Ocean disposal of waste products exerts significant influence on physical properties of marine sediments. Little has been done to assess some of the long-term implications of ocean dumping or spilling of chemical compounds on the depositional and physical properties of sediments. In this research the effects of three such materials on depositional characteristics, microstructure, and some index properties of laboratory prepared marine clays were studied.
The contaminants used were fly ash, activated sewage sludge, and fuel oil. The clay samples were kaolinite, illite, and a mixture called “marine clay,” which consisted of illite, kaolinite, chlorite, and Ca-montmorillonite. The test setup consisted of rectangular settling columns with four sampling ports along one side. Clay soil was premixed with a designated amount of contaminant and transformed into slurry using distilled water. The slurries were then transferred into the settling columns, mixed thoroughly with more distilled water, and allowed to settle in a water column approximately 0.5 m high. Time-settlement, time-concentration, and concentration-depth curves were generated for various mixtures of clay and contaminant. At the completion of the sedimentation, core specimens were taken for index property and pH measurements and samples for scanning electron microscope analysis.
The effect of chemicals on the sedimentation trend, index properties, and the microstructure was evaluated based on phenomena such as flocculation, agglomeration, dispersion, and electrostatic forces between particles. The hypotheses were supported by the sedimentation data and the observations of some microstructure features.