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Historically, mine ventilation practices as it was referred to then and which was enforced by legislation of those days, focused primarily on the conditions in the working place and little attention given to actual exposures of workers to contaminants in the working environments. With the advent of the Leon Commission of Inquiry into Safety and Health in the South African Mining industry in 1994, findings in the report indicated that more attention should be given to occupational health of workers. The upshot of this report resulted in the promulgation of the new Mine Health and Safety Act (MHSA) with certain sections of it devoted to all the aspects of occupational medicine and occupational hygiene. This paper describes the present situation with regards to statistics on occupational hygiene performance and compensation paid out to persons who have contracted occupational diseases, as well as the way forward in terms of legislation implemented in September 2002 on the chronic and acute issues affecting the mining industry in SA.

Jan 1, 2003

Introduction The Homestake Mining Co. has always been big on gold. After 108 years in the business, the company and its principal product are almost synonymous. The relationship continues. On Sept. 28, 1985, Homestake held formal dedication ceremonies for its newest gold mine - McLaughlin. The McLaughlin open-pit operation is located in northern California, some 113 km (70 miles) northeast of San Francisco. It lies near the boundaries of three counties - Napa, Yolo, and Lake - and a portion of its facilities are located in each. McLaughlin was originally the site of the Manhattan mercury mine that produced nearly 80,000 flasks of the quicksilver from the 1860s to 1978. At the September dedication, Homestake renamed the mine in honor of the late Donald H. McLaughlin. McLaughlin was with Homestake for nearly 60 years. He rose from exploration geologist to his ultimate positions of chief executive officer, director, chairman of the board of directors, chairman emeritus, and chairman of the executive committee. The discovery of the McLaughlin deposit occurred in 1978, the last year of operation for the Manhattan mine. Homestake geologists used a newly developed model and found surface gold at the mine site. That same year, Homestake signed an agreement with the property owner and began a two-and-a-half year exploration program. An initial discovery announcement of 31.1 t (1 million oz) of gold was made in 1980. In 1981, this was revised to 93.3 t (3 million oz), or 18 Mt (20 million st) of ore grading 5.2 g/t (0.152 oz per st). Expected mine life is 20 years. Construction began in September 1983, following the issuance of stage one permits. Start-up of operations took place in early 1985 and the first gold-silver dore bar was poured on March 4. Since then, more than 540 kt (600,000 st) of ore has been milled, producing about 1.6 t (50,000 oz) of gold. Of special interest at McLaughlin is the use of three autoclaves for gold extraction. According to Homestake, this is a first. The autoclaves are designed for a 90% gold recovery rate. Early results have proven yields at this rate and higher. Geology The McLaughlin deposit is about 1.5 km (5000 ft) long. It occurs as a wedge-shape, narrowing to a verti-

Jan 1, 1986

By Eugene M. Trisko

Presentation Overview State-Of-The-Art Scrub/Switch Analyses > Allegheny Power System > PSI Energy UMWA Phase I Coal Interests > 16 Phase I Scrub Plant Coal Profiles > Coal Price/Emission Allowance Interaction Southern Company Case Study > 2+ Million Ton Phase II Allowance Purchases > 10+ Million Ton Phase I Coal Switch > Georgia PSC Proposed Fuel Price Cap > Shift/Avoid Georgia Scub Costs Through System Allowance Purchases

Jan 1, 1993

By Leons Kovisars

Introduction Labor is the major cost element for most mining operations. Labor costs are continually increasing, both in nominal and constant terms. This is true in developed as well as less developed countries. There are two ways to control unit labor costs - labor costs per ton of ore mined. Replace labor with capital (increased mechanization) or improve productivity (reduce the labor force). Every miner is aware of specific inefficiencies at his or her particular operation. But the miner has no comparative measurement standards. So it is difficult to know whether these inefficiencies are major or minor. The miner may also be unaware of large-scale inefficiencies because ongoing labor practices may have caused management complacency. Met Research studied mining labor productivity. The firm collected pilot data by sending direct-mail questionnaires to 320 nonferrous mining operations around the world. The response rate was 27%, of which 78 operations provided full data on production and employment.

