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By Ping Zhang, Shahram Mozaffari, Andreas Ylmefors

The risk associated with mining induced seismicity and the related rock bursts has become one of the major threats to the safety and sustainability of mining at the Kiirunavaara mine. The causes of mining induced seismicity at the Kiirunavaara mine are very complex and have affected our understanding on the source mechanisms of seismicity and further the mitigation of the seismic risk. Detailed analysis of historical mining induced seismicity at the Kiirunavaara mine was conducted. The focus of this analysis was placed on the classification of large seismic events and the evaluation of the influential factors on the classified seismic events. 145 events with local magnitude larger than 1.5 that occurred between January 1, 2011 and March 31, 2021 were analyzed. For this analysis, seismic events located in the hanging wall were not included, as these have not been observed to cause large damages to the mine itself. It was found that the magnitude of the events had good correlation with the stress change in relation to the production location. The seismic events were classified as mining-front associated, ore-pass associated, mining-front and ore-pass associated and others, according to their hypocenter location. Most of the mining-front associated events, concentrated around the production levels and slightly above and below them, generally correlated with shear cracks, and most of them occurred when the ore flow between two production levels started. The numerical modelling showed that slip of the geological discontinuity, due to unclamping between hanging wall and footwall, could be the major causative mechanisms, which further supports this finding. The ore-pass associated events are located close to the ore passes. Large seismic events located between ore passes have the source mechanism of both fault-slip and non-shear, but events located at the outer side of ore passes were all fault-slip type. By checking with the ore pass scanning data, it was concluded that the most of the events located between ore passes could be pillar bursts. An elastic core concept has been then used to define a critical pillar width. The paper is not intended to be prescriptive but rather to initiate discussion of the possible classification of seismic events at the Kiirunavaara mine and to present new perspectives of the causes of the seismicity for improving the present seismic risk management.

Apr 26, 2022

By A. B. Cecala

The Bureau of Mines has been performing research to lower the dust exposure of workers at mineral processing operations for a number of years. This research has mainly been directed at source control techniques in an effort to lower a worker's dust exposure at a particular job function. In some cases, this control technology provided a carryover effect in lowering the exposure of workers at other locations, but for the most part had very little effect in lowering dust levels throughout an entire mill building. Recently, the Bureau became aware of several mineral processing operations having problems with high over-all mill dust levels. These operations were all using baghouse-type collectors to address their most serious dust contamination areas. Although these major dust sources were being controlled, there were numerous minor dust sources that were not. These minor dust sources were causing dust levels in these operations to gradually increase as the day or shift progressed. The intent of this work was to determine general guidelines and design criteria for operations that may be interested in implementing a total mill ventilation system. Most mill buildings can be considered a closed system and thus any dust that is not being controlled within the structure, will cause dust levels to gradually increase over the shift. A total mill ventilation system should be designed to draw clean make-up air in near the base of the mill. This air provides general purging and may clear some dust laden areas throughout the mill structure. This air should be discharged at or near the top of the structure, where it is not a contaminant to plant personnel working outside. Without this exhaust system, dust can exit the building through open doors, windows, etc., and contaminate outside plant workers. This dust can also be recirculated back into the mill building causing additional contamination problems. A total mill ventilation system is not a stand-alone technique, but is a supplemental technique to assist other localized dust control systems.

Jan 1, 1994

By P. S. Hettinger

Land Application Discharge (LAD) is a useful method of disposing of waste water from mining operations and in certain climatic regimes, stormwater runoff. LAD systems function under the premise that metals, salts and nutrients in water are dispersed over a large area and are effectively assimilated into the soil profile. Depending on the soil structure, migration or mobilization of dissolved metals through the soil profile can be Substantially reduced. Land application of treated effluent from sewage lagoons or waste water plants was probably the first general use of land applied water. LAD has gained popularity with the mining industry as a means of disposing of waste water and process water. In addition, large volumes of snow meltwater and stormwater are often placed in storage in Montana during spring, and Land Application Discharge has shown to be an effective method for disposing of stormwater during the dry, summer season. LAD can also provide an alternative to recycling or treating waste water at on-site waste water treatment plant&. Application of stormwater or process water can result in little or no change to the background concentrations of metals in baseline water quality samples. One cautionary note about LAD: high salt concentrations and pH values are associated with process water from heap-leach facilities and are known to cause burning of local vegetation. Some pre-treatment of process water may be necessary to prevent such environmental problems.

