Effect of ocean environmental particles on compressibility, electrical resistivity, and stiffness characteristics of mixtures

The influence of diatoms, which have distinct physico-chemical characteristics, is a key factor in the investigation of deep-sea sediments. The objective of this study was to investigate the compressibility, electrical resistivity, and stiffness of sand–silt–diatom mixtures performing oedometer tests. The specimens were prepared by mixing fines containing silts and diatoms into sand, and the fines contents were 0%, 10%, 20%, and 30% in weight (FC00, FC10, FC20, and FC30). The oedometer test was carried out from 5 to 640 kPa, and the electrical resistivity, shear wave velocity, and compressional wave velocity were obtained during loading and unloading. The test results show that the electrical resistivity and compressional wave velocity have transitional behavior at FC10 owing to the dominant effect of fines. The shear wave velocity decreases with an increase in fines contents despite a lower void ratio due to the fines. Moreover, the equivalent bulk modulus of the mineral from back-calculation also exhibits a transition at FC10. However, both compression indices from the measured data and the asymptotically-sound compaction model equation exhibit the transition at FC20. In addition, FC20 is located on the boundary between the sand-dominant and transitional mixtures in the triangular chart of ternary mixtures. The results suggest that the transitional fines content of mechanical behavior changes at the points of large and small strains.