Stress-strain Characteristics Of Overconsolidated Soil Considering Anisotropy

Naturally deposited soils are often found with the behavior of anisotropy,which can be treated as one of the structural characters of soils and has a great influence on stress-strain relationship and strengths of soils while loaded in different directions.Based on the study of previous research on anisotropic strength criterion and stress-strain relationship,this paper attempts to analyze the anisotropic failure mechanism of soils through tests observation and present a new criterion describing the anisotropic strength of soils.Most of the existing anisotropic strength criterions are constructed in the principal stress space,while natural soils are actually deposited in the physical space under general coordinates.Also these classic criterions are derived in the case of constant principal stress axes direction,which is inconsistent with the real situation.In this paper,in order to solve the problem,a transformation between the principal stress space axis and the general stress space axis is proposed to ensure that both coordinates can rotate freely.SMP(Spatially Mobilized Plane)criterion,proposed by Matsuoka et al.,is one of the isotropic strength criterions with specific physical definition and can well exhibit the impact of intermediate principle stress.Based on SMP criterion,a new failure criterion is proposed for anisotropic geomaterials.Through the the transformation between the principal stress space and the physical space,the normal vector of the SMP is transformed to the physical space.Assuming that the friction angle is changed with the angle between deposition surface and the SMP,a new expression of anisotropic peak strength M? is proposed,which can represent the anisotropy associated with particles orientation distribution.M? is the function of ? which is the minimum angle between deposition surface and the SMP.The basic parameters can be obtained from the conventional triaxial tests of anisotropic soils.Verification by experiment data shows that the anisotropic strength criterion can be used to describe the anisotropy of soil strength variation.