Search Documents

By Mustafa Fener, Masoud Rostami, Sair Kahraman, Behnaz Dibavar

Roadheaders are commonly used in coal mines for roadway excavations. The prediction of roadheader performance is necessary for the planning of roadway projects and the estimation of costs. Recently, a new rock mass cuttability classification (RMCC) system has been introduced for roadheaders used in coal mines. In this study, the validity of the RMCC system was investigated for different types of roadheaders and different coal mines. Four different coal mines were visited, and the performance measurements of different axial and transverse roadheaders were carried out during the excavation of roadways. Uniaxial compressive strength, volumetric joint count, the strike and dip of joints, joint aperture, the Cerchar abrasivity index, and water ingress were determined in field and laboratory studies to calculate the RMCC index. The analysis of the data demonstrated that the correlation coefficients between the net cutting rates and the RMCC indices were higher than 0.94, suggesting that the RMCC system was valid. It was concluded that the RMCC system could be reliably used for the evaluation of roadheader performance in coal mines.

Jun 21, 2023

Paper written on project work carried out in partial fulfilment of BSc Engineering (Mining) The aim of this project is to determine whether certain pillars occurring within the no. 1 shaft and no. 2 sub-shaft ground are feasible for extraction. The extraction of these pillars is essential in prolonging the life of Kloof Main Shaft as its VCR resource becomes depleted. Extraction of these pillars will require a combination of designs and factors, with rock mechanics and ventilation being the main considerations. Primarily for the pillar extraction, an initial production target of150 kg gold, mine able in one year from commencement of ?opening up? was set. The planned target has been exceeded and the feasible pillars identified are expected to yield an additional 1 390 kg of gold to the shaft?s production profile. However, not all the required ventilation designs have been completed to date, the reason being that at the time of the project, many of the pillar areas were inaccessible and thus ventilation conditions are unknown. This project is therefore an ongoing process and will require further design once all targeted pillar areas have been opened up. A preliminary costing analysis of the pillar mining was performed and it was found that all targeted pillars with the exception of 38?61 pillar are profitable.

Jan 1, 2005

By J Knoblauch, D, P J. J Strobos, C Foggo

The Sally Malay Project is located 120 km north of Halls Creek in the eastern Kimberley region. Since commissioning, ongoing improvements on the plant have resulted in recoveries now greatly exceeding the initial design targets. The continual optimisation endeavours of the Sally Malay metallurgy department included an automation project that was done in close collaboration with Mintek. In this team effort, several problem areas were addressed and the FloatStar advance control system was successfully commissioned to stabilise and optimise the flotation circuit. The remote location of the Kimberley Nickel Mines operation, fly-in, fly-out roster and the current mining boom makes the acquisition of experienced flotation staff difficult. The implementation of an automated flotation control system reduces this burden and contributes to the training of inexperienced staff. This paper illustrates not only the process control improvements achieved as a result of the installation of the FloatStarÖ advanced control system, but also how it has assisted operational personnel with their understanding of the process.

Jan 1, 2006

By H. Guo

There are a number of methods available for the determination of the fracture toughness of rock. Some of the most recognised methods include the hollow pressured cylinder, the short-rod, the chevron - edge-notched round bar in bending and the disc-shaped compact specimen. Most of these tests are difficult and expensive to conduct. In this paper the simple Brazilian testing of discs for tensile strength has been used to determine their fracture toughness. Tests were conducted on six different rock types and the values of the fracture toughness obtained for each type are in close agreement with the results of the well recognised the chevron edged types. Details of the tests, and analytical validation of the technique, are presented

