Compressibility moduli for porous materials incorporating volume fraction

Traditional deformation parameters such as drained, unjacketed, and pseudo-bulk compressibilities are developed for a saturated porous medium, assuming they can be uniquely determined by measuring the liquid pressure, confining pressure, and changes in volume. Physically, however, the liquid volume fraction (porosity for a saturated porous medium) plays an important role, yet it is not directly measurable. In this paper the compressibilities are defined in terms of the experiments used to evaluate them and then mathematically related to the compressibilities of the liquid and solid phases and the volume fraction. The results can then be used to determine the effects of the volume fraction and compressibilities of each phase on the deformation properties of the porous medium. This theory is then shown to be a generalization of previous work, and comparisons are made with previously derived relationships of Zimmerman, Biot, and Gassmann.