CONSTITUTIVE MODEL FOR K₀ OVERCONSOLIDATED STRUCTURE CLAY

K₀ consolidated clay is widely distributed in nature. It usually has both overconsolidation property and natural structural property, and it is a significant difference for the property of overconsolidation of K₀ to the normal consolidation of K₀ clay. In order to effectively describe the overconsolidation properties of K₀ consolidated clay, three improvements were made on the basis of the natural structure consolidated model for clay, so that the original model can be extended to a constitutive model that consider both the properties of K₀ overconsolidation clay and the effects of natural structures for natural clay. (1) The relative stress ratio is introduced into the yield surface equation to describe the yield property, and the initial anisotropic consolidation stress ratio parameter ξ is introduced into the yield surface equation to express the influence of the initial anisotropy on the position of the yield surface in p-q space. (2) Based on the given yield surface equation, the phase transformation stress ratio parameter was derived, and the phase transformation stress ratio was introduced into the unified hardening parameter. The unified hardening parameter can effectively describe both the initial anisotropic shearing behavior and the dilatancy behavior, strain hardening and softening phenomenon for initial anisotropic consolidated clay. (3) The cementation parameter p_e, which reflects the structural cementation, is introduced into the yield surface equation and the decay evolution equation of p_e with deviatoric plastic strain is given. The dilatancy properties of structural clay can be described by using the cementation parameter. The comparison between the prediction and the test results shows that the proposed K₀ consolidation model can effectively describe the stiffness enhancement effect of K₀ overconsolidated clay, the Bauschinger effect of clay, the cementation strength loss phenomenon and the strain softening phenomenon of structural clay. The applicability and rationality of the proposed model are proved.