Jan 11, 1983

By K. Oraee

Mining of copper ore and the related industries play an important role in Iran?s economy. Copper ore production in Iran accounts for 75% of the total production in the Middle East. All activities related to copper, that is, exploration, production, refinement etc are owned and managed by state owned companies. Decisions have been made to privatize all these activities. To assess the success of this privatization process, different components of the industry must be subject to economic analysis. In this paper, the cost estimation of all operations has been carried out. The total potential and attainable revenues have also been estimated using historical data available from the industry. Risk is a major factor in all mining activities and the copper industry of Iran has been subject to risk factors arising from many internal and external variables. These variables have been recognized and their effects evaluated. The effect of risk on the economic feasibility of the operations in the industry has also been analyzed.

Jan 1, 2011

By J. B. Gwiazda

S.S. Peng The highlights of this paper are : • The shield supports with lemniscate links will exert a tangential force on the roof strata, causing unnecessary and harmful roof movements, thus damaging the roof structure. The principal source of the tangential force is the horizontal movement of the point O, the pivotal joint between the canopy and the caving shield. When the support height is changed during setting, the point O will move along a curve upward and rearward toward the gob. As a result, it produces a vertical movement, causing the roof to move up a distance of ?d, and a horizontal movement toward the gob, creating vertical fractures in the roof. • The major purpose for employing the lemniscate-link system is to protect the hydraulic legs against the action of the bending moments induced by the tangential force that causes deformation or destruction of the legs. • Based on these two points, the author suggested that, in order to eliminate the harmful effects of the lemniscate-link system and strengthen its advantageous features, a shield support with a new design of that mechanism has been developed. With the new design, the conventional rigid lemniscate links are replaced by hydraulic rams. When the pressure inside the rams reaches a certain level, the ram will yield.

Jan 12, 1986

By Jie Zhou

Mining mobile equipment is becoming larger in order to lower operation cost and increase productivity; however, their performance characteristics are often limited by the tire capabilities. Although considerable progress has been made in the field of tire research, the lack of comprehensive knowledge on tire performance characteristics impedes the advancement of off-the-road tires. Longer haul roads, and a severe operating environment make tires more vulnerable than other components of a vehicle. Furthermore, due to a limited availability of large tires, mines are facing shortages. Thus mines and tire service companies are keen to improve tire performance, extend tire life and hence lower operating costs. This paper reviews the relevant tire performance research, analyzes tire interactions with the surrounding environment, tire maintenance practices and operational issues using a case study based on data collected during an ongoing project with Fountain Tire.

May 1, 2006

By E N. Isaev, L E. Levin

New data on the geology of the Late Jurassic to Holocene sediments cover of the World and associated mineral resources (oil, gas, ferromanganese nodules, ores of massive sulphides and other metals) have been compilled in the Atlas at scale 1:25,000,000 and 1:10,000,000. The work was performed by scientists from four Institutes of Russia (VNIIzarubezhgeologia, VNIIoceangeologia, Vernadsky Institute of Geochemistry and Analytical Chemistry of theRussian Academy of Sciences and Geological Institute of the Russian Academy of Sciences). The Atlas shows variation of thickness and formational composition of the large complexes (Upper Jurassic-Early Cretaceous, Upper Cretaceous Eocene, Oligocene-Neogene, Pliocene-Pleistocene), distribution of oil/gas and ore deposits in each complex, data of deepsea drilling (leg 1-130),  thermo-pressure condition in the sedimentary basins within Circum-Pacific Rim.

