Complex Stress Paths Constitutive Model for Clay Considering the Effect of Cohesion

The existing constitutive model considering the tensile properties of clay cannot reasonably reflect the elastoplastic deformation of clay when the average principal stress increases or decreases, especially the elastoplastic deformation of the soil under the loading path when the minimum principal stress is less than zero. A new constitutive model need to be established to solve the above problem. The mechanical mechanism of cohesive strength and friction strength on soils was revealed by the friction block model. Then an expression of shear strength for soils was given. Combining the features of cohensive strength, c hardening area and φ hardening area were denoted in the meridian plane. In φ hardening area, the influence of overconsolidated state was taken into the complex stress paths constitutive model and then the plastic strain was determined. In c hardening area, the realtion between the cohensive stress and the deviatoric strain was fitted by a hyperbolic curve, then the volumetric strain increment was determined through the dilatancy equation. Based on the above view, a complex stress paths constitutive model for clay considering the effect of cohesion was built. The established model has only 6 material parametes and all of them have clear physical meanings. Comparisons between model predictions and experimental results indicate that the established model can reasonably describe the stress strain relationship of soils under tensile condition.