In the present study, the mechanical properties of granular biomass of pine origin (sawdust, shavings, long shavings and pellets) were determined. The bulk and tapped densities were determined in a cylindrical chamber. The compacted density was measured, and the influence of the moisture content on this quantity was examined in a vane tester. The flowability and strength properties were determined using a direct shear tester (Jenike box) 210 mm in diameter and standard Schulze ring shear tester. The tests in the Jenike tester complied with the Eurocode 1 procedure for normal pressure (σ n) of 15 and 30 kPa and speed of shearing of 0.17 mm s −1. Ring shear testing was conducted using a Schulze annular shear cell of 195 mm outer diameter. Tests were performed for 10 and 20 kPa pre-shear σ n. A prototype vane tester was constructed for determining the torque, shear strength, and relaxation of a consolidated sample of granular biomass. σ n was exerted by a pneumatic system with a rubber air spring and yoke. The torque and density were measured for moisture content in the range of 10-50% and for σ n in the range of 5-30 kPa. The torque was observed to be affected by σ n and the moisture content, whereas no relationship between the torque and the rotational speed was observed.
This paper is an extension of the recent work of Wiącek (Granul Matter 18:42, 2016), wherein geometrical parameters of binary granular mixtures with various particle size ratio and contribution of the particle size fractions were investigated. In this study, a micromechanics of binary mixtures with various ratio of the diameter of small and large spheres and contribution of small particles was analyzed using discrete element simulations of confined uniaxial compression. The study addressed contact normal orientation distributions, global and partial contact force distributions and pressure distribution in packings of frictional spheres. Additionally, the effect of particle size ratio and contribution of particle size fractions on energy dissipation in granular mixtures was investigated. The particle size ratio in binary packings was chosen to prevent small particles from percolating through bedding. The bimodality of mixtures was found to have a strong effect on distribution of contact normal orientation and distribution of normal contact forces in binary mixtures. Stress transfer in binary packing was also determined by both, particle size ratio and volume fraction of small particles. Dissipation of energy was higher in mixtures with higher particle size ratios and decreased with increasing contribution of small spheres in system.
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