Microscale characterization of energy dissipation mechanisms in liquefiable granular soils

Shamy, Usama El; Denissen, Christina

doi:10.1016/j.compgeo.2010.07.004

Cited by 29 publications

(15 citation statements)

References 23 publications

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“…One convenient way of verifying the applicability of these analytical solutions is by simulation using a well-regarded DEM code. Simulations were run using the PFC2D 4.00 software [30] with the aim of verifying (14), (16), (41) and (47). Each simulation was run for a single time-step, and input parameters were varied individually to investigate the effect on the error.…”

Section: Verification In a Discrete Element Methods Codementioning

confidence: 99%

“…When validating (16), the main interest was in confirming that the variation of with R was captured correctly. Figure 11 demonstrates that this is the case for k n = 1 MN m 1 , jv i j D 1 m s 1 , C D 1:39 10 6 kg and t D 1 10 8 s. The absolute differences are approximately eight orders of magnitude smaller than .…”

Section: Verification In a Discrete Element Methods Codementioning

confidence: 99%

“…Equation (14) is recovered by substituting m˛D mˇD m into (16). As in Section 2.1, the initial distribution of relative velocity among the particles does not affect the truncation error, that is, whether the heavier particle has the greater or lesser speed does not affect .…”

Section: Effect Of Dissimilar Particles On Truncation Errormentioning

confidence: 99%

“…For systems containing particles of differing masses, (15) remains applicable, but it is commonplace for the mass in (15) to be chosen conservatively as the minimum particle mass: m˛in this case. Substituting for t in (16), s / C R jv i j 2 as plotted in Figure 2(b). The direct proportionality of s and C again indicates that increasing the particle masses will degrade the accuracy of a simulation time-step.…”

Section: Effect Of Dissimilar Particles On Truncation Errormentioning

confidence: 99%

“…The increased complexity of (21) compared with (16) makes it difficult to ascertain whether increases or decreases in magnitude when the degree of polydispersity is increased. In fact, either scenario is possible depending on the parameters chosen for the model.…”

Section: Effect Of Contact Model On Truncation Errormentioning

confidence: 99%

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Analytical study of the accuracy of discrete element simulations

Hanley

O’Sullivan

2016

Numerical Meth Engineering

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The numerical errors in idealised discrete element method (DEM) simulations are investigated analytically by comparing energy balances applied at the beginning and end of one time-step. This study focuses on the second-order velocity-Verlet integration scheme due to its widespread implementation in DEM codes. The commercial DEM software PFC2D was used to verify the correctness of key results. The truncation errors, which are larger than the round-off errors by orders of magnitude, have a superlinear relationship with both the simulation time-step and the interparticle collision speed. This remains the case regardless of simulation details including the chosen contact model, particle size distribution, particle density or stiffness. Hence, the total errors can usually be reduced by choosing a smaller time-step. Increasing the polydispersity in a simulation by including smaller particles necessitates choosing a smaller time-step to maintain simulation stability and reduces the truncation errors in most cases. The truncation errors are increased by the dissipation of energy by frictional sliding or by the inclusion of damping in the system. The number of contacts affects the accuracy and one can deduce that because 2D simulations contain fewer interparticle contacts than the equivalent 3D simulations, they therefore have lower accrued simulation errors

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Section: Verification In a Discrete Element Methods Codementioning

confidence: 99%

Section: Verification In a Discrete Element Methods Codementioning

confidence: 99%

Section: Effect Of Dissimilar Particles On Truncation Errormentioning

confidence: 99%

Section: Effect Of Dissimilar Particles On Truncation Errormentioning

confidence: 99%

Section: Effect Of Contact Model On Truncation Errormentioning

confidence: 99%

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Analytical study of the accuracy of discrete element simulations

Hanley

O’Sullivan

2016

Numerical Meth Engineering

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Discrete element method simulations of the seismic response of shallow foundations including soil‐foundation‐structure interaction

Shamy

Zamani

2011

Num Anal Meth Geomechanics

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SUMMARYA novel three-dimensional particle-based technique utilizing the discrete element method is proposed to analyze the seismic response of soil-foundation-structure systems. The proposed approach is employed to investigate the response of a single-degree-of-freedom structure on a square spread footing founded on a dry granular deposit. The soil is idealized as a collection of spherical particles using discrete element method. The spread footing is modeled as a rigid block composed of clumped particles, and its motion is described by the resultant forces and moments acting upon it. The structure is modeled as a column made of particles that are either clumped to idealize a rigid structure or bonded to simulate a flexible structure of prescribed stiffness. Analysis is done in a fully coupled scheme in time domain while taking into account the effects of soil nonlinear behavior, the possible separation between foundation base and soil caused by rocking, the possible sliding of the footing, and the dynamic soil-foundation interaction as well as the dynamic characteristics of the superstructure. High fidelity computational simulations comprising about half a million particles were conducted to examine the ability of the proposed technique to model the response of soil-foundation-structure systems. The computational approach is able to capture essential dynamic response patterns. The cyclic moment-rotation relationships at the base center point of the footing showed degradation of rotational stiffness by increasing the level of strain. Permanent deformations under the foundation continued to accumulate with the increase in number of loading cycles.

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CFD-DEM Simulations of Seepage Induced Erosion

Xiao¹

2020

Dam Breach Modelling and Risk Disposal

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Increases in seepage force reduce the effective stress of particles and result in the erosion of particles, producing heave failure and piping. Sheet piles/cutoff walls are often employed in dams to control the seepage. In this study, a computational fluid dynamics solver involving two fluid phases was developed and coupled with discrete element method software to simulate the piping process around a sheet pile/cutoff wall. Binary-sized particles were selected to study the impact of fine particles on the mechanisms of seepage. The seepage phenomenon mainly appeared among fine particles located in the downstream side, with the peak magnitudes of drag force and displacement occurring around the retaining wall. Based on the particle-scale observations, the impact of seepage produced a looser condition for the region concentrated around the retaining wall and resulted in an anisotropic condition in the soil skeleton. The results indicate that heave behavior occurs when the drag force located adjacent to the boundary on the downstream side is larger than the corresponding weight of the bulk soil.

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Microscale characterization of energy dissipation mechanisms in liquefiable granular soils

Cited by 29 publications

References 23 publications

Analytical study of the accuracy of discrete element simulations

Analytical study of the accuracy of discrete element simulations

Discrete element method simulations of the seismic response of shallow foundations including soil‐foundation‐structure interaction

CFD-DEM Simulations of Seepage Induced Erosion

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