Experimental validation study of 3D direct simple shear DEM simulations

Bernhardt, Michelle L.; Biscontin, Guido; O’Sullivan, Catherine

doi:10.1016/j.sandf.2016.04.002

Cited by 62 publications

(28 citation statements)

References 22 publications

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“…The inter-particle friction we applied during isotropic compression is smaller than the final value we used during shearing. As noted by Bernhardt et al [22], this will lead to almost no contact sliding at the beginning of shearing. Therefore, the response at the initial stage of loading is much stiffer and more dilative than that of a real soil.…”

Section: Overview Of Dem Simulationsmentioning

confidence: 87%

DEM analysis of the onset of flow deformation of sands: linking monotonic and cyclic undrained behaviours

et al. 2018

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Z 2018, 'DEM analysis of the onset of flow deformation of sands: linking monotonic and cyclic undrained behaviours', Acta geotechnica. https://doi. AbstractThis study explores the link between the monotonic and cyclic undrained behaviour of sands using the discrete element method (DEM). It is shown that DEM can effectively capture the flow deformation of sands sheared under both monotonic and cyclic undrained loading conditions. When subjected to cyclic shearing, flow-type failure is observed for a loose sample, while cyclic mobility is observed for a dense sample. A strong correlation between the monotonic and cyclic loading behaviour that has been revealed experimentally is also confirmed in DEM simulations: a) flow deformation occurs in the compressive loading direction when the cyclic stress path intersects the monotonic compression stress path prior to the monotonic extension stress path, and vice versa; b) the onset of flow deformation in q-p' space is located in the zone bounded by the critical state line and the instability line determined from monotonic simulations. Hill's condition of instability is shown to be effective to describe the onset of flow failure. Micro-mechanical analyses reveal that flow deformation is initiated when the index of redundancy excluding floating particles drops to below 1.0 under both monotonic and cyclic loading conditions. Flow deformation induced by either monotonic or cyclic loading is characterized by abrupt change of structural fabric which is highly anisotropic. The reason why the dense sample * Corresponding author: Email: xhuang@tongji.edu.cn; Phone: +86 (0)21 6598 4551; Fax: +86 (0)21 6598 4551 2 dilated during monotonic loading but showed cyclic mobility (temporary liquefaction) during cyclic loading is attributed to the repeating reversal of loading direction, which leads to the periodic change of microstructure.

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Section: Overview Of Dem Simulationsmentioning

confidence: 87%

DEM analysis of the onset of flow deformation of sands: linking monotonic and cyclic undrained behaviours

et al. 2018

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“…However, the response quickly becomes physically reasonable upon shearing (within 0.2% shear strain for Bernhardt et al, 2016) so this initial phase does not materially affect the results at critical state. Fig.…”

Section: Dem Simulationsmentioning

confidence: 98%

“…Increasing µ before shearing can cause an unrealistic, artificially stiff response at small strains because contacts are prevented from sliding at the very initial stage of loading (Bernhardt et al, 2016). However, the response quickly becomes physically reasonable upon shearing (within 0.2% shear strain for Bernhardt et al, 2016) so this initial phase does not materially affect the results at critical state.…”

Section: Dem Simulationsmentioning

confidence: 99%

“…The interparticle friction coefficient was then increased to 0.25 before shearing. As discussed by Bernhardt et al (2016), when this approach is used contacts are far from being in a sliding state at the start of shearing. When the same µ value was used during sample preparation and shearing to create the loose sample, frictional dissipation could occur from the first time-step.…”

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confidence: 99%

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Energy dissipation in soil samples during drained triaxial shearing

2018

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The discrete element method was used to simulate drained triaxial compression of large-scale, polydisperse numerical samples at a range of void ratios while tracing all relevant energy components.The frictional dissipation and boundary work are almost equal regardless of sample density. The volumetric work reaches a steady value at large strain. However, the distortional work increases continually as sample deformation continues post-critical state. There is a preferential orientation for frictional dissipation at around 45° to the major principal stress direction. This matches the orientation at which there is the largest number of sliding contacts. The work equations, which are fundamental in most commonly used constitutive models, are linear when plotted against deviatoric strain. The Modified Cam Clay work equation substantially over-predicts the frictional dissipation for dense samples. An alternative, thermodynamically-consistent work equation gives a much better description of frictional dissipation and is therefore recommended to ensure accuracy in modelling.

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“…Moreover, only post-peak behaviour was studied. A large number of spherical elements (as in our studies) were used in [21,22]; however, there is a lack of grain-level studies. Notice that, the discrete methods have limitation nowadays due to the computational power [23,24].…”

Section: Introductionmentioning

confidence: 99%

3D DEM simulations of basic geotechnical tests with early detection of shear localization

Grabowski

Nitka

2020

Studia Geotechnica Et Mechanica

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This paper deals with elementary geotechnical tests: triaxial and direct shear of cohesionless sand using the discrete element method (DEM). The capabilities of the numerical DEM code are shown, with a special focus on the early phenomena appearance in localization zones. The numerical tests were performed in 3D conditions with spherical grains. Contact moments law was introduced due to simulate not perfectly round sand grains. The influence of different physical parameters was studied, e.g. initial density or confining pressure. The sieve curve corresponded to the Karlsruhe sand [1]; however, in some tests, it was linearly scaled. Special attention was laid on the behaviour of the sand grains inside localization, e.g. rotation, porosity, fluctuations, etc. and forces redistribution. Emphasis was given on the pre-failure regime and early localization predictors.

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Experimental validation study of 3D direct simple shear DEM simulations

Cited by 62 publications

References 22 publications

DEM analysis of the onset of flow deformation of sands: linking monotonic and cyclic undrained behaviours

DEM analysis of the onset of flow deformation of sands: linking monotonic and cyclic undrained behaviours

Energy dissipation in soil samples during drained triaxial shearing

3D DEM simulations of basic geotechnical tests with early detection of shear localization

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