Particulate modeling of cementation effects on small and large strain behaviors in granular material

Ning, Zhangwei; Khoubani, Ali; Evans, T. Matthew

doi:10.1007/s10035-016-0686-1

Cited by 17 publications

(17 citation statements)

References 37 publications

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“…Because the triaxial specimens and the external loading are both symmetric about the z axis, deformations in the x‐y plane are nearly symmetric. Therefore, the ratio of the eigenvalues around the x and y axes is very close to 1.0 for all of the strain values considered . Thus, λ z /λ x is used for observing fabric evolution.…”

Section: Microscale Analysis Of Simulation Resultsmentioning

confidence: 78%

“…Anisotropy tensors for contact orientation (R) and normal force (F) are calculated based on Equations and :

R_{ij} = \frac{1}{N} \sum_{cϵV} n_{i}^{c} n_{j}^{c}

F_{ij}^{n} = \frac{1}{N} \sum_{cϵV} f_{n}^{c} n_{i}^{c} n_{j}^{c}

where N is the total number of contacts in the assembly,

n_{i}^{c}

( i = 1, 2, 3) is the i th component of the normal vector at contact point c , and

f_{n}^{c}

is the magnitude of the normal force at contact c . Each tensor possesses 3 eigenvalues (λ 1 , λ 2 , λ 3 ), and the ratios of each pair of eigenvalues are used as the fabric descriptors . Evolution of anisotropy of contact orientation and contact normal force with axial strain are shown in Figure .…”

Section: Microscale Analysis Of Simulation Resultsmentioning

confidence: 99%

“…where N is the total number of contacts in the assembly, n c i (i = 1, 2, 3) is the i th component of the normal vector at contact point c, and f c n is the magnitude of the normal force at contact c. Each tensor possesses 3 eigenvalues (λ 1 , λ 2 , λ 3 ), and the ratios of each pair of eigenvalues are used as the fabric descriptors. 50 Evolution of anisotropy of contact orientation and contact normal force with axial strain are shown in Figure 16. Because the triaxial specimens and the external loading are both symmetric about the z axis, deformations in the x-y plane are nearly symmetric.…”

Section: Microscale Analysis Of Simulation Resultsmentioning

confidence: 99%

“…Therefore, the ratio of the eigenvalues around the x and y axes is very close to 1.0 for all of the strain values considered. 50 Thus, λ z /λ x is used for observing fabric evolution. It is evident that for all cases the rigid specimen develops a larger degree of fabric anisotropy, indicating greater inhomogeneity in deformation due to the rigid confinement.…”

Section: Microscale Analysis Of Simulation Resultsmentioning

confidence: 99%

See 3 more Smart Citations

An efficient flexible membrane boundary condition for DEM simulation of axisymmetric element tests

Khoubani

Evans

2017

Num Anal Meth Geomechanics

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Summary The mechanical response of an assembly of particles depends on the applied boundary conditions. Robust calibration of numerical discrete systems to laboratory results is also a primary step in many studies of granular materials. In this study, a new membrane model was developed for simulating axisymmetric element tests. This membrane model uses a simple algorithm of an array of independently controlled walls and is computationally efficient. The effect of boundary flexibility on the system response was investigated by simulating a series of triaxial tests on dense and loose specimens. At the specimen scale, differences in shear strength and volume change of specimens were observed. It was shown that localization pattern depends on the applied boundary conditions. At the particle scale, particle‐membrane contact forces, coordination number, local void ratio, and anisotropy of fabric were all affected by the boundary flexibility.

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Section: Microscale Analysis Of Simulation Resultsmentioning

confidence: 78%

“…Anisotropy tensors for contact orientation (R) and normal force (F) are calculated based on Equations and :

R_{ij} = \frac{1}{N} \sum_{cϵV} n_{i}^{c} n_{j}^{c}

F_{ij}^{n} = \frac{1}{N} \sum_{cϵV} f_{n}^{c} n_{i}^{c} n_{j}^{c}

where N is the total number of contacts in the assembly,

n_{i}^{c}

( i = 1, 2, 3) is the i th component of the normal vector at contact point c , and

f_{n}^{c}

Section: Microscale Analysis Of Simulation Resultsmentioning

confidence: 99%

Section: Microscale Analysis Of Simulation Resultsmentioning

confidence: 99%

Section: Microscale Analysis Of Simulation Resultsmentioning

confidence: 99%

See 2 more Smart Citations

An efficient flexible membrane boundary condition for DEM simulation of axisymmetric element tests

