Abstract
AbstractThis work presents results from oedometric compression of coarse granular material. Coarse granular media exhibit significant deformations making it complicated to predict the settlement of structures. In this paper, a measurement technique was developed for the analysis of two‐dimensional (2‐D) images of a deforming coarse granular medium to investigate its deformation. This was achieved by realising grain‐based image correlation to measure the grain transformation in gravel with the use of a digital image correlation technique. The 2‐D displacement fields enable us to explore the behaviour of granular media at different scales: microscopic, mesoscopic and macroscopic scales. The mesoscopic scale is defined from branches that connect the centres of three neighbouring grains, using a Delaunay triangulation to account for an equivalent continuum media. Whereas the consistency of the macroscopic strain and the average mesoscopic strain is assessed, it is shown that a deviation from the normalised microscopic vertical displacement is an indicator of the heterogeneity of the mesoscopic strain field. The proposed mesoscopic analysis allows us to investigate these heterogeneities. Another important result is that even if the amplitude of the microscopic strain is small (approximately 100 times smaller) compared with the other strain measures, it confirms that the grains are not rigid and that their ultimate strain can be estimated using the proposed approach.
Highlights
This study focuses on the behavior of coarse granular media under compression
We present an experimental exploratory work to understand the mechanisms of coarse granular media deformation under oedometric compression
The challenge was to extract quantitative information from 2D images to understand the mechanics at play, and to elucidate and validate the pertinent scale to accomodate for the macroscopic strain
Summary
This study focuses on the behavior of coarse granular media under compression. Rockfill media are coarse media composed of quarry rock debris or crushed rock fragments with a characteristic size of up to 1 m. CLAIRE SILVANI ET AL bands in granular materials (such as sands) in triaxial loading paths with X-ray micro-tomography, and with experiments carried out in situ (Desrues et al 1996 [8], Viggiani et al 2004, [31], Hall et al 2009 [10]) or during plane strain compression (Rechenmacher 2006 [24] and Rechenmacher et al 2011 [25]) with the use of Digital Image Correlation (DIC) to obtain the grain kinematics These investigations provided important data concerning shear band features such as orientation and width, patterns of shear band formation, and their evolution (Viggiani et al, 2001 [32]). The following sections examine the results of the experiments through different scales (macro-, micro-, and mesoscales) and conclude with a comparison between these different scales and the possible relationships between them
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