A Lode Angle Dependent Formulation of the Hardening Soil Model

This paper presents a new formulation of a well known double hardening model often referred to as the Hardening Soil model. As an alternative to the existing Hardening Soil model’s Mohr-Coulomb failure surface, the new formulation allows for the incorporation of smooth failure surfaces, such as the failure surface proposed by Matsuoka & Nakai or that proposed by Lade & Duncan. Although the incorporation of all other failure criteria that can be formulated as a function of the Lode angle is also possible, the examples presented at the end of this paper concentrate on the Hardening Soil model with Matsuoka-Nakai failure criterion. The Lode angle dependent formulation with Matsuoka-Nakai yield surface is validated in element tests and in an excavation example. A comparison between results obtained from the Hardening Soil model with the Mohr-Coulomb type yield surface and that with the Mastuoka-Nakai type yield surface reveals the failure criterion’s actual influence on material strength and stiffness when applied in the Hardening Soil Model in plane strain conditions.