INCREMENTAL THEORY OF PLASTICITY FOR ROCK.

The associated flow law which is a natural conclusion of the D. C. Drucker postulate is not fit for experimental results of dilatant materials. In this paper an alternative of the incremental plasticity theory is proposed; the incremental constitutive relation is determined by differentiating the response function for stress and plastic strain. The response function is specified in a simple manner using the concept of Laplace transformation spectrum if the response function is smooth and monotone. It is shown that Drucker's postulate implies only nonnegative definiteness of the incremental constitutive tensor, and that the flow law is not appropriate to describe a multi-parameter response system involving deviatoric and volumetric components. (Edited author abstract. )