FAILURE CRITERIA INTERPRETATION BASED ON MOHR-COULOMB FRICTION

The use of numerical methods such as finite elements to make accurate predictions of failure or collapse of geomaterials must utilize a suitable failure criterion that is able to represent the shear strength for all stress paths likely to be encountered. The best-known failure criterion is that of Mohr-Coulomb, but several others have been proposed. Using a dimensionless form of principal stress space, this paper reviews some of these other criteria in a unified way by presenting them in terms of the equivalent Mohr-Coulomb friction angle implied at various locations on their periphery. Circular conical surfaces in stress space can greatly overestimate the strength of soil for certain stress paths, and sometimes contain singularities as implied by an equivalent friction angle of 90°. Noncircular conical surfaces have also been considered. These give a more acceptable range of equivalent friction angles, as they are based on actual test data. These “sophisticated” criteria can still predict equivalent friction angles that differ from each other by several degrees, however. © ASCE.