The effect of salinity on the rigidity and settling behavior of reconstituted water-saturated kaolinite sediments

In sandy sediments, the salinity of the pore water only affects the sound speed of the mixture by way of affecting the sound speed of the pore water. With clay mineral and saltwater mixtures, the intergranular forces that depend on the salinity of the pore water affect the sediment acoustic properties beyond simply affecting the sound speed of the pore water. These dependencies were investigated via image analyses of prepared samples of two kaolinite clay types (Flat DS and RSA) via analyses of their settling dynamics, porosity, and rigidity as a function of pore water salinity. There exists an observable dependence on salinity to mixture porosity and rate of settling. In addition, three regimes of slip-stick dynamics are shown to exist at different salinity ranges: (a) an immediate transition to liquid-like behavior; (b) a viscoelastic transition to liquid-like behavior with long term creep; and (c) a delayed transition to viscoelastic behavior with long term creep. [Work supported by ONR.]