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By E. J. Haas

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health. Reference to specific brand names does not imply endorsement by the National Institute for Occupational Safety and Health. ABSTRACT Leadership is a critical component to an organization’s safety culture and influences the ways that health and safety is enacted on site. Therefore, it is not surprising that improving leadership will also improve safety. Worker perceptions of management practices are shaped through unique leader-employee interactions over time. However, few details are known about the communicative support (i.e., emotional, informational, and tangible) offered by supervisors and its impact on miners’ perceptions and performance. Using pre and post-interview data with 20 supervisors and 48 workers during six-week interventions, researchers identified positive and negative instances of supervisor support and its implications on worker performance. This paper highlights the common support tactics offered by supervisors and desired by workers to help practitioners identify ways to improve their safety culture and subsequently, the proactivity and compliance of their workforce. INTRODUCTION Supervisory leadership is a critical component to the effective implementation of an organization’s health and safety management system (HSMS). Specifically, supervisors serve as representatives of an organization and their actions are indicative of the organization’s safety culture (Eisenberger et al. 1986). Senior management has been shown to serve as a frame of reference for guiding safe behaviors in the workplace (Mearns et al. 1998) and, more recently, research has related supervisory enforcement to workers’ safety compliance (Petitta et al., 2017). Therefore, it is not surprising that by improving leadership, perceptions of management and subsequent safety outcomes are likely to improve as well (Zohar, 2002). Perceptions of management are shaped through unique leader-employee interactions over a period of time (Hofmann and Morgeson, 2004, 1999). How these unique interactions impact worker performance, however, remains unexamined. As a result, understanding how supervisor-employee relationships operate in high-risk environments is unclear (Mirza and Isha, 2017; Denis et al., 2010). A starting point to better recognize the idiosyncrasies of these relationships is by way of examining the communicative support offered by front-line management and received by industry workers. To this end, this paper uses pre- and post-interview data to study the communicative aspects of supervisor-employee interactions at mine sites. The analysis uses a social support framework to identify positive and negative instances of supportive communication. From interview data with 20 managers and 48 mineworkers, data emerged that shows how supervisors’ unique types of support contribute to workers’ perceptions, motivation, and follow-through of safe work behavior.

Jan 1, 2019

By Peter G. Dunn

Geologic studies during development at Copper Flat were directed at acquiring the information necessary in evaluating a low-grade porphyry copper deposit. In addition to the geologic mapping and core-logging of a typical exploration project, these studies included the following : (1) careful checks on the sampling and assaying (2) selection of representative samples used to establish the recoverable amounts of precious metals in the ore (3) examination of underground workings driven to provide samples both for metallurgical testing and for assay comparisons (4) evaluation of plant site and waste dump areas as non-mineral, including a placer examination of the taillngs disposal area (5) location of an adequate water supply. All these investigations were carefully documented to provide the necessary data both for the engineering design and, more importantly, for the feasibility studies required for successfully financing the project.

Jan 1, 1981

By Alen Shibu Joseph, Arvind Rajnarayan Singh, Mudila Dhanunjaya Rao, Kamalesh K. Singh

In this article, the cementation of major impurities from zinc sulphate leach solution by the addition of zinc dust was studied by considering different parameters including time, mesh size, and percentage of excess zinc dust. The output obtained from various experiments was utilized for the design of experiments. A multi-level categorical factorial design with a quadratic model was employed during this study. Results were predicted to minimize the concentration of impurity metals in the solution by altering the parameters. Furthermore, these predicted results were validated by performing another experiment. Successfully, it showed that the predicted and experimental data values were close to each other. The predicted optimized values were 40 min, 100% excess zinc dust, and 300 mesh size for copper; 42 min, 100% excess zinc dust, and 300 mesh size for cobalt; 37 min, 100% excess zinc dust, and 300 mesh size for cadmium; and 34 min, 100% excess zinc dust, and 300 mesh size zinc dust for nickel. At these optimized values, the experimental results showed 99.99%, 55.7%, 99.6%, and 76.6% cementation efficiencies for copper, cobalt, cadmium, and nickel respectively. The statistical design of experiments for the effective cementation of impurities corroborates the economic feasibility of optimizing parameters for the proposed process.

