Design, analysis and manufacture of a Rocprop dome end
- Authors: Bolton, Jason Charles
- Date: 2012-08-16
- Subjects: Pillaring (Mining) -- Design and construction , Ground control (Mining) , Mine roof control , Coal mines and mining -- Safety measures , Gold mines and mining -- Safety measures
- Type: Thesis
- Identifier: uj:9534 , http://hdl.handle.net/10210/5961
- Description: M.Ing. , Safety within the mining industry is a primary concern for everyone involved. More specifically, active below-ground stope support for South African Mines is becoming increasingly important due to a renewed emphasis on the safety and well-being of the people actually working underground. It is imperative that all stope support systems are rigorously tested, continuously, both under laboratory conditions and in-situ to prove their performance and manufacturing standards. The Rocprop was initially manufactured in 1995 with the first two hundred props being installed at East Driefontein Consolidated Gold Mine in the Carletonville area. In the three years since the first introduction over three hundred thousand Rocprops have been manufactured and sold to South African Mines with the number steadily increasing. The Rocprop is a tubular support consisting of two tubes — a Ø139mm 'inner' tube and a Ø152mm 'outer' tube. One end of each tube is sealed by dome ends which are welded onto the tube mouths. The two tubes, cut to identical lengths, fit inside one another and extend telescopically during installation. Once the desired height has been reached, leaving enough tube overlapping to ensure the support does not buckle, the wedge is hammered in locking the prop at that height. The water is then removed after which the prop will provide active support of the rock mass above it. One of the components responsible for the Rocprops success is a dome end. This is either a forging or a pressing welded onto each end of the support and allows continual concentric loading throughout the life of the Rocprop. At present the dome ends are pressings, manufactured into hemispheres from 10mm mild steel plate in one action. The reason for the Rocprop's success is its performance characteristics. It's all metal construction, ease of installation, reliability and predictability in both seismic and static conditions, fire resistance, blast resistant, economically viability and versatility have made the prop successful. Reasons for the research were to investigate the dome end forming process in general and to investigate current numerical analysis techniques ability to predict loads during manufacture, the final shape, spring-back and other local deformation areas. Also to investigate alternate manufacturing methods such as cold forming, which provides advantages such as better mechanical properties and higher structural capabilities. The use of alternate materials in the Rocprop manufacture has been an ongoing process for MSP, manufacturer and current licensee holder of the Rocprop. A substitute for the current dome end manufactured from mild steel was investigated. For the substitute to be viable the material should be stronger, weigh less and be cost effective. In depth knowledge about the forming of the dome end at various velocities was gathered, providing information for further optimisation of the component.
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Geological controls on no. 4 seam roof conditions at New Denmark Colliery, Highveld Coal Field, Karoo Basin, South Africa
- Authors: Stanimirovic, Jasmina
- Date: 2009-01-28T09:43:30Z
- Subjects: Facies (Geology) , Coal , Stratigraphic geology , Sedimentology , Mine roof control , Karoo Supergroup , Mpumalanga (South Africa)
- Type: Thesis
- Identifier: uj:14849 , http://hdl.handle.net/10210/1971
- Description: M.Sc. , The coal-bearing Permian Vryheid Formation of the Ecca Group (Karoo Supergroup) was investigated at New Denmark Colliery, situated in the north east section of the Karoo Basin, South Africa. The lithostratigraphy of the sequence is defined in terms of conventional lithostratigraphic terminology but also by applying detailed genetic stratigraphic schemes that have previously been proposed for the adjacent coalfields. The succession is divided up into depositional sequences named after the underlying and overlying coal seams, the No. 2, 3, 4 and 5 seam sequences. The sedimentary succession was divided up into five facies, namely: conglomerate facies, sandstone facies, interlaminated sandstone-siltstone facies, siltstone facies and coal facies. These were interpreted hydrodynamically. Facies assemblages were then interpreted palaeoenvironmentally. Glacial, fluvial, deltaic and transgressive marine sequences were responsible for forming this sedimentary succession. Attention was then focussed on the main economic No. 4 seam, which is mined underground at the colliery. Detailed subsurface geological cross-sections, core sequences and isopach maps of the No. 4 seam coal and the lithologies above, were used to determine specific aspects of the depositional environment that could contribute to unstable roof conditions above No. 4 seam. Coarsening-upward deltaic cycles, fining-upward bedload fluvial cycles, glauconite sandstone marine transgressions and crevasse-splay deposits are recognized in the overlying strata. Poor roof conditions occur parallel to palaeochannel margins because the interbedded channel sandstone and adjacent flood plain argillites cause collapsing along bedding plane surfaces. Rider coals overlying thin crevasse-splay sequences in close proximity to the No. 4 seam, create one of the most serious roof conditions; complete collapse occurs along the rider coal contact with the underlying splay deposits. Differential compaction of mudrock/shale/siltstone over more competent sandstone causes slickensided surfaces that weaken the roof lithologies. Correct identification of these sedimentological features will enable the prediction of potential poor roof conditions during mining operations and mine planning.
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