Jan 1, 1992

By Ramin Motamed, Joseph A. W. Toth

Evaluation of the capacity of large-diameter drilled shafts using current load test methods present challenges when considering the magnitude of loads required to fully mobilize their capacities. Often, these full scale tests do not fully mobilize the capacity through side resistance. Therefore, the need for innovative solutions to extrapolate side resistance and interpret nominal capacity are of key interest. In this study, we evaluate three methodologies for extrapolating unit side resistance based on bi-directional load test data. Fellenius (2001) presented these methods for interpretation of pile capacity using static load tests. Our interpretations are based on the evaluation of 116 load tests. Unit side resistance was calculated and reviewed for each load test and categorized using three criteria of mobilization; (A) full, (B) partial and (C) linear. This study specifically focuses on load tests that showed fully mobilized unit side resistance behavior (Criteria A). The three methodologies were applied assuming Criteria (A) load tests were mobilized to 50% of their measured values. Subsequent comparisons of each extrapolation were then compared against the full measured values for each test and generally showed good agreement. INTRODUCTION It is widely accepted that conducting load tests such as standard top-down tests or bi-directional (i.e. O- cell) tests can help designers understand load-settlement behavior and the nominal resistance of drilled shaft foundations. These load testing methods provide the advantage of confirming design assumptions as well as improving the reliability of the foundation design. The potential cost savings from the application of these methods for mid to large size projects is self-evident. For example, in a recent project in Northern Nevada, an O-cell test on a 6.9 ft diameter, 114.8 ft length drilled shaft imposed an initial cost of $125k to the project, resulting in a 15% reduction on the total foundation cost; equivalent to $1.3 million in overall savings (Pease, 2014). However, the costs of implementing such methods on smaller projects can be prohibitively expensive (Hagerty et al, 2016). Despite the clear advantages of drilled shaft load testing, the current practice is not without limitations. Performing load tests on large-diameter drilled shafts with high capacities is a challenge considering the significant loads required to fully mobilize the capacity of such foundations. In some cases, the feasibility of these tests is impractical because the associated initial cost is not guaranteed to outweigh the final savings. As a result, large scale load tests are sometimes ruled out from the design phase of projects. Furthermore, in the majority of load tests the magnitude of loads applied are specifically selected to not approach failure, so the shafts can be used in the future foundation system (i.e. production shafts). This practice of field testing restricts our knowledge of the true capacity of the drilled shaft at failure; hence the nominal resistance remains unknown.

Jan 1, 2018

By Andy Cole, Ken Thomas, Stephen Durn, Jacques McMullen

"The roasting and gas handling circuits of the Barrick Gold’s new Roasting Facility at the Goldstrike Mine in Nevada, USA incorporate well proven technologies in a unique combination. During the design of the plant, every effort was made to utilize the best available technologies from the perspective of capital, environment and operating costs.Product from the up-stream dry grinding circuit requires roasting to maximize gold recovery. The roaster utilizes Freeport-McMoRan whole ore roasting technology with pure oxygen as the oxidizing gas. This process was chosen based on its proven application on Carlin-type “double refractory” ores. Double refractory is indicative of the gold being difficult to direct leach due to a combination of pyrite encapsulation and the carbonaceous preg-robbing of the ore.A very extensive gas cleaning train follows the roaster and comprises direct cooling, dust scrubbing, indirect cooling, wet electrostatic precipitation, mercury scrubbing, SO2 scrubbing, CO incineration and NO, reduction before venting to the atmosphere.The roasted calcine is quenched, neutralized and then thickened before leaching in the carbon-in-leach-circuit.INTRODUCTIONBarrick’s strategic development plan integrated the production of gold from Goldstrike’s carbonaceous ore reserves by 2000. A due diligence review of carbonaceous ore processing options was initiated during the second half of 1 996. Processes considered included autoclaving followed by a proprietary ammonium thiosulfate leaching process, fine grinding/autoclaving as practiced then by Santa Fe, and whole ore roasting as practiced by then Independence Mining and Newmont. The objective by year-end was to recommend the most robust and economical process for Goldstrike’s carbonaceous resources. In the fall of 1996, a detailed review of roasting as a processing alternative for Goldstrike was initiated."

Jan 1, 2001

By E. D. Gardner

This paper is the third of a series of three on placer mining in the western United States. The first paper4 discusses the history of placer mining in the Western States and the production of placer gold, geology of placer deposits, location of placer claims on public lands, sampling and estimation of gold placers, and classification of placer-mining methods, together with hand-shoveling and ground-sluicing. The second papers deals with hydraulicking, sluice boxes and riffles, recovery of gold and platinum from placer concentrates, treatment of amalgam, and marketing of placer gold. The discussion of sluice boxes and subsequent subjects in the second paper applies to all forms of placer mining. The present paper treats of dredging and other forms of mechanical handling of placer gravels, and drift mining.

Jan 1, 1934

By Rashmi Ramesh

Zinc oxide nanoparticles and nanostructures form an active area of research in the recent years. It can be doped to modify electronic, optical and other properties. Synthesis and characterization of zinc oxide is of extreme importance in order to understand the structure property relationship in this material which is now being considered of importance next to carbon nanotubes. Microstructure of zinc oxide nanomaterial is extremely sensitive to the preparation conditions. Nanocrystalline pure and Mn and Mg doped zinc oxide samples were prepared by wet-chemical method under different growth conditions. The samples were investigated for crystalline phase, microstructure, morphology and luminescence characteristics. The effect of Mn and Mg doping on the characteristics of ZnO have been discussed.