Jul 18, 2022

By YONGQIONG YANG, Ning Wang, CHONGGUANG LUO, LI ZHU, Hanjie Wen, SHENGJIANG DU, Hannian Gu

Niobium in kaolin clay from the Late Permian sequences was reported in the range of several hundreds of micrograms per gram and was considered as a potential resource for its high concentrations and large areal distribution. Ti-bearing minerals associated with kaolin clay were identified as the main host phase for niobium in some case studies. However, the correlation between the concentration of niobium and titanium is poor, and the types of Ti-bearing minerals and modes of occurrence of niobium are not clear. Typical kaolin clay samples from the Late Permian sequences from southwest China were characterized, and the final products derived from kaolin clay sample were investigated using XRF, ICP-MS, XRD, SEM, and TEM (EDS). The results reveal that there were three types of TiO2 mineral phases in the clay samples: (a) massive TiO2 minerals and (b) aggregates of nano TiO2 minerals did not contain niobium while (c) granular TiO2 minerals were the source of niobium from the EDS analysis. The granular TiO2 minerals included anatase and rutile, both of which were the sources of niobium in kaolin clay in the current study. The findings are of great theoretical implication for source and origin study of Ti-bearing minerals and guidance for separation and recovery of niobium from kaolin clay.

Nov 30, 2020

By Lancelot E. Kun

The high-rate floc blanket clarification process developed by the Anglo American Corporation of South Africa is capable of continuously clarifying gold and uranium pregnant solutions containing 200-2500 mg/L suspended solids to below 25 mg/L solids at an average rising velocity of 8 m/h at the low process cost of R0,001-0,002 per ton of liquid treated. Overall process cost savings are mainly due to increased polishing filtration cycle times.

Jan 1, 1984

By Sandro Moro, Giuseppe Tiberti, Giovanni Plizzari, Antonio Conforti

"During TBM operations, thrust jacks apply high-concentrated forces to the last installed precast segment. These loads generate a disturbed region in the precast segment under the thrust jacks, in which significant tensile stresses (defined as splitting or bursting stresses) occur perpendicular to the load direction. In addition, due to the demand of compatibility, the combined effect of TBM high-concentrated loads determines tensile spalling stresses in the area far from the loads. Therefore, local rebars or fiber reinforcement are required in these areas. This paper focuses on the study of the effects generated by high-concentrated loads exerted by TBM hydraulic jacks, mainly in terms of both spalling and splitting phenomena. Experimental tests on small-scale specimens showed that polypropylene fiber reinforcement significantly enhances both the bearing capacity and the ductility. Moreover, polypropylene fibers resulted in very effective control of compatibility cracks.INTRODUCTIONTunnel segments are generally reinforced by conventional rebars (RC segments) in order to resist the tensile stresses both at Serviceability (SLS) and Ultimate Limit States (ULS).In the two last decades, Fiber Reinforced Concrete (FRC) has been used in many precast tunnel segments (sometimes also in combination with conventional rebars). Steel Fiber Reinforced Concrete (SFRC) is generally used for these applications even though there is a growing industry interest on macro-synthetic fibers for structural applications. Conforti et al. (2015) showed that polypropylene (PP) macro fibers can be used as shear reinforcement in both wide shallow and deep beams. Referring to precast tunnel linings, very few early experiences are reported in literature. Bonalumi et al. (2015) developed full-scale tests on tunnel elements reinforced by PP fiber reinforcement and conventional rebars (hybrid solution). The design process of segmental concrete tunnel linings generally models the standard load cases of demolding, storage, transportation, positioning and embedded ground condition. In all these stages the ring can be modelled as simple curved beam elements (having a height equal to the lining thickness and a width equal to the segment length). During these loading conditions, flexural demand is generally limited; thus, in case of conventional RC elements, a rather low ratio of longitudinal curved rebars is usually adopted (?s of about 0.2-0.3%)."

