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By M. A. Islam, H. Mischo, G. Barakos

Among the thirty-five declared critical raw materials (CRM) in the United States, there is no sustainable domestic production for the fourteen of them, while for some others domestic supply does not meet the national demand. Numerous potential critical raw material projects are in advanced exploration stages. However, the price uncertainties for many of these commodities put feasible future production into question and come into contrast with overly optimistic price forecasts published in all feasibility studies related to such exploration projects. Thus, in this work, a newly developed smart computational tool is used to evaluate the real perspectives of several CRM exploration projects implementing actual commodity prices, and to conduct reverse calculations in order to find the prices at which each project can be viable.

Mar 2, 2022

By J. Kretschmann, K. van de Loo, J. Brune

In 2018, the German Federal government decided to phase-out the energy production using coal-fired power plants and to terminate lignite mining completely by 2038 at the latest. This decision will impact approximately 60,000 jobs. It will have an enormous impact on the socioeconomic development especially in all German lignite mining regions. To avoid economic and political friction, it is of utmost importance to achieve a sustainable transition towards a post-mining era and to offer residents in the mining districts perspectives for a good future that include adequate job opportunities. In this context, the German government is providing massive structural aids early on. As previous closure experiences from the German hard coal mining industry have shown, it takes at least a generation to overcome the effects of a strategic closing decision of this magnitude. Therefore, the planned closure process appears to be a long time at first glance. In fact, however, it is not.

Mar 2, 2022

By J. Killian, S. Cox

Many questions exist within the geotechnical industry as to the applicability of Strength Reduction Factor (SRF) values to the design acceptance criteria (DAC) of mining operations. There are many factors that contribute to changes in the SRF estimate, some of which are numerical (e.g. dilation angle) and some of which are geometric (e.g. model grid size)[1]. Numerous studies have confirmed equivalent values of SRF and FOS are found for soil slopes of limited height as presented in, [2] and [3]. However, significant deviation of the SRF value was observed for highly cohesive materials (rock slopes) of heights typically encountered in mining, [4]. This paper builds on the work presented in [4], providing a more rigorous examination of the modeling parameters that control the SRF estimate. The failure mechanism assumed for this study was a simple circular shear surface in a uniform material. Both LEM and numerical methods are suited well for analysis of this failure mechanism. A parametric study was completed to evaluate and test the relationships of key numerical variables that affect the estimated value of the SRF using Itasca’s Fast Lagrangian Analysis of Continua (FLACTM) software. The effect of groundwater has been tested and may be significant but is not presented as part of this body of work for brevity and simplicity of presentation.

Mar 2, 2022

By W. Missildine, J. K. Hrica, I. Benbourenane, T. J. Orr, J. L. Bellanca

Each year, haul truck accidents account for a large portion of mining injuries and fatalities. To better understand why these accidents continue to occur, researchers from the National Institute for Occupational Safety and Health (NIOSH) utilized a cognitive task analysis methodology to identify the user requirements of surface haul truck operators and assess differences in perceptions between operators, managers, health and safety professionals, trainers, and maintenance personnel. Additionally, researchers used the critical decision method to focus on better understanding the cognitive demands, decision-making, and problem solving during nonroutine incidents. The preliminary results of this study identify and explore themes within the broad categories of hazards, skills & expertise, and training and provide detailed accounts of nonroutine incidents such as near-misses, loss of control, and collisions. These accounts reveal insights into operator decision making and event progressions that can then be used to build more realistic training scenarios and address hidden hazards and root causes of these incidents. These results, along with potential solutions offered by study participants, can inform future research and help identify creative interventions that can be used by mine operators to address haul truck safety issues