Jan 1, 2010

By AIME AIME

WITH the example of the steel open-hearth men and their round table conference before the copper men, the query naturally arose "Why cannot we do likewise?" The advantage of pooling and comparing knowledge on smelting in the copper reverberatory furnace seems particularly pertinent at this time when all metallurgical economies possible must be rigorously enforced. A great deal of data had also been obtained and filed during the period of litigation over the Carson patent, and it would naturally be available with the cessation of further suits. With these ideas in mind, H. Foster Bain took up the advisability of holding such a conference directly with the heads of all the companies in the United States operating copper reverberatories, and found a nearly unanimous response. The mining companies appointed representatives directly, or indicated to the heads of various metallurgical operations what members of their staffs should be sent to such a conference.

Jan 1, 1930

By V. Bush, T. G. Killingsworth, E. P. Ruffel

Effective and sustained corporate energy management programs are becoming a necessity for energy users as electricity deregulation laws are enacted on a state-by-state basis across the country and environmental regulations pertaining to emissions become more prevalent. The “Total Energy Asset Management” (TEAM) approach has been developed to assist energy end users with the development and implementation of corporate energy management programs designed to reduce energy risks and increase energy cost savings. This paper highlights the ways in which this approach can be applied to the mining industry while minimizing initial program implementation costs and increasing potential program benefits. Nearly the entire mining industry has become very focused on identifying opportunities to reduce costs per unit of yield. The industry as a whole has increasingly faced pricing pressures in large part due to the effects of global competition. The result of international marketplace participation and the emergence of higher efficiency recovery techniques have resulted in flat or even decreased prices for mining products. Thus, opportunities to reduce costs are actually opportunities to gain a competitive edge over similar mining operations. Due to the energy-intensive nature of many mining operations, the costs associated with energy are often a substantial percentage of operating costs. Therefore, it becomes very important to develop the corporate mentality that energy is an asset whose use should be optimized globally. In addition to the cost benefits of the TEAM approach, other benefits may occur such as reductions in facility greenhouse gas emissions.

Jan 1, 2002

By S. C. Richardson

The electrowinning (EW) circuit involves using DC current in the electro-deposition of metal ions dissolved in an electrolyte solution. This paper reviews a method to generate an electrical model of an EW circuit and the resulting DC current flow and voltage distribution within the circuit. Topics include: calculations of electrolyte conductivity and the equivalent electrical resistance of the electrolyte within the electrolyte pipelines connected to the EW circuit; the breakdown and classification of the EW cell voltage into thermodynamic and ohmic potentials; methods to calculate current flow and voltage distribution throughout the EW circuit; and the development of an interactive visual computer model to simulate an actual EW circuit. Stray current can pose an electrical shock hazard to employees in electrolytic tankhouses. Increased awareness and understanding of the voltage distribution and potential stray current in an EW circuit can help mitigate the risk of tankhouse workers becoming exposed to electrical shock hazards. INTRODUCTION Copper electrowinning tankhouses include rectifiers that deliver large amount of DC current to a series of electrolytic cells consisting of electrolyte solution and electrode pairs. The design also includes metallic conductors in the circuit which include the rectifier’s positive and negative busbar, inter-cell busbar, and the anode and cathode frames. The electrolyte acts as an electrical conductor that transfers current via ions between the anodic and cathodic electrodes within the cell. Electrolyte, as a conductor, is also capable of conducting DC current outside the main EW circuit through the connected electrolyte feed and return pipe systems. DC current that follows a path other than the intended path through the series of electrolytic cells is referred to as “stray current”. Developing an electrical model enhances understanding of voltage distribution and current flow in an EW circuit. This paper discusses the derivation of the various representative components of the model as well as the output from the model. An interactive visual computer simulation incorporates the model output in order to aid in the understanding of voltage distribution and current flow throughout the EW circuit.

Jan 1, 2019

By Robert L. Lagace

This final report documents the work done by Arthur D. Little, Inc. (ADL) on behalf of the U.S. Bureau of Mines, Pittsburgh Mining and Safety Research Center (PMSRC), on Contract H0122026 (which began in August of 1971). Under this contract ADL provided technical assistance to the Bureau on a task basis on virtually all aspects of the Bureau's programs related to present and planned emergency and operational communications and miner location systems for underground coal mines. The work consisted of independent investigations, analyses, experiments, breadboard and prototype hardware development, workshops and technology transfer seminars on mine communications, and on-going evaluations and guidance related to the Bureau's contracted programs on electromagnetic noise, mine communications systems, and trapped miner location. This final report documents the work in two volumes, Volume I, "Emergency and Operational Mine Commun¬ications," and Volume II, "Seismic Detection and Location of Isolated Miners." The Tables of Contents of both Volumes are included in each Volume.

