Micromechanical Study of Mechanical Behavior of Granular Media Accounting for the Role of Particle Shape PDF Download
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Author: Zhaochen Liu
Publisher:
ISBN:
Category : Granular materials
Languages : en
Pages : 138
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Author: Zhaochen Liu
Publisher:
ISBN:
Category : Granular materials
Languages : en
Pages : 138
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Author: Larry R. Meachum
Publisher:
ISBN:
Category : Granular materials
Languages : en
Pages : 548
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Author: Bernard Cambou
Publisher: Springer
ISBN: 370912526X
Category : Technology & Engineering
Languages : en
Pages : 403
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Book Description
This book presents a complete and comprehensive analysis of the behaviour of granular materials including the description of experimental results, the different ways to define the global behaviour from local phenomena at the particle scale, the various modellings which can be used for a D.E.M. analysis to solve practical problems and finally the analysis of strain localisation. The concepts developed in this book are applicable to many kinds of granular materials considered in civil, mechanical or chemical engineering.
Author: Aleksandr F. Revuzhenko
Publisher: Springer Science & Business Media
ISBN: 9783540338710
Category : Technology & Engineering
Languages : en
Pages : 324
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Book Description
This monograph covers phenomena of deformation and machining of granular media: macroscopic particles of different size, shape, and surface properties which typically exhibit behavior similar to fluids, as well as the behavior of solids under deformation. The book analyses the behavior of granular media in soils, rocks and stones, metals and various synthetic materials, presenting a theoretical description, applications and understanding of basic phenomena in granular matter.
Author: Wei Zhang
Publisher:
ISBN:
Category : Discrete element method
Languages : en
Pages :
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Book Description
Engineering behavior of saturated granular materials under rapid loading as during earthquakes is reasonably well explored empirically. Presently, theoretical models developed within concepts of classical soil mechanics are generally adequate for engineering design. Nevertheless, even such basic soil mechanics questions, for example, as the influence of soil gradation on the stability of hydraulically placed fills can be hotly debated in engineering offices. This is due to lack of a well-developed physical framework for understanding soil behavior at a particle level, specifically in undrained conditions. The main objective of the present study is to explore micromechanics of undrained behavior of granular media using numerical simulations in which motions of discrete particles are coupled with pore fluid movements caused by deformations of individual pores. The latter are modeled as forming an interconnected network. The rate of fluid transfer between pores is considered proportional to pressure differential between pores so that macroscopically the system follows the Darcy's Law. The fluid is considered elastic in response to pore volume change. It is demonstrated that this type particle-fluid coupling results in macroscopic Biot-Terzaghi poroelastic behavior when the system of intergranular contacts is fixed and the contact force vs interparticle displacement relationship is linear. In the case of unbound granular assemblies, when the mechanical behavior under shear deformations involves creation and disintegration of intergranular contacts, the key modeling challenge addressed in this thesis is development of a robust algorithm that tracks modifications of the pore space preserving fluid mass balance. This substantially extends the range of applications for the simulation methodology developed by Dr. R. Olivera at the University of Waterloo in 2004. The developed algorithm is based on identification of sub-volumes in the assembly containing pore groups with one-to-one mapping into uniquely identified sub-volumes in the configuration that existed at the previous computational step. These related sub-volumes contain pores that coalesced due to contact disintegration or where larger pores became subdivided into smaller pores due to creation of contacts. The subdivision of space into related sub-volumes makes it possible to accurately maintain fluid mass balance to practically any strain level as the assembly undergoes through dramatic microstructural changes. Numerical simulations of granular samples under axial loading and constant lateral stress carried out at different void ratio and consolidation stress qualitatively resemble the mechanical response of granular soils in conventional laboratory testing, including static liquefaction of loose samples. This comparison demonstrates that the developed simulation methodology reasonably reflects physical processes in undrained granular media. As an application of the developed simulation methodology the thesis presents a study of the effects of granular soil permeability on undrained behavior. In this particular study the base material is taken as a loose granular assembly of medium to fine particles where permeability was varied by changing the rate of fluid transfer from pore to pore. This physically reflects addition of fine particles into pores to impede flow (without taking into account the effect of fines on interparticle interactions). Simulations demonstrate that restricting fluid transfer from pore to pore results in increased undrained strength. Similar results were obtained in a published laboratory study that concluded that addition of fines to a granular material can prevent static liquefaction. The present study confirms this conclusion. The mechanism of this phenomenon is discussed in the thesis based on examination of the way permeability indirectly influences distributions of intergranular forces. In addition to conventional stress-strain characterization of mechanical behavior, results of all simulations are examined in terms of micromechanical descriptors that characterize changes in the number of intergranular contacts with strain, their spatial anisotropy and average contact forces. Although all micromechanical descriptors in drained and undrained conditions evolve to some asymptotic values at large shear strain, only in the case of drained deformations the same asymptotic state is reached at the same mean stress level irrespective of the initial state of packing. This mean stress-dependent “critical state” corresponds to specific values of void ratio and average coordination number induced in the course of shear deformations. Evolution of simulated granular assemblies towards the same state is not observed in undrained conditions although steady state is always reached. Envelopes of asymptotic states as function of mean stress identified for simulated samples with different initial void ratio, the so-called critical and steady state lines, are somewhat different in cases of drained and undrained deformations, as far as void ratio and coordination numbers are concerned. There appears to be no distinction in values of induced asymptotic anisotropy in drained and undrained conditions. This topic requires further studies and various avenues for further research in this area are identified in the concluding chapter of the thesis.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 164