Jan 1, 1994

By Ernest E. Thurlow

"Western Coal" in this paper is limited to those deposits of subbituminous coal and lignite in the States of Montana, Wyoming, and North Dakota. The characteristics of the coal are discussed as well as the history of mining and current mining operations for steam coal. The future of the region is tied closely to the ultimate conversion of coal to oil and gas products. Problems of industrial water supply and environmental considerations are covered together with a brief review of current legislation's actions affecting strip mining.

Jan 1, 1973

By Yongsik Jeong, Kwangmin Kim

Most tailings storage facility (TSF) failures occur in active, upstream-type TSFs, often due to extreme and unexpected weather conditions—specifically, heavy rainfall and strong winds. This case study of a TSF in southern Arizona examines the use of the optimum safe beach distance (Doptimal, the optimum distance between the crest and decant pond) as a tool for monitoring geotechnical stability and reducing catastrophic failures. A digital model of the TSF was used to determine the critical beach distance (Dcritical) under normal weather conditions, and Doptimal was then determined by adding incremental distances to account for the effects of heavy rainfall (Drainfall) and strong winds (Dwind). To overcome accessibility issues, a drone was used to map the TSF geometry and create a digital model. This model served as the basis for conducting a coupled stress-seepage, finite-element (FEM) analysis with a safety factor of 2.0 to assess geotechnical stability (Dcritical). The safe beach distance increments were determined using the PMP (probable maximum precipitation) and possible maximum wind speed. Based on this analysis, the optimal safe beach distance at the study site was identified as 202.2 m. Since the current beach distance (371 m) exceeds this value, the TSF was considered to be stable and satisfied the design safety factor of 2.0. However, this distance should be reassessed periodically to account for changes in the TSF geometry and other conditions. Furthermore, it applies only TSFs that are well-managed and feature a smooth, non-undulating beach surface with a consistent slope.

By B. K. Cantrell

The U.S. Bureau of Mines and others have conducted a number of occupational exposure surveys since the publication of the International Agency for Research on Cancer report of 1989, which labeled diesel exhaust as a probable human carcinogen. These surveys have assessed diesel exhaust exposure using measurement of diesel aerosol and/or specific polycyclic aromatic hydrocarbons as indicators of exposure. This paper reviews present diesel emission standards, available diesel exhaust aerosol measurement techniques, and the results of the occupational exposure surveys. In the surveys, diesel aerosol was emphasized because it is a major component of diesel exhaust, is suspected to contribute to the health hazard, and is readily measurable. Three primary aerosol measurement techniques were used: respirable combustible dust, size-selective sampling, and measurement of the elemental carbon fraction. Occupations surveyed included mine workers, railroad workers, forklift operators, fire fighters and truck drivers. The studies found mean diesel aerosol concentration levels in the range of 0.004 to 1.74 mg/m3? Highest aerosol exposures were in confined spaces such as mines where heavy diesel equipment is used. Polycyclic aromatic hydrocarbons typically are found at very low concentration levels and are not unique to diesel exhaust.

Jan 1, 1996

By Kenneth J. Miller

A novel two-stage froth flotation process to remove pyritic sulfur from fine- size coal is described. The process consists of a first-stage, standard coal flotation step in which high-ash refuse and some of the pyrite are removed as tailings. The first-stage clean coal froth concentrate is then repulped in fresh water, and a coal depressant, a pyrite collector, and a frother are added to float the remaining pyritic material. Laboratory and pilot plant flotation results with coals from the Lower Freeport and Pittsburgh beds are given. The pilot plant test results show that up to 80 percent pyritic sulfur reduction was achieved with the Lower Freeport bed coal and up to 50 percent with the Pittsburgh bed coal. Laboratory and pilot plant results were in excellent agreement, indicating that the process is a viable means of removing much of the sulfur from some coals.

Jan 1, 1974

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 G. ALBORNOZ, S. Utili, A. AGOSTI, C. VALDERRAMA, R. PELL, N. Morales

The steepness of the slopes of an open pit mine has a substantial influence on the financial return of the mine. The paper proposes a novel design methodology where overall steeper pitwalls are employed without compromising the safety of the mine. In current design practice pitwall profiles are often planar in crosssection and the profile in between ramps especially tend to be planar and defined by a constant inter-ramp angle. Sometimes rock layers exhibiting different strengths require the inclination of the profile to vary with depth, but the inclination across each layer is usually constant. Here instead, a new geotechnical software, OptimalSlope, is employed to determine optimal pitwall profiles of depth varying inclination. OptimalSlope seeks the solution of a mathematical optimization problem where the overall steepness of the pitwall, from crest to toe, is maximized for an assigned lithology, geotechnical properties and Factor of Safety (FoS). Bench geometries (bench height, face inclination, minimum berm width) are imposed in the optimization as constraints which bind the maximum local inclination of the sought optimal profile together with any other constraints such as geological discontinuities that may influence slope failure. The obtained optimal profiles are always steeper than their planar counterparts (i.e. the planar profiles exhibiting the same FoS) up to 8 degrees depending on rock type and severity of constraints on local inclinations. The design of a copper mine is first carried out employing planar pitwalls, secondly adopting the optimal pitwall profiles determined by OptimalSlope. The adoption of optimal slope profiles leads to a 34% higher net present value and reductions of carbon footprint and energy consumption of 0.17 Mt CO2 eq and 82.5 million MJ respectively due to a 15% reduction of rockwaste volume.