Jan 1, 1974

By Xiaowen Liu

The DSC/TG, IR and XRD analysis were used to characterize the heating phase transformation of illite, which came from Ouhai deposit, China. It was discovered that the dehydration and de-hydroxylation of illite carried out stage by stage during heating. The adsorptive water and layer-inter water were dehydrated from room temperature to 500°C; and dehydroxylated in the range 500°C~800°C. In these stages of process, illite?s layer structure kept almost unchanged. After 800°Cillite began to change into disorder structure. At about 1100°C, the layer structure of illite had been destroyed, and amorphous SiO2 and mullite crystallite appeared. At about 1200°C the structure of illite completely destroyed and mullite crystal phase had become perfect..

Jan 1, 2006

By Jack S. Greber

The mining industry generates an estimated 2.3 billion tons of solid waste each year and the total accumulated mineral resource solid waste at both active and inactive mine sites, approaches 30 billion tons. Five industries generate 85 percent of mine solid waste: copper, phosphate, iron, uranium, and coal. Over the past several years, the Federal government has shown increasing interest in the proper disposal of solid wastes generated by the mining industry. Three new pieces of federal legislation have been passed recently beginning with the most comprehensive regulatory authorization passed in 1976, the Resource Conservation and Recovery Act (RCRA) which has been amended to the Solid Waste Disposal Act Amendments of 1980. RCRA is implemented and enforced by the Environmental Protection Agency (EPA) and intended to control municipal and industrial solid wastes. Next came the passage of the Surface Mining Control and Reclamation Act (SMCRA) of 1977 which is implemented and enforced by the Department of Interior to control coal surface mining and the surface effects of underground coal mining, and finally, the recent Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978 implemented by EPA and enforced by the Nuclear Regulatory Commission (NRC) to control uranium mill tailings disposal.

Jan 1, 1981

By A Kitchen

For the past decade, demand for Australian resources has reached unprecedented levels, thanks mainly to the emerging superpowers of China and India. Meeting demand has meant miners and governments alike have ploughed billions into capital expenditure projects for logistics infrastructure such as roads, rail and ports, to support the ever expanding number of mines and mineral volumes. In more recent times, however, the effect of the global economic crisis has led to a decline in demand for Australian minerals. The downturn has seen companies lay off workers in droves, and delay or cancel expansion projects, in an attempt to preserve cash flow. Whilst the current economic cycle has hit the mining sector hard, it is an opportunity for companies to take stock of their existing operations and plan for the future. As mining companies grapple for scarce capital resources, it is inevitable that industry consolidation will ensue. This presents challenges and opportunities for both buyers and sellers alike, looking to expand operations, or sell off assets to raise cash.

Jan 1, 2009

By Alessandra Savazzini dos Reis

A crescente preocupação em relação às áreas de proteção ambiental e ao alto consumo de argila, matéria-prima da cerâmica vermelha, ocasiona a indisponibilização progressiva de reservas de argilas no Brasil. Com isso, vê-se a necessidade de incorporar resíduos na massa argilosa para confecção de produtos de cerâmica vermelha. A indústria de cerâmica vermelha brasileira consome cerca de 10 milhões de toneladas de argila ao mês para produção de telhas e blocos. Na própria olaria são gerados resíduos, tal como, o resíduo de massa cerâmica crua originado na etapa de conformação das peças. Este trabalho visa incorporar o resíduo de massa cerâmica crua na massa argilosa usada em cerâmica vermelha. O resíduo foi caracterizado por meio de ensaios de FRX, DRX, limites de Atterberg e distribuição de tamanho de partículas. Corpos de prova feitos com massa argilosa e resíduo em teores variando de 10% a 90% (massa) foram conformados, secos à 110ºC, queimados à 900ºC em forno industrial e submetidos a ensaios de absorção de água, porosidade aparente, massa específica aparente e resistência à compressão. Os resultados evidenciaram que as propriedades cerâmicas avaliadas nos corpos de prova da massa argilosa incorporada com o resíduo atendem aos valores das argilas-padrão brasileiras para cerâmica vermelha.

