Natural clays have their structure caused by inhomogeneity of the cementation. In order to provide theoretical bases for finite element method of structural soils,based on the theoretical framework of breakage mechanics,the weakly form of elastoplastic constitutive of binary medium for soils was given by Eshelby eigenstrain self-consistent method with the consideration of the compatibility for strain and the continuity for stress between bonding elements and frictional elements.A typical example showed that mechanical properties of bonding elements and frictional elements,breakage laws of bonding elements,loading histories,loading modes and states of stress have a great effect on the mechanical property of binary medium for soils, and the constitutive relationship could take it into account.