Mar 2, 2022

By Jr. Winters

The United States continues to be the largest producer and consumer of copper in the world. Table 1 on the following page shows several production statistics for 1974, the most recent year which the non-communist world copper industry might consider a good year, and for 1976 and 1977. In 1974 an estimated 24 percent of the non-communist world's newly mined copper was mined in the United States, and. 87 to 89 percent of that was from the western porphyry coppers. In 1976 U. S. new mine production was down to 22 percent of the non-communist world's newly mined copper, and the percentage of U. S. new mine production supplied by the porphyry coppers had risen to 89 to 91 percent. In 1977 the statistics remained the same as in 1976. U. S. porphyry copper production represented about 65 percent of U. S. refined copper consumption in 1974, rose to 75 percent in 1976, and dropped back to 61 percent in 1977 as imports of foreign copper into the United States began to swell.

Jan 1, 1978

By Richard L. Sanford

The generalized rail haulage simulator described in this paper is an outgrowth of the need to expand a previously developed single level simulator to permit analysis of production problems where intermediate car storage is used. Many of the ideas of the former single level simulator, which is an integral part of an Underground Generalized Materials Handling Simulator (UGMHS), have been used in model development. In addition, experience gained in applying the earlier model to a variety of operating conditions has been heavily relied on. The generalized rail haulage simulation model can operate as an independent system and, as such, can be used to analyze rail haulage systems using production distributions as data input. In addition, this model is designed to replace the present rail haulage sub-assembly in the UGMHS model and the linking procedure has been integrated into the model. The flow of coal from production sections in UGMHS, for example, fill the mine cars and a condition of no empty cars at a loading station will shut down in by production systems.

Jan 1, 1974

By R. E. Thill

An ultrasonic, pulse-immersion apparatus and method are described for determining the effects of moisture on the dynamic elastic properties of rock. The method provides an alternative approach for assessing the moisture sensitivity of rocks. Ultrasonic wave velocities are continuously monitored in immersed rock samples as a function of water absorption and time up to saturation. Moisture effects on compressional wave velocity vary as a function of the type of rock and the time and amount of water absorption. Regression analyses are used to curve-fit plots of the data and to derive empirical expressions for compressional wave velocity as a function of water content for different categories of rock. Results indicate that compressional wave velocity can be used to predict both the moisture content and its effect on strength and deformational properties of rock. These results have potential for detecting or monitoring bad roof conditions in situations where the mine rock exhibits strength degradation with moisture absorption.

Jan 1, 1986

By Felicia F. Peng

The manganese removal from aqueous solution containing high Mn2+ concentration by adsorption and oxidation was studied using manganese oxide particles as the adsorbent. The operating parameters including pH, flow rate, initial manganese concentrations, and oxidant dosage affect the performance of Mn2+ removal were evaluated in a laboratory packed column. In the multi-column adsorption tests, each additional column doubled the time for complete manganese removal. No further decrease of pH was also observed once it was lowered to pH 4.5 to 5. This finding implied the possibility of complete high manganese removal without further pH adjustment during adsorption. Oxidation of Mn2+ by dissolved oxygen was found to be insignificant for manganese removal for high Mn2+ concentration. Adsorption was the predominated mechanism involved with manganese removal. Extremely low H+/Mn2+ stoichiometry compared to the reported values was measured. These low values suggested that different adsorption mechanisms such as chemisorption other than H+/Mn2+ ion exchange might play an important role at low pH. This paper presents the quantity and explanation of the results obtained for the mechanism of adsorption and oxidation of high concentration manganese on the manganese ore particles.

