Effects of particle breakage on the compression behaviour of gap graded carbonate sand–silt mixtures

Abstract

Isotropic compression tests were conducted on a series of gap graded mixtures of a carbonate sand (CS) from the South China Sea and a fine crushed quartz silt to reveal how particle breakage of the CS can affect the compression behaviour of these soil mixtures. The weaker CS originally exhibited a unique compression line whereas the stronger quartz silt originally had a stable soil fabric leading to non−convergent compression lines. It was found that the threshold fines content (FC) indicating a change from CS to silt dominated soil matrix, together with the suppression of particle breakage, have governed the change from converging to non−converging compression behavior and from non−stable to stable soil fabric for these gap graded soil mixtures. For FC ≤ 30%, the soil mixtures exhibited a unique compression line because of the substantial breakage of the weaker CS particles in the CS dominated soil matrix. However, for FC ≥ 40% (threshold FC), non−convergent compression lines were observed for the soil mixtures. It was suggested that since the weaker CS particles did not actively participate in load bearing of the silt dominated soil matrix, there was insignificant particle breakage of the CS and the initial soil fabric remained stable at high stress level.