and the Duncan-Chang parameter values obtained at the 90° sampling angle are found.The analysis result value is in good agreement with the deformation trend of the field measured value.Therefore,it is recommended that the mechanical sampling of the undisturbed soil sample should be sampled at 90° as far as possible in order to ensure its original anisotropy.