Jan 1, 2016

By Paul Soros

There has been a steady increase in shiploading capacities in the last 20 years. One of the reasons has been the general increase in ship sizes, with the largest vessels currently around 280,000 DWT in the bulk trades. Obviously, the large vessels can accept loads faster and their economic utilization justifies higher loading rates, up to a point. The high capacity facilities have loading rates far beyond this point. The economic logic of these facilities is based on the fact that for a given annual throughput the capital and operating cost of a single high capacity system is less than that of two smaller systems. Thus, where the projected throughputs are large, there is a great incentive to reduce capital costs by maximizing capacity. Tubarao, in Brazil, designed for a 100 million ton per year throughput with one finger pier and one high capacity berth is a successful demonstration of this approach. In the current state of the art, the high capacity systems have shiploading capacities in the range of 10,000 - 16,000 TPH, for annual throughputs of 20 million tons and larger per loading berth.

Jan 1, 1982

By Wei Victor Liu, Omer Faruk Ugurlu, Chengkai Fan, Bei Jiang

Accurate prediction of truck productivity plays a pivotal role in improving the efficiency and profitability of openpit mining operations. This paper proposes a deep neural network (DNN) model to overcome the challenge of predicting truck productivity in openpit mines. The prediction model was built using eight variables and was optimized by considering different train-test split ratios, numbers of hidden layers and neurons, and activation functions. The proposed model’s performance was evaluated using various metrics and compared with other commonly used machine learning algorithms. The results showed that the proposed model outperformed traditional machine learning models by achieving higher prediction accuracy. Moreover, a single-variable sensitivity analysis showed that haul distance is the most influential variable for predicting truck productivity. This study marks a pioneering effort in employing DNN to predict truck productivity in openpit mining, signifying a notable advancement in the field.

Jul 1, 2024

By E. A. Gyawu, L. L. Eng, M. Fikru, K. Awuah-Offei

Investors and other stakeholders are increasingly concerned about the quality and quantity of sustainability disclosures as well as the extent to which such disclosures correlate with sustainability practices of mining firms. This is because disclosure policies vary widely across firms in terms of extensiveness, materiality, and disclosed topic. In this paper, we conduct a preliminary examination of the relationship between sustainability performance and disclosure. We use sustainability performance indicators such as water and energy use and the Sustainability Accounting Standards Board’s (SASB’s) standards to evaluate disclosures. Our preliminary results show that some measures of sustainability performance (energy use) are negatively correlated to the amount and quality of disclosures while others (water use) are not. Thus, investors should not judge sustainability performance based solely on the amount and quality of sustainability disclosures. In addition, our results suggest that firm size and ownership as well as institutional membership could impact the strength of correlations between disclosure policy and sustainability performance

Mar 2, 2022

By Rod L. Norfleet

Cemented tungsten carbides are a sintered powder - metallurgical product essential to modern industry. Because of their moderate unit price and our dependence upon foreign sources for the component raw materials, a growing recycling industry has developed in the United States. There are two basic approaches taken to recycling cemented carbides; those which leave constituting materials unaltered or direct-reuse and those which separate the constitutes back to the raw components. To separate the carbides back to their raw components usually requires expensive chemical processing and is thus confined to the lower value materials such as grinding sludges. The direct-reuse methods recycle cemented carbides back to an intermediate level, a powder capable of being recompacted and resintered into a functional end-product. The three most commonly used methods of direct-reuse recycling, the coldstream process, bloaching and the Bernard or zinc process, are reviewed,

Jan 1, 1984

By Ashish Ranjan Kumar, Barbara Arnold, Luis Sanchez Gonzalez

The health and safety of miners is critical in the industry. Prolonged exposure to dust-laden air results in irreversible ailments like pneumoconiosis that have a severe impact on their lives. Operations use various personal protective devices (PPEs) to alleviate their exposure to respirable dust. Powered Air Purifying Respirator (PAPR) is one such device that uses high- efficiency filters and positive pressure masks to shield miners from airborne contaminants. Used in the medical and other industries, these respirators efficiently protected healthcare workers during the COVID-19 pandemic. Recently, the mining industry has shown a growing interest in adopting this PPE to ensure safe working conditions for the miners. We present an introduction to the PAPRs and discuss their dust capture efficacy in this manuscript.

