Term of Award

Fall 2014

Degree Name

Master of Science in Applied Engineering (M.S.A.E.)

Document Type and Release Option

Thesis (open access)

Department

Department of Mechanical Engineering

Committee Chair

N. Mike Jackson

Committee Member 1

Gustavo Maldonado

Committee Member 2

Peter Rogers

Abstract

Geotextile tubes are a proven cost-effective technology offering speed, efficiency, and minimal impact to the environment for dewatering of sediment or sludge from dredging operations. Common applications include: removal of solids from municipal water and waste water treatment, agricultural remediation, marine dredging operations, construction dewatering, and beach preservation and protection. Geotextile tubes are manufactured in a variety of configurations.

Geotextile tubes are used for a wide variety of environmental applications including dewatering and slurry containment. One of the most important design aspects of the tubes themselves is the ability to be flexible and expand and hold form under high pressure as they are being filled with slurry. Due to their flexibility and high tensile strength, along with their great efficiency to dewater, they are being used more frequently, and have been developed for a variety of different applications. Many approaches have been developed to analyze the different outcomes of slurries as they enter the tube.

The purpose of this study is to investigate fabrics of varying reported water flow characteristics for their speed and effectiveness in dewatering treated sludge from a full-scale dredging and dewatering project in Jackson Mississippi. The field results are documented, and compared to lab tests performed on materials from the same job site. The specific gravities, along with the type of tubes and other characteristics from the lab tests will be inputted into a program called SOFTWIN. Data collected in the field is to be compared to lab data, and then further compared to the SOFTWIN application, by inputting the same data collected in the field. This program is new to the geotextile tube industry, and is not widely used by any companies due to the fact that it has not been made available to the public yet. This program has not been verified publically until now that it is in fact a reliable source. It will be proved and justified that this program is not only helpful to predicting field conditions, but also that it is accurate and should be considered an approved device for dredging operations. This involves different scenarios in which geotextile tubes are used while dewatering, different types of sludge and slurries which are dewatered, and differences relating to the chemical flocculants that are used.

The dewatering process using geotextile tubes consists of multiple cycles of filling with slurry and subsequent volume reduction of the slurry within the tube. This process results in a final volume containing an increased concentration of solids. Previous studies by Satyamurthy and Bhatia, and Sieck and Pickett, have generated calculations that developed relationships between the final volumes and the concentration of solids. However, as the rate of the volume reduction increases over time, more sophisticated modeling approaches are necessary to perform the complex analysis that is necessary. Calculations of the solids percentage, tensile stresses of the tube, height, and circumference of the tube prove difficult to predict, and computations performed by hand often result in significant errors, which is where the SOFTWIN program proves to be a great asset to the dredging and dewatering world.

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