Influence of grain shape and intergranular friction on material behavior in uniaxial compression: Experimental and DEM modeling

The influence of particle shape and interparticle friction on mechanical response of a granular assembly in a uniaxial compression was determined in laboratory experiment and in DEM simulations. The test chamber of rectangular cross-section was used. In laboratory testing seeds of pea and bean were used, while in numerical simulations spherical and non-spherical particles of aspect ratios, which are ratios of the longest to the smallest particle dimensions, in the range from 1 to 2.8 were tested. After the seeds were filled in the chamber the load was applied to the assembly through a top platen driven by a testing machine. The vertical and horizontal forces were measured with load cells supporting the apparatus wall and bottom platen. Numerical results showed that an increase in particle aspect ratio strongly affected the mechanical response of specimen under uniaxial compression. The lateral-to-vertical pressure ratio was predicted to decrease as particle aspect ratio increased from unity to 1.6 and thereafter remained relatively stable with further increase in aspect ratio. Comparison of numerical and experimental results has shown that DEM predicted fairly close the effective modulus of elasticity of the system composed of perfect uniform spheres when compared to the physical tests on peas while a weaker quantitative agreement with experimental results was obtained in the case of oblong particles.