Investigation of diatomaceous sand using elastic and electromagnetic waves in oedometer tests

The small-strain and electromagnetic behaviors of soils significantly change due to compression. The objective of this study was to investigate the small-strain stiffness and electrical resistivity of diatomaceous sand by modifying the conventional setup of oedometer tests (1D-compression tests). The specimens used were pure sand and sand with 20% diatoms by weight. The vertical displacement was directly observed using a digital gauge at the top of the compression cap during compression. At the end of each loading step, shear waves (S-waves) are measured using a pair of bender elements installed on the top and bottom compression caps. In addition, electrical resistance was measured using a pair of electrodes installed horizontally in the middle of the compression cylinder. The test results show that the compression index increased but the swelling index decreased according with the increase in the amount of the small and crushable diatom particles. The presence of diatom particles weakened the interparticle contacts and softened the soil skeletons. In addition, the electrical resistivity increased with the increase in diatom contents, which increased the surface conduction. Our work suggests that the S-wave velocity and electrical resistivity of diatomaceous sand can be characterized by modifying the conventional oedometer tests.