EXACT EFFECTIVE-STRESS RULES IN ROCK MECHANICS

The standard paradigm for analysis of rock deformation arises from postulating the existence of "an equivalent homogeneous porous rock." However, data on the pore-pressure dependence of fluid permeability for some rocks cannot be explained using any equivalent homogeneous porous medium. In contrast, a positive result shows that deformation measurements on both high-porosity sandstones and low-porosity granites can be explained adequately in terms of an equivalent two-constituent model of porous rocks, for which exact results have recently been discovered.