South African Gold Mines Research Articles

Novel method for the evaluation of particle sharpness : Steward, N R; Ruthert, H J S Afr Inst Min MetallV93, N5, May 1993, P121–127

An understanding of wear in systems conveying solids is extremely important from the standpoints of design and economics. The lifetime of any bulk solids-handling system depends on the type of solids present and the operating parameters of the transportation system. The relationship between wear in backfill pipelines on South African gold mines and the transportation system's operating parameters is well understood. However, the effect of the transported solids on the pipe wear is less well understood, because of an inability to characterize particle sharpness. The sharpness of the particles, together with their size and hardness, is responsible for the aggressivity of particles, or their ability to cause damage and wear. This paper presents a novel method for the characterization of particle sharpness. The results presented rank particles according to the sharpness of their surfaces.

Tradition and Transition in Southern Africa: Festschrift for Philip and Iona Mayer

Speaking for themselves, William Beinart Social existence and the practice of personal integrity - narratives of resistance on the South African gold mines, Dunbar Moodie Kalela, Beni, Asafo, Ingoma and the rural-urban dichotomy, John Argyle Migration, incapsulation and ethnicity - Italian villagers in London, Robin Palmer The origins of the Indlavini - male associations and migrant labour in the Transkei, William Beinart Using ritual to resist domination in the Transkei, P.A. McAllister Polygyny as myth - towards understanding extramarital relations in Lesotho, Andrew D. Spiegel. (Part contents).

Corrosion problems and their solutions in South African deep level gold mines

Deep level gold mining, with its conditions of high humidity, the presence of large quantities of corrosive, chloride containing underground waters and high levels of abrasives, and the need to accommodate men, machinery, and ore handling systems safely and efficiently, presents great challenges to the practising corrosion engineer. In the present harsh economic climate, it is essential that these corrosion problems are effectively solved. One of the most critical areas in a gold mine is the shaft, steelwork in which is exposed to all the corrosive conditions. Any corrosion protection method must satisfy the requirements of long term durability and minimum maintenance. Hot dip galvanised steel, either on its own or used in conjunction with a paint system, has been found to be successful, although many practical difficulties had to be overcome before its success could be firmly established. This method has also been applied to other steel applications, such as materials handling equipment and piping. Most modern gold production plants are based on the carbon in pulp process, which uses concentrated hydrochloric acid, caustic soda, and sodium cyanide at elevated temperatures. Practical experience and dedicated research have led to the development of successful materials of construction, which are effectively handling these difficult process conditions and serving to protect the associated plant and equipment. Many corrosion problems have also been solved by innovative designs. The advent of deeper gold mines and the introduction of mechanised mining methods will place an even greater emphasis on materials selection and cost effective corrosion protection. With higher levels of capital expenditure and longer payback periods, as well as greater emphasis on safety, the challenges for the corrosion engineer will be to recognise the benefits and limitations of current practices and to make sound technical innovations for the anticipated harsher environments.

Energy Expenditure, Silica Dust Exposure and Silicosis in White South African Gold Miners

Energy Expenditure, Silica Dust Exposure and Silicosis in White South African Gold Miners

Risk of silicosis in a cohort of white South African gold miners.

The risk of silicosis was investigated in a cohort of 2,235 white South African gold miners who had, on average, 24 years of net service from 1940 to the early 1970s and who were followed up to 1991 for radiological signs of onset of silicosis (ILO category 1/1 or more). There were 313 (14%) miners who developed signs of silicosis at an average age of 55.9 years. The latency period was largely independent of the cumulative dust exposure. In 57% of the silicosis, the radiological signs developed, on average, 7.4 years after mining exposure ceased. The risk of silicosis increased exponentially with the cumulative dust dose, the accelerated increase being after 7 mg/m3-years. At the highest exposure level of 15 mg/m3-years, which represents approximately 37 years of gold mining at an average respirable dust concentration of 0.4 mg/m3, the cumulative risk for silicosis reached 77%. In conclusion, the risk of silicosis was strongly dose dependent; however, the latency period was largely independent of the dose.

The Invention of the ‘Tropical Worker’: Medical Research and the Quest for Central African Labor on the South African Gold Mines, 1903–36

In 1903 the South African mining industry began recruiting African labor from Central Africa in order to shore up their labor supplies. From the outset, Central African recruitment was problematic, for Central African mine workers died at very high rates. The primary source of Central African mortality was pneumonia. In response to this high mortality the Union government threatened to close down Central African recruitment, a threat which they carried out in 1913. From 1911 to 1933, the mining industry fought to maintain, and then after 1913 to regain access to Central African labor. Of central importance in this struggle were efforts to develop a vaccine against pneumonia. While the mine medical community failed to produce an effective vaccine against pneumonia, the Chamber of Mines successfully employed the promise of a vaccine eventually to regain access to Central African Labor in 1934. The mines achieved this goal by controlling the terrain of discourse on the health of Central African workers, directing attention away from the unhealthy conditions of mine labor and toward the imagined cultural and biological peculiarities of these workers. In doing so the mines constructed a new social category, ‘tropical workers’ or ‘tropicals’. The paper explores the political, economic and intellectual environment within which this cultural construction was created and employed.

