http://hdl.handle.net/10204/938 Sun, 26 May 2013 04:57:41 GMT 2013-05-26T04:57:41Z http://hdl.handle.net/10204/6739 Title: Detection of mining-induced fractures around a stope in Ezulwini gold mine, South Africa, by using AE events with similar waveforms Authors: Moriya, H; Naoi, M; Nakatani, M; Murakami, O; Kgarume, T; Ward, AK; Durrheim, R; Philipp, J; Yabe, Y; Kawakata, H; Ogasawara, H Abstract: The ability to predict rock failure is desirable for the prevention of disasters in mines. The acoustic emission (AE) method is a well-known tool for monitoring fracture growth in rock masses that is used to help ensure safety during excavations. In mines, AE can indicate the location of fractures and damage zones. If AE could be used to detect the initiation and extension of fractures in rock masses and determine their precise source locations, that information would be helpful in forecasting the locations of rock failure. A study of AE in the Ezulwini gold mine in South Africa has been conducted under the Japan–South Africa collaborative project titled “Observational studies to mitigate seismic risks in mines”, in which a large number of events have been detected around the mining front. In this paper, we report on the determination of the source location of AE by the joint hypocenter method and multiplet analysis, and we delineate structures in the AE cloud. Description: Progress in Acoustic Emission XVI, The Japanese Society for NDI, Okinawa Prefecture Municipal Center, Naha City, 27-30 November 2012 Thu, 01 Nov 2012 00:00:00 GMT http://hdl.handle.net/10204/6739 2012-11-01T00:00:00Z http://hdl.handle.net/10204/6730 Title: What role can ISO 17025 play in the South African mining industry? ; Article Authors: Pretorius, CJ; Chesalokile, T Abstract: The ISO/IEC 17025 Standard was developed by the International Standards Organisation (ISO) to provide a mechanism to enable laboratories to manage the quality of their analytical results and to produce internationally comparable results. The Standards Division of the South African Bureau of Standards has adopted the ISO/IEC 17025:2005 as South African National Standard 17025:2005. There are, however, many misconceptions about what the ISO 17025 standard involves and the importance of such a standard in analytical measurements within the mining industry. This paper gives an overview of the standard, and explains what the standard requires and how it is applied in analytical measurements of respirable, silica-containing dust. The recent Mankayi case shows there is a need for the improvement and standardisation of analytical measurements within the mining industry. The ISO 17025 provides the framework in which these can take place. Description: Copyright: 2013 Mine Ventilation Society of South Africa. This is an ABSTRACT ONLY. The definitive version is published in Journal of the Mine Ventilation Society of South Africa, vol. 66(1), pp 15-17 Fri, 01 Mar 2013 00:00:00 GMT http://hdl.handle.net/10204/6730 2013-03-01T00:00:00Z http://hdl.handle.net/10204/6724 Title: Guided elastic waves produced by a periodically joined interface in a rock mass Authors: Yenwong Fai, AS; Durrheim, RJ; Hildyard, MW Abstract: Mining-induced seismic events pose a serious risk to workers in deep mines. Accurate numerical simulations are useful in analyzing the problem and developing mitigation strategies. Here we tackle the problem of guided interfacial elastic wave propagation in a periodically joined interface of two half spaces. The problem is viewed as a mixed boundary-condition plane strain problem and a displacement discontinuity model is used to model the boundary condition. The coupled set of first order linear differential equations for stress and velocity for an elastic continuum are replaced by an explicit finite difference scheme that is implemented on a regular rectangular staggered grid. Phase velocity dispersion curves for the guided interfacial wave modes are obtained via a phase spectra analysis method. The analysis reveals that longer wavelengths travel faster than shorter ones and that the phase velocity dispersion curve is a function of many model parameters including: source type (shear or dilatation), source time function, inherent periodicity at the model interface and size of periodic strips joining the interface. Lastly, we observe that the medium acts like some sort of “soft” frequency filter. Description: 8th South African Conference on Computational and Applied Mechanics (SACAM 2012), Johannesburg, South Africa, 3-5 September 2012. Not part of the 8th SACAM Conference Proceedings. Sat, 01 Sep 2012 00:00:00 GMT http://hdl.handle.net/10204/6724 2012-09-01T00:00:00Z http://hdl.handle.net/10204/6722 Title: The Status of silicosis in the world: Feedback on the ASTM Silica Symposium Authors: Pretorius, CJ Abstract: The second ASTM Silica Symposium was held in Oct 2012 where speakers reported on the status of silicosis in their respective countries. Speakers reported on findings of research that they carried out on sampling equipment and analytical techniques that are used in the monitoring of respirable dust that contains crystalline silica. This paper summarises some of the work presented. Description: The Mine Ventilation Society of South Africa 2013 Conference, Emperors Palace, Johannesburg, 27 February - 1 March 2013 Sat, 01 Jun 2013 00:00:00 GMT http://hdl.handle.net/10204/6722 2013-06-01T00:00:00Z