Jan 1, 1995

By Braam Blom

PK2 Ventilation shaft is part of Paardekraal No 2 twin shaft system that is being developed to replace depleting Merensky reef production at Paardekraal shaft complex. The sinking team at this shaft faced considerable challenge of improving the total sinking cycle in order to be able to deliver the fully equipped shaft on time and on schedule. The cladding support cycle was identified as the tedious and time consuming activity in the overall shaft sinking operation. Reduction in the time required for handling and setting up the support installation equipment, and the time required for subsequent installation of the necessary support has a direct impact on the overall cycle time, and consequently the overall productivity and efficiency of the sinking operation. This reduction in support cycle was achieved by making use of machine carousel. The objective of this paper is to describe the support methodology that was used during the ventilation shaft sinking and the use of the machine carousel to reduce the cladding support cycle. The machine carousel replaces the traditional use of machine kibble in conventional vertical shaft sinking and has been designed specifically for installation of sidewall support at the shaft bottom during the sinking process.

Jan 1, 2009

The income of the Institute is derived from dues, subscriptions to MINING AND METALLURGY and sale of publications. These sources are fortunately supplemented by the interest from invested funds now amounting to over $500,000, a considerable portion constituting endowments for especial purposes. Aside from the medal funds the principal endowments are the James Douglas Fund for support of the Library, the Rocky Mountain Fund and the Seeley W. Mudd Memorial Fund. The income from the two last named is available for the support of research and a variety of other purposes. It is allocated by the Board of Directors upon recommendation of standing committees in each case. An active effort is being made to increase the endowments of the Institute, it being felt that unusual opportunities exist for research and public and professional service through the organization and at a minimum of expense. J. V. W. Reynders is chairman of the Endowment Committee.

Jan 1, 1923

By Paul D. Tomlingson

Editor's note: This is the first of two articles on maintenance. Part two, "Effective maintenance downsizing techniques," will appear in the October issue of MINING ENGINEERING. Most mine managers are aware that the cost of maintenance rarely goes down unless work is done less often and with fewer people. Fewer people translates into downsizing and seldom means making maintenance more efficient. Even so, mines that have struggled unsuccessfully to improve maintenance and are now pressed to reduce maintenance costs may opt for downsizing. On the other hand, mines with an immediate need to reduce costs may be forced to downsize because they cannot wait for needed improvements to take effect. This can be bad news for maintenance. In any case, the mine must downsize correctly to ensure effective maintenance is sustained.

Jan 1, 1994

By Laura Suarez, Jörgen Kajberg, Pär Jonsén

In recent years, slag, a residue from pyrometallurgical processes, has become more attractive in circular economy frameworks to increase the efficient use of resources throughout the life cycle of steel products and help in the reduction of carbon emissions. Its applicability is strongly dependent on the particle size, and therefore, the optimization of breaking processes should be approached by increasing the knowledge of the dynamics of slag to promote fracture. Increasing the knowledge on themechanical response ofmanganese slag opens up the potential for the development of cost-effective numerical models, e.g., constitutive models based on inverse engineering calibration frameworks or digital twins. In this study, rate-dependent tests of manganese slag have been performed using a split Hopkinson pressure bar device for testing its dynamic mechanical response. In order to obtain information about the crack initiation and fracture process, 2D ultra-high speed imaging was implemented with a sampling frequency of 663,200 fps for diametrically loaded specimens. Full-field deformation measurements using digital image correlation (DIC) techniques showed a staggered fracture process where failure points on mechanical response curves vary due to the internal events happening in the material. Localized frictional occurrences and inertial effects acting inside the pre-cracked matrix have a strong effect on the global mechanical response, and therefore, a great variability of strengths was obtained.