Mineralogical controls on the bacterial oxidation of refractory Barberton gold ores

The effect of mineralogical characteristics of gold ore minerals on the nature of sulphide oxidation during a bacterial leaching process was investigated. Three different ore types from the South African goldmines were used, i.e. an arsenopyritic-pyritic ore (Sheba goldmine), a pyritic ore (Agnes goldmine) and a loellingitic-arsenopyritic ore (New Consort goldmine). Detailed mineralogical characterization of each ore was performed. Thereafter, polished sections of the sulphides were suspended in a bacterial leach pulp in an air-stirred vessel for various periods of time. The effect of bacterial oxidation on the sulphides was monitored. Different types of gold-bearing arsenopyrite exist, each type having its own characteristic behaviour during the bacterial oxidation process. The rate of oxidation is controlled by the amount of defects in the crystal structure, and the amount of defects is again controlled by the composition of the arsenopyrite crystal. The distribution of refractory gold in the sulphide minerals can be correlated with the presence of compositional zones and structural deviations. These same mineralogical features also control the sites and rates of bacterial oxidation. Thus. refractory gold occurs at sites which are preferentially leached by the bacteria. The rate of gold liberation from sulphides is therefore being enhanced during the early stages of bacterial oxidation. Defects in a crystal structure influence the rate of bio-oxidation, and can be related directly to the crystal structure of the sulphide mineral, the crystallographic orientation of the exposed surfaces, and differences in chemical compositional and mechanical deviations in the crytals. A combination of all of these mineralogical factors influences the bacterial oxidation process. To optimize and to understand the leaching of an individual ore it is important to establish its controlling factors.

The abrasion and abrasion-corrosion properties of a 9% chromium steel

A 9Cr2Ni0.7Mo steel was assessed for its dry abrasion and abrasion-corrosion performance using a laboratory test which simulates the conditions experienced by rock conveyors in South African gold mines. The alloy is found to exhibit abrasion and abrasion-corrosion properties comparable with most and better than several higher chromium containing alloys designed for mining applications. The good dry abrasion performance of the alloy is attributed to the good combination of high hardness, strength and toughness imparted to the alloy by its duplex microstructure of lath martensite and thin film of interlath retained austenite. The good abrasion-corrosion results are a product of the good dry abrasion performance coupled with the excellent corrosion properties in the simulated mine water. The favourable corrosion properties are linked to the effect of the Ni and Mo additions on suppressing pitting tendencies thereby imparting corrosion resistance equivalent to higher chromium containing steels. Experimental evidence however shows that the alloy is operating at the limit of its passivity for the 46 h corrosion period employed in the corrosion-abrasion test. Exposure for periods much in excess of this figure will lead to breakdown and poor corrosion-abrasion performance relative to higher chromium containing steels. The production variables of prior cold working and plate thickness are found to exert negligible influence on dry abrasion and abrasion-corrosion properties.

Cor pulmonale and silicosis: a necropsy based case-control study.

The presence of cor pulmonale at death in relation to other factors such as emphysema, silicosis, and thromboembolism was analysed in a case-control study of 732 South African gold miners. Marked emphysema was the highest risk factor with an odds ratio of 21.32 (95% confidence interval (95% CI) 5.02-90.7), then extensive silicosis (OR 4.95, 95% CI 2.92-8.38) and thromboembolic disease (OR 1.92, 95% CI 1.37-2.69). Age and smoking were not significant predictors of cor pulmonale.

Power and surveillance on the South African gold mines

(1992). Power and surveillance on the South African gold mines. Journal of Southern African Studies: Vol. 18, No. 4, pp. 825-844.

Ethnic violence on South African gold mines

(1992). Ethnic violence on South African gold mines. Journal of Southern African Studies: Vol. 18, Political Violence in Southern Africa, pp. 584-613.

Note on fault-slip motion inferred from a study of micro-cataclastic particles from an underground shear rupture

Mining of a highly-stressed remnant in a deep South African gold mine was accompanied by considerable seismic activity and some significant rockbursts. The larger seismic events were registered some 60 km away at a WSSN station and several shear ruptures corresponding to these events were encountered during mining operations.

Loss of lung function associated with exposure to silica dust and with smoking and its relation to disability and mortality in South African gold miners.