Jan 1, 1997

By A. Bieg, M. Samson, Z. Bell, A. Zinsser, J. Schuyler

As the world progresses toward the renewable energy transition, the demand for minerals increases exponentially. According to the International Energy Agency (IEA) 2021 Net Zero by 2050 Report, critical mineral production needs to grow six times to combat climate change. It’s estimated that four to seven percent of global greenhouse gas (GHG) emissions come from the mining sector’s Scope 1 and 2 (direct and indirect) emissions. Including Scope 3 (upstream, downstream, and embedded) emissions, the sector accounts for 28% of global GHG emissions. In a typical mining operation, diesel fuel is the biggest source of direct GHG emissions, and haulage is often the main source of diesel emissions. Large haul trucks have been the industry standard for over 50 years and offer flexibility, relatively low capital cost (especially with equipment lease options), and guaranteed technology with known maintenance. The challenge will be to justify their continued use when there are more economical options that lead to significant reductions in GHG emissions. The purpose of this study is to compare five haulage options in terms of GHG emissions, using the methodology defined by the Greenhouse Gas Protocol Scopes 1, 2, and 3 (Category 2). Additionally, this analysis compares operating and capital costs associated with the five haulage options (emerging and proven technologies): 1) Diesel-Electric Haul Trucks, 2) Battery-Electric Haul Trucks, 3) Fuel Cell Haul Trucks, 4) Railveyor, and 5) Conveyor. This analysis looks at the emissions and costs associated with operating the equipment (fuel and electricity), the embedded emissions and costs associated with the construction and installation of the equipment itself, and the associated infrastructure (roads, powerlines, and rail).

Feb 1, 2023

By T. J. Lutz, D. S. Yantek, L. Yan, J. R. Srednicki, J. A. Yonkey, G. T. Homce

Federal regulations require the installation of refuge alternatives in underground coal mines. Of the inuse refuge alternatives, more than 95 percent are mobile refuge alternatives, with the remainder being built-in-place (BIP) refuge alternatives. Heat/humidity buildup has been one of the major concerns with mobile refuge alternatives. For BIP refuge alternatives, however, there is a lack of in-mine heat/humidity test data to determine the extent of heat and humidity buildup. To quantify heat/humidity buildup in BIP refuge alternatives, the U.S. National Institute for Occupational Safety and Health (NIOSH) performed a series of heat/humidity tests on a 60-person BIP refuge alternative with and without a borehole air supply. At various times during the year, tests were performed with cooled, heated or unconditioned borehole air to examine how various outdoor temperatures may affect the thermal conditions inside a BIP refuge alternative. The results show that the air supplied to a BIP refuge alternative may require heating or cooling, depending on the outside air temperatures and the temperature of the mine. For example, during tests with an external ambient temperature above 21 °C (70 °F) and a relative humidity of 90 percent, providing 13 °C (55 °F) dew point air at 775 scfm, which is slightly higher than the mandated flow rate of 12.5 scfm per person, kept the internal apparent temperature below the mandated 35 °C (95 °F). Results for each test case are presented.

Jan 1, 2018

By Hongsheng He, Xiaofang Lv, Jianfeng Wang

This paper provided an overview of characteristics of limonite ores as well as their influence on sintering performance. Evaluation experiments focusing on basic characteristics, granulation characteristics, and high temperature sintering characteristics had been conducted by using two types of limonite ores, then the principles of high effective utilization technology of limonite ores were discussed, and the sintering pot tests were conducted. Limonite ores possessed low total iron content, high combined water content, high SiO2 content, large average particle size, low adhering particles proportion, high porosity, high water absorption rate, short water absorbing time, poor granulation ability, high melt formation ability, low melt fluidity ability, low melt penetration ability, high melt absorption ability, low bonding phase strength, and high forming ability of SFCA. By taking the technical measures of ore-proportioning optimization, increasing the proportion of burntlime and segmentation granulation, the usage of limonite ores could reach 50% in sintering.

Aug 27, 2021

By Y. Zhang, M. Yekich, C. Zhou, C. Jobes, J. Galanko, D. Tuchman, J. Srednicki, J. Carr

The continuous personal dust monitor (CPDM) is an essential instrument for working in hazardous environments, is used to monitor real-time coal dust exposure, and is mandated by the Mine Safety and Health Administration (MSHA) for underground coal mines. Researchers from the National Institute for Occupational Safety and Health (NIOSH) found that it is possible for electromagnetic interference (EMI) between a CPDM and a proximity detection system (PDS) to occur. Various approaches have been taken by researchers and manufacturers to address this EMI issue. Administrative controls were recommended to keep the CPDM six inches away from the wearable PDS device. Shielding pouches were made to contain the electromagnetic (EM) emission from the CPDM. Metal shielding was added to major EM emitting components. EMI filtering with large capacitors was introduced to mitigate EMI. Most recently, a novel magnetic-field-cancellation-based approach was developed and achieved remarkable results. In this paper, we provide a comparison between these approaches. The pros and cons of each approach are presented and discussed, so that mining device manufacturers and operators can best evaluate the technology and controls that improve the health and safety of mine workers.

