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By Jr. Abel

Subsidence is controlled by a complex combination of mining and geologic factors. For example, a world-wide compilation of data shows that, as the percentage of shale in the overying rock mass decreases and the amount of sandstone increases, the angle of draw (and the area affected by subsidence) decreases. Limestone in the overburden appears to cause as much as a three-fold decrease in the angle of draw compared to a like amount of sandstone. Increased amounts of sandstone were accompanied by a greater surface subsidence relative to the mining height. The total thickness of overburden did not appear to influence the subsidence magnitude above super-critical panels. The greater the thickness extracted the smaller percentage of that thickness that shows up at the surface as subsidence. The greater the percent of the seam extracted, the greater the subsidence reaching the surface. The maximum subsidence above room and pillar panels is dependent on the pillar height and minimum width as well as the other factors listed.

Jan 1, 1980

By J. R. Kunkel, V. Lishnevsky

At mine sites, the operational and required storage volumes of solution and water storage ponds and reservoirs are usually calculated based upon a water-balance approach. Many climatological variables including precipitation, air temperature, solar radiation, pan evaporation and relative humidity along with operating parameters, are used in the water-balance model. The water-balance model often seeks to find a “critical period” of wet or dry climatological sequences which result in a “maximum” pond storage volume or water demand. The problem with this approach is that the designer usually does not know when the project will come on line in relation to the historical record. To avoid this pitfall, we use a more robust approach. In the more robust method, the water-balance calculations begin in each year of the historic climatological record. This method results in the same number of water-balance runs (or realizations) as the number of years of climatological record. Results of this type of analysis guarantee that the critical period or maximum required pond volume will be found if it is assumed that the historical climatological record repeats itself or if a synthetic time series is used. In addition, this method permits calculation of the likelihood (probability) that a given pond volume will be equaled or exceeded in any given month of the operational life of the facility. In this paper, the results of the sizing of a heap leach pad solution pond are presented along with the probabilities of a given solution pond size being equaled or exceeded based on the robust water-balance approach.

Jan 1, 2002

By B. Cousins

Flotation reagents are critical to the optimum performance of flotation circuits. How a flotation reagent performs within the first few cells of a flotation train is a key indicator of how well it will perform throughout the entire circuit. A method to compare reagent performance was recently developed by Ashland Water Technologies. The procedure involves collecting a timed sample of concentrate from each cell and then measuring the volume of the settled solids. An estimate of the percentage of concentrate collected from each cell can then be mathematically determined, providing an understanding of the recovery changes in each cell. Data from trials at a coal flotation circuit are used to demonstrate the method's validity.

Feb 27, 2013

By Albert Musschoot

The expanding applications of vibrating feeders for controlling the flow of bulk materials, and their adaptation for processing requirements, have developed considerable interest in stockpiling and reclaim systems. The general design of these units consists of a material transporting trough, or platform, driven by a vibratory force system. Design flexibility and variety is limited only by engineering ingenuity. The basic motion of the vibratory trough, or work member, is a controlled directional linear vibration that produces a material tossing or hopping action. Material travel speeds vary from 0 to about 30 m/min, depending on the combination of frequency, amplitude, and slope vibration angle.

Jan 6, 1981

By Xiaoyan Luo, Congcong Dai, Gaipin Cai, Xin Liu, Lu Zong

To overcome the difficulty of accurately judging the load state of a wet ball mill during the grinding process, a method of mill load identification based on the singular value entropy of the modified ensemble empirical mode decomposition (MEEMD) and a probabilistic neural network (PNN) classifier is proposed. First, the MEEMD algorithm is used to decompose the vibration signals recorded under different load states to obtain the intrinsic mode components, and a correlation coefficient threshold is used to select the sensitive mode components that characterize the state of the original signal. Second, singular value decomposition is used to obtain the singular value entropy. Finally, the load state of the wet ball mill is judged based on the magnitude of the singular value entropy. A characteristic mill load vector is constructed from the singular value entropies of the cylinder vibration signals recorded under different load conditions and is used as the input to a PNN, which then outputs the predicted ball mill load state; in this way, a load state identification model is established. Grinding experiments are presented to verify the effectiveness of the proposed method, showing that the method can accurately identify the load state of a wet ball mill. ()

By F. J. Brenner

The Slippery Rock Watershed Coalition was organized to restore a 70 km2 portion of the headwaters of the Slippery Rock Watershed in northwest Pennsylvania. Thirteen passive treatment systems have been installed with engineering and funding provided by private industries, county government and the Commonwealth of Pennsylvania. In addition, experimental systems have been installed at the Jennings Environmental Education Center which, in addition to monitoring the systems installed within the watershed, provide an array of educational and research opportunities for secondary, college and university students. The coalition sponsors an annual seminar for students to present the results of their research and field trips for public officials and private citizens to learn how public and private partnerships work together to restore the Slippery Rock Creek watershed.