Mar 2, 2022

By W. G. Pariseau

Reliable stress measurement using hollow inclusion gauges and monitoring stress change using borehole stress meters and borehole deformation gauges in anisotropic rock remains a challenge for the rock mechanics community. In this regard, the complex variable method advanced in 1983 for deducing stress in anisotropic rock is flawed and software is privileged. Fortunately, advances in computer hardware and software now enable fast, reliable reduction of hollow inclusion stress measurement data for determining stress in anisotropic rock. Monitoring stress change in anisotropic rock poses a different challenge but is also subject to numerical analysis. Stress measurement using a hollow inclusion (HI) gauge such as the triaxial Australian HI is done in four steps: 1) drilling a measurement hole, 2) installation of an HI, 3) stress relief of the HI by overcoring, and 4) data reduction. The last step, data reduction, is the focus of this work. The process is well-known in linearly elastic, isotropic rock (Worotniki and Walton 1976, Duncan Fama and Pender 1980). However, in case of linearly elastic, anisotropic rock the requisite technology is not readily available. This situation is somewhat surprising because anisotropy is more often the rule rather than the exception, especially in the neighborhood of ore bodies. Rahn (1984) has pointed out the potential for significant errors with neglect of anisotropy and the adverse consequences for engineering design. Amadei (1984) has also pointed out the potential for errors with neglect of anisotropic rock properties in stress measurement. Worotniki (1993) cites other studies that indicate potential for serious errors when doing measurements in anisotropic rock. In both theoretical cases (isotropy and anisotropy), data reduction is essentially a composite of solutions to boundary value problems in linear elasticity. In the finite element approach, the analysis is a simulation of gauge hole drilling, installation and overcoring. Two important advantages with the finite element approach are a more faithful representation of the conditions of HI stress measurement than approximated in theory and the capability for handling rock whether isotropic, transversely isotropic or fully anisotropic

Mar 2, 2022

By N. Rocco, G. Johnson

Implementation of post-closure draindown estimates for tailings facilities are important predictive tools for reclamation planning and often influence jurisdictional bonding. Simplified estimates of draindown have been proposed in the past but these methods are not able to capture many of the site-specific nuances as well as operational and material parameters that influence robust draindown estimates. This paper discusses an iterative approach that relies on unsaturated flow models to predict draindown rates and associated pond inventory water balances that track inputs into underdrain pond systems, solution storage volumes, implementation of active evaporation, and necessary recirculation of solution back to the tailings facilities. Specific design criteria such as climate, facility geometry, material properties, and initial conditions, as well as active closure operational considerations that can influence draindown estimate will be discussed. Concepts presented will be valuable for operators, designers, and regulators to guide closure planning and predictive analytical analyses that support draindown estimates.

Mar 2, 2022

By E. Gutierrez, P. Gillies

Asset Maintenance Readiness (AMR) provides a tailored reliability and maintenance strategy specific to operational needs. AMR delivers reliability and maintenance foundations for the plant and equipment before start-up. Having a dependable reliability and maintenance strategy before start-up is critical, particularly in those first weeks and months during ramp up to stable production. The Asset Maintenance Readiness is the integration of Reliability and Maintenance Engineering analysis/studies at the earliest stages of the new Production System concept and design and during the Capital Project CapEx phases; adding this analysis to the Capital Project CAPEX cost, will have an impact of 2% to 3% of total project cost, but will deliver a good compendium of benefits far from the AMR costs, and those results will be shown upon commissioning and during the life cycle of the plant.

Mar 2, 2022

By R. Kealey, D. Huo, Q. Zhang, Y. A. Sari

Greenhouse gas (GHG) emissions from primary mineral and metal production account for ~10% of global GHG emissions. One of the main sources of GHG emissions in mining operations is fuel consumption by haul trucks. Given their size and carrying capacity, the fuel consumption of haul trucks can approach 250 liters per hour. An average of 30% of the idle time of the trucks is spent while waiting in the queue. Inefficient truck dispatch planning can waste resources, cause dilution and elevate GHG emissions. In this research, a machine learning based truck dispatch approach was developed to dynamically route the haul trucks based on the loaded material, the road traffic, the estimated wait time, and the maintenance needs of the trucks. The GHG reduction potential of this smart fleet management approach was estimated by calculating and comparing the related carbon emissions versus scenarios using traditional fleet allocation approaches. Results suggest that this dynamic fleet allocation approach can significantly reduce GHG emissions at mineral production sites by optimizing waiting times and the overall distance travelled while achieving the same production levels.

