Microscopic particle crushing of sand subjected to high pressure one-dimensional compression

It is commonly accepted that the yield point during one-dimensional compression is related to the initiation of marked particle crushing. Different materials have clear to very amorphous yield points depending on the compression line curvature. In order to examine the relationship between the curvature and slope of the compression line and the statistics of individual particle crushing taking into account particle size and overall grading, high pressure one-dimensional compression tests on silica sand samples seeded with marked particles were carried out. Five levels of particle damage were obtained and defined from microscopic observations of the particles before and after testing. A statistical analysis was carried out on the data for the observed levels of damage to investigate the frequency variation with increasing applied stress. Additionally, one-dimensional compression tests were conducted to examine the effects of initial void ratio and grain size distribution on soil crushability and consequently the compression behaviour. It was found that even for the same material the yielding characteristics were dependent on the grading curve with much more marked yielding occurring for uniformly graded sands in comparison with well graded sands. This was related to the nature of the microscopic particle crushing during yielding. As the material changed from uniform to well graded, the nature of the particle crushing changed from the sudden catastrophic onset of splitting to the gradual splitting of smaller size particles, breaking of the smaller asperities and grinding of the surface.