UH Model For Anisotropic Clays

Owning to the nature of the deposition process,soil particles primarily oriented toward the horizontal direction,which leads to the physical and mechanical properties of soils anisotropic The comprehensive understanding of anisotropy effects on stress-strain-strength behavior is needed to establish rational constitutive models for describing the failure and deformation for anisotropic soils,which can provide accurate theoretical foundation for geotechnical analysis and designs of slope stability,foundation deformation,land subsidence,etcThis dissertation commences from the comparisons of research methods,experimental study of intact soils in the Olympic Forest Park and physical interpretation of tests results for anisotropic soils.Experimental evidence indicates that the smaller the minimum value of angles between the depositional plane and the spatially mobilized planes is,the lower the shear strength of cross-anisotropic soils is.The main achievements could be summarized as follows:(1)Anisotropic transformed stress method:The controlling factors of anisotropy effect were deeply analyzed.Based on the experimental laws that the smaller the minimum value of angles between the depositional plane and the spatially mobilized planes(?)is,the lower the strength of cross-anisotropic soils is,an anisotropic peak stress ratio Ma is defined as a linear function of ?.The anisotropic transformed stress method is proposed through a revision of the original transformed stress method.In the anisotropic transformed stress space the anisotropic soils can be taken as an equivalent isotropic material(2)Cross-anisotropic soil failure criterion:The proposed cross-anisotropic failure cri-terion is involving with the the anisotropic transformed stress method.Main features of the proposed cross-anisotropic failure criterion is illustrated through comparisons with the SMP criterion.The capability of the proposed cross-anisotropic failure criterion is well demon-strated by comparing predictions with experimental data for Santa Monica Bench sand and San Francisco Bay mud(3)Three-dimensional unified hardening model for anisotropic clays:Building on a modification of the UH model,a three-dimensional(3D)elastoplastic constitutive model for anisotropic clays is proposed.The anisotropic transformed stress tensor,relative stress ratio,state stress ratio and the anisotropic phase transformation stress ratio are introduced into the proposed model to account for the effect of anisotropy and the influence of K0 consolidation on the stress-strain behavior of clays.A series of undrained triaxial tests on K0 consolidated kaolin clay,normal consolidated intact varved clay and San Francisco Bay Mud are success-fully predicted using the proposed extended UH model.The agreement between typical model predictions and experimental data demonstrates the capability of the extended UH model well The anisotropic effects on deformation of soil subjected to principal stress axes rotation is an-alyzed.The comparisons between measured and predicted results of Toyoura standard sands subjected to drained pure principal stress axes rotational shear show that the anisotropic UH model can also describe the effect of principal stress axes rotation on sand deformation quali-tatively.