Particle breakage in gap-graded soil

One-dimensional compression tests to high stresses were performed on gap-graded soil specimens in order to investigate their breakage behaviour. Gap-graded specimens were produced by combining small and large soil particles with ratios of large to small grain diameters varying between 5 and 15, and with varying proportions of small grains. Breakage was observed as the particle size distribution evolved with stress level. It was found that, unlike most soils and in contrast to what is usually assumed, the gap-graded specimens did not tend towards a fractal grading curve. Instead, the particular shape of their initial grading curve constrained the organisation of the breakage. The ratio between large and small grain diameters does not seem to affect the amount of small grains created or the relative breakage. A fractal dimension could still be computed from the number of particles, and it was found to increase slightly with small grains content. Finally, it was observed that the shape of particles does not change upon breakage.