Electrokinetic dewatering and consolidation of dredged marine sediments

Malekzadeh, Mona (2016) Electrokinetic dewatering and consolidation of dredged marine sediments. PhD thesis, James Cook University.

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Abstract

Large amounts of marine sediments are produced every year as a result of capital and maintenance dredging works at major ports and these materials must be disposed of. Reuse of these dredged marine sediments for land reclamation is a sustainable and responsible method of disposal management. When the dredged sediments are utilized as a fill material in reclamation sites and are pumped into paddocks, there are two key concerns: 1) whether there is adequate storage capacity at the site 2) workability of the material. Since the dredged marine sediments possess a high water content, typically more than 250% and therefore are in the form of a slurry, self-weight settlement can take many years to complete. This is also due to the low permeability nature of the sediments. To improve the drainage of water and the settlement of these dredged muds, soil stabilization methods such as prefabricated vertical drains and vacuum preloading are commonly used. However, application of these methods is still time consuming and clogging during vacuum consolidation can be a limitation of this technique.

In this study the potential application of electrokinetic stabilization to improve the geotechnical properties of dredged mud in land reclamation areas is investigated as an alternative treatment method. In essence, electrokinetic stabilization is the application of electric potential to the soil through electrodes. When electric current occurs, the pore water flows from the anode to the cathode due to electroosmosis, soil particles move due to electrophoresis, and ions move toward the opposite charged electrode due to electromigration. The combination of all these three phenomena result in favourable and permanent changes in the soil. Electrokinetic stabilization is an environmentally friendly and time efficient method, however, a lack of standard design guidelines draws the attention of the geotechnical engineers away from this method.

In this study, key parameters influencing the efficiency of electrokinetic stabilization are investigated with the aim of maximizing the settlement of the dredged mud. For this purpose, a series of laboratory experiments have been undertaken to explore: (1) the most desirable electrode configuration, (2) effect of electrode materials, (3) the effective type and magnitude of the applied electric potential, and (4) the alteration of physiochemical properties. It is concluded that firstly, dredged marine sediments have significant potential to be improved by electrokinetic stabilization. Secondly, polyaniline coated anodes improve the technique at lower applied voltages. Thirdly, soil compressibility reduces with depth, if the anode is placed at the bottom. Finally, higher settlement is achieved when the anode is placed at the bottom.

Item ID: 49416
Item Type: Thesis (PhD)
Keywords: compressibility, consolidation, dewatering, dredged mud, electric current, electrochemical changes, electrode configuration, electrokinetic stabilization, electroosmosis, electroosmotic dewatering, intermittent current, marine sediments, one-dimensional electonkinetic, one-way drainage, physiochemical changes, polypropylene fiber, soil resistivity, soil salinity, stainless steel electrodes, swelling clays, tensile strength, two-way drainage, unconfined compression, zeta potential
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Malekzadeh, Mona, Lovisa, Julie, and Sivakugan, Nagaratnam (2016) An overview of electrokinetic consolidation of soils. Geotechnical and Geological Engineering, 34 (3). pp. 759-776.

Malekzadeh, Mona, and Sivakugan, Siva (2017) One-dimensional electrokinetic stabilization of dredged mud. Marine Georesources & Geotechnology, 35 (5). pp. 603-609.

Malekzadeh, M., and Sivakugan, N. (2016) Experimental study on intermittent electroconsolidation of singly and doubly drained dredged sediments. International Journal of Geotechnical Engineering, 11 (1). pp. 32-37.

Malekzadeh, M., and Sivakugan, N. (2017) Double drain electrokinetic stabilization of dredged mud using stainless steel electrodes and application of surcharge. KSCE Journal of Civil Engineering. (In Press)

Malekzadeh, Mona, and Bilsel, Huriye (2012) Effect of polypropylene fiber on mechanical behaviour of expansive soils. Electronic Journal of Geotechnical Engineering, 17 (A). pp. 55-63.

Date Deposited: 19 Jun 2017 04:24
FoR Codes: 09 ENGINEERING > 0905 Civil Engineering > 090501 Civil Geotechnical Engineering @ 70%
09 ENGINEERING > 0904 Chemical Engineering > 090403 Chemical Engineering Design @ 30%
SEO Codes: 87 CONSTRUCTION > 8703 Construction Materials Performance and Processes > 870302 Metals (e.g. Composites, Coatings, Bonding) @ 45%
87 CONSTRUCTION > 8702 Construction Design > 870201 Civil Construction Design @ 35%
85 ENERGY > 8505 Renewable Energy > 850504 Solar-Photovoltaic Energy @ 20%
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