Micromechanical Analysis and Theoretical Modelling of Non‐Orthogonal Plastic Flow for Sand

ABSTRACT A systematic study on the non‐orthogonal plastic flow of sand is conducted using discrete element modelling, where particles representing the shapes of Toyoura sand are used, enabling the quantitative prediction of material behaviour in triaxial compression. The direction of plastic strain increment obtained by stress probing is analysed with respect to the normal to memory surfaces, which are determined based on a newly developed method. Within the memory surface, the plastic strain increment is small and follows the direction of stress increment. When the stress state is on the memory surface, sand has much lower stiffness, and the plastic strain increment is controlled by both the current stress state and stress increment. A non‐orthogonal flow rule for predicting the maximum plastic strain increment direction is evaluated. The underlying mechanism for non‐orthogonal flow of sand is analysed by comparing with the plastic response of metal. A bounding surface framework for modelling the full stress‐strain relationship is presented.