Mar 2, 2022

By E. Watkins, S. J. Schatzel, V. Gangrade, R. Kimutis, J. Addis, C. Hollerich

The recent shale gas revolution in the United States has led to the drilling of hundreds of unconventional shale gas wells in active and future coal reserves in traditional coal-mining regions of Pennsylvania, West Virginia, and Ohio. This paper summarizes the impact of a shale gas well breach on the mine ventilation system of an operating longwall panel. This study utilizes a 1:30 scaled Longwall Instrumented Aerodynamic Model (LIAM) to simulate a single-panel longwall operation. The LIAM will be utilized to identify flow pathways and distribution patterns of gas from breached gas well scenarios in an operating longwall in the Pittsburgh Coal Seam. Sulfur hexafluoride (SF6) tracer gas is utilized to simulate a breached gas well. Preliminary findings suggest that the breached gas is diluted to regulatory levels and does not accumulate in the mine entries or in the longwall gob when the longwall panel is adequately ventilated. Overall, this study characterizes the potential interaction between shale gas wells and the mine environment in the event of a gas well breach, which provides critical information to the industry and regulatory agencies for improving safety, health, and welfare of miners.

Mar 2, 2022

By F. Sime, X. Wang, J. D. Miller, T. Akinseye, S. Assemi, L. Pan

Respirable coal mine dust (RCMD) is a complex mixture of carbonaceous and mineral particles with a variation in size and shape. Accumulation of RCMD in the lungs of underground coal miners results in severe respiratory damage and ultimately progressive pneumoconiosis known as the black lung disease. The occurrence of the black lung disease dropped to a low of 2.1% in 1990s but has increased to 3.1% in 2000s [1], prompting more research on coal mine dust mitigation. In addition to surveying the impact of new mining technologies on the size of generated dust and exposure measurement, a comprehensive characterization of physico-chemical properties of RCMD particles are essential for a better understanding of the adverse health effects of coal mine dust. Such vital factors include particle size, surface charge, morphology, composition, and agglomeration state. The respirable fraction of RCMD, has been designated as particles < 10 μm in diameter, and almost all studies on the RCMD toxicity have focused on micron-sized particles. However, recent toxicological studies have shown that nanoparticles (particles with one dimension less than 100 nm) can have a magnified toxicity compared to the larger particles with the same chemistry [2]. Nanoparticles have a much higher specific surface area compared to the same mass of larger particles and are thus more reactive. Most micron-size particles can be cleared by the body’s defense mechanism. However, inhaled nanoparticles can easily deposit in all regions of the respiratory tract and can translocate to vital organs. [2].

Mar 2, 2022

By L. Berwick, A. Karunanayake, D. Skutt, H. Heath, J. Wang

Thallium (Tl) is a highly toxic heavy metal, soluble over a wide pH range. Tl levels may exceed discharge limits in mining-influenced water associated with processing gold, lead, cadmium, zinc, and copper ores. In this work, the effect of sodium permanganate (CARUSOL® C liquid permanganate) on Tl removal from mining wastewater was studied. Factors influencing Tl removal, namely permanganate dosage/demand, coagulant and flocculant use, order of chemical addition, and co-existing metal ions were examined. The results show that permanganate addition is very effective at removing Tl to below target limits and can provide a unique solution for improving wastewater quality and optimizing overall treatment costs. In addition, several on-line monitoring techniques were evaluated for process optimization. The Hach DPD Free Chlorine method was optimal, allowing plant operators to rapidly and easily spot check effluent samples for excess permanganate dose.

Mar 2, 2022

By C. Anderson, D. Kolstad, M. Unger

Operators are often challenged with the management of water throughout the life cycle of a mine. High water levels can lead to physical or chemical instability of water-retaining structures. Operators need to predict changes in water levels to make timely operational decisions and plan for contingencies, particularly in remote legacy mines. A closed mine in northern Canada with no permanent on-site personnel had a simple water balance model that was effective for decades to inform annual water treatment operations. In recent years challenging water quality and more stringent effluent quality criteria has strained those treatment operations and led to more water being stored. Additionally, the region has experienced more precipitation and higher water levels, which have triggered emergency response activities. A calibrated probabilistic model was used to provide enhanced prediction capabilities and to identify key sensitivities in the water balance for monitoring. A several-year case study shows the value that this modelling tool provided for mobilizing personnel and performing response actions, particularly the inclusion of probability paired with forecasted pond water levels. Annual drawdown targets were subsequently established which provided more certainty in scheduling of annual treatment operations