Jan 1, 2002

By Levent Ozdemir, Bjorn Nilsen

For several recent TBM tunnel projects, unexpected ground conditions have been encountered, causing extra cost, considerable delay, and in some cases major claims. Undoubtedly, insufficient and/or irrelevant site investigation and testing are among the main causes of such incidents. The purpose of this paper is to review the main investigations and tests relevant for hard rock TBM projects, with particular emphasis on the considerable development that has taken place over the last few years. Also, guidelines for defining optimum scope and extent of site investigations and testing are discussed, as well as the importance of adjusting the investigations and tests according to complexity of the ground conditions and project type.

Jan 1, 1999

By K. R. Griffin

Atmospheric conditions underground are constantly changing and from a safety perspective, it is critical to identify when conditions are trending abnormally. Atmospheric monitoring in underground coal mines allows mine operators to analyze atmospheric conditions underground in real-time. Real-time monitoring can then be used to identify whether atmospheric conditions underground have become problematic. The implementation of a risk assessment and management process allows operators to then use a risk-informed decision making to identify comprehensive site specific ventilation parameters. Establishing risk-informed ventilation parameters and tracking conditions relative to these parameters, management can modify ventilation plans as mine conditions develop to manage evolving risks. Ventilation risk assessment and management allows developing atmospheric monitoring technologies to be fully utilized in order to increase safety standards in the United States. This paper reviews general risk assessment approaches, state of the art ventilation based risk assessment, and the risk assessment and management application within the United States regulatory framework.

Feb 27, 2013

By S. J. Neethling

The flotation froth structure and motion determines the amount of entrained gangue that is collected to the concentrate. Despite this important role in the overall performance, the behaviour of the froth is still ill understood. To date, predominantly empirical models have been developed to describe entrainment. A fundamentally based model is described and used here in an attempt to improve the understanding of entrainment. This general froth simulator (UMIST FrothSim) allows the modelling of a wide range of flotation conditions, as it takes account of a large number of the physical phenomena that occur within flotation froths. The model firstly describes gas motion and bubble coalescence, and the water motion based on gravitational, viscous and capillary effects. The motion of the solids distinguishes between various solids classes based on hydrophobicity, particle size and density and models them by including the effects of Geometric and Plateau border dispersion, particle settling and the motion of the water. The aim of this paper is to show the applicability of this model to explain the observed entrainment and collection of gangue. This is done by comparing model predictions with the experimentally observed relationship between the gangue and water recoveries. The model predicts the identical trends, which are explained in terms of the interaction between the linear effects of water motion and hindered settling and the non-linear effect of particle dispersion.

Jan 1, 2001

INTRODUCTION From its beginnings in the first decade of this century, flotation has gradually moved to a predominant role in mineral separation. There are several reasons for this, the continuing trend toward treat¬ment of lower-grade and more finely disseminated ores being the major one. Not only has this been true for sulfide ores to which the process was first applied commercially, but also for most nonsulfide ores as well. A second factor has been the broad applicability of the process with respect to particle size; it is effective from 8 to 10 mesh to below 10m. Finally, more so than for any other separation process, flotation has almost no limitations in separating minerals. Gravity, magnetic, or electrostatic processes are either applicable to particular minerals, or to a restricted number of mineral combinations. Flotation, on the other hand, can utilize the wide range of surface chemical differences among minerals, and an equally wide range of reagents. The recent availability of selective flocculation capabilities on a commercial scale as an adjunct to flotation should remove one of the limitations to the process in the very fine particle range. History Although flotation was anticipated in a 19th century patent to Haynes, its first significant industrial uses were in the early 20th century in Australia. According to Hoover,' the Pottter-Del-prat pro¬cess had a "measure of success" at Broken Hill's Block 14 mine in 1905-1906, and was definitely successful at the BHP Mine, where it produced 80,000 tpy of zinc concentrates. Both the Mineral Separa¬tion and the Elmore processes had early trials in Australia also, with both successes and failures. The first application in the United States was in 1911, when the Hyde process was used by the Butte and Superior Copper Co. on a zinc ore in Montana. By 1916 Hoover could list 46 applications to copper, lead, and zinc ores, mainly in the United States. Ten years later Taggart2 listed almost a thousand patents covering processes and reagents which with few exceptions laid the foundations for modern practice. Included were: sulfidizing of oxides; leach-precip¬itation-flotation; cyanides, sulfites, sulfides, and oxidants for selective depression of sulfides; starch, tannin, and glue as depressants; and xanthates, dithiophosphates, and oleic acid as collectors. Within an¬other 20 years, all of these were in commercial use along with amines for floating silica from phosphates, and synthetic frothers were com¬peting with pine oil and cresylic acid. Flotation machine development followed a different course. Of the 170 patents listed by Taggart in 1927,1 those incorporating film and oil flotation-about a third of the total-were no longer then

Jan 1, 1985

By G. A. Johnson

Basic management principles will be discussed (as they apply to minerals education efforts), especially in light of the changing nature of volunteerism in today’s society. Also, the “minerals education tree” will be presented, along with public opinion / public policy realities.

