Compressibility, stiffness and electrical resistivity characteristics of sand-diatom mixtures

The engineering characteristics of ocean sediments are significantly affected by fine particles such as diatoms. The objective of this study is to investigate experimentally the compressibility, small-strain stiffness and electrical resistivity of sand-diatom mixtures by way of oedometer tests. Sand-diatom mixtures are prepared at a fixed density with varying diatom contents ranging from 0 to 20% by weight. The vertical displacements are monitored during oedometer tests, and shear wave, compressional wave and electrical resistance are measured using bender elements, piezo-disc elements and an electrical resistance probe, respectively, at the end of each loading step. The test results show that the compression index increases, whereas the swelling index and shear and compressional wave velocities decrease with increasing diatom content because of the small and crushable diatom particles. The attenuation of shear and compressional waves increases continuously, while the shear and compressional wave velocities decrease with an increase in the diatom content due to weak inter-particle contact and a soft soil skeleton. In addition, the sand specimens with a lower compression index, Cc, a higher swelling index, Cs, a higher shear wave factor, α, and a lower shear wave exponent, β, gradually change to clay-like soils, which exhibit a higher Cc, a lower Cs, a lower α and a higher β as the diatom content increases. This study suggests that diatoms may affect the compressibility, small-strain stiffness and electrical resistivity of soil.