Granular Matter (2012) 14:469–482 DOI 10.1007/s10035-012-0353-0 ORIGINAL PAPER Three dimensional fabric evolution of sheared sand Alsidqi Hasan · Khalid Alshibli Received: 14 February 2011 / Published online: 5 May 2012 © Springer-Verlag 2012 Abstract Granular particles undergo translation and rolling when they are sheared. This paper presents a three-dimen- sional (3D) experimental assessment of fabric evolution of sheared sand at the particle level. F-75 Ottawa sand speci- men was tested under an axisymmetric triaxial loading con- dition. It measured 9.5 mm in diameter and 20 mm in height. The quantitative evaluation was conducted by analyzing 3D high-resolution x-ray synchrotron micro-tomography images of the specimen at eight axial strain levels. The analyses included visualization of particle translation and rotation, and quantification of fabric orientation as shearing continued. Representative individual particles were successfully tracked and visualized to assess the mode of interaction between them. This paper discusses fabric evolution and compares the evolution of particles within and outside the shear band as shearing continues. Changes in particle orientation dis- tributions are presented using fabric histograms and fabric tensor. Keywords Sand · Particles · Fabric · Synchrotron micro-tomography Electronic supplementary material The online version of this article (doi:10.1007/s10035-012-0353-0) contains supplementary material, which is available to authorized users. A. Hasan (B ) School of Civil and Resource Engineering, The University of Western Australia, Room 2.20 Civil & Mechanical Engineering Building, Crawley, WA 6009, Australia e-mail: alsidqi.hasan@uwa.edu.au K. Alshibli Department of Civil and Environmental Engineering, University of Tennessee, 73A Perkins Hall, Knoxville, TN 37996, USA e-mail: alshibli@utk.edu 1 Introduction The overall strength and deformation characteristics of gran- ular materials are highly influenced by many factors such as particle morphological properties (roughness, shape, and sphericity), fabric, particle-to-particle interaction, boundary conditions, loading mode, and applied stresses. The fabric or structure of soils is defined as the arrangement of parti- cles, particle groups, and the associated pore space [21]. The fabric of soils has a profound influence on engineering prop- erties of soils. Granular particles transmit forces to adjacent particles and to boundaries during shearing, which results in particle rearrangements and fabric evolution. Most classical stress-dilatancy models take into account translation mech- anism and ignore particle rotation/rolling, e.g. [31]. Recent constitutive theories, e.g. [3, 33], incorporated particle rota- tion factors into the constitutive models to better predict the behaviour of granular materials. The literature lacks three-dimensional (3D) experimen- tal measurements of the fabric evolution of sheared gran- ular materials at the particle level. As a result, many researchers used discrete element method (DEM) to quantify particle translation and rolling. For example, Bardet [10] con- ducted DEM simulations with idealized spherical particles and showed that the particles rotate during shearing, and such rotations significantly affect the shear strength. Oda et al. [27] introduced resistance against free rotation into DEM simu- lations of spherical particles and showed that some rotations still exist, especially within the shear band. Furthermore, Shodja and Nezami [32] performed DEM simulations on biaxial compression using oval granules and concluded that rolling is an important mechanism during shear. The number of rolling contacts was larger than the translation contacts, especially for higher inter-granular friction angles. Experi- mental visualization of particles during shearing using the 123