ABSTRACT
The application of plasticity theory to frictional materials such as sand, clay, rock, and concrete introduces a number of complications, the most prominent of which relates to the flow rule. As is well known, the flow rule associated with a relevant yield criterion, for example Mohr-Coulomb, predicts excessive plastic dilation. Consequently, a nonassociated flow rule must be used.Although seemingly straightforward, the introduction of a nonassociated flow rule gives rise to a number of complications that manifest themselves particularly in the numerical solution of boundary value problems.These complications can be divided into two categories.