Nov 3, 2023

By T. Nghipulile, G. Dzinomwa, J. Kurasha, M. Amwaama, B. Mapani, K. Maweja, T. E. Moongo

The effect of mineralogy on the grindability was investigated using three copper ores – two sulphides and one oxide. The dominant copper minerals were identified by optical microscopy and mineral chemistry derived from SEM-EDS analysis. The sample designated sulphide 1 was borniterich, sulphide 2 ore was mainly chalcopyrite, and the oxide ore was predominantly malachite and minor azurite. The gangue minerals were identified using semi-qualitative XRD analysis. Sulphide 1 contained more than 80% (w/w) of quartz compared to about 70% in the other two ores. The Bond work indices were 13.8, 21.6, and 17.3 kWh/t for sulphide 1, sulphide 2, and oxide ore respectively. This suggested that the chalcopyrite-rich ore is the hardest, while the malachite-rich ore has intermediate hardness, and the bornite-rich ore is the softest. The brittleness indices of the ores were calculated using the chemical composition of the gangue, and a good correlation between brittleness indices and Bond work indices was observed, which highlights the importance of the gangue composition in determining the fracture behaviour of the ores. There is scope for further investigation into the relationship between ore mineralogy and comminution behaviour using other breakage characterization techniques.

Mar 30, 2023

By Didier Kasongo NYEMBWE

The paper circumscribes the base metal casting industry in Southern Africa. It essentially consists in the founding of copper and zinc alloys. The challenge related to the scarcity and the unaffordable quality patterns and dies faced by the industry is discussed. New manufacturing technologies for foundry tooling called Rapid Prototyping that can possibly be used to alleviate the above mentioned challenge are then presented and their benefits assessed.

Jan 1, 2007

By Mark R. Pettitt

Noise surveys conducted in underground coal mines have consistently indicated that auger mining machines subject the operator and helpers to excessive noise exposure. The machine cutting heads have been identified as the primary noise source. This report documents the research program conducted to (1) investigate the nature of the cutting head noise problem, (2) develop noise control concepts, (3) devise in-mine survivable techniques to implement the noise control concepts, and (4) build and demonstrate prototype reduced-noise auger miner cutting heads. The dynamic forces generated during coal cutting by the brittle fracture of coal are predominently low frequency. The low-frequency (less than 1500 Hz) structural response of the cutting head, therefore, determines the noise radiated by the cutting head. The most feasible methods of reducing the cutting head low-frequency response are to increase both the structural stiffness and the low-frequency damping. A technique was devised to achieve these goals. The standard plate helix was replaced by a sand-filled hollow helix of triangular cross section, and the core diameter was increased with an attendant reduction in helix depth. Extended in-mine tests demonstrated the operational capability of the reduced-noise auger cutting heads. The simple noise control concepts are valid for all continuous miner cutting heads. The sand-filled hollow helix technique, which achieved a 10 dB(A) noise reduction for the auger, can be used on any helix-bearing Cutting head.

Jan 1, 1983

By Douglas E. Pollock

Recent NIOSH published information has shown an increase of rapidly progressive coal workers? pneumoconiosis (CWP) in the southern Appalachian coal region (SAR) of the U.S., despite the fact that compliance data indicates that most coal miners have been exposed to coal mine dust concentrations below the statutory limit of 2 mg/m³. While the exact cause of these elevated CWP levels in the SAR has not been established, several factors may be contributing to the increase in occupational lung disease among coal miners. The mining of high rank coal is known to lead to higher CWP rates, and this type of coal is mined in a portion of this region. Also, a high percentage of the mines in the region are on reduced dust standards because of the high silica content of the airborne dust resulting in miners possibly being exposed to excessive amounts of respirable silica dust. Exposure to excessive amounts of respirable silica dust can lead to silicosis, a disabling and potentially fatal lung disease. NIOSH?s Respiratory Hazards Control Branch has been investigating the possible causes that would account for the observed higher trends in disease progression through literature review, data analysis and in-mine surveying. The investigation to date has revealed that underground mines are faced with cutting large amounts of rock in order to maintain haulage clearances. Cutting rock not only increases the potential for silica exposure, it increases the requirement for machine maintenance, which was a concern observed during dust surveys conducted by NIOSH. Over half of the mines operating in the SAR are on reduced standards due to high silica content. Adequate face ventilation of the continuous miner and roof bolter and limited down-wind operations from the miner are also issues of concern and items that require the constant attention of miners operating in these conditions.

