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- Combe, G., et al.
(författare)
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Experimental evidence of granulence
- 2013
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X. ; 1542, s. 453-456
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Konferensbidrag (refereegranskat)abstract
- We present an experimental study of velocity fluctuations in quasistatic flow of a 2D granular material deformed in a shear apparatus named 1γ2ε [1]. Radjaï and Roux [2] revealed systematic similarities between velocity fluctuations observed in discrete element simulations of quasistatic flow of granular material and turbulent flows in fluids. The character of these velocity fluctuations - named granulence by [2] - manifests as a non-Gaussian broadening of the probability density function of the fluctuations as the length of the analyzed shear-window is decreased, and exhibits some space and time scaling. The experiments presented are simple shear tests on granular samples composed of about 2000 wooden rods. The kinematics of the rod centers was followed by means of 2D Particle Image Tracking (PIT) technique applied to a sequence of 24 Mpixels digital pictures acquired throughout the duration of the loading at a frequency of 0.08 image/s. This analysis confirms the existence of granulence features in a real experimental test, which is comparable to that previously observed in numerical simulations of [2]. The experimental results obtained open up a new avenue for further studies on fluctuations in granular materials.
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| 3. |
- Andò, E., et al.
(författare)
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Experimental micro-mechanics of granular media studied by x-ray tomography: Recent results and challenges
- 2013
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Ingår i: Geotechnique Letters. - : Thomas Telford Ltd.. - 2049-825X .- 2045-2543. ; 3:JULY/SEPT, s. 142-146
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Tidskriftsartikel (refereegranskat)abstract
- Combining x-ray tomography and three-dimensional (3D) image analysis has finally opened the way for experimental micro-(geo)mechanics, allowing access to different scales of interest. When these correspond to a scale that has been imaged at high spatial resolution, high-quality measurements can be obtained (e.g. 3D displacements and rotations of individual grains of sand sample under load). However, there are issues when the scale of interest is smaller, for example the characterisation of grain-to-grain contacts (their orientations and evolution) or production of fines by grain breakage. This paper presents a short selection of new grain-scale measurements obtained using existing techniques. The challenges associated with smaller scale measurements on the same images are also discussed through a few examples from ongoing work.
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| 6. |
- Vitone, C., et al.
(författare)
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Localized deformation in intensely fissured clays studied by 2D digital image correlation
- 2013
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Ingår i: Acta Geotechnica. - : Springer Science and Business Media LLC. - 1861-1133 .- 1861-1125. ; 8:3, s. 247-263
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Tidskriftsartikel (refereegranskat)abstract
- Acta Geotechnica June 2013, Volume 8, Issue 3, pp 247-263 Localized deformation in intensely fissured clays studied by 2D digital image correlation C. Vitone, G. Viggiani, F. Cotecchia, S. A. Hall … show all 4 hide Citations 368 Downloads 200 Citations 9 Comments » Download PDF (3,181 KB) » View Article Abstract This paper represents a further step in a longstanding research on the influence of fissuring on the mechanical behavior of natural clays. The results of an experimental investigation into the influence of fissure orientation on the evolution of strain localization in the intensely fissured scaly clay from Santa Croce di Magliano (south of Italy) are reported. The experimental program involved plane strain compression tests where the effects of the combination of different factors, such as the specimen size and the orientation of fissuring, were investigated. A key aspect to this work is that the standard global stress–strain measurements were augmented by full-field displacement and strain measurements through 2D digital image correlation. Access to incremental strain fields provided information about slight details or anomalies as well as the complexity of deformation processes, which is of crucial importance for proper interpretation of test results at the global, macroscopic level.
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