(De)compaction of porous viscoelastoplastic media: Model formulation. Issue 6 (29th June 2015)

• Record Type: Journal Article
• Authors: Yarushina, Viktoriya M.; Podladchikov, Yuri Y.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 6(2015:Jun.)
• Page Start: 4146
• Page End: 4170
• Publication Date: 2015-06-29
• Subjects: nonlinear poroelasticity -- effective media theory -- constitutive theory -- bulk compressibility -- bulk viscosity; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2014JB011258
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: A nonlinear viscoelastoplastic theory is developed for porous rate‐dependent materials filled with a fluid in the presence of gravity. The theory is based on a rigorous thermodynamic formalism suitable for path‐dependent and irreversible processes. Incremental evolution equations for porosity, Darcy's flux, and volumetric deformation of the matrix represent the simplest generalization of Biot's equations. Expressions for pore compressibility and effective bulk viscosity are given for idealized cylindrical and spherical pore geometries in an elastic‐viscoplastic material with low pore concentration. We show that plastic yielding around pores leads to decompaction weakening and an exponential creep law. Viscous and plastic end‐members of our model are consistent with experimentally verified models. In the poroelastic limit, our constitutive equations reproduce the exact Gassmann's relations, Biot's theory, and Terzaghi's effective stress law. The nature of the discrepancy between Biot's model and the True Porous Media theory is clarified. Our model provides a unified and consistent formulation for the elastic, viscous, and plastic cases that have previously been described by separate "end‐member" models. Key Points: A thermodynamically consistent theory of poroviscoelastoplasticity is developed Effective mechanical properties of poroviscoelastoplastic materials are proposed Bulk rheology shows decompaction weakening and an exponential creep law