Feb 1, 2025

By Edward A. Nowatzki

The purpose of this paper is to present an example of the application of a theoretically derived mathematical model for track-soil interaction to the evaluation of the mobility of large-scale mining equipment used in open pit operations. The model described by Karafiath and Nowatzki (1978) and presented in detail by Karafiath (1978) was used to predict the performance characteristics of four different bucket wheel excavators (BWEs) on rwo types of copper mill tailings at various moisture conditions. The BWEs considered In the analyses are two-and three-tracked continuous excavators. Most have boom-mounted rotating buckets and swinging side- or rear-discharge conveyors. The analyses were performed at the request of Dames and Moore for the Kennecott Corporation's proposed remining of selected tailings deposits at the McGill, Nevada, concentrator. The objectives of the analyses were to determine whether BWEs would have sufficient mobility In the tailings deposit to achieve satisfactory production rates, and TO compare the predicted performance of the various BWEs evaluated. Good qualitative agreement was obtained between the results of the theoretical analyses performed for the McGil1 operation and the actual performance of BWEs in two South African gold mine tailings impoundments.

Jan 1, 1980

By Raúl Castro, René Gómez

In underground mining, rock fragment size is a key variable for productivity because it impacts equipment selection and mining structure design. This study characterizes granular material fragmentation during its flow to understand its characteristics and mechanisms. Tests were conducted using a laboratory setup to emulate various heights where material is drawn. The fragment-size distribution was measured before and after tests for clay, concrete fragments, and gravel. Results showed that fragmentation mainly occurs in minor sizes, with significant increases in fine material as travel distance increases.

Jan 10, 2022

By M. Werner

Mining in the Coeur d'Alene Mining District has been going on for over 100 years with a long- term continuation very likely. Mining is presently carried out at depths below the -5000' horizon. As mining continues at ever increasing depths, higher in-situ rock stresses and subsequent rock deformation is encountered making mining costly and hazardous. To provide access for men and materials in such areas, a wooden raise preparation structure is typically built. Although these structures provide adequate support and access, they have proved to be very costly to construct and maintain.

Jan 1, 1986

By Iwasaki I.

This article discusses the effect of physical and chemical modifications of starches on the anionic and cationic flotation of silica from oxidized iron ores and magnetite-taconite concentrates, and the results of the interaction of starch, pH, and calcium ions on the flocculation, clarification, and filtration of iron ore slimes and magnetite-taconite tailings. Starches, particularly when anionically modified, were found to be effective depressants in anionic silica flotation. British gums and dextrins were beneficial for oxidized iron ores, but none of the starches or starch derivatives appeared to have any effect on magnetite-taconite concentrates. The flocculation and filtration of iron ore slimes were most strongly affected by the level of starch, to a lesser degree by the pH, and were virtually independent of the level of calcium chloride. The clarification of iron ore slimes was complexly dependent on these three factors. The flocculation of magnetite-taconite tailings depended mainly on the level of starch, whereas their clarification depended on the level of lime. As previously reported in the literature, selective flocculation and partial upgrading of a semi-taconite could be readily attained with starch and calcium chloride.

