Discrete element method analysis of non-coaxial flow under rotational shear

Authors

  • Zhaoxia Tong,

    1. School of Transportation Science and Engineering, Beihang University, Beijing, China
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  • Pengcheng Fu,

    1. Atmospheric, Earth, and Energy Division, Lawrence Livermore National Laboratory, Livermore, CA, U.S.A.
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  • Yannis F. Dafalias,

    1. Dept. of Civil and Environmental Engineering, University of California, Davis, CA, U.S.A.
    2. Dept. of Mechanics, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Athens, Greece
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  • Yangping Yao

    Corresponding author
    1. School of Transportation Science and Engineering, Beihang University, Beijing, China
    • Correspondence to: Yangping Yao, School of Transportation Science and Engineering, Beihang University, Beijing 100191, China.

      E-mail: ypyao@buaa.edu.cn

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SUMMARY

This study focuses on non-coaxial flow behavior of cohesionless soil undergoing cyclic rotational shear, with a special interest in the effects of particle-scale characteristics. To this end, we perform a series of 2D discrete element simulations with various particle shapes, inter-particle coefficient of friction, initial density, and stress ratios. The validity and efficacy of the numerical model is established by systematically comparing numerical simulation results with existing laboratory testing results. Such comparison shows that the numerical simulations are capable of capturing mechanical behavior observed in laboratory testing under rotational shear. We further demonstrate and quantify a strong yet simple relationship between the deviatoric part of the normalized strain increment and the non-coaxial angle, denoted by math formula and ψ, respectively. This quantitative correlation between ψ and math formula is independent of applied stress ratio, initial and current void ratio, and the number of cycles applied, but dependent on the principal stress orientation and particle-scale characteristics. At the same math formula, specimens with higher inter-particle friction angle or smaller particle aspect ratio show greater non-coaxial angles. A simple model math formula is able to fit this ψ-math formula relationship well, which provides a useful relationship that can be exploited in developing constitutive models for rotational shearing. Copyright © 2014 John Wiley & Sons, Ltd.

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