Advances in Computed Tomography for Geomaterials: GeoX 2010

Characterization of the Evolving Grain-Scale Structure in a Sand Deforming under Triaxial Compression

S. A. Hall¹ — N. Lenoir² — G. Viggiani¹ — P. Bésuelle¹ — J. Desrues¹

¹Laboratoire 3S-R,CNRS – Grenoble UniversitiesDomaine UniversitaireBP 5338041 [e-mail]

 

²Previously at Laboratoire 3S-R,Now at Institut Navier - LMSGC2, allée Kepler77420 Champs-sur-Marne

ABSTRACT. This paper is a snapshot of work in progress in which the aim is to analyze possible evolving grain-scale structures associated with localized deformation in a sand specimen undergoing triaxial compression. 3D digital image analysis of in-situ-acquired x-ray tomograms provides a characterization of porosity, contact density and grain coordination number distributions. These characteristics are compared with strain fields derived by 3D-volumetric digital image correlation (DIC), which reveal the development of a localized shear band. Structures conjugate to the main shear band have been observed clearly in incremental DIC-derived shear strain images and also in porosity images. New results on grain contact and grain coordination number distributions suggest that lower values of both exist in the localized strain zone, but bridges of higher coordination-number grains appear to traverse this zone.

 

KEYWORDS: localization, granular media, in-situ x-ray tomography, digital image analysis, digital image correlation ...