Clay particles are flat, or plate-shaped and pack as random stacks of particles. Because of this random packing, the solids are not as effective as spheres are in occupying a unit volume. If they were perfectly stacked like bricks in a wall, then they would very easily fill all the space. The randomly packed material is less dense than silt or sand. Particle size and shape have a significant effect on the soil bulk density.
Sand grains are relatively large and angular in shape.
Large-sized pores predominate because smaller silt and clay particles do not fill the spaces between sand grains. The single grain structure does not contribute to the enhancement of the bulk volume as do other types of structure. As the texture becomes finer, or as silt plus clay increases, total pore space increases together with the range and diversity of pore sizes and shapes. This in turn influences pore size distribution. It would be expected that the greater diversity of particle size would result in a massive or compacted soil since the small particles may fit between the larger particles.