Numerical study of the packing of wet coarse uniform spheres

The discrete-element method was extended to investigate the effect of liquid addition on the packing of monosized spheres. By explicitly taking into account the interaction forces between particles, such as contact forces and capillary force, the packing of wet spheres can be simulated by the method. Simulations are performed under the so-called poured packing, where a different amount of water is added to spheres of different sizes. Comparison with data in the literature shows that the simulations yield a satisfactory agreement in the relationship between porosity and moisture content, macroscopically verifying the proposed model. The packing structure is then analyzed in terms of microscopic properties such as the radial distribution function and coordination number and are shown to vary with liquid content for a given particle size. The relationship between porosity and capillary force is finally quantified, which confirms those derived based on macroscopic assumptions.