Specific surface area is more informative than grain size for fine-grained sediments where 13 S s >1m 2 /g. In fact, specific surface area plays a central role in engineering properties and processes 14 in fine-grained soils including pore size and bioactivity; fabric, plasticity and rheology; hydraulic 15 and electrical conductivity; compressibility and residual friction angle; and all forms of coupled 16 processes. This research advanced a dye adsorption method using digital image colorimetry 17 implemented with smartphone technology. In particular, adopted a water-based approach to reach 18 internal surfaces in platy phyllosilicates, selected short dye molecules to reduce the range of potential 19 molecular contact area, and developed a physics-based adsorption model to analyze the complete 20 dataset to minimize the uncertainty in specific surface area determinations. The study involved fine-21 grained soils with distinct mineralogy and specific surface area (from 1 to 600 m 2 /g), and various 22 cationic dyes and a protein to explore the effect of molecular size and shape and pH effects. Crystal
Near-surface seafloor properties affect offshore mining and infrastructure engineering. Shallow seafloor sediments experience extremely low effective stress, and consequently, these sediments exhibit very low in-situ density, shear wave velocity, and shear stiffness. We combined data extracted from the literature with new laboratory and field results to develop a comprehensive understanding of shallow seafloor sediments. First, we explored the sediment-dependent self-compaction characteristics starting with the asymptotic void ratio at the interface between the water column and the sediment column. The asymptotic void ratio depends on the particle size and shape in coarse-grained sediments and on mineralogy and pore fluid chemistry in fine-grained clayey sediments; overall, the asymptotic void ratio correlates with the sediment-specific surface and compressibility. Second, we developed a fork-type insertion probe to measure shear wave velocity profiles with depth. Detailed data analyses confirm the prevalent role of effective stress on shear wave velocity V s ¼ αðσ 0 m =kPaÞ β , and the inverse relationship between α and β parameters reveals that electrical interactions alter the velocity profile only in very high specific surface area sediments at very low effective stress and shows that ray bending affects the computed velocities only in the upper few centimeters (for the probe geometry used in this study). Probe insertion causes excess pore fluid pressure and effective stress changes; the ensuing time-dependent diffusion detected through shear wave velocity changes can be analyzed to estimate the coefficient of consolidation. Shear wave velocity profiles and velocity transients after insertion provide valuable information for sediment preclassification and engineering design.
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