Jan 1, 2001

By J. Kretschmann, H. Mischo, O. Drusche, S. Krause

Mining is and will be inevitable in spite of the increasing implementation of circular strategies. The energy transition and population growth will boost the demand for critical raw materials. It is the opportunity for miners to reinvent their business models. Generating attractive new business cases with sustainability-oriented innovations meets investor and stakeholder expectations from the beginning. This contribution guides managers on their pathway towards sustainable success. Contextual sustainable business model patterns will be presented that can be adjusted individually, regardless of actor’s size. It will also point out, how sustainable value creation can be measured on business model level.

Feb 1, 2023

By B. Ballard

Engineers at a West Virginia coal preparation plant owned by one of the nation's largest coal producers sought a fire suppression system for the plant's MCC and cable spreading rooms. Officials considered the traditional options of water-based sprinklers, dry chemical, and clean agent systems; however, each of those options presented challenges. Sprinklers can damage electrical equipment, proper delivery of the agent and adequate coverage/protection can be an issue with dry chemical systems, and clean agent systems require room integrity. An alternative to traditional systems was discovered in the Victaulic Vortex Fire Suppression System. The first hybrid inert gas/water mist system (FM 5580), Vortex adequately addressed these concerns. The system, which deploys a high-velocity, low-pressure mixture of water and nitrogen, is not damaging to electrical equipment and extinguishes fires in open, ventilated areas. This is one of the first installations of the Vortex system in a prep plant, and is a compelling example of how new technology can overcome the challenges of traditional technologies. The paper will detail plant specs, situation, and system evaluation, selection, and configuration.

Feb 23, 2014

By R. Hedin, M. Dunn

The Pennsylvania Department of Environmental Protection (US EPA 319 program) provided funding to aid a public-private effort in the installation of an environmentally-friendly system to treat abandoned mine drainage at Jennings Environmental Education Center (Pennsylvania Department of Conservation and Natural Resources). Through this cooperative effort among state and federal agencies, mining, excavation, and environmental companies, college and home school students, Girl Scouts, and volunteers, a successful multi-component passive system, readily accessible for upgrades and public education/research activities, was built. 90 people were directly involved in construction of this award-winning system and about 1000 people annually benefit from the educational opportunities.

Jan 1, 2002

By Michael J. Miller

In the design of a modem mill, a stockpile storage system for raw and/or semi-processed ore has become almost indispensable. This paper discusses the benefits of such stockpile storage as well as the various types of belt conveyor stockpiling units available. Particular attention is given to large radial stackers since they offer the greatest flexibility. Stacker control systems and accessory equipment are briefly discussed. Various alternative reclaiming arrangements for stockpiles are reviewed and a discussion of the advantages and drawbacks of each arrangement is included.

Jan 1, 1979

By David D. DiPonio, John DiPonio, Roger Van Omen

The greatest opportunity to attain the most favorable prices for underground construction projects occurs during the competitive bidding period. The Owner, Engineer, and Contractor need to have a thorough understanding of the project’s design concept, how it is going to be built, and what it is going to cost. This paper presents the opinions of three engineering professionals who are well established in their sectors of heavy civil underground public works construction. This paper will outline and summarize the considerations that the three principal contracting parties of Owner, Engineer, and Contractor need to make to obtain good price quotes at the time of bids.

Jan 1, 2005

By William H. Mount

Since the late 19405, St. Joe has operated rubber-tired, trackless mining equipment underground in its Southeast Missouri Lead Belt operations. At first, the trackless equipment was operated in conjunction with rail haulage equipment in the room-and-pillar operations, but was to later replace rail haulage completely. The first pieces of equipment to travel on pneumatic rubber tires were short-haul shuttle cars of 12-ton capacity hauling rock from the heading to the mainline railroad. Early-model drill jumbos were the next pieces of production equipment to be carried on rubber, along with mobile slusher ramps. Mobile diesel equipment, in the form of conventional rear-dump trucks, made its appearance underground in the early 1950s, introducing the era of relatively high-speed mobile equipment as compared to the electrically powered shuttle cars. Haulage distances for rubber-tired vehicles were no longer dictated by trolley lines and trailing cables and tires were subjected to increasingly severe applications. St. Joe's first completely trackless mine, the Hayden Creek Mine, was opened in 1952, employing rubber-tired drill jumbos, electric shuttle cars, and for the first time, an articulated diesel truck consisting of the tractor unit of a conventional earthmoving scraper and a rear-dump rock wagon. Those machines rolled on the first true earthmover tires to be used underground by St. Joe. The articulated truck concept proved to be very successful, and constitutes an In- creasing portion of the underground haulage today.

