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Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface
Dissertation (MSc)--University of Pretoria, 2017.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2017
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| _version_ | 1867613588144783360 |
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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 | © 2017 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 | Dissertation (MSc)--University of Pretoria, 2017. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/63229 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:38:30.789Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| 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:2263/63229 Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface Dippenaar, Matthys Alois luke.brouwers@gmail.com Brouwers, Luke Bernhard UCTD Geotechnical centrifuge modelling Variably saturated flow Soil-rock interface Capillary flow Hydraulic gradients Natural and agricultural sciences theses SDG-06 Natural and agricultural sciences theses SDG-09 Natural and agricultural sciences theses SDG-11 Dissertation (MSc)--University of Pretoria, 2017. The underlying mechanisms governing unsaturated flow from soil into fractured rock in the intermediate fractured vadose zone is still poorly understood despite occurring in numerous areas of application. To gain a better understanding of these mechanisms, a series of physical experiments using a geotechnical centrifuge are performed. The centrifuge model comprises of two Perspex® sheets bent to form a clean smooth parallel 1mm aperture single discrete fracture that is inclined 90º, 75º and 60º from horizontal, where dry sand is placed on top and water is supplied as continuous and intermittent influx styles. The presence of the interface shows the development of perched water system and saturated wetting front along the interface, which supports the capillarydominant conceptual models for the fractured vadose zone. Breaching through the interface occurred from preferential feeding pathways in the soil as multiple point sources in the fracture and flow regimes composing of droplets, tendrils with droplet formation and numerous types of rivulets indicating that fluxes within the fracture range between 1 x 10-8 < Q < 1 x 10-4 m3/s per m. Changing the influx styles did not alter the flow mechanisms occurring within the fracture. However, intermittent influx did provide larger saturated wetting fronts along the interface while continuous influx promotes flow instability within the fracture. Altering the fracture inclination influenced the dominant flow mechanisms within the fracture but full saturation is never achieved but rather only a potential 5 - 30% cross-sectional area contributes to flow, which further decreases with depth due to merging of rivulets in upper regions of the fracture. Although the results from the geotechnical centrifuge model may not be scaled to prototype conditions due to similitude not being achieved between the Capillary and Bond numbers, observations of breaching of the soil-rock interface, flow mechanisms and flow instabilities within the fracture are similar in both the 1g and 20g experiments indicating gravity driven flow instability maintains similitude and the geotechnical centrifuge model offers a representative indication of natural conditions. The contrasting support for both conceptual models regardless of fracture inclination indicates that variably saturated flow at the soil-rock interface is a combination of the two current conceptual models, with capillary flow dominating in soil material and the dominant flow regime present within the fracture dependant on the interaction of interfacial capillarity, gravitational and viscous forces. Ultimately the improved conceptualisation and understanding gained from these experiments will benefit hydrogeological as well as geotechnical areas of application such as hillslope hydrology, contaminant transport, groundwater recharge, slope stability, differential settlement, waste disposal, rock mass stress distributions, grouting and seepage into excavations. Water Research Commission bs2026 Geology MSc Unrestricted SDG-06: Clean water and sanitation SDG-09: Industry, innovation and infrastructure SDG-11: Sustainable cities and communities 2017-11-20T11:59:01Z 2017-11-20T11:59:01Z 2017 2017 Dissertation Brouwers, LB 2017, Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface, MSc Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/63229> S2017 http://hdl.handle.net/2263/63229 en © 2017 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 Geotechnical centrifuge modelling Variably saturated flow Soil-rock interface Capillary flow Hydraulic gradients Natural and agricultural sciences theses SDG-06 Natural and agricultural sciences theses SDG-09 Natural and agricultural sciences theses SDG-11 Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface |
| title | Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface |
| title_full | Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface |
| title_fullStr | Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface |
| title_full_unstemmed | Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface |
| title_short | Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface |
| title_sort | geotechnical centrifuge modelling of variably saturated flow at the soil rock interface |
| topic | UCTD Geotechnical centrifuge modelling Variably saturated flow Soil-rock interface Capillary flow Hydraulic gradients Natural and agricultural sciences theses SDG-06 Natural and agricultural sciences theses SDG-09 Natural and agricultural sciences theses SDG-11 |
| url | http://hdl.handle.net/2263/63229 |