Discrete element modelling of flexible membrane boundaries for triaxial tests

Qu, Tongming; Feng, Y. T.; Wang, Yong; Wang, Min

doi:10.1016/j.compgeo.2019.103154

Cited by 80 publications

(40 citation statements)

References 78 publications

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“…Shear localization is a remarkable sign of the instability of ductile solid materials, such as granular materials. When the material deforms sufficiently into the plastic state, a homogeneous deformation pattern gives way to highly localized deformation featured as a “shear band.” 38 It mainly occurs in dense granular materials under large deformations. The conventional RVE model with homogeneous deformation assumption is unable to reasonably reflect such a strain localization phenomenon at the RVE level.…”

Section: Numerical Examplesmentioning

confidence: 99%

An adaptive granular representative volume element model with an evolutionary periodic boundary for hierarchical multiscale analysis

Feng

Wang

2021

Numerical Meth Engineering

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The hierarchical multiscale analysis normally utilizes a microscopic representative volume element (RVE) model to capture path/history‐dependent macroscopic responses instead of using phenomenological constitutive models. However, for problems involving large deformation, the current RVE model used in geomechanics may lose representative properties due to the progressive distortion of the RVE box, unless a proper reinitialization is applied. This work develops an adaptive RVE model in conjunction with an evolutionary periodic boundary (EPB) algorithm for hierarchical multiscale analysis of granular materials undergoing large deformation based on a recent RVE model proposed for coupling molecular dynamics and the material point method. The proposed adaptive RVE model avoids the reinitialization of the RVE box that even undergoes extremely large shear deformation; meanwhile, it accounts for the deformation history of the RVE model and treats the interaction between boundary particles and other image particles in a more efficient way. Numerical examples with extremely large deformation are used to illustrate the adaptive granular RVE model enhanced by the proposed EPB algorithm. Furthermore, some key features of this new methodology are further discussed for clarification.

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Section: Numerical Examplesmentioning

confidence: 99%

An adaptive granular representative volume element model with an evolutionary periodic boundary for hierarchical multiscale analysis

Feng

Wang

2021

Numerical Meth Engineering

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“…The conventional triaxial test is one of the standardized laboratory tests, which plays a fundamental role in geotechnical engineering researches 1 . By using the equipment, the stress–strain curve of a rock block under special confining pressure can be obtained, so as to investigate the deformation and failure process of the rock under complicated conditions.…”

Section: Introductionmentioning

confidence: 99%

A three-dimensional discrete element model of triaxial tests based on a new flexible membrane boundary

Yan

Liu

Zhang

et al. 2021

Sci Rep

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Based on a new elastic clump model, a flexible membrane is proposed for the discrete element numerical simulations of triaxial tests. Conversional triaxial tests of sandstone under the confining pressures of 2 MPa and 8 MPa were carried out, in order to validate the effectiveness of the proposed numerical simulation method. The numerical model is validated by comparing the numerical results with the test results. The deformation and failure process of numerical model is analyzed by stress–strain curves, micro fractures, displacement fields, stress fields and energy fields. The model shows an X-shape shear failure zone, of which the angle is very close to that of the test; the dip angle of most shear fractures is close to the angle of the internal friction; and there is a large amount of slipping frictional heat generated on the failure surface. During the loading process, the stress chain and stress concentration appear in the middle of the model, which lead to displacement zoning in the model. The failure of the model is associated with the growth of the micro tensile- and shear fractures. This study provides an effective tool for the macro–micro investigation of rock failure processes.

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“…Many studies have confirmed the ability of discrete element modelling (DEM) to capture intrinsic features of granular materials . However, the choices of DEM parameters are often made in a trial and error manner . A barrier to determining reasonable contact parameters is that a direct measure of particle‐scale parameters is difficult for granular systems with several different constituents.…”

Section: Introductionmentioning

confidence: 99%

A hybrid calibration approach to Hertz‐type contact parameters for discrete element models

Feng

Zhao

et al. 2020

Num Anal Meth Geomechanics

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This study aims at providing a hybrid calibration framework to estimate Hertztype contact parameters (particle-scale shear modulus and Poisson ratio) for both two-dimensional and three-dimensional discrete element modelling (DEM). On the basis of statistically isotropic granular packings, a set of analytical formulae between macroscopic material parameters (Young modulus and Poisson ratio) and particle-scale Hertz-type contact parameters for granular systems are derived under small-strain isotropic stress conditions. However, the derived analytical solutions are only estimated values for general models.By viewing each DEM modelling as an implicit mathematical function taking the particle-level parameters as independent variables and employing the derived analytical solutions as the initial input parameters, an automatic iterative scheme is proposed to obtain the calibrated parameters with higher accuracies. Considering highly nonlinear features and discontinuities of the macro-micro relationship in Hertz-based discrete element models, the adaptive moment estimation algorithm is adopted in this study because of its capacity of dealing with noise gradients of cost functions. The proposed method is validated with several numerical cases including randomly distributed monodisperse and polydisperse packings. Noticeable improvements in terms of calibration efficiency and accuracy have been made. K E Y W O R D Sadaptive moment estimation, calibration, constitutive law, discrete element method, Hertz-Mindilin contact model, nonlinear elastic model

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Discrete element modelling of flexible membrane boundaries for triaxial tests

Cited by 80 publications

References 78 publications

An adaptive granular representative volume element model with an evolutionary periodic boundary for hierarchical multiscale analysis

An adaptive granular representative volume element model with an evolutionary periodic boundary for hierarchical multiscale analysis

A three-dimensional discrete element model of triaxial tests based on a new flexible membrane boundary

A hybrid calibration approach to Hertz‐type contact parameters for discrete element models

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