• Citer

Cracking-induced permeability alterations in geomaterials: a comparison of experiments and computational predictions

par Massart, Thierry,Jacques ;Selvadurai, Patrick A.P.S.
Référence American Geophysical Union Fall meeting(December 2012: San Francisco, USA), Proceedings of the American Geophysical Union Fall meeting 2012
Publication Publié, 2012-12-10

Abstract de conférence

• Détails
• Contenu

Résumé :

Poroelasticity is the most widely used geomechanics model for examining critical problems of current importance to environmental geosciences. A fundamental assumption in poroelasticity is that the material properties such as the deformability or the permeability remain unchanged during the coupled interaction between the porous skeleton and the saturating fluid. However, it is known that the porous fabric can experience micro-mechanical damage due to the application of stresses or to the transport of reactive fluids that can lead to changes in the deformability, strength and permeability characteristics. By far the most common action that can alter the properties of the porous geomaterials is the micromechanical damage resulting from the application of stresses. Experimental results conducted on granite and limestone indicate variations in permeability with an increase in deviatoric stress states well below the peak failure loads. This can in turn drastically influence the duration of transient processes involving pore fluid pressure dissipation. In this research, we present a multi-scale computational approach for investigating permeability evolution in a heterogeneous porous quasi-brittle geomaterial. Three-dimensional representative volume elements are produced to replicate the geomaterial with a heterogeneous fabric by means of different techniques (Voronoi tessellation, ...). Fine scale constitutive laws are used to model the progressive mechanical degradation under stress at the level of individual cracks. Interfacial cohesive laws are used for this purpose, which incorporate measurable mechanical parameters such as tensile strength, cohesion and related fracture energies. A fine-scale coupling is then used to translate the local crack features into evolving local permeability quantities, and a versatile computational homogenization technique is developed to upscale mechanical and transport properties corresponding to heterogeneous microstructures towards continuum descriptions. Using this procedure, the effect of progressive microcracking on the overall permeability properties of quasi-brittle geomaterials is investigated. The procedures are used to estimate the variation of permeability with the confining pressures and deviatoric stresses applied in triaxial testing. The influence of fine-scale phenomena such as stiffness degradation or crack dilatancy on the resulting macroscopic permeability and its anisotropic evolution are scrutinized. The obtained quantities are compared with experimental results for the permeability evolution in granite samples, and it is shown that the computational approach is able to satisfactorily match the experimental results.