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Investigating cavity propagation to the surface through centrifuge trapdoor experiments
Dissertation (MEng)--University of Pretoria, 2017.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2018
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| _version_ | 1867613591282122752 |
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| access_status_str | Open Access |
| author2 | Jacobsz, Schalk Willem |
| author_browse | Jacobsz, Schalk Willem |
| author_facet | Jacobsz, Schalk Willem |
| collection | Thesis |
| dc_rights_str_mv | © 2018 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 (MEng)--University of Pretoria, 2017. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/66387 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:38:34.940Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| 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:2263/66387 Investigating cavity propagation to the surface through centrifuge trapdoor experiments Jacobsz, Schalk Willem Oberholzer, Benjamin Matthys Beukes UCTD Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-11 SDG-11: Sustainable cities and communities Dissertation (MEng)--University of Pretoria, 2017. The theory of soil arching can aid a study into the field of sinkhole development to enable researchers to understand possible mechanisms that may mobilise in the overburden material when existing underground cavities propagate to the surface to ultimately manifest as sinkholes. An understanding of these failure mechanisms could lead to improved estimations of the likely sinkhole diameter which is required for the design of infrastructure in sinkhole-prone environments. Current methods for the estimation of sinkhole size are very conservative, leading to an over-prediction of sinkhole size, often rendering sinkhole-prone land too costly to develop. A need exists for improved guidelines to assess probable sinkhole size which should eventually culminate in less stringent building regulations in sinkhole-prone environments. Preliminary studies indicated that cavities propagate upwards in a near-vertical fashion, raising questions about the conical funnel-shape as suggested by current building regulation for dolomitic areas in South Africa. This prompted further investigation. Plane-strain deep trapdoor experiments were performed using two different grades of silica sand (a fine and coarse sand) in which active displacement of a trapdoor underneath the soil was modelled to simulate progressive failure of cavity walls and roof. These experiments were performed under dry and moist conditions with varying trapdoor widths and were carried out in a geotechnical centrifuge. Photographs of the models were analysed using Particle Image Velocimetry (PIV) to produce plots of displacement and strain that indicated the geometry of failure mechanisms in the overburden material as the trapdoor displacement increased. Surface settlements were also measured during the experiments using a combination of LVDT surface readings and PIV analyses. These results were compared to form an understanding of the influence of the said variables on failure mechanisms and surface settlement. Zones of influence above trapdoors in all tests tended to propagate vertically upwards rather than in a funnel shape. Surface settlement initially tended to follow a Gaussian shape, but rapidly deepened once the influence zone above the trapdoor (failure mechanism) reached the soil surface so that the Gaussian shape was no longer accurate. The trapdoor size tended to have very little effect on the general failure mechanism, but the propagation of the zone of influence above the trapdoor did advance more rapidly towards the surface when considering surface settlement versus normalised trapdoor settlement. The spatial frequency of shear zone formation in the sand was found to be related to the trapdoor width, with narrow trapdoors resulting in a denser shear band spacing. Increased trapdoor widths resulted in more symmetric shear zone formation. Civil Engineering MEng Unrestricted 2018-08-30T09:03:38Z 2018-08-30T09:03:38Z 2018 2017 Dissertation Oberholzer, BMB 2017, Investigating cavity propagation to the surface through centrifuge trapdoor experiments, MEng Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/66387> A2018 http://hdl.handle.net/2263/66387 en © 2018 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 Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-11 SDG-11: Sustainable cities and communities Investigating cavity propagation to the surface through centrifuge trapdoor experiments |
| title | Investigating cavity propagation to the surface through centrifuge trapdoor experiments |
| title_full | Investigating cavity propagation to the surface through centrifuge trapdoor experiments |
| title_fullStr | Investigating cavity propagation to the surface through centrifuge trapdoor experiments |
| title_full_unstemmed | Investigating cavity propagation to the surface through centrifuge trapdoor experiments |
| title_short | Investigating cavity propagation to the surface through centrifuge trapdoor experiments |
| title_sort | investigating cavity propagation to the surface through centrifuge trapdoor experiments |
| topic | UCTD Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-11 SDG-11: Sustainable cities and communities |
| url | http://hdl.handle.net/2263/66387 |