Fabric, force and strength anisotropies in granular materials: a micromechanical insight

Li, X.; Yu, Hai‐Sui

doi:10.1007/s00707-014-1120-6

Cited by 30 publications

(19 citation statements)

References 37 publications

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“…A qualitative analysis of the DEM simulations and the HCA test results from the current study shows a similar variation of the pre-failure stress ratios with different loading directions. Based on the established StressForce-Fabric (SFF) relationship (Rothemburg and Bathurst 1989, Li and Yu 2013a), Li and Yu (2013a) explained that when material approaches the peak stress ratio, the direction of the force anisotropy and fabric anisotropy are generally coaxial with loading direction. Therefore, the magnitude of peak stress ratio is dependent on the developed degrees of force anisotropy and fabric anisotropy.…”

Section: 12! Strength Anisotropymentioning

confidence: 99%

“…Li and Yu (2009) presented 2D DEM simulation results that gave insight into strength anisotropy and deformation non-coaxiality. Li and Yu (2013b) explained the micromechanics with the aid of the established Stress-Force-Fabric (SSF) relationship of granular materials (Li and Yu 2013a). The material strength and the degree of non-coaxiality were determined analytically in terms of a fabric tensor characterizing the anisotropy of material internal structure and contact force distributions characterizing the anisotropy of particle interactions (Li and Yu 2013b).…”

Section: ! Introductionmentioning

confidence: 99%

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Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Yang

et al. 2015

Geomechanics and Geoengineering

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Abstract:! This paper presents an experimental investigation revisiting the anisotropic stress-strainstrength behaviour of geomaterials in drained monotonic shear using Hollow Cylinder Apparatus. The test program has been designed to cover the effect of material anisotropy, preshearing, material density and intermediate principal stress on the behaviour of Leighton Buzzard sand. Experiments have also been performed on glass beads to understand the effect of particle shape. This paper explains phenomenological observations based on recently acquired understanding in micromechanics, with attention focused on strength anisotropy and deformation non-coaxiality, i.e., non-coincidence between the principal stress direction and the principal strain rate direction. The test results demonstrate that the effects of initial anisotropy produced during sample preparation is significant. The stress-strain-strength behaviour of the specimen shows strong dependence on the principal stress direction. Pre-loading history, material density and particle shape are also found to be influential. In particular, it was found that non-coaxiality is more significant in preloaded specimens. The observations on the strength anisotropy and deformation non-coaxiality were successfully explained based on the Stress-

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Section: 12! Strength Anisotropymentioning

confidence: 99%

Section: ! Introductionmentioning

confidence: 99%

Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Yang

et al. 2015

Geomechanics and Geoengineering

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“…Thus, the development of a methodology that would allow rigorous assessment of soil fabric evolution upon nonproportional loading scenarios is in order for both carbonate and non-carbonate soils. This would help extend previous rigorous research (Li and Yu 2014) on the role of fabric on the mechanical behavior of soils.…”

Section: Introductionmentioning

confidence: 64%

“…Parameters such as β and θ 0 (or others that might relate to major particle axis orientation, for example), can be quantified from micro-computed tomography analysis and then systematically compared to the observed stress-strain response (Li and Yu 2014).…”

Section: Micro-computed Tomographymentioning

confidence: 99%

Linking Carbonate Sand Fabric and Mechanical Anisotropy from Hollow Cylinder Tests: Motivation and Application

Fook¹,

Carraro²,

Gourvenec³

2017

Geotechnical Frontiers 2017

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In addition to density and stress, fabric is also a key state variable strongly affecting soil behavior. While fabric influence on mechanical behavior of soils has been investigated experimentally, the available database is limited in terms of boundary conditions and soil types tested. Offshore carbonate sediments are of special interest for offshore geotechnical analyses due to their prevalence in tropical waters and unique mechanical behavior that stems from their mostly biogenic origin. A key gap in the availability of experimental data on soil fabric relates to the anisotropy of offshore carbonate sediments. In practice, anisotropy studies (whether rigorously correlated to fabric or not) are typically carried out experimentally for simple boundary conditions such as idealized plane strain and axisymmetric states. In real geotechnical applications, stress paths subjected to soil elements in the field are far more complex, often involving the combined variations of both the orientation and magnitude of all three principal stresses. This paper presents a new multiscale approach to assess soil fabric at the micro-scale level and relate it to the macromechanical response observed for generalized loading conditions. A new sampling method is illustrated that enables preservation and evaluation of the fabric of offshore sediments specimens following generalized stress disturbances imparted by a hollow cylinder apparatus. The link between fabric evolution and the observed stress-strain behavior of sand is discussed along with preliminary results. The approach is part of a broad framework that will be used to systematically study the evolution of soil fabric and anisotropy and their relationship to multi-directional loading scenarios.

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“…[10,11]. It is worth to analyse the evolution of soil fabric in the current cyclic loading conditions.…”

Section: Fabricmentioning

confidence: 99%

Micromechanics of soil responses in cyclic simple shear tests

2017

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Abstract. Offshore wind turbine (OWT) foundations are subjected to a combination of cyclic and dynamic loading arising from wind, wave, rotor and blade shadowing. Under cyclic loading, most soils change their characteristics including stiffness, which may cause the system natural frequency to approach the loading frequency and lead to unplanned resonance and system damage or even collapse. To investigate such changes and the underlying micromechanics, a series of cyclic simple shear tests were performed on the RedHill 110 sand with different shear strain amplitudes, vertical stresses and initial relative densities of soil. The test results showed that: (a) Vertical accumulated strain is proportional to the shear strain amplitude but inversely proportional to relative density of soil; (b) Shear modulus increases rapidly in the initial loading cycles and then the rate of increase diminishes and the shear modulus remains below an asymptote; (c) Shear modulus increases with increasing vertical stress and relative density, but decreasing with increasing strain amplitude. Coupled DEM simulations were performed using PFC2D to analyse the micromechanics underlying the cyclic behaviour of soils. Micromechanical parameters (e.g. fabric tensor, coordination number) were examined to explore the reasons for the various cyclic responses to different shear strain amplitudes or vertical stresses. Both coordination number and magnitude of fabric anisotropy contribute to the increasing shear modulus.

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Fabric, force and strength anisotropies in granular materials: a micromechanical insight

Cited by 30 publications

References 37 publications

Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Linking Carbonate Sand Fabric and Mechanical Anisotropy from Hollow Cylinder Tests: Motivation and Application

Micromechanics of soil responses in cyclic simple shear tests

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