A Two-Surface Model with Anisotropic Hardening and Nonassociated Flow Rule for Geomaterials

Abstract

A two-surface model is proposed to describe various volumetric behavior with change in the direction of a stress-controlled path. The model is formulated using the following concept of the isotropic-kinematic hardening. For overconsolidated soils, the nonassociated flow rule is used because of the occurrence of volumetric change, which is beyond the descriptive capabilities of the associated flow rule, during the loading with an abrupt change of stress path. The proposed model consists of nine material parameters that can be determined with a few triaxial tests. The model is verified by comparing model predictions with experimental results. In addition, the shear strength increases for the material that has the characteristic of stress path dependency are evaluated. Experimentally stabilized behavior which contradicts the theoretical condition for material stability by Drucker is discussed.