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''Antonio Gens<sup>1</sup>, Matteo O. Ciantia<sup>1</sup>, and Marcos Arroyo<sup>1</sup>''
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==Abstract==
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The mechanical behavior of granular materials is characterized by strong non-linearity and irreversibility. These properties have been described by a variety of constitutive models, a large proportion of them are developed within an elasto-plastic framework. On top of the usual grain rearrangement mechanism, the presence of crushable grains adds one extra source of irreversibility to granular materials, a source that is frequently associated with instabilities. In his context, it is very instructive to obtain incremental responses of crushable granular materials but the experimental difficulties are formidable [<span id='cite-1'></span>[[#1|1]]]. This contribution describes a procedure to obtain incremental responses of this type of materials using the discrete element method [<span id='cite-2'></span>[[#2|2]]].
  
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The DEM model is calibrated to represent Fontaineblau sand. The resulting granular assembly is incrementally tested starting from an initial oedometric (no lateral deformation) condition. The incremental behavior of the numerical models is studied by performing axisymmetric stress probes of equal magnitude but varying direction. Recent advances to enhance the efficiency of the numerical procedure are adopted [<span id='cite-3'></span>[[#3|3]]]. The cascading nature of crushing events complicates stress probe control but damping is effectively used to overcome this problem.
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The contribution of grain crushing to the incremental irreversible strain is identified and separately measured. Three components of the incremental strains are distinguished: elastic, plastic-unbreakable and plastic-crushing. Particular focus is placed on the effects of crushing on the direction of plastic flow.
  
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== Recording of the presentation ==
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{| style="font-size:120%; color: #222222; border: 1px solid darkgray; background: #f3f3f3; table-layout: fixed; width:100%;"
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|(<sup>1</sup>) Department of Geotechnical Engineering and Geosciences (ETCG)
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| Universidad Politécnica de Cataluña
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| Campus Nord UPC, 08034 Barcelona, Spain
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| {{#evt:service=youtube|id=https://www.youtube.com/watch?v=CksqiT00w9U|alignment=center}}
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| Location: Technical University of Catalonia (UPC), Vertex Building.
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| Date: 1 - 3 September 2015, Barcelona, Spain.
 
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==Abstract==
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== General Information ==
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The mechanical behavior of crushable granular materials is characterized by strong non-linearity and irreversibility. In this paper, the incremental behavior of crushable granular soils is investigated by numerically simulating three dimensional stress probing experiments on Distinct Element models consisting of a random assembly of spheres. Particle breakage is permitted and the initial high stress condition ensures that crushing will occur along some of the loading directions. The results obtained show that particle crushing considered as an additional source of plastic mechanism induces a change in the direction of the plastic flow and that this direction change is independent of the incremental loading path. This result is independent of damping and the magnitude of plastic strains tends towards an asymptotic value as damping increases.
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* Location: Technical University of Catalonia (UPC), Barcelona, Spain.
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* Date: 1 - 3 September 2015
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* Secretariat: [//www.cimne.com/ International Center for Numerical Methods in Engineering (CIMNE)].
  
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'''keywords''' Discrete element method, granular materials, incremental non linearity, particle crushing.
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== External Links ==
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* [//congress.cimne.com/complas2015/frontal/default.asp Complas XIII] Official Website of the Conference.
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* [//www.cimnemultimediachannel.com/ CIMNE Multimedia Channel]
  
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==References==
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{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
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<div id="1"></div>
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[[#cite-1|[1]]] D. Costanzo, G. Viggiani and C. Tamagnini, “Directional response of a reconstituted fine‐
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! Recording of the presentation
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grained soil—Part I: experimental investigation”, International journal for numerical and
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analytical methods in geomechanics, 30, 1283-1301 (2006).
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| <embedvideo service="youtube">https://www.youtube.com/watch?v=CksqiT00w9U</embedvideo>
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<div id="2"></div>
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[[#cite-2|[2]]] P. Cundall, O. Strack, “A discrete numerical model for granular assemblies”. Géotechnique, 29,
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47–65 (1979).
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<div id="3"></div>
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[[#cite-3|[3]]] M.O. Ciantia, M. Arroyo, F. Calvetti and A. Gens, “An approach to enhance efficiency when
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modelling soils with crushable grains in DEM”, Géotechnique (in press) (2015)

Latest revision as of 16:09, 19 July 2016

Abstract

The mechanical behavior of granular materials is characterized by strong non-linearity and irreversibility. These properties have been described by a variety of constitutive models, a large proportion of them are developed within an elasto-plastic framework. On top of the usual grain rearrangement mechanism, the presence of crushable grains adds one extra source of irreversibility to granular materials, a source that is frequently associated with instabilities. In his context, it is very instructive to obtain incremental responses of crushable granular materials but the experimental difficulties are formidable [1]. This contribution describes a procedure to obtain incremental responses of this type of materials using the discrete element method [2].

The DEM model is calibrated to represent Fontaineblau sand. The resulting granular assembly is incrementally tested starting from an initial oedometric (no lateral deformation) condition. The incremental behavior of the numerical models is studied by performing axisymmetric stress probes of equal magnitude but varying direction. Recent advances to enhance the efficiency of the numerical procedure are adopted [3]. The cascading nature of crushing events complicates stress probe control but damping is effectively used to overcome this problem.

The contribution of grain crushing to the incremental irreversible strain is identified and separately measured. Three components of the incremental strains are distinguished: elastic, plastic-unbreakable and plastic-crushing. Particular focus is placed on the effects of crushing on the direction of plastic flow.

Recording of the presentation

Location: Technical University of Catalonia (UPC), Vertex Building.
Date: 1 - 3 September 2015, Barcelona, Spain.

General Information

External Links

References

[1] D. Costanzo, G. Viggiani and C. Tamagnini, “Directional response of a reconstituted fine‐ grained soil—Part I: experimental investigation”, International journal for numerical and analytical methods in geomechanics, 30, 1283-1301 (2006).

[2] P. Cundall, O. Strack, “A discrete numerical model for granular assemblies”. Géotechnique, 29, 47–65 (1979).

[3] M.O. Ciantia, M. Arroyo, F. Calvetti and A. Gens, “An approach to enhance efficiency when modelling soils with crushable grains in DEM”, Géotechnique (in press) (2015)

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