Date of Award

12-2013

Embargo Date

2014

Degree Name

Master of Science (MS)

Department

Civil and Environmental Engineering

Advisor(s)

Shobha K. Bhatia

Keywords

centrifuge test, dewatering, filtration, geotextile tubes, polyacrylamide, pressure filtration test

Subject Categories

Engineering

Abstract

The dewatering of low percent solids wastes from tailings ponds, harbors, and waterways presents a challenge in the U.S. and abroad, given the vast amounts that need to be dewatered annually. The United Stated Corps of Engineers estimate about 8.5x109 ft3 of dredged sediments are removed annually in order to keep waterways functional. Dewatering may be achieved with the aid of high strength synthetic textiles, such as geotextiles, which may be sewn lengthwise to form a geotextile tube. Typically, dredged material is mixed with flocculants such as polyacrylamide (PAM), and then pumped into geotextile tubes. In doing so, the flocculants promote aggregation of the particulates, which increases the sedimentation rate and allows for water to drain more freely and quickly through the porous geotextile. The use of geotextile tubes and flocculants are well established in literature and practice, and although many studies have been carried out on sediment-flocculent interactions, few studies have considered role of sediment properties on its interactions with geotextile tubes, sedimentation behavior, compressibility of the sediments, and filtration within the context of geotextile tube dewatering.

In order to gain a more comprehensive understanding of the system, this study characterized 15 dredged sediments from across the U.S. and Canada, and 5 standard materials both chemically (zeta potential, particle charge density, carbon nitrogen ratio, pH, organic content, and cation exchange capacity), and physically (grain size distribution, specific gravity, specific surface area), and then conducted performance tests (sedimentation test, jar tests, centrifuge tests, and pressure filtration) as a way to understand how different sediment properties affect its performance within the context of geotextile tube dewatering. Additionally, the performance tests were conducted using the sediments with and without flocculants (low-, med- high- charge density PAM).

In conducting this study, the chemical properties of the sediments were not found to be prominent indicators of their performance as opposed to the physical parameters. Additionally, the use of flocculants were found to increase the compressibility of the sediments and hasten the dewatering rate, while at the same time slightly increasing the volume of the sediments.

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Open Access

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Engineering Commons

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