Application of a generalized continuous Mohr–Coulomb criterion

Abstract

This paper presents an application of a generalized failure criterion for soils. The presented formulation was originally adopted by the authors to round the corners of the Mohr–Coulomb (MC) yield surface in principals stress space. The formulation was later extended to a generalized yield criterion that, in addition to the rounded MC, includes the Matsuoka-Nakai, the Lade-Duncan yield criterion and other wellknown criteria. Two additional material parameters controls the alternative Lode angle dependencies. It has certain advantages over already existing generalized yield criteria: It is general, but still mathematically rather simple. It is infinitely differentiable, meaning that derivatives of any order may be calculated anywhere in stress space. The criterion defines a unique, single yield surface and does not suffer from false solutions in other octants in principal stress space (due to unwanted secondary surfaces that is present in many other formulations). Convexity may be analytically checked. Analytical relations between parameters for the formulation and existing criteria have been derived and some are presented in the paper as a function of the friction angle in triaxial compression. Because of its general formulation and beneficial properties, the criterion offers a convenient alternative for implementation in numerical methods using elasto-plasticity. One unified implementation covers several failure criteria by selecting appropriate parameters. The uniqueness of the criterion and its derivatives contribute to numerical stability and robustness. The paper compares numerical result with the proposed failure criterion in a FEA of a plane strain passive earth pressure problem. Different parameters, such that the criterion corresponds to the different criteria mentioned above, are used.