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The electromechanical stabilization of unsaturated dispersive clay and electro-osmotic control of infiltration
Dissertation (Ph. D.) -- University of Stellenbosch, 1995.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867614003915653120 |
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| access_status_str | Open Access |
| author | De Wet, Marius |
| author2 | Hugo, F. |
| author_browse | De Wet, Marius Hugo, F. |
| author_facet | Hugo, F. De Wet, Marius |
| author_sort | De Wet, Marius |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Dissertation (Ph. D.) -- University of Stellenbosch, 1995. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/54883 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:45:08.467Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/54883 The electromechanical stabilization of unsaturated dispersive clay and electro-osmotic control of infiltration De Wet, Marius Hugo, F. Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. Soil stabilization Soil mechanics Clay soils Settlement of structures Dispersion Electro-osmosis Electrokinetics Dissertations -- Civil engineering Dissertation (Ph. D.) -- University of Stellenbosch, 1995. Dispersive clays are encountered on many different geological formations in Southern Africa, and on all continents around the globe. These clays deflocculate in the presence of relatively pure water and, as such, are prone to erosion. The origins of the dispersive tendency are in the chemical composition of the adsorption complex of the clay minerals and a high exchangeable sodium percentage is the single most adverse factor. Many failures of soil structures, including embankment dams, slopes and canals, have occurred as a result of the erosive properties of dispersive clays. Dispersive clay may be stabilized by adding calcium or other polyvalent cations prior to compaction but existing soil structures cannot be treated in the same way. A method of in-situ stabilization was investigated by which such soils may be converted into erosion resistant materials. The principles of electrokinetics were utilized as basis since it involves ion movement by electrical gradients. The method was found an effective means of removing adsorbed and dissolved sodium and magnesium ions from a dispersive clay soil and replacing them with calcium. During treatment of laboratory samples the exchangeable sodium percentage of the soil decreased by more than eighty percent and chemical, as well as mechanical, methods classified the material as non-dispersive afterwards. To evaluate the method for practical use, the effects of initial moisture content, treatment period and electric current intensity were evaluated. It was found that while variations in moisture content did not have a considerable influence on the amount of sodium removed per unit of electrical charge passed, it had a major effect on the electrical energy consumption during the process. By decreasing the electric current intensity the energy consumption could be reduced, but the treatment period required was subsequently increased. In practice the current intensity should be adjusted to optimize the energy requirements and period of treatment for a given volume of soil and initial moisture content conditions. Previous work on electrokinetic effects had concentrated on saturated soils. Dispersive clay in structures could be in a state of low moisture content and consequently the investigation was extended to study electro-osmosis in partially saturated soils. Mathematical models were developed to predict the electrokinetic behaviour of unsaturated soils and the effects of electro-osmosis on infiltration into these materials. The existence of electro-osmosis in a compacted clay soil at very low moisture conditions was experimentally verified and it was found that the models adequately described electro-osmosis. Coefficients of electro-osmotic hydraulic conductivity for a soil over a range of degrees of saturation, starting at air-dried, were determined experimentally; it was also verified that the rate of infiltration of free water into an unsaturated soil could be controlled by the application of an electrical potential gradient. Doctoral 2012-08-27T11:36:47Z 2012-08-27T11:36:47Z 1995 Thesis http://hdl.handle.net/10019.1/54883 en Stellenbosch University 296 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Soil stabilization Soil mechanics Clay soils Settlement of structures Dispersion Electro-osmosis Electrokinetics Dissertations -- Civil engineering De Wet, Marius The electromechanical stabilization of unsaturated dispersive clay and electro-osmotic control of infiltration |
| title | The electromechanical stabilization of unsaturated dispersive clay and electro-osmotic control of infiltration |
| title_full | The electromechanical stabilization of unsaturated dispersive clay and electro-osmotic control of infiltration |
| title_fullStr | The electromechanical stabilization of unsaturated dispersive clay and electro-osmotic control of infiltration |
| title_full_unstemmed | The electromechanical stabilization of unsaturated dispersive clay and electro-osmotic control of infiltration |
| title_short | The electromechanical stabilization of unsaturated dispersive clay and electro-osmotic control of infiltration |
| title_sort | electromechanical stabilization of unsaturated dispersive clay and electro osmotic control of infiltration |
| topic | Soil stabilization Soil mechanics Clay soils Settlement of structures Dispersion Electro-osmosis Electrokinetics Dissertations -- Civil engineering |
| url | http://hdl.handle.net/10019.1/54883 |
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