Mar 2, 2022

By T. A. Farr, I. A. Gibbs, F. Guevara, S. R. Simms, G. Nojima

This paper describes an installation of a medium-voltage adjustable frequency motor drive (AFD) on a high starting torque regrinding mill. This type of application is typically found in the mineral industry dealing with hard ore. The AFD electrical architecture is introduced from line to load. The type of closed loop encoder feedback motor control algorithm is briefly described. The results of the AFD motor identification auto-tuning are compared against the manufacturer’s supplied data. The motor drive performance results are shown for pre-ramp DC fluxing, high starting torque with overload current, excessive load torque stall condition, and blocked rotor. The instrumentation and arrangement for the two watt-meter method to capture low frequency data are presented. The data shown is from the input power quality meter, the AFD computer tool, the output motor protection relay, an oscilloscope, and load shaft connected strain gauge (rotating telemetry for torque assessment). These types of high starting torque constant torque loads are found in mining and process industry applications employing AC adjustable frequency drives. Using field results should help demystify the use of voltage matching output transformers in AFD applications including constant torque loads

Mar 2, 2022

By J. Armstrong, J. Bourgeois, S. Warren

The application of statistical analysis software programs has proven useful for investigation of rockfall runout distance along a designed slope. Rockfall modeling programs are continually being upgraded with more sophisticated analysis tools, such as the use of the rigid body versus lump mass models. Engineers at mine sites utilizing the software may have varied experience related to these models, their associated input parameters, and how to interpret the generated results. To address this concern, researchers at the Spokane Mining Research Division (SMRD) of the U.S. National Institute for Occupational Safety and Health (NIOSH) investigated the influence of slope height, slope angle, slope material, and rock size for both rigid body and lump mass models in a 2-D statistical analysis program. Based on a literature search and industry input, specific ranges common to that of an open pit mining environment were chosen for each of the input parameters to determine 90% rock runout distance as well as their sensitivity to change. Data collected from this numerical analysis and simulation will be compared to empirical rockfall data gathered through the duration of the Highwall Safety project conducted by NIOSH from 2022–2026.

Mar 2, 2022

By J. Kretschmann, P. Goerke-Mallet, C. Melchers

Mining always leaves a mark behind. Dealing with this legacy is not only a tremendous challenge in Germany, but internationally too. The Technical University Georg Agricola (THGA) in Bochum, Germany, has established a Research Center for Post-Mining. Researchers combine expertise from a variety of technical and nontechnical fields in their quest to shape the post-mining era that completes the mine life cycle. In this respect, the Research Center focuses on four research areas: Perpetual tasks and mine water management, Geomonitoring, Material sciences and site transition. With more than 200 years of successful partnership with the mining industry in Germany and abroad, THGA offers a perfect setting for fresh and sound ideas in order support mining’s social license to operate. The aim of the paper is to describe the Post-Mining Research Center along with exemplary research projects that are of interest to the mining industry globally and to foster technical communication and research networking.

Mar 2, 2022

By G. V. Campbell, O. T. Holdsworth, M. G. Nelson

A senior design project is required by all accredited mining engineering degree programs. Often referred to as the capstone of a student’s education, this project is expected to include all the important components of the preliminary economic assessment of a mineral prospect, including orebody modeling, grade and reserve estimation, selection of mining and processing methods, preliminary mine design, access and utilities, environmental compliance and reclamation, and financial analysis. Two of the authors (Campbell and Holdsworth) completed a senior project in 2021. They analyzed the Akie zinc deposit located in Canada. This paper summarizes the economic analysis portion of that project. The two primary objectives of this economic analysis were risk reduction and integration of economics and engineering. Addressing risk is important as risk is one of the primary concerns in mining investments. Risk reduction was the primary concern through the entirety of this economic analysis. Integration of financial analysis and engineering design was the first component of a risk reduction design. This allowed for financial and engineering design to be optimized in conjunction with one another. This produced benefits from both a financial and an engineering prospective. From a market, economic, and financial risk perspective, risk was reduced by forecasting multiple metal price scenarios, and then addressing the Akie project’s economic viability at each price point. Lastly, risk was address through consideration of nontraditional financing options. The project also sought to minimize financial and human capital risk, by proposing mutually beneficial cooperative social relationships and favorable work, schedules. Description of that work is not included in this paper.

