A μCT investigation of the collapse of a loose unsaturated sand specimen: Comparison between macroscopic and mesoscopic scale

摘要

The progressive collapse of loose unsaturated sand during suction controlled water imbibition was investigated in an oedometric cell at both macroscopic and mesoscopic scales by means of x-ry CT on a specimen of Hostun sand. Various degrees of saturation were progressively reached by controlling suction by using the negative water column method. A significant collapse was observed at macroscopic level. Volumetric Digital Image Correlation (V-DIC) was also applied on reconstructed images to quantify strains and water content changes at mesoscopic scale. V-DIC reveals that local heterogeneities of strains and water contents appear during imbibition, principally due to the effect of gravity. However, in spite of these local heterogeneities, comparison between mesoscopic and macroscopic scale analyses showed that macroscopic parameters (i.e., water retention curve, and imbibition-induced strain) were representative of the local mesoscopic response of the material.