Jan 1, 1968

By J. Stachurski

Flotation tests were carried out on 6 coal samples of different rank as well as their oxidized samples. A mixture of diesel oil and alcohols was used in these tests. Surface oxidation caused a distinct decrease of the flotation recovery with some improvement in the grade The reduction in the recovery increased with increasing the concentration of the oxidizing agent. The floatability of low rank coals was affected by oxidation to a higher degree than medium and high rank coals. The recovery size curves of oxidized samples mere similar in shape to that of non-oxidized coals.

Jan 1, 1990

By Alexander E. McHugh

A study of some variables affecting the recovery of molybdenum from oxidized molybdenum minerals was made. The effects of variations in contact time, temperature, pulp density, particle size, and solvent concentration on the recovery of molybdenum using acid and alkaline solvents were investigated. Chemical analyses, screen analyses and microscopic examinations were made and the presence of important elements determined. A hydrometallurgical method was developed to recover the molybdenum from the oxidized molybdenum ore by simultaneous dissolution of the molybdenum with sulfuric acid, adsorption on activated charcoal and flotation of the charcoal. The molybdenum was extracted from the activated charcoal with sodium hydroxide, precipitated with calcium hydroxide as calcium molybdate and this regenerated sodium hydroxide for additional stripping. A solvent extraction method, using mines, was also studied to recover molybdenum from both alkaline and acid molybdenum solutions. Satisfactory results were obtained.

Jan 1, 1967

By Robert A. Cummings

Disintegration of the immediate shale roof in coal mines interferes with ventilation, production, and safety. The effect is seasonal and correlates with high levels of moisture in the intake ventilation air. Disintegration, though not completely understood, is caused by shale dilation and weakening upon exposure to atmospheric moisture. Fluctuating moisture conditions are particularly deleterious, and may be at least partially controlled by "tempering" the air before it is brought to the working places. Roof behavior was studied in an operating mine during a 12-month monitoring period. This approach can be used in developing criteria to reduce or prevent shale roof deterioration.

Jan 1, 1981

By Lake H. E.

The request to participate on your theme panel was accepted with some reluctance but indeed as an honor. My subject was outlined to cover 'Energy Resources - both nuclear and conventional' as related to your theme 'Minerals - Treasure Trove of the West'. This is indeed quite an order and I hope you will forgive me for concentrating mainly on the nuclear-uranium portion with brief references only to conventional fuels some of which will be covered in detail later in your conference. In regard to Uranium, I am speaking on the fringe of the area containing half the uranium reserves in your country and no doubt to many who are very conversant with knowledge of these resources. Nevertheless since our two countries have been very closely allied in both nuclear developments and uranium supplies I hope an exchange of information may be mutually beneficial. Concentration on the nuclear fuel resources is I hope understandable as nuclear energy is the coming source of power which will augment the rapid demand in the industrialized countries and provides hope for economic power in many of the more underdeveloped countries. The situation regarding conventional fuel resources is more widely known and their expanding future revolves around production cost reductions, research into diversified uses, plus more assurance of imports from countries less effected by international controversies determining export policies.

Jan 1, 1967

By W. K. Collins, C. L. Dahlin, D. C. Dahlin, W. K. O’Connor, G. E. Rush

Direct mineral carbonation was investigated as a process to convert gaseous CO2, into a geologically stable final form. The process utilizes a slurry of water, with bicarbonate and salt additions, mixed with a mineral reactant, such as olivine (Mg2SiO4) or serpentine [Mg3Si2O5(OH)4]. Carbon dioxide is dissolved into this slurry, resulting in dissolution of the mineral and precipitation of magnesium carbonate (MgCO3). Optimum results were achieved using heat-pretreated serpentine feed material and a high partial pressure of CO2 (Pc02). Specific conditions include 155°C, PC02 = 185 atm and 15% solids. Under these conditions, a 78% conversion of the silicate to the carbonate was achieved in 30 minutes. Process mineralogy was utilized to investigate the appropriate feed characteristics, identify the process products and interpret the mineral dissolution and carbonate precipitation reaction paths. Key words: Mineral carbonation, Carbon dioxide sequestration, Carbonates

Jan 1, 2003