The data from a lung function study on 2209 white 45-54 year old South African gold miners in 1968-71 and at a five year follow up examination, were analysed to establish the actual loss of lung function associated with exposure to silica dust and with smoking. Ex-smokers were excluded from the analysis. Of the remaining 1625 subjects, 1249 had the five year follow up test of lung function. The estimated excess loss of lung function for a 50 year old gold miner, associated with 24 years of underground dust exposure of an average respirable dust concentration of 0.30 mg m-3 (14.4 ghm-3) was 236 ml of FEV1 (95% confidence interval (95% CI 134-337) and 217 ml of FVC (95% CI 110-324). By comparison, the effect of smoking one packet of cigarettes a day over 30 years was associated with an estimated loss of 552 ml of FEV1 (95% CI 461-644) and 335 ml of FVC (95% CI 170-500). The cumulative dust exposure was not associated with the longitudinal loss of FEV1 or FVC when the initial FEV1 and FVC were adjusted in the models. According to the predicted values, however, gold miners appear to have a greater loss of lung function from 50 to 55 years of age than that predicted for a general population.

Case studies on large rockbursts in South African gold mines : Brummer, R K; Rorke, A J Proc 2nd International Symposium on Rockbursts and Seismicity in Mines, Minneapolis, 8–10 June 1988P323–329. Publ Rotterdam: A A Balkema, 1990

Case studies on large rockbursts in South African gold mines : Brummer, R K; Rorke, A J Proc 2nd International Symposium on Rockbursts and Seismicity in Mines, Minneapolis, 8–10 June 1988P323–329. Publ Rotterdam: A A Balkema, 1990

ACCOUNTING FOR GOLD: THE SOUTH AFRICAN CASE

Real output measures in the UN System of National Accounts should be continually re‐evaluated, to ensure they are providing indicators appropriate for user needs. The South African gold mining industry is an intriguing case in which the conventional output indicators are highly misleading for various analytical purposes, largely because the usual background assumptions are particularly invalid. Due to the size of the industry, its precise treatment can have sizeable effects on estimates of the growth of GDP, particularly over periods when the price of gold changes. A number of easily produced additional output measures are suggested to help analyse productivity growth and differences between the growth of real output and real incomes.

Development of the Slurry Precipitation and Recycle Reverse Osmosis (SPARRO) Technology for Desalinating Scaling Mine Waters

Conventional desalination technologies such as electrodialysis reversal and reverse osmosis cannot be directly used to economically treat those waters encountered in the South African gold mining industry which are scaling with regard to calcium sulphate. The Chamber of Mines of South Africa Research Organisation therefore decided, in the early 1980's, to undertake research into the development of seeded reverse osmosis technology for treating scaling mine waters. This research culminated in the development of foe Slurry Precipitation and Recycle Reverse Osmosis (SPARRO) technology. Extensive pilot plant investigations were undertaken and it was shown that the SPARRO process is technically capable of producing a high quality product water at water recoveries of around 95 per cent. Problems were encountered, however, with fouling of the tubular cellulose acetate membranes, resulting in declines in the flux rate. It is postulated that the fouling is mainly due to the presence of quartzitic suspended material, although the mechanism of fouling cannot be explained. Further research is being undertaken to clarify the potential fouling mechanisms and to optimize the membrane cleaning regimes. The capital cost for a 46.3 1/s (4Ml/d) SPARRO plant has been estimated at R16.2 million, with an estimated operating cost of R 1.48/m3 of product water.

Moment tensors of ten witwatersrand mine tremors

Ground motions, recorded both underground and on the surface in two of the South African Gold mining districts, were inverted to determine complete moment tensors for 10 mining-induced tremors in the magnitude range 1.9 to 3.3. The resulting moment tensors fall into two separate categories. Seven of the events involve substantial coseismic volumetric reduction-ΔV together with normal faulting entailing shear deformation ΣAD, where the summation is over fault planes of areaA and average slipD. For these events the ratio-ΔV/ΣAD ranges from 0.58 to 0.92, with an average value of 0.71. For the remaining three events ΔV is not significantly different from zero; these events are largely double-couple sources involving normal faulting. Surprisingly, the two types of source mechanism appear to be very distinct in that there is not a continuous distribution of the source mix from ΔV=0 to-ΔV≈ΣAD. Presumably, the coseismic closure indicates substantial interaction between a mine stope and adjacent shear failure in the surrounding rock, under the influence of an ambient stress for which the maximum principal stress is oriented vertically.

Chronic Airflow Limitation in South African Gold Miners: Reply

"Chronic Airflow Limitation in South African Gold Miners: Reply." American Review of Respiratory Disease, 144(6), pp. 1423–1424

Chronic Airflow Limitation in South African Gold Miners

"Chronic Airflow Limitation in South African Gold Miners." American Review of Respiratory Disease, 144(6), p. 1423

Pillar foundation failure studies at a deep South African gold mine : Proc 2nd International Symposium on Rockbursts and Seismicity in Mines, Minneapolis, 8–10 June 1988 P65–69. Publ Rotterdam: A A Balkema, 1990

Pillar foundation failure studies at a deep South African gold mine : Proc 2nd International Symposium on Rockbursts and Seismicity in Mines, Minneapolis, 8–10 June 1988 P65–69. Publ Rotterdam: A A Balkema, 1990