Abstract: Natural soils are structured and anisotropic in the process of sedimentation. Within the theoretical framework of breakage mechanics for geomaterials, a new binary medium model (BMM) for structured soils with initial stress-induced anisotropy is formulated. Breakage mechanics for geomaterials idealizes the structured geomaterials as binary medium consisting of bonding blocks (the bonding element) with strong bonding and weakened bands (the frictional element) without bonding; and the bonding blocks will break and transfer to weakened bands gradually during the loading process. The bonding blocks are assumed as elastic-brittle constitutive model with transverse-isotropy; and the weakened bands transferred from the bonding blocks are assumed as nonlinear elastic Duncan-Chang model. By introducing the breakage ratios and local strain coefficients reflecting the influence of soil structure and anisotropy, the binary medium model for structured soils with initial stress-induced anisotropy is established; and the determination of model parameters in detail is given. Finally the capability of the new model to model the stress-strain properties of anisotropic structured soils is verified and compared with the triaxial tests of artificial structured soils with initial stress-induced anisotropy. The computational results demonstrate that the proposed constitutive model can simulate the mechanical properties, including stress-strain and volumetric deformation, of structured soils with initial stress-induced anisotropy.

Key words: anisotropy, structured soils, breakage mechanics, binary medium model (BMM)