MINERALOGY AND CHEMISTRY, AND THEIR CORRELATIONS WITH THE GEOTECHNICAL PROPERTIES OF MARINE CLAYS IN ARIAKE BAY, JAPAN - COMPARISON OF QUICK AND NONQUICK CLAY SEDIMENTS

This article describes the mineralogy, chemistry, and geotechnical pro perties of quick and nonquick clay profiles in Ariake Bay, Japan, and the correlations of the mineralogy and chemistry of the clays with the ir geotechnical properties. The chemistry is discussed in terms of sal ine environment at the time of deposition, and postdepositional weathe ring processes. The principal clay minerals identified were smectite, mica, and kaolinite. The salinity in pore water of nonquick clay varie d, according to changes in sea level from brackish to marine, and then brackish toward the surface. The higher iron oxide contents of the cl ay profiles were attributed to the production of iron hydroxide by pyr ite oxidation, due to exposure of the clays to atmosphere for the nonq uick clay sediment and due to the supply of oxygen from fresh water pe rmeating through the clays during leaching process for the quick clay sediment. The major factors which increase the activity of the clay we re both smectite and salinity in pore water for the nonquick clay, and smectite for the quick clay. The greater C-u/p values of the clays we re associated with the higher iron oxide contents. There was a negativ e correlation between the sensitivity and salinity in pore water, and a positive correlation between the sensitivity and liquidity index for the combined data on quick and nonquick clays. The compression index of undisturbed clays was found to be represented as a function of the liquid limit and sensitivity.