Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
The settling behavior of slurries produced by dredging operations was studied by performing settling tests in a 5.5-in. inside diameter, and 6-ft. high plexiglass column with sediment samples collected from the proposed dredging site at Lake Panorama, located in Guthrie County, Iowa. The test results show that a sharp interface, separating the clear supernatant water from the sediment laden water, forms as the average concentration of the slurry reaches a critical value. After the interface has formed, there is no jockeying for position by the particles, and the slurry settles as if all the particles have been locked into a three-dimensional, interconnected lattice. This phenomenon was defined as zone settling process by previous researchers. A literature review revealed that the classical theories used by mining and chemical engineers for describing the zone settling mechanism of particles in a fluid emphasized mainly the "sedimentation" phenomenon in which particles are borne by hydrodynamic forces, and neglected that particles will eventually come into contact, develop effective stresses and consolidate under their own weight;This study provides experimental evidence that zone settling behavior of the slurry is actually the result of self weight consolidation. The self weight consolidation theory, which employs Lagrangian coordinates, is used to describe the zone settling behavior of slurries. It is found that the ratio of actual to modified material height relates the theoretical consolidation curves to actual zone settling curves, and an approach for estimating the apparent coefficient of consolidation, C(,F), of a settling test is proposed;Because the proposed method for calculating the C(,F) requires only the zone settling test data, elaborate density and pore pressure measuring devices are not needed, and the test procedures are greatly simplified. The method should also result in a better description of the zone settling behavior of slurries, because the point at which self weight consolidation begins is precisely defined.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Lin, Tso-Wang, "Sedimentation and self weight consolidation of dredge spoil " (1983). Retrospective Theses and Dissertations. 7643.