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Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence
Dissertation (MSc)--University of Pretoria, 2015.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2016
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| _version_ | 1867613450742530048 |
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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 | © 2016 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, 2015. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/57291 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:36:20.940Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| 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:2263/57291 Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence Dippenaar, Matthys Alois Jacobsz, Schalk Willem warrenvt@hotmail.com Van Tonder, Warren Deon UCTD Centrifuge modelling Permeability Coal mine backfill Heterogeneous backfill Backfill sequence Natural and agricultural sciences theses SDG-09 Natural and agricultural sciences theses SDG-12 Natural and agricultural sciences theses SDG-15 Dissertation (MSc)--University of Pretoria, 2015. Opencast mining has been and continues to be a favoured method for the extraction of the vast coal reserves in the Highveld of South Africa. Previously backfilled and restored open cast areas are generally zoned for agricultural uses, but with growing pressures on land use, such areas are increasingly being considered for the expansion of infrastructure and regional development. Understanding the backfill permeability and hydraulic behaviour is therefore an important component in defining the land use restrictions placed on a previously backfilled area. Centrifuge modelling provides a means of better understanding the hydraulic behaviour and measuring the permeability of opencast backfill under controlled laboratory conditions. Based on a preselected backfill prototype, an appropriate centrifuge model was developed. Using miniature pore pressure transducers, the pore pressures were measured at discrete locations in the model during falling head tests in a geotechnical centrifuge. Using the measured volumetric discharge, spacing between the transducers and the measured pore pressures, the permeability of the backfill was calculated. Due to polarized opinions on the scaling of permeability in a centrifugal field, a control model was tested at 1g and 23g to validate this scaling law. It was demonstrated that the respective permeabilities calculated at 1g and 23g were effectively the same and that it is in fact the hydraulic gradient that is scaled N times in the centrifuge. Knowing this allowed the calculated centrifuge permeabilities to be directly related to the prototype represented by the model. To determine the accuracy of the centrifuge model, the results of field percolation tests were compared to the results of an analogous centrifuge model. There was no correlation between the results and it was not considered meaningful to compare the results, as the model and percolation test site (prototype) conditions differed significantly. To simulate the preselected prototype backfill sequence, a model configuration that represented the geometry and material properties of the prototype was tested at 35g (half scale) and 70g (full scale) in the centrifuge. The results of the centrifuge model were used to make reasonable predictions on the long term permeability and hydraulic behaviour of the backfill prototype. It was found that the permeability of the backfill is likely to decrease over time due to consolidation settlement. The bottom of the backfill sequence is expected to have the lowest permeability and the top is likely to maintain a higher permeability. It was further demonstrated that the horizon interfaces acted as flow restrictors and resulted in poor vertical permeability between the horizons in the backfill sequence. Overall the centrifuge methodology provided a unique and efficient means of modelling the long term permeability and hydraulic behaviour of the backfill sequence. tm2016 bs2026 Geology MSc Unrestricted SDG-09: Industry, innovation and infrastructure SDG-12: Responsible consumption and production SDG-15: Life on land 2016-10-14T07:33:07Z 2016-10-14T07:33:07Z 2016-09-01 2015 Dissertation van Tonder, WD 2015, Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence, MSc Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/57291> S2016 http://hdl.handle.net/2263/57291 en © 2016 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 Centrifuge modelling Permeability Coal mine backfill Heterogeneous backfill Backfill sequence Natural and agricultural sciences theses SDG-09 Natural and agricultural sciences theses SDG-12 Natural and agricultural sciences theses SDG-15 Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence |
| title | Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence |
| title_full | Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence |
| title_fullStr | Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence |
| title_full_unstemmed | Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence |
| title_short | Centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence |
| title_sort | centrifuge modelling of permeability in a heterogeneous coal mine backfill sequence |
| topic | UCTD Centrifuge modelling Permeability Coal mine backfill Heterogeneous backfill Backfill sequence Natural and agricultural sciences theses SDG-09 Natural and agricultural sciences theses SDG-12 Natural and agricultural sciences theses SDG-15 |
| url | http://hdl.handle.net/2263/57291 |