Effect of Particle Shape on the Mechanical Behavior of Granular Materials. A Discrete Element Study.
Final rept. 1 Nov 91-31 Oct 95,
MASSACHUSETTS UNIV LOWELL DEPT OF CIVIL AND ENVIRONMENTAL ENGINEERING
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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.
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