Jan 2, 2010

By Mark Svinkin

The purpose of this paper is to present an overview of recommended existing criteria of ground vibrations generated by blasting. It is shown that these criteria have limited liability because they were found for specific categories of structures. A new approach based on measurement of structure vibrations is suggested for assessment of damage in structures subjected to blasting vibrations. This approach provides the flexibility of implicitly considering a variety of soil-structure interaction and structure conditions. It is explained a new frequency-independent safe-level criterion of 51 mm/s (2 in/s) for the PPV of structural vibrations. Attention is brought to use seismographs properly calibrated for the required frequency range. Positive flexibility is demonstrated in assessment of structure and component of concern vibrations from blasting.

Jan 1, 2003

By T. R. Ellis

The author attempted to concurrently apply the US Uniform Standards of Professional Appraisal Practice and the Australian VALMIN Code to a complex mineral property appraisal assignment. This led the author into many severe difficulties. These difficulties included the high standards needed in the work of others, and information and statements needed from the client. The exercise also highlighted many positive features of both documents. Some conflicts were found between the two documents. Implications and thoughts regarding the development of a set of US minerals appraisal standards are discussed.

Jan 1, 2000

By F. N. Kissell, C. D. Litton

Abstract-This study predicts the level of smoke that miners might meet while trying to escape a coal mine fire and describes how smoke would impede their safe escape. For this study, the authors assumed that miners exit through an escapeway adjacent to the burning entry, that some air would leak from the burning entry to the escapeway. The following conclusions were made: • A very low amount of air leakage to the escapeway can produce a critical level of visual obscurity from smoke. This shows that intake airways may be as susceptible to smoke visibility problems as return airways. • This critical level of smoke obscurity is reached much before a critical level of carbon monoxide is reached. • Small fires can cause a severe sensory irritation that further limits vision. Thus, reliable eye protection is very important. These results show that methods to guide miners through dense smoke will contribute greatly to saving lives during mine fires.

By Wenjie Zhu

Hexavalent chromium is a widespread environmental contaminant. An Achromobacter sp. strain nominated Ch1 can reduce soluble and toxic chromate to insoluble and non toxic Cr(III) in aerobic cultures, and no Cr(VI) decrease was observed in anaerobic cultures. In contrast with other Cr(VI) reducing microorganisms, Ch1 showed higher Cr(VI) reduction at high pH. Reduction performed under alkaline conditions at pH 7 to 11, and the optimal pH was 10. During the reduction, pH decrease was observed may caused by production of acidic metabolic byproducts from aerobic respiration. In the present study, the ability of Achromobacter sp. Ch1 to reduce Cr(VI) during growth was evaluated with lactate as an electron donor. In NB medium, Ch1 reduced 100% of 24mM of Cr(VI) in 35h, but only 73% of 30mM of Cr(VI) after 48h of inoculation. Reduction was inhibited by metal ions like Ag+, Cu2+, Zn2+, slightly inhibited by Mn2+, and not affected by Mg2+. Results revealed that reduction rate of Cr(VI) also increased with the increasing of concentrations of lactate, and complete reduction was achieved at the concentrations above 40 mM. HPLC analysis demonstrated Cr(VI) reduction was associated with the consumption of lactate. There was a large quantity of dark blue sediment generated in the culture during Cr(VI) reduction by Ch1. Energy dispersive X-ray (EDX) analysis showed that the major element composed the formed sediment was chromium presented as Cr(OH)3 precipitate. The features characterizing Cr(VI) reduction by Achromobacter sp. Ch1 are high Cr(VI) concentrations and high pH.

Jan 1, 2006