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An existing two dimensional Discrete Element numerical model which incorporates elliptical particles is used to simulate the biaxial shear of particulate systems. Comparisons are made with physical tests on circular and oval shaped rod systems. Good quantitative agreement was found with the circular rod data, but significantly weaker and softer response was found compared with the oval rod data. This discrepancy is attributed to differences in particle shape in the physical and numerical tests. Additional simulations were conducted using bedded, strongly anisotropic systems at varying degrees of particle flatness. These exhibit distinctly different stress strain and strength behavior, as well as different controlling mechanisms, as function of particle flatness and bedding plane orientation. Shear bands were observed in some flatness and bedding combinations. Interparticle interlocking, dilatancy and inhibition of particle rolling were all observed. Samples with bedding normal to the principal stress direction exhibited the highest shear resistance, as well as largest dilatancy. In systems composed of flat particles with bedding parallel to one of the planes of maximum obliquity, shear bands sometimes formed in the maximum obliquity plane opposite to the bedding plane.
Author: Amal Kumar Dutta
Publisher:
ISBN:
Category :
Languages : en
Pages : 216
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Book Description
The mechanics of granular material is an important issue that governs many geotechnical engineering applications. Two types of particles having similar particle size, but different shape are used in this research to evaluate the role of particle morphology on the physical properties of its assemblage. Experimentation of 1-D compression behavior at constant axial strain rate under laterally confined conditions is performed for these two particulate materials and the behavior of the stress path is analyzed in relation to the initial material packing and physical characteristics of the granules. The behavior of granular assemblages under imposed loading conditions are also evaluated by analyzing the macro and micro level morphological changes (in terms of shape and size distribution) resulting from 1-D compression tests. Various experimental procedures and techniques are employed for characterizing the size and shape aspect of these particles. The mechanical properties (hardness, modulus, and time dependent creep parameters) of the individual particles are determined and analyzed using nanoindentation technique. Nanoindentation has emerged recently as a powerful tool for precise measurements of mechanical properties of materials. Considering its potential applicability in the broad area of micromechanics associated with granular materials, an in-depth study of its application is performed. Since a rigorous study of the nanoindentation technique for finite size particles has not been done to date, initial testing for developing appropriate experimental and interpretation procedures required testing reference material such as fused quartz and novel composite materials to gain additional insight and experience. For this reason, besides granular materials, the changes in mechanical properties for structured materials (blended single wall carbon nanotube-epoxy composite specimens) are also included in this research. The micromechanical analysis of granular assembly using computer simulation through the program PFC2 [superscript D] (2-Dimensional Particle Flow Code), an application of Distinct Element Method (DEM) is also performed. The material micro-properties such as particle shear stiffness and normal stiffness values are assigned from the nanoindentation test results for the two granular materials. The particle contact behavior, nature of force chain structure, and uniformity of deformation associated with 1-D compression on granular materials having different shape and mechanical properties are analyzed.
Author: Masao Satake
Publisher: Elsevier Publishing Company
ISBN:
Category : Granular materials
Languages : en
Pages : 392
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Book Description
This proceedings volume contains papers from researchers in Japan, the United States and England who have made fundamental contributions to the micromechanics of granular materials. The purpose of the seminar was to facilitate an exchange of ideas between scientists working with statistical and continuum theories, computer simulations and experiments on both static and dynamic behaviour. In describing the solid like behaviour of granular materials, many new ideas on the constitutive relations are introduced in this volume. As an application of the analysis, the mechanism of liquefaction is discussed. Computer simulations have become a vital tool in establishing the micromechanical approaches which otherwise would not be experimentally tested. In numerical simulations and theoretical analyses of rapid granular flow, various modifications on the nature of materials and boundaries are given. Possible applications of the techniques of the stereology and analysis based on geometrical statistics are also included. The papers collected in this volume signify that the promotion of a good understanding of the mechanics of granular materials has been and will continue to be valued in a variety of technical disciplines.
Author: 羅曉東
Publisher:
ISBN:
Category : Granular materials
Languages : en
Pages : 0
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Author: Andrés Alfonso Peña Olarte
Publisher:
ISBN: 9783921837597
Category :
Languages : en
Pages : 131
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