Strain localization analysis of elasto-viscoplastic soil considering structural degradation

Abstract

Natural deposits are affected by chemical bonding or the cementation between soil particles during the sedimentation process. Under the effect called `aging', aggregations and linkage between assemblages are formed in the soil structure. It is known that the structure affects the characteristics of the strength, the deformation, and the strain localization. Strain localization is generally considered to be important as a presage of failure. It has recently been recognized that strain localization may occur also during compressive deformation, particularly for porous materials with large confining stress, and the localized compressive deformation may cause large displacement. The aim of the present paper is to study the effect of structural degradation on the localization of both shear and compressive strain for water-saturated clay. Firstly, an elasto-viscoplastic constitutive model considering structural changes with the viscoplastic deformation is proposed in the present paper. Structural collapse is expressed as the shrinking of both the overconsolidation boundary surface and the static yield surface with increasing viscoplastic deformation in the model. Secondly, finite element analyses of undrained and partially drained compression tests under plane strain conditions are conducted to study the effect of structural changes on strain localization. It is seen in the results that the localization of both shear and compressive strain is promoted by the degradation of the soil structure.