Dispersion in poroelastic systems - art. no. 011303

We address one key source of the known discrepancies between theory and exp eriment in poroelasticity, i.e,, the fact that Gassmann's equations for the bulk and shear moduli predict that the shear modulus is independent of the saturating fluid properties, whereas it is observed on the contrary that a t high enough frequencies the shear modulus can in fact depend on the fluid 's elastic properties in many porous materials. One clue to understanding t his behavior comes from effective medium theory, which shows that the shear modulus does depend on the fluid properties in many circumstances. In comp arison to values predicted by effective medium theory, Gassmann's equations predict different, smaller values for both the effective bulk and shear mo duli of porous media. Sorting through these apparent (but not actual) disag reements among theory and theory, and theory and experiment is the main thr ust of the paper.