Mar 2, 2022

By R. Wu, R. Howell, J. Dase

Turquoise Ridge is an underground gold mine located in the Potosi Mining District, approximately 64 km northeast of Winnemucca, Nevada. Turquoise Ridge Underground is accessed via two shafts and a system of internal ramps and utilizes underhand drift and fill mining methods with cemented rockfill. The mine also employs mechanical mining as well as sill benching as mining methods. Ground conditions at Turquoise Ridge Underground are poor, and the Rock Mass Rating (RMR) may be less than 20, or very poor, in ore headings. Current production rate is 2,700 tonnes of ore per day. Key challenges in increasing production levels and reducing costs are the development of sufficient stoping areas and the transition from top-cut development to undercut stoping. Completion of the infrastructure development in the North Zone is necessary to achieve and optimize higher production levels. The #3 Shaft project is well underway and is expected to be commissioned in mid. 2022. The shaft will drastically decrease the haulage requirements in the North Zone

Mar 2, 2022

By P. Mendoza, R. Siwale, H. Amini, R. Silva, M. Richards, V. Ngcoza, D. Rivera, C. Canaza, R. van Reenen

Development of a realistic flotation model to predict its performance is of paramount importance to the processing plant and operators, a model that accounts for predictive and no-predictive maintenance simulating individual equipment downtime and the effect of it in the metallurgical performance on the flotation bank with final recoveries and grades has a huge advantage on optimizing the flotation circuit/bank in terms of mechanical and metallurgical side. The Model was developed in a dynamic environment that allows for a better and more realistic simulation of the flotation bank. The maintenance model accounts for the Failure rate, Mean Time Between Failures (MTBF), Mean Time to Failure (MTTF) and Reliability (R(t)) those characteristics are combined to a multi-compartment process model that consists of a slurry recovery model, two options of froth recovery models, entrainment and carry capacity as a final check for the system. In addition to the maintenance and process model, a dynamic dart valve model was added to the simulation in order to have a realistic model to control the slurry level at the flotation cell. The paper goes over a study case for a current flotation operation trying to explore all the elements and the simulator to optimize the Rougher flotation bank.

Mar 2, 2022

By D. M. Abbott

The requirements of the International Mineral Property Valuation Standards Template (IMVAL Template) (includes Petroleum), 4th edition of April 14, 2021, are based on six principles: 2.1.1 competence, 2.1.2 materiality, 2.1.3 transparency, 2.1.4 objectivity, 2.1.5 independence, and 2.1.6 reasonableness. The IMVAL Template describes “reasonableness” as, “The Valuer must ensure the Reasonableness of the Valuation. Any Valuation, assumptions applied, and any method relied upon should be reasonable within the context of the purpose of the Valuation and the Basis of Value. A method applied to the subject Mineral Property should be within the expected capability and consideration of an assumed likely buyer or lessee of the property.” The IMVAL Template’s Guidance 3.6 on Reasonableness states, “The test of Reasonableness is to consider what appropriately qualified and experienced Valuers, acting reasonably, would conclude in the circumstances. The Valuer must form an opinion that is reasonable in the circumstances, that is, what a Valuer believes is rational and plausible in the circumstances and would be viewed as such if considered by other appropriately qualified and experienced Valuers with the same information and at the same time.” Finally, the IMVAL Template’s Definition 4.26 states Reasonableness “[m]eans that other qualified and experienced Valuers with access to the same information for the same Valuation Date and Basis of Value would consider the Valuer's estimate of Value to be within a reasonable range.”

Mar 2, 2022

By N. Damiano, C. Zhou, R. Jacksha, J. Srednicki

Modern electronic devices and systems used to enhance miner safety and health are becoming commonplace in underground coal mines. The ability for these devices and systems to function properly in the presence of electromagnetic emissions from other electronic and electrical devices and systems is not entirely understood. To investigate potential electromagnetic compatibility issues of critical mine electronic devices and systems, researchers from the National Institute for Occupational Safety and Health (NIOSH) are conducting surveys of electromagnetic emissions in underground coal mines. This paper presents the measurement system, methods, and results of electric field electromagnetic emission surveys conducted in three underground coal mine environments in the frequency range of 10 kHz to 1000 MHz. The survey data show that in some environments electric field electromagnetic emissions in underground coal mines approached or slightly exceeded limits as defined by other industrial sectors.

Mar 2, 2022