Mechanics of a marine clay based on physico-chemical interactions with organic contaminants

Abstract

The effects of municipal (sewage) sludge and crude oil on physi- cal and mechanical properties of laboratory prepared marine clays were investigated. Contaminants appeared to influence the development of clay microstructure and thus some of the physical and mechanical properties of sedimented marine clay. A mixture of illite, Ca-montmorillonite, kaolinite and chlorite minerals constituted the laboratory prepared ''marine clay''. The samples were prepared by allowing the marine clay slurry to settle in rectangular settling columns with sampling ports. Marine clay was premixed with the predetermined amount of contaminant and transformed into a slurry using saline water. The slurries were then poured into the settling columns, mixed in place and allowed to settle in a water column of 0.6 m of height. When the sedimentation was completed the water above the interface was drained through the sampling ports and undisturbed samples of the sediment were obtained by inserting a thin walled plastic tube into the sediment. Among the physical and mechanical properties measured or observed are physico-chemical properties, index properties, microst- ructure, shear strength, stiffness, permeability and compressibility. The influence of crude oil and sludge on these physical and mechani- cal properties and the microstructure was evaluated based on criteria such as flocculation, dispersion and Coulombic forces between the particles and the contaminants.