Khoubani

Evans

2017

Num Anal Meth Geomechanics

Self Cite

View full text Add to dashboard Cite

show abstract

“…The discrete element method (DEM) originally proposed by Cundall & Strack [20] has been used across a wide range of disciplines, including civil engineering, chemistry, physics and bioscience [21]. It is well documented that DEM is capable of capturing the mechanical behaviour of soils ranging from the small-to large-strain levels under both static and dynamic loading conditions [22][23][24][25][26][27][28]. Wang & Wei [29] found that the Mean Neighboring Particle Distance (MNPD) they proposed has the best correlation with the post-liquefaction shear strain development based on DEM simulations.…”

Section: Introductionmentioning

confidence: 99%

Jamming analysis on the behaviours of liquefied sand and virgin sand subject to monotonic undrained shearing

Huang

Hanley

Zhang

et al. 2019

Computers and Geotechnics

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It is well documented in the experimental literature that liquefied sands behave differently from virgin sands without a shearing history. In this study, undrained DEM simulations were performed on both a virgin sample and samples liquefied by cyclic loading. An identical critical state was reached regardless of liquefaction history. The fundamental mechanisms underlying the difference in the stress-strain responses between the liquefied sands and virgin sand were interpreted within the framework of jamming transition. The virgin sample was jammed throughout the simulation, characterised by a fully-percolated force transmission network of increasing resilience and mechanical stability. In contrast, the initially liquefied samples experienced an apparent phase transition from unjammed to jammed states. A fully-percolated force transmission network did not exist, and thus the unjammed samples flowed during the initial stage of loading. As loading proceeded, the force transmission network became fully percolated, and its resilience and mechanical stability developed. All of the micro-scale parameters reflecting the resilience and mechanical stability of the force transmission network reached identical values at the critical state independent of liquefaction history. Finally, a micro-scale approach based on the degree of indeterminacy was proposed to identify the four-stage post-liquefaction behaviour.

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3D DEM modeling of biocemented sand with fines as cementing agents

Liang

et al. 2022

Num Anal Meth Geomechanics

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Microbially induced calcium carbonate precipitation (MICP) has attracted much attention as a promising green technique for soil improvement. Despite the significance of precipitation pattern in mind, constitutive relations or numerical models considering the finite-strain mechanical effects of the various precipitation patterns are rarely developed. In this paper, we propose a novel 3D DEM modeling scheme by using coarse particles to represent sand grains and fines as cementing agents, to reproduce the various precipitation patterns in MICPtreated sand. Based on the topological relations with adjacent particles and the contribution to the mechanical improvement, the cementing fines are classified into effective, partially effective, surface coating, and pore filling ones. The microstructural characteristics and their evolution upon external loading are investigated quantitatively after a careful calibration and validation. The microstructural variation in experiments can be well reproduced, pinpointing this variation as a possible cause for the fluctuation in experimental data. Massive coating fines are produced accompanying the microstructural degradation, which is initiated by the breakage of effective bonds. The breakage of partially effective bonds may become dominating later in the medium to strong cemented specimens. One weakly cemented specimen shows diffuse failure with simultaneous bond-breakage and friction. In contrast, the medium to strong cemented specimens show localized failure with the dominating mechanism transiting from bond-breakage to friction producing notable pore filling fines. We propose a relation between unconfined compressive strength and the equivalent effective volume fraction of cementing agents normalized by the pretreatment porosity, which reveals the coupling effects of the initial configuration and the precipitation pattern on the mechanical improvement.

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Particulate modeling of cementation effects on small and large strain behaviors in granular material

Cited by 17 publications

References 37 publications

An efficient flexible membrane boundary condition for DEM simulation of axisymmetric element tests

An efficient flexible membrane boundary condition for DEM simulation of axisymmetric element tests

Jamming analysis on the behaviours of liquefied sand and virgin sand subject to monotonic undrained shearing

3D DEM modeling of biocemented sand with fines as cementing agents

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