Aug 17, 2017

The Mineral Sector Development Project, sponsored by the World Bank, has been set up to revise the legal, regulatory and fiscal framework for the minerals industry in Tanzania, with a view to attracting mining companies and investors to the country and facilitating future minerals development. One component of this project, the Environmental Management Framework for the Mineral Sector, was awarded to Wardell Armstrong of the UK and ENV Consult of Tanzania. In developing a new framework of environmental regulations, emphasis was placed on developing realistic standards which reflect local conditions and prevailing values. The main corner-stones of this approach are; effective environmental impact assessment procedures; establishment of environmental management procedures; and monitoring and auditing of companies? performance. The favoured approach involves a three-tier framework, as follows: ?Framework environmental provisions within the new Mining Act; ?Regulations covering more detailed environmental requirements ?Guidelines and/or Codes of Practice, which may in future become regulations in their own right. Careful consideration has been given, in developing the framework, to the limited resources likely to be available for implementation to the Ministry of Energy and Minerals and this has influenced the approach that has been adopted. This paper outlines the main components of the environmental management framework and discusses some of the important issues raised by these proposals.

Jan 1, 1998

By Mark K. Larson

Calibration of LaModel for deep coal mines begins with adjustment of overburden stiffness for load transfer distance. This calibration determines whether mining induced stresses are concentrated in the immediate abutment of the gob, or spread over a wider area. In the absence of site information, an empirically-based estimate is often used. Where data is available, a recommended calibration procedure can be followed, as is done in this case study at a deep western longwall mine, with minor modifications and extensions. In this case, data sources included borehole pressure cells, flatjacks installed in series with support Cans, and observed changes in ground conditions. Calibration was based on the first detection of mining-induced stress from the advancing longwall. Detection was found to depend on the type and sensitivity of measurement. Borehole pressure cell data with a 20-psi-increase detection threshold were chosen as the standard, in accord with data used in deriving empirical relationships. Application of this standard produced a load transfer distance estimate roughly four times the empirical relationship developed by Peng and Chiang (1984). This is a significant deviation with important implications for panel design at this site. Data from flatjacks, ground condition observations, and borehole pressure cells with higher threshold values, were tightly clustered and show load transfer distances from two to four times empirical guidance. Ratios between various measurements can be used to adjust measurements to the standard (although they may depend on mine geology). Once established, ratios can be used to adjust estimates, say from support flatjacks or ground observations, to the standard, where borehole pressure cell data is not available.`

Jan 1, 2012

"The first SkimAir flash flotation cell was installed in Outokumpu’s Hammaslahti Copper Concentrator in 1982 to prevent overgrinding of soft sulphides in the milling circuit. Since this first installation the popularity of the flash flotation has fluctuated depending on metal market conditions and regional preferences. Units have been installed in many commodities including copper, lead, gold, PGMs, silver and nickel. Though it has been successfully employed in many operations around the world, flash flotation technology is still not well understood by many in the mining industry. This paper will discuss aspects of flash flotation flowsheet development along with some of the metallurgical and engineering considerations required to successfully incorporate flash flotation into new or existing milling circuits. This paper will also try and debunk some of the myths that exist around flash flotation cells and their operation. Case studies of flash flotation implementation will be discussed.IntroductionModern flash flotation technology was developed several decades ago by Outokumpu, with the first commercial installation of this technology being at the Hammaslahti concentrator in Finland in 1982 (Kallioinen & Niitti, 1985). This was a relatively modestly sized SK80 cell producing final grade copper concentrate directly from the flash flotation cell operating in the grinding circuit. Since that time the size and number of flash flotation cells installed globally has grown considerably to the point where today, it is a widely known application of flotation technology for amenable ores. Owing to their long history in developing the technology, Outotec are the market leader with their SkimAir range of flash flotation cells. Though there is a general awareness of flash flotation process in the mineral processing industry, there is a lack of detailed understanding of the process and the benefits it can provide to new and existing operations."

Jan 1, 2017

By Richard R. Klimpel

During the last 28 years, I have had the very challenging and rewarding experience of working as an engineering professional in a large multinational company, both as a manager of engineers and engineering projects as well as an inventor and generator of new engineering processes and products. Due to the diversified geographic and tech¬nical nature of my employer's business, my responsibilities have taken me all over the world. This has included interactions with people in different industries including minerals, coal, chemicals, petroleum, pulp and paper, agriculture and pharmaceuticals. As diverse as my experience may seem, it has always amazed me how common the basic underlying technology and economic trends are that shape the working environment that any given engineer in any given geographic loca¬tion will experience. I would like to discuss the industrial evolution from micro to macro engineering. One of the basic truths behind how industry must and will operate is "change," including: • the creation of conditions for change, • the anticipation of change, • the resistance to change, • the rewards that being part of a change can bring and • the destruction that change can bring to the unprepared. This fact was well stated by Heractitus around 500 BC.: "There is nothing permanent except change." This simple truth has been valid since the dawn of time and, if anything, is accelerating in nature every decade.

Jan 1, 1993