Pressure-Sensitive Materials for Isotropic Elastoplastic

Experimental investigations indicate that the third stress invariant; Lode angle cy affects significantly the behavior of pressure sensitive materials. The present com- munication presents a formulation to account for cy in isotropic pressure-sensitive elastoplastic materials. Seven Lode dependences are reviewed. A new one, referred to as LMN, in proposed to generalize Lade and Duncan, and Matsuoka and Nakai failure surfaces. The formulation is general enough to introduce CY into the isotropic elastoplastic modes which are only developed in terms of first and second-stress invariants. As an illustration, several Lode dependences are introduced into Roscoe and Burland model. The performance of the modQiied model is estimated by com- paring experimental and analytical results in the case of true triaxial loadings on normally consolidated clay.