Numerical analysis of critical state behaviors of granular soils under different loading conditions

Zhao, Xinlei; Evans, T. Matthew

doi:10.1007/s10035-011-0284-1

Cited by 50 publications

(19 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, discrete element simulations (DEM) without modeling a breakage mechanism also exhibit fluctuations in bulk time series in the high strain limit. 6 Due to system size (i.e., number of virtual grains in a DEM) the fluctuations are typically more pronounced than observed in the laboratory. 7 We take the view in concert with others 3,9 that these fluctuations in the stress are a result of dynamical instabilities at critical state; and indeed, the rise and fall of the macroscopic stress, reminiscent of stick-slip motion, is a reasonable analogue to earthquake dynamics in fully developed fault gouges.…”

Section: Introductionmentioning

confidence: 99%

“…A granular assembly which is compressed in the axial direction at a constant rate (displacement-controlled) and confined laterally under constant pressure, ultimately reaches a nearsteady so-called "critical state" regime, in which the bulk stress, measured through the stress ratio, fluctuates about a near constant value. 3,5,6,13,25 In discrete element simulations and experiments on initially homogeneous and dense granular materials (e.g., sand), these episodic fluctuations in the global stress (also known as stick-slip) often coincide with the presence of fully-developed, persistent shear bands of around 8-10 mean particle diameters in thickness. 25 It is possible for critical state to be approached without localization but here we focus on the dynamics exhibited by a sample which does fail by localization.…”

Section: B Dynamical Behavior In Granular Assemblesmentioning

confidence: 99%

“…The assumption of additive Gaussian noise is reasonable here because the linear fit of the parameters k i as well as the computation of minimum description length both employ it. The noise variance r 2 will be some fraction of the total mean-square error of the model fit to the 013113- 6 Small et al Chaos 23, 013113 (2013) data: one assumes that the model prediction error is composed both of dynamic and observation noise. It should be clear that this model class is rather generic.…”

Section: B Modelingmentioning

confidence: 99%

“…1 This limit state is posited, in critical state soil mechanics, to occur when dense, and also loose, granular media, subject to compression, reach the same void ratio at large strains independent of the initial density state. [2][3][4][5][6] A "true" steady-state (i.e., observed constant trace of time series measurements of the macroscopic stress) is difficult to achieve experimentally as stress and volume fluctuations, albeit small in amplitude, are still present. 7,8 This failure to reach an asymptotic steady-state behavior is often attributed to the process of particle breakage, or comminution.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Characterizing chaotic dynamics from simulations of large strain behavior of a granular material under biaxial compression

Small

Walker

Tordesillas

et al. 2013

Chaos: An Interdisciplinary Journal of Nonlinear Science

View full text Add to dashboard Cite

For a given observed time series, it is still a rather difficult problem to provide a useful and compelling description of the underlying dynamics. The approach we take here, and the general philosophy adopted elsewhere, is to reconstruct the (assumed) attractor from the observed time series. From this attractor, we then use a black-box modelling algorithm to estimate the underlying evolution operator.We assume that what cannot be modeled by this algorithm is best treated as a combination of dynamic and observational noise. As a final step, we apply an ensemble of techniques to quantify the dynamics described in each model and show that certain types of dynamics provide a better match to the original data. Using this approach, we not only build a model but also verify the performance of that model. The methodology is applied to simulations of a granular assembly under compression. In particular, we choose a single time series recording of bulk measurements of the stress ratio in a biaxial compression test of a densely packed granular assembly-observed during the large strain or so-called critical state regime in the presence of a fully developed shear band. We show that the observed behavior may best be modeled by structures capable of exhibiting (hyper-) chaotic dynamics. Inferring dynamical structure of a deterministic nonlinear system from noisy time series data is a long standing problem. Here, we demonstrate the application of a range of methods to a problem of particular interest in the study of granular materials. An initially dense assembly of grains under biaxial compression with constant confining pressure reaches a near steady-state behavior (modulo fluctuations) in the large strain regime. The dynamics of this system at this limit are the focus of this paper-and of significant interest within the soil mechanics literature. Understanding the dynamical response of the granular structure in this regime is crucial for prediction and control in many industrial and geophysical systems. Our analysis indicates that the dynamics of this system in the presence of a fully developed shear band are consistent with a form of transient chaos-characterized by a bistable system which switches between two chaotic regimes, one with large slow oscillations and one with smaller and faster dynamics.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: B Dynamical Behavior In Granular Assemblesmentioning

confidence: 99%

Section: B Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Characterizing chaotic dynamics from simulations of large strain behavior of a granular material under biaxial compression

Small

Walker

Tordesillas

et al. 2013

Chaos: An Interdisciplinary Journal of Nonlinear Science

View full text Add to dashboard Cite

show abstract

“…Several definitions are available in literature [83,196,223] to define the deviatoric magnitude of the strain. For the sake of simplicity, we use the following definition of the deviatoric strain to account for all active and inactive directions in a triaxial experiment, regardless of the deformation mode,…”

Section: Strainmentioning

confidence: 99%

Micro-macro and jamming transition of polydisperse granular materials

Kumar¹

View full text Add to dashboard Cite

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

Khoubani

Evans

2017

Num Anal Meth Geomechanics

View full text Add to dashboard Cite

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.

show abstract

Numerical analysis of critical state behaviors of granular soils under different loading conditions

Cited by 50 publications

References 37 publications

Characterizing chaotic dynamics from simulations of large strain behavior of a granular material under biaxial compression

Characterizing chaotic dynamics from simulations of large strain behavior of a granular material under biaxial compression

Micro-macro and jamming transition of polydisperse granular materials

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

Contact Info

Product

Resources

About