Abstract
The sedimentation and self-weight consolidation processes of thoroughly disturbed soft marine clay are relevant both to land reclamation work and to sediment accumulation on tidal flats of coastal lowland plains. The influences of grain-size distribution, iron oxide content and organic matter content on these processes and the final water contents of a low-activity mud were investigated at water contents from 500 to 6,000% over salinities ranging from 30 to 0.5g/L. Particle size distribution had a large effect; specifically, the lower the clay content the more rapid the differentiation of an upper sediment boundary and the self-weight consolidation of the accumulated sediment. Iron oxide addition had little effect on these characteristics for this low activity clay. Peroxide destruction of the original organic matter suggested that it had a mildly flocculating effect; the addition of 5% organic matter, in the form of fulvic and humic acids, had a dramatic dispersing effect and inhibited sediment accumulation and consolidation for all conditions tested. The experiments indicate that use of dredged mud with low organic matter content, lesser clay contents and lesser swelling clay content, applied at the lowest water content that is feasible, will provide for the most rapid sedimentation and self-weight consolidation in reclamation projects.
