Underground Gold Mine Research Articles

Practical aspects of mineral resources and ore reserves measurement and accounting

Mineral resources and ore reserves estimation, mine planning, measurement of mine and plant performance and the reconciliation of production results with original expectations are continuous processes during the operation of a mine. These activities involve members of several disciplines over an extended period. Although operating conditions, policies and personnel may change, estimating and reporting practices must be applied consistently to achieve accuracy in periodic evaluations and reconciliation.Operational practices are considered against the background of refinement of the definitions of 'resources' and 'reserves' in an effort by mining and regulatory institutions to achieve conformity. The examples relate to underground gold mining, but the principles are adaptable to other situations. Many elements of the systems described are in place at some operations, but may not be consistently used. At other mines systems may be modified on an ad-hoc basis, with the result that not everyone understands them or some may misinterpret the data. This may have serious consequences when ownership or key staff changes occur or third parties have to interpret inconsistently stated resources, reserves and production data—for example, during due-diligence studies.The monitoring of resources and reserves estimation efficiency and the effective reporting of trends are discussed. Some standard terms and ratio definitions are noted that can be adapted for most situations, and the verified mineral resource estimate is suggested for use as an internal tool to provide an ultimate mineral resource check from observations made immediately before mining takes place. The importance of realistic planning and tracking of both stoping and development material and their contributions to production is stressed, especially in narrow-vein mines, where planning and control of development ore output and quality can have a major effect on extractive performance. The translation of resources to reserves, the treatment of 'not-in-reserve' ore and the accounting of remnant ore reserves are discussed, as are shaft call and plant call factors, which combine to create the more familiar mine call factor. Ore-reserve reconciliation procedures are outlined that comprise two stages: the results of the ongoing resources and reserves estimation and monitoring, followed by the accounting of additions and depletions from the reserves due to exploration, mining and changing conditions. Procedural flowcharts and suggestions for reporting formats are included.

Blast Damage and Blast Dilution Control: The Application of Bulk Emulsion Systems at the WMC St Ives Junction Mine

The application of modern bulk emulsion explosive systems at an underground gold mine resulted in a 57% improvement in gold dilution. While this improvement is impressive and could be expected to be achieved at other sites, the work required to assess and demonstrate the benefits is painstaking. Forty-eight rings involving a total of approximately 50 000 tonnes of ore were monitored using various modern surveying instruments over a 6-month period. The geometric data included blasthole locations and deviation, and the cavity monitoring of stopes. Implementation of a bulk emulsion system not only provided logistical benefits but it also has the desirable explosive properties associated with reducing the effects of blast damage and blast dilution.

Pareto analysis and condition-based maintenance of underground mining equipment

The analysis of historical data on equipment failure is shown to provide a basis for the selection of potential candidates for condition-based maintenance (CBM). Problem areas highlighted by such analyses can also be used to identify inadequacies in existing CBM programmes. The overall methodology is illustrated through a case study of the mobile equipment fleet at an underground gold mine, which focuses on CBM of engines as prescribed by oil analysis. The results from the case study are used to investigate the cost savings potentially achievable through effective application of CBM in mining.

Lobomycosis in three Venezuelan patients.

Case 1. A 52‐year‐old Brazilian man consulted us for a growth on his forehead (Fig. 1). He came from the Amazon region, had been a gold miner for many years, and had noticed a papule on his forehead that had grown slowly for 3 years. On inspection, a 3‐cm, smooth, shiny, elastic nodule was found, the same color as the skin. The clinical diagnosis was lobomycosis; a small sample was taken with a scalpel blade, placed in KOH 20%, and numerous round cells in small chains were seen. Biopsy confirmed the diagnosis. He was treated with surgical excision and was lost to follow‐up.Case 1: growth on the foreheadimageCase 2. An 83‐year‐old Venezuelan man was brought to us by his daughter for an ulcerated verrucous plaque, measuring 6 cm by 4 cm, on his right sole (Fig. 2). The lesion was firm, had started at the age of 63 years as a papule, and later became a plaque which had ulcerated recently. He had been a gold and diamond miner for most of his life, in the southeastern Venezuelan state of Bolívar. The clinical diagnosis was epithelioma cuniculatum. The histology showed pseudoepitheliomatous hyperplasia, numerous cells in giant cells, and histiocytes; Grocott stain showed chains of uniform round to oval cells (Fig. 3 and 4). Over the years, he was treated with ketoconazole and itraconazole to no avail; new nodules appeared on the dorsum of the foot and on his leg (Fig. 5). He is now 98 years old, and fit except for lobomycosis. He has no lymphadenopathy and no neoplastic degeneration of his lesions.Case 2: ulcerated verrucous plaque on the soleimageCase 2: histology (hematoxylin and eosin)imageCase 2: nodules on the footimageCase 3. A 64‐year‐old man from the gold mining region of El Callao, in Bolívar state, was hospitalized for severe heart failure; a mass of nodules was noticed on his right arm (Fig. 6) and we were asked for a consultation. He had worked for many years in the underground gold mines and the lesions had been present for more than 25 years. On inspection, a mass of smooth, shiny, firm, pedunculated, and sessile nodules was seen on the posterior lateral aspect of his right arm; some were hypopigmented, others hyperpigmented. The impression was of a bunch of plums, measuring 6 cm by 12 cm. The clinical diagnosis was plexiform neurofibromas vs angiofibromas. The biopsy showed atrophic epidermis, numerous round cells in giant cells, and no lymphocytic infiltrate; Grocott stain showed single budding with chain formation. The patient was treated with partial surgical excision, but was lost to follow‐up.Case 3: mass of nodules on right armimageDiscussion

