Depositional and post-depositional geochemistry, and its correlation with the geotechnical properties of marine clays in Ariake Bay, Japan

Abstract

The mineralogy, geochemistry and geotechnical properties of clay samples in Ariake Bay, Japan are presented. The mineralogy and geochemistry are discussed in terms of depositional and post-depositional processes, and the correlations of the clay mineralogy and geochemistry with the geotechnical properties were examined by multiple regression analysis. The most predominant clay mineral in the deposits was found to be smectite. The vertical distribution of trace elements in the deposits was indicative of the periodical changes in the parent materials involved in the depositional processes. The chloride concentration in the pore water varied, according to a change in the sea level, from brackish to marine, and then brackish towards the surface. The higher iron oxide contents near the surface and in the deepest zones were the results of pyrite oxidation in the deposits due to weathering under subaerial conditions. Smectite content was the most predominant governing factor for the consistency limits and activity; the iron oxide content was the most predominant for the sensitivity, the Cu/p value, and the over-consolidation ratio. Overconsolidation characteristics in the near-surface zone and in the deepest zones were attributed to interparticle cementation by the iron oxides produced by pyrite oxidation. L'article présente les propriétés minéralogiques, géochimiques et géotechniques d'échantillons argileux de la baie d'Ariake, Japon. La minéralogie et la géochimie sont étudiées pendant et après le dépôt. Les propriétés géotechniques sont ensuite corrélées, à l'aide de diverses régressions, à la minéralogie et à la géochimie. La smectite est le minéral argileux le plus courant. La distribution verticale des éléments-trace dans les dépôts est représentative des variations périodiques des matériaux originels impliqués dans les processus de dépôt. Selon le niveau de la mer, la concentration en chlorures de l'eau interstitielle vane: en remontant vers la surface, elle est typique de l'eau saumâtre, puis de l'eau de mer, puis de nouveau de l'eau saum7acirc;tre. Les teneurs en oxydes de fer les plus élevées, situées à proximité de la surface et dans les zones les plus profondes, résultent de l'oxydation, par altération sous conditions subaériennes, de la pyrite contenue dam ces dépâts. Les teneurs en smectites et en oxydes de fer sont les principaux paramàtres contrôlant les limites de consistance et Pactivité pour la premiàre, la sensibilité, la valeur de culP et le degré de surconsolidation pour la seconde. Les caractéristiques de surconsolidation dans les zones proches de la surface et dans les zones les plus profondes sont sans doute dues à une cimentation de l'espace interparticulaire par des oxydes de fer issus de l'oxydation de la pyrite.

Application of shear wave velocity for characterizing clays from coastal regions

“…In this direction, efforts have been made to develop correlations between the moisture content, specific surface area and proportions of clay minerals by earlier researchers (Bojana, 2006). Empirical correlations between hygroscopic moisture content of the soil with its surface area, cation exchange capacity, liquid limit, swelling potential and electrical properties (conductivity and dielectric constant) have also been proposed by the earlier researchers who have studied the influence of depositional and post-depositional geochemistry and its correlation with the geotechnical properties of the marine clays (Ohtsubo et al, 1995;Shah and Singh, 2006).…”

Cr(VI) concentration from batch contact/tank leaching and column percolation test using fly ash with additives

“…The clayey soil adopted to mix with the fly ashes in this study was Ariake clay with a liquid limit (w l ) of 116.6% and plastic limit (w p ) of 57.5% and clay content (<2 m) of about 31.0%. The dominant clay mineral in the Ariake clay is smectic one [6]. The pH value of the solution from the clay/distilled water mixture with a solid/liquid ratio of 1:10 was 7.64.…”

Effect of effective overburden pressure on geomembrane/soil interface transmissivity

“…The particle size distributions of the soils are shown in Figure 2. The Ariake clay had a liquid limit of 116.6% and plastic limit of 57.5%, and consisted primarily of smectite clay mineral (Ohtsubo et al 1995). For the decomposed granite, compaction tests (JIS A 1210) (Japanese Geotechnical Society, 2000) yielded an optimum water content of about 13% and a maximum dry unit weight of 19.0 kN/m 3 .…”