Evaluation of anisotropic sand under undrained conditions based on an elasto-plastic constitutive model

Sands deposited under water have been shown to be anisotropic. Their undrained response therefore depends on the direction of σ₁ (major principal stress) in relation to the depositional direction. As a result the contractive behaviour has been observed in triaxial extension while on the other hand in compression the response is dilative at the same initial void ratio. This paper presents an analysis for the anisotropic undrained behaviour of sands under triaxial conditions. The following conclusions were reached. (1) the proposed model successfully simulates the undrained behaviour of sands under both triaxial compression and extension. (2) the cross section on the π plane of M (the stress ratio at the maximum volumetric contraction) has a major influence on the strength-deformation characteristics of sand.