Influence of Aging Effect of Clay on Consolidation and Strength Characteristics

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Electron micrograph showed that association between iron oxide and kaolinite particle is affected by the initial pH of the complex. The iron oxide in the complex prepared at initial pH3 was retained on the surface of the particle even after the pH of the complex was raised to 9.7. The iron oxide of the complex prepared at initial pH9.5 is independent with clay particles above isoelecric point (pH8). Below pH8, some parts of iron oxide is retained on the clay surfaces, and complete association of iron oxide and clay particle need the reduction of pH below 4.The effect of iron oxide on Bingham yield stress differs according to the form of association between iron oxide and clay particles. The iron oxide that is not associated with clay particles contribute to enhance Bingham yield stress more than the iron oxide precipitated on the surface of clay particles. This is attributed to the electrical interparticle bridge of iron oxides that are not associated with clay particles.Chlorine concentration in the pore water for Ariake clay decreased from 10.8 to 0.011g/L by salt leaching. Undisturbed shear strength of the clay was reduced markedly compared with remoulded shear strength, resulting in the increase of sensitivity from 20 to 594. Consolidation coefficient decreased by about 50% by salt leaching for both undisturbed and remoulded clay samples. This is brought about by the reduction of permeability of the clay samples.Smecitite content of marine clay is 10 to 60% for Isahaya clay and 36 to 85% for Hachirogata clay. With increase of smectite percentage, the liquid limit and compression index of the clay increase while the permeability and consolidation coefficient of the clay decrease.