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Evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in South Africa
Thesis (PhD (Engineering Geology))--University of Pretoria, 2024.
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| Language: | English |
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University of Pretoria
2025
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| _version_ | 1867613629927391232 |
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| access_status_str | Open Access |
| author2 | Dippenaar, Matthys Alois |
| author_browse | Dippenaar, Matthys Alois |
| author_facet | Dippenaar, Matthys Alois |
| collection | Thesis |
| dc_rights_str_mv | © 2023 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Thesis (PhD (Engineering Geology))--University of Pretoria, 2024. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/100985 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:39:11.828Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/100985 Evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in South Africa Dippenaar, Matthys Alois duanswart@gmail.com Swart, Duan UCTD Sustainable Development Goals (SDGs) Relict rock structure Decomposition Structural prominence Residual soil Weathering profile Thesis (PhD (Engineering Geology))--University of Pretoria, 2024. Weathered rock profiles are frequently encountered during geological, engineering, hydrological, ecological and forestry projects in South Africa. The soil-end exists in the most decomposed portion of a weathering rock profile. This zone comprises residual soil and completely weathered rock, both of which can be excavated as a soil. In this study, completely weathered rock retains the parent rock fabric and macro-structure with secondary minerals forming in place of the primary rock-forming minerals. Residual soil forms through further intensive chemical weathering to the point where most parent rock structure and grain relations have been lost either through decomposition or volumetric strain or a combination of both. The study was conducted with the use of traditional geotechnical laboratory methods, of which the results were compared and analysed with advanced visual techniques. The laboratory testing included particle size analysis and Atterberg limits testing, chemical testing methods, compression testing in oedometers, and saturated permeabilities in a triaxial cell. The advanced visual testing comprised X-Ray Computed Tomography (XRCT) scan that allowed for the modelling of 2D and 3D porosity and density models. These models provide invaluable insight on the structural properties that govern the compression behaviour the completely weathered rock and residual soils. The soil texture of the completely weathered rock and residual soil can be determined from simple field tests that only require water and common stationery. These tests make use of well understood behaviour characteristic of fine-sand, silt, and clay at varying moisture to determine the plasticity of the material, and subsequently the soil texture. The process through which completely weathered rock and residual soil form is governed by the physical and chemical changes caused by chemical weathering. The degree of weathering decreases with an increase in depth into the ground profile. The state of weathering can be quantified with the use of chemical weathering indices. The close relationship between the chemical and physical states of completely weathered rock, allows for the determination of structural prominence, which characterises the degree to which the relict rock structure influences compression behaviour. The structural prominence decreases as weathering increases and, consequently, this increases the compressibility of the material, regardless of the material’s void ratio or dry density. The novel concept of structural prominence can be used to assist engineering geologists and geotechnical engineers to better understand the behaviour of completely weathered rock and residual soil and has been shown in this study to be a better predictor of soil compressibility than the dry density or void ratio. Geology PhD (Engineering Geology) Unrestricted Faculty of Natural and Agricultural Sciences SDG-06: Clean water and sanitation 2025-02-17T10:23:27Z 2025-02-17T10:23:27Z 2025-04 2024-11 Thesis * A2025 http://hdl.handle.net/2263/100985 NA en © 2023 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Sustainable Development Goals (SDGs) Relict rock structure Decomposition Structural prominence Residual soil Weathering profile Evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in South Africa |
| title | Evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in South Africa |
| title_full | Evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in South Africa |
| title_fullStr | Evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in South Africa |
| title_full_unstemmed | Evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in South Africa |
| title_short | Evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in South Africa |
| title_sort | evaluating hydraulic and mechanical properties of weathered intrusive and chemical sedimentary bedrock in south africa |
| topic | UCTD Sustainable Development Goals (SDGs) Relict rock structure Decomposition Structural prominence Residual soil Weathering profile |
| url | http://hdl.handle.net/2263/100985 |