Seismic parameters and rockburst hazard at Mt Charlotte mine

Results of the first modern seismic monitoring program in Australia undertaken in an underground mine are presented. A new dimension to mining at Mt Charlotte underground gold mine commenced with the commissioning of a portable seismic system (PSS) in 1994. Since that time useful data have been collected, assisting mine planning in practical terms, providing data for scientific research and providing insight into the dynamic behaviour of rock in relation to local geology and mine production. Conventional data assessment involving one or two seismic parameters was found to have shortcomings for seismic hazard identification. A new method, “departure indexing”, is being developed to provide a robust tool for rockburst hazard evaluation, and possibly for rockburst prediction in the longer term.

Seismic parameters and rockburst hazard at Mt Charlotte mine

Results of the first modern seismic monitoring program in Australia undertaken in an underground mine are presented. A new dimension to mining at Mt Charlotte underground gold mine commenced with the commissioning of a portable seismic system (PSS) in 1994. Since that time useful data have been collected, assisting mine planning in practical terms, providing data for scientific research and providing insight into the dynamic behaviour of rock in relation to local geology and mine production. Conventional data assessment involving one or two seismic parameters was found to have shortcomings for seismic hazard identification. A new method, “departure indexing”, is being developed to provide a robust tool for rockburst hazard evaluation, and possibly for rockburst prediction in the longer term.

Occupational exposure to hand vibration in northern ontario gold miners

Nineteen underground gold mine drillers who operate vibration equipment and a control group of 16 gold mill workers without vibration exposure were evaluated. Assessment included static two-point discrimination, moving two-point discrimination, vibration threshold, and cutaneous pressure threshold. Provocative tests, including Tinel, pressure, and Phalen signs, were performed at the carpal and cubital tunnels. Mean age of the miners was 35 years, and the mean age of the control group was 31 years. The mean time of vibration exposure was 14 years. Numbness, pain, and weakness was reported in 12 miners and 1 control subjects. The Symptoms of vibration white finger were found in 16 miners and 3 control subjects. The miners had a higher incidence of positive provocative tests at the carpal and cubital tunnels and higher cutaneous pressure thresholds than the control group. Significantly higher vibration thresholds were found in the miners versus the control subjects. A correlation between years of vibration exposure and vibration threshold was found.

Combined effect of silica dust exposure and tobacco smoking on the prevalence of respiratory impairments among gold miners.

The combined effect of underground gold mining dust with a high content of free silica and tobacco smoking on the prevalence of respiratory impairment was examined among 2209 South African gold miners and 483 nonminers. The subjects were grouped as having normal function; minimal, moderate or marked obstruction; marked obstruction with restriction; or pure restriction on the basis of their lung function profiles. Each profile group was compared with the normal group for exposure prevalences, and additive and multiplicative relative risk models were applied to test for departure from the additivity of individual effects. Departure from additivity was found to increase progressively with the severity of obstructive impairment. The results indicated that approximately 94% of the cases with the most severe respiratory impairment (N = 191) could have been prevented through the elimination of tobacco smoking. In conclusion, tobacco smoking was found to potentiate the effect of dust on respiratory impairments.

Performance Analysis of Acute Exposure to Hand-Arm Vibration among Underground Drillers

The U.S. Bureau of Mines, the Ontario Mining Health and Safety Branch, and an underground gold mining operation cooperated in a research study to evaluate the pre-and post-shift response to hand-arm vibration (HAV) exposure among underground drillers. The acute effect of HAV exposure was evaluated using three distinct measurement tools, including a test of sensitivity to varying levels and frequencies of vibration using a vibrometry system, a test of hand strength using a grip strength dynamometer, and tests of both gross movements of hands and arms and fine fingertip dexterity using the Purdue Pegboard tasks. Paired T-tests found no significant differences between pre-shift and post-shift vibrometry scores among shifts. Right-hand pegging, assembly, and the combined pegging scores were significantly higher for the post-shift testing when shifts were combined. None of the three measurement tools used appeared to be adequately sensitive to determine the effects of acute exposure to hand-arm vibration.

Time variations of dust concentration and elemental composition in a gold mine

Dust samples were collected over a period of several weeks on a continuously moving strip of membrane filter (Florida State University streaker sampler type) in the return airway of an underground gold mine. The filters were then analysed stepwise by particle-induced X-ray emission (PIXE), yielding elemental concentrations in the dust at 2 h intervals. Elements measured include Al, Si, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn and Pb. Time sequence and average diurnal plots of elemental concentrations are presented. Results of multi-variate factor analysis provide insight into the source processes and materials. The possible sources of the Cl, Pb, Ca and Zn components in the dust are discussed, as is the relevance of these results to the proposed introduction of a gravimetric dust standard for South Africa gold mines. The results are presented to show how the quartz content of airborne dust may be estimated using energy-dispersive X-ray elemental measurements of Si, Al and K.