Feb 1, 2023

By C. G. Clifton

The Oatman District produced approximately 2.2 x 10 6 ounces of gold and 0.8 x 10 ounces of silver between 1897 and 1942. A total of 3.8 x 10 tons of ore averaging 0.58 O/T gold and 0.17 O/T silver was extracted from eight major orebodies and a number of lesser deposits. Oatman lies at the center of a trachyte-latite-rhyolite volcanic complex which contains at least one resurgent caldera. The orebodies are typical epithermal quartz-calcite + adularia lode deposits which are very deficient in sulfur. Ore deposition has occurred within dilatant zones on faults which radiate from a common point within-the complex. Fischer-Watt Mining approached the Oatman District with an integrated exploration program utilizing four basic procedures to define the characteristics of past productive areas the results of which were applied to unexplored portions of the vein system. These procedures, listed in their order of usefulness, in defining known and prospective mineralized zones are: vein contouring, detailed alteration mapping, fluid inclusion temperature determinations, and geochemical sampling.

Jan 1, 1980

By K. V. Raj, M. McNinch, A. L. Miller, J. Wilson, D. A. Parks

Diesel particulate matter (DPM) has been shown to contribute to various adverse health effects on underground miners. In order to reduce worker exposures, it is critical to measure the levels of DPM in the active work settings and in real time. However, the 5040 method, developed by the National Institute for Occupational Safety and Health (NIOSH), which quantifies the mass of elemental carbon (EC) and organic carbon (OC) in the samples, is based on full-shift samples, and can take days or even weeks for results. Use of real-time monitors could significantly reduce the risk of DPM exposure to miners, and available monitors have been shown to quantify DPM, mainly using the EC and other surrogates. The NIOSH Spokane Mining Research Division is conducting research aimed at developing a field-portable DPM monitor that is able to quantify both EC and OC. One part of this work is to understand the effect of OC on currently available real-time DPM monitors. This paper will present the results from experiments that were designed to observe the effect of OC on real time monitors and compare the results with the NIOSH 5040 method. BACKGROUND Diesel engines remain ubiquitous in mining environments and, as such, are one of the primary sources of ultrafine- and nano-aerosols in the mining environment in the form of diesel particulate matter (DPM). As a result of their small size, DPM has longer residence times in a mine atmosphere than the typically larger mechanically generated dust [1]. In addition, the small size enables DPM to penetrate deeply into the respiratory system [1], and exposure to DPM has been shown to contribute to various adverse health outcomes of the pulmonary system [2] and cardiovascular system [3]. Diesel exhaust has been classified as a carcinogen to humans (Group 1) by the International Agency for Research on Cancer [4]. Due to mounting concern about adverse health outcomes, extensive efforts are being made to reduce workers’ exposure to DPM, with the high exposures that often occur in underground mines being of particular concern [5]. New technologies are being developed to reduce engine emissions and thereby airborne DPM levels, including advanced engine technologies, a host of aftertreatment systems [6], and a variety of alternative fuels. The latter have been shown to markedly decrease respirable DPM and other hazardous components of diesel emissions from mining vehicles [7], yet high exposures persist, especially in underground mines [8]. In order to reduce worker exposures, it is critical to measure the levels of DPM in active work settings. In mine settings, exposures to DPM are measured by collecting air samples on filters (usually full-shift samples) and sending them to a lab for analysis using the Mine Safety and Health Administration (MSHA) P13 method, a variant of the National Institute for Occupational Safety and Health (NIOSH) 5040 method. The 5040 method is designed to quantify the mass of elemental carbon (EC) and organic carbon (OC) on the samples [9], which is then used to determine the concentration in the sampled air. MSHA has set a limit for exposure, which is based on the concentration of total carbon (TC), or the sum of both EC and OC. The allowable TC in the air (time-weighted average over the shift) is 160 μg/m3 of TC [10].

Jan 1, 2019

By H. Sevim

Mining engineering curriculum has been discussed and debated in meetings and conferences, and opinions and recommendations have been published in the literature since the inception of the official degree-granting mining engineering program at the Columbia School of Mines in 1864. The deliberations have usually been heightened during the periods of boom-and-bust cycles experienced by the mining industry since the 1920s. Currently, the global natural resource industry is undergoing another cycle, called ?super cycle,? characterized by elevated prices for metals and other natural resources. The super cycle is occurring as a result of the large deficit between the global supply and demand for natural resources, due, in large part, to economic expansion and development in countries such as China, India and Brazil. Because of this cycle, there is a shortage of mining engineers in the U.S., Canada and Australia.

Jan 1, 2012