ETD Collection

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    The impact of HIV/AIDS on mortality at a South African platinum mine
    (2008-05-14T11:37:50Z) Dowdeswell, Robert Joseph
    ABSTRACT Background: There is a paucity of empirical data on the impact of HIV/AIDS on mortality in the mining industry in the pre-ART era. Such data will provide a baseline against which the efficacy of antiretroviral treatment can be measured into the future. Objectives: To measure all-cause mortality in a population of platinum miners between 1992 and 2002, the impact of HIV/AIDS on mortality in this group and to determine the pattern of other cause-specific mortality. Methods: This was a primary analysis of mortality in an open cohort of male semi- and unskilled workers at a platinum mine. Using Poisson regression, all-cause, HIV/AIDSrelated and other cause-specific mortality rates and rate ratios were calculated by age and calendar year. Results: There were 1986 deaths in the cohort of 29954 subjects who contributed 200657 person years of follow up over the 11 year period of the study. Crude all-cause mortality increased from a base of 5.1 per 1000 person years at risk (pyar) (95% CI 4.2- 6.2) in 1992 to 20.4 per 1000 pyar (95% CI 18.3-22.8) in 2002. Age-adjusted all-cause mortality increased more than three-fold from 1992 to 2002 (RR 3.2, 95% CI 2.5-4.0). The excess mortality was attributed to HIV/AIDS-related deaths which increased from 0% in 1992-1994 to 5.1% of total deaths in 1995 and reached 63.3 % of deaths in 2002. Mortality due to other communicable diseases, non-communicable diseases and injuries remained stable throughout the study period. Conclusion: The impact of the HIV/AIDS epidemic on mortality in this group of platinum mine workers has been profound and comparable to that experienced by the general South African population. The data reported here provide a baseline to measure the impact of antiretroviral treatment on the future course of mortality due to the epidemic.
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    Determination of the factors affecting the performance of grout packs
    (2007-02-26T13:31:18Z) Grave, Douglas Marcus Hadley
    In tabular mining, common in South African gold and platinum mines, the removal of the tabular ore body by mining operations leaves behind excavations known as stopes. These stopes form the production areas of a mine and have to be supported in order that a safe working environment is created. Stopes generally have widths of close to a metre but, in some areas and on certain reefs, may be much wider. Prior to the 1980s, a combination of in-stope pillars and timber was used to support these stopes, but innovations from the 1970s have produced grout packs as a viable support option. These packs are cast in situ through the use of cemented classified tailings gravitated from surface and placed in reinforced geotextile bags at the stope face. As these packs cure and become rigid they are able to bear load when compressed by stope closure. In this way, the packs keep the working areas open. To quantify the load-bearing capacity of grout packs, a range of sizes and designs was tested in a laboratory press and, thereafter, a select few were tested underground. Initially, two aspects of grout packs that had not been adequately quantified previously were addressed. These were: the in situ load / compression characteristics of different forms of grout packs; and the relationship between laboratory test results and in situ performance. The laboratory test programme was extended to allow for an investigation into methods of improving the yieldability of grout packs and the possibility of using them to replace in-stope pillars. It was found that the factors that most affect the initial strength and post-failure characteristics of a grout pack are: the grout strength; the amount and type of steel reinforcement; the inclusion of ancillary columnar support; and the height and diameter of the pack. It was also found that grout packs could be used to replace in-stope pillars, but that pack strength and spacing should be conservatively calculated before implementation. A provisional relationship between the behaviour of packs tested in a press and those placed underground was determined.