A simple non-associated three surface kinematic hardening model

The three-surface kinematic hardening (3-SKH) model (Stallebrass, 1990) has been shown (Stallebrass & Taylor, 1997) to be capable of modelling the effects of recent stress history in clays, and it can reproduce much of the anisotropic behaviour of soil with a simple isotropic state boundary surface. However, the model suffers from the restrictive assumption of associated flow, and as the bounding surface is of the Modified Cam clay type (Roscoe & Burland, 1968), this will lead to an over-prediction of the coefficient of earth pressure at rest, K₀, during one-dimensional normal compression....