Jan 1, 1975

By Syd S. Peng

Introduction The most commonly used ground control design in coal mining is the determination of pillar size by various pillar strength formulae for mine layout (Bieniawski, 1983; Holland, 1973; Hustrulid, 1976; Obert and Duvall 1967; Wilson and Ashwin, 1972). However, there have been few documented case histories concerning the validity of those strength formulae. Recently there are indications that those strength formulae tend to overdesign considerably. From a safety point of view, there is nothing wrong with overdesign. But an overdesign with large chain pillars reduces the flexibility of machine movement and decreases production. It also reduces coal recovery and, thus, shortens the reserve's life. This is especially true for small operators who own a limited reserve. Those small mines, through past practices or out of necessity, experiment with smaller pillars than those predicted by the strength formulae. Conclusive ev¬idence has been collected that points to the need of a new concept of coal pillar design. Two case studies will be cited to illustrate this point. 3-D US pillar strength formulae Figure 1 shows a sectional layout of a one-unit mine. The seam was about 1.3 m (50 in.) thick with a uniform cover of 64 m (210 ft). A house was located near the center of the section. The homeowner demanded that no surface subsidence and domestic well dewatering should ever be allowed as a result of underground room-and-pillar mining. Physical properties - strength and Young's modulus - of the rock strata including coal were obtained by testing small samples in the laboratory. The uniaxial compressive strength of the coal was 3660 kPa (823 psi). Using various pillar strength formulae, the homeowner recommended that square chain pillars be at least 11 m (35 ft) wide. The coal company, however, desired to pursue optimum coal recovery in the safest and most economical manner. They engaged in three-dimensional finite element analysis of the section taking into account the complete stratigraphic sequence of the overburden. Results indicated that the section can be developed by 5.5 m (18 ft) wide entries at 21 m (70 ft) center-to-center. In retreat, the pillars can be splitted along both centerlines leaving a stump pillar of 5.5 m (18 ft) square at each of the four corners. The 5.5 m (18 ft) square stump pillars still maintained a safety factor of 1.5, although the safety factors calculated by various pillar strength

Jan 11, 1986

By Shahab Alizadeh, Ahmad Khodadadi Darban, Mehdi Mohseni, Mahmoud Abdollahy

This study probed the selective separation of lanthanum and yttrium in a nitrate medium in the presence of aluminum and calcium impurities using di-(2-ethylhexyl) phosphoric acid (D2EHPA). The factors studied in a central composite design (CCD) included extractant concentration, pH, concentration ratio of total impurities to rare earth elements, and interaction of these three factors. The extraction mechanism and types of extracted metal-containing species were delineated by the slope analysis method. The obtained thermodynamic data showed that lanthanum and yttrium extraction by the D2EHPA extractant was exothermic. The extraction of both rare earth elements was accompanied by an entropy reduction. The negative magnitude of ΔS in yttrium extraction reaction suggests stronger D2EHPA-Y(III) complexation relative to La(III). As entropy decreased and enthalpy increased, the extraction process became unspontaneous. Using the proposed flowsheet, lanthanum and yttrium products with > 90% purity were obtained.

Aug 10, 2021

By Johann Steynberg

The design and construction of a Concentrator based on initial pilot plant work is rarely perfect. Palabora's plant was no exception although the basic objective to produce copper in a safely conservative manner was certainly achieved in a profitable manner. identification of the metallurgical and mechanical deficiencies of the plant through operating experience and a better concept of the minerology of the orebody enabled the development of a more efficient process both in terms of the metallurgical performance and cost effectiveness. To maintain and improve this level of efficiency, continuous inspection and revision of the plant metallurgy and engineering standards is required. In this presentation a few of the investigations and changes are described: 1.0 Alternative methods to restrict and eliminate the detrimental effect of critical size material on the performance of an autogenous mill. 2.0 An analysis of the environmental condi¬tions in Palabora's grinding circuit and the introduction of high chrome balls as grinding media. 3.0 The role of magnetite in the beneficiation process at Palabora. 1.0 Alternative methods to restrict and eliminate the detrimental effect of critical size material on the performance of an autogenous mill.

Jan 1, 1985