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The work deals with evaluation and simulation of the thermal discrete element method (TDEM) for particle-particle collision and thermal conduction in a packed bed. The effects of different granular properties, such as particle size, stiffness factor or compression degree, thermal diffusivity, void fraction or concentrations, and packing states, on the thermal conduction and insulation characteristics of granular assembly are discussed. The thermal conductivity and diffusion still play dominant roles in the overall thermal conduction and insulation of the granular bed. However, it is also indicated that increasing compression degree, reducing particle size and void concentration will increase the thermal conduction throughout the granular materials, and vice versa. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims at investigating the influence of grading on the undrained behavior of granular materials. Series of undrained triaxial tests were carried out with two different materials, glass balls and Hostun sand. For each material, samples with different gradings and similar relative densities were prepared. Experimental results show that the undrained shear strength decreases when the coefficient of uniformity increases from 1.1 to 20. The conditions of instability for the selected granular materials were also analyzed, based on the sign of the second-order work during undrained triaxial loading. The results demonstrate a significant influence of the grading: increasing the coefficient of uniformity heightens the potential of static liquefaction and the materials become more unstable. Furthermore, numerical tests using the three-dimensional discrete element method (DEM) were conducted on assemblies of spheres. The DEM inter-particle parameters were derived from the experimental test results on glass balls. The DEM simulations showed similar behaviors compared to experimental results and confirmed the influence of the grain size distribution on the stress–strain relationship and instability phenomena. [Copyright &y& Elsevier]