Influence of fabric on liquefaction and densification potential of cohesionless sand

Nemat‐Nasser, Sia; Tobita, Yoshio

doi:10.1016/0167-6636(82)90023-0

Cited by 74 publications

(14 citation statements)

References 21 publications

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“…The reduced liquefaction resistance is probably due to the change of fabric by the pre-shearing histories of seismic loading. Similar observations have also been confirmed by other researchers (Nemat-Nasser & Tobita, 1982;Suzuki & Toki, 1984;Oda et al, 2001;Ye et al, , 2016.…”

Section: Introductionsupporting

confidence: 92%

Discrete-element method analysis of initial fabric effects on pre- and post-liquefaction behavior of sands

Wei

Wang

2017

Géotechnique Letters

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The initial fabric has great influence on the cyclic behaviours of sands. In this study, numerical simulations by the discrete-element method (DEM) were conducted to study the effects of the initial fabric of sands on their cyclic liquefaction resistance and post-liquefaction behaviour. Nine samples with different initial fabric but the same void ratio were prepared by the pre-shearing method, and then subjected to 47 cyclic simple shear tests. The DEM simulation demonstrated that samples with higher degrees of fabric anisotropy have much lower liquefaction resistance compared with an isotropic sample. By incorporating the initial fabric, a single equation can be used to characterise the liquefaction resistance of all the prepared samples. On the other hand, post-liquefaction deformation is not significantly influenced by the initial fabric such that all samples demonstrate similar cyclic behaviour after liquefaction.

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Section: Introductionsupporting

confidence: 92%

Discrete-element method analysis of initial fabric effects on pre- and post-liquefaction behavior of sands

Wei

Wang

2017

Géotechnique Letters

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“…In parallel, the form of Equation (22) makes the deviatoric component f evolve only upon dilation (due to the Macauley brackets), thereby simulating conclusions from micromechanical studies depicting important changes in the sand particle contact normal orientation distribution only upon the dilative phase of monotonic shearing (e.g. Nemat-Nasser and Tobita [44]). Because of the negative sign in front of N in Equation (22), the f component evolves in the opposite sense to tensor [Cn+f], and in this way, the f : n term in the denominator of Equation (20) becomes non-zero, only upon shear reversal following a dilative shearing phase, and this is due to the change in the direction of n. In such a case, the response is characterized by larger plastic strains (due to a decrease of K p ), which under undrained conditions provides the well-known intense contraction following dilation at small p values, which may eventually lead to liquefaction or cyclic mobility.…”

Section: Plastic Modulus and Dilatancymentioning

confidence: 97%

Explicit integration of bounding surface model for the analysis of earthquake soil liquefaction

Andrianopoulos

Papadimitriou

Bouckovalas

2009

Num Anal Meth Geomechanics

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SUMMARYThis paper presents a new plasticity model developed for the simulation of monotonic and cyclic loading of non-cohesive soils and its implementation to the commercial finite-difference code FLAC, using its User-Defined-Model (UDM) capability. The new model incorporates the framework of Critical State Soil Mechanics, while it relies upon bounding surface plasticity with a vanished elastic region to simulate the non-linear soil response. Stress integration of constitutive relations is performed using a recently proposed explicit scheme with automatic error control and substepping, which so far has been employed in the literature only for constitutive models aiming at monotonic loading. The overall accuracy of this scheme is evaluated at element level by simulating cyclic loading along complex stress paths and by using iso-error maps for paths involving change of the Lode angle. The performance of the new constitutive model and its stress integration scheme in complex boundary value problems involving earthquake-induced liquefaction is evaluated, in terms of accuracy and computational cost, via a number of parametric analyses inspired by the successful simulation of the VELACS centrifuge Model Test No. 2 studying the lateral spreading response of a liquefied sand layer.

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“…Differences in soil response during the later stages of testing have been attributed to variations in the initial fabric of the sample even when the samples are created at the same densities (Jefferies and Been (2006), Nemat-Nasser and Tobita (1982), Mulilis et al (1977), Vaid and Sivathayalan (2000)). If DEM simulations are to provide meaningful insight into soil response observed in element tests, it is important for the initial state (packing density and stress level) and fabric anisotropy of the computer generated sample to closely match the physical reality.…”

Section: Introductionmentioning

confidence: 97%

Macro- and Micro-Scale Effects of Pluviation Based Sample Preparation in DEM

2012

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Previous laboratory studies and Distinct Element Method (DEM) simulations have shown that the preparation method used to create samples for testing can affect the sample fabric and hence the mechanical response observed. The specimen preparation methods traditionally used in the laboratory were developed to recreate a given depositional pattern or in-situ soil fabric. Differences in soil response have been attributed to variations in the initial fabric of the sample even when the samples are created at the same densities. If DEM simulations are to provide meaningful insight into soil response observed in element tests, it is important for the initial state (packing density and stress level) and fabric anisotropy of the computer generated sample to closely match the physical reality. This is particularly true where element tests are used to validate DEM models. A key challenge is the lack of quantitative data on the fabric of real physical test specimens.Several approaches have been documented in the literature for generating the initial configuration of specimens for DEM simulations, i.e. artificially creating a percolating (stress transmitting) granular material. Approaches that are commonly used include radius expansion, compression using rigid boundaries, and pluviation under gravity loading. This paper examines the influence of the method chosen on the macro-and micro-scale properties of the material generated. The methods considered involved generating particles as a diffuse cloud at their target size, followed by pluviation under gravity loading with and without a mesh that modeled a sieve. The study fits within a broader research project in which multidirectional simple shear tests on steel spheres will be replicated in DEM simulations.

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Influence of fabric on liquefaction and densification potential of cohesionless sand

Cited by 74 publications

References 21 publications

Discrete-element method analysis of initial fabric effects on pre- and post-liquefaction behavior of sands

Discrete-element method analysis of initial fabric effects on pre- and post-liquefaction behavior of sands

Explicit integration of bounding surface model for the analysis of earthquake soil liquefaction

Macro- and Micro-Scale Effects of Pluviation Based Sample Preparation in DEM

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