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By Donald R. Williamson

Statistical studies at Cyprus Pima Mine indicate that samples from 22 blastholes are necessary for determining average copper grades, within a desired range of precision, for mine-model blocks by arithmetic averaging. The average number of holes in such blocks is 14. Many considerations show that more holes will not be drilled for sampling. A way to determine block grades more reliably than by" arithmetic averaging was sought. Thus far arithmetic averaging has proven to be the best procedure for the particular operation characteristics despite the small number of samples. It naturally follows that expenditure of great effort in sampling blasthole cuttings is unwise.

Jan 1, 1977

By Missy Isaman

"Mixed ground tunnels come in all kinds. In rock tunnels with possible faults and high pressure water, the challenges are many. With the advent of Crossover TBMs, contractors can minimize machine wear in such conditions while maximizing efficiency. The newest generation of Crossover is exemplified by two projects in Albania and Turkey. A 5.56 m Crossover TBM destined for Turkey’s Gerede Water Transmission will be assembled using Onsite First Time Assembly (OFTA) from within an existing tunnel. The unique machine will bore through 30 fault zones requiring the TBM to be sealable to up to 20 bar so pre-consolidation grouting can be done. If boring under pressure is required, the TBM will bore sequentially using the screw conveyor fore and aft gates. Skewing further towards hard rock, a unique 6.2 m diameter Double Shield TBM with Crossover features was designed for Albania’s Moglicë Headrace Tunnel. The machine features closure doors and a sealing system to contain inrushes of water until they can be grouted off. This paper will discuss the unique aspects of the Crossover designs, including their inception as based on past projects in difficult ground, and their utilization at the two current projects. INTRODUCTION Specialized tunnel boring machines have been made for years to tackle specific types of ground conditions. Traditional types of TBMs bore within a specific set of ground conditions. If a project is located in a competent granite face, then a Main Beam machine is a good solution. In soft ground, Earth Pressure Balance (EPB) machines are the method of choice. Years of experience and engineering advancements have made both types of machines fast and economical solutions for tunneling. Unfortunately not all ground conditions are a perfect swath of one material, and the need for a more diverse machine is apparent."

Jan 1, 2016

By Robert L. Russell

Production at Freeport Indonesia's Ertsberg open pit copper-gold mine started in 1972 at a rate of 7.5 kt/d (8270 stpd). Mill throughput remained at that rate for several years until the discovery of the Ertsberg East (GBT) ore body. This discovery prompted three succes¬sive expansion stages from 1981 to 1988 that boosted production to 20 kt/d (22,000 stpd). In 1988, the discovery of the huge Grasberg porphyry copper deposit launched an era of much larger expansions. The first of these was the installation of a fourth primary mill in 1989 that increased throughput to 32 kt/d (35,270 stpd). That was followed by an expansion of the crushing and screening plant and in 1991 the addition of a new south concentrator to bring production to 57 kt/d (62,830 stpd). The addition of a primary ball mill and the changeout of the original Denver flotation cells in 1993 brought production to its current level of 66 kt/d (72,750 stpd).

Jan 1, 1994

By A. M. Raichur

Flocculation of fine coal is usually accomplished with the addition of commercially available organic flocculants. Recently it has been shown that biopolymers derived from microorganisms can be used to flocculate coal. The biopolymers flocculate coal efficiently and render the coal surface hydrophobic. The increase in hydrophobicity can be utilized either to separate the coal flocs from mineral matter. It can also be used for reducing the moisture content of fine coal. In this regard, flocculation and settling tests of fine coal with biopolymers and synthetic flocculants was undertaken and the results are discussed here. Also, a transport model was developed for the time-dependent settling tests for fine coal.

Jan 1, 1996

By Edmund H. Warner

Any city dweller who has walked alone along a remote mine passageway has to be impressed by the eerie silence - the total absence of noise except for ones own breathing and scuffing of boots on the bottom. An underground mine can have tremendous contrasts, from complete silence to the ear piercing clatter of percussion drills working on the mine roof. Noise in underground mining machines is both useful and detrimental. Without characteristic noises that are recognizable to miners, operators would have a more difficult job operating their machines. Noise serves as a warning of approaching machinery, and changes in noise give indication that breakdowns may occur. But excessive noise is a health hazard. In recognition of this fact, our Congress included noise exposure as a part of the "Coal Mine Health and Safety Act of 1969". As Fig. 1 indicates, allowable noise exposure is established by specifying a time duration permitted at different noise levels. This is the well known "Walsh-Healey" criteria which governs noise exposure in many industries.

Jan 1, 1977

By Kenneth N. Han

The effect of anions such as sulfate, chloride, and nitrate on the solubility of rare earth element-bearing phosphates and fluorocarbonates has been examined using relevant thermodynamic data. The study has found that these anions have significant influences on the overall dissolution of rare earth elements (REEs) from various sources in the aqueous media. The thermodynamic calculations in this study have indicated that the speciation of REEs with the anions tends to increase the overall solubility of the REE-bearing minerals. However, in some cases, strong precipitation of REEs with some of these anions causes an adverse effect on the solubility of these elements. It has been found that sulfate ion has the most pronounced effect on the solubility compared to nitrate and chloride, in which the latter two acids exhibited almost identical results. The calculated results have indicated that REE-oxide (hydrated) is the easiest compound to dissolve, followed by carbonate, phosphate, fluoride, sulfate, fluoro-carbonate, and oxalate in that order.

By R. E. Hucko

The principal thrust of the U.S. Department of Energy (DOE) Coal Preparation R&D Program is to develop technology to reduce the ash and sulfur contents of United States coals to levels such that the resultant product can be formulated into a high quality solid or slurry fuel that could replace oil or natural gas in both new and retrofit applications. Specifically, the objective is to develop and refine cost-effective physical and chemical beneficiation processes to extract 85-95 percent of the total sulfur and ash. The Coal Preparation program is implemented by the Pittsburgh Energy Technology Center (PETC) and is conducted both in-house and by a cross section of industrial organizations, universities, and national laboratories. Research is subdivided into three areas -coal characterization, beneficiation, and ancillary unit operations. This paper will provide a brief overview of many of the research projects being carried out in these areas in fiscal year 1984.

Jan 1, 1984

By T. H. Dubaniewicz, J. E. Chilton

The U. S. Bureau of Mines is investigating the application of fiber optic technology to methane and carbon monoxide monitoring. A methane monitoring system is described that is based on differential absorption of infrared light. It can detect concentrations as low as 0.2% and as far away as 2 km via fiber optic cable. The upper range is 100% methane. The system requires no electrical power within the mine so it should operate safely under mine disaster conditions. A hybrid carbon monoxide monitoring system is described that combines a low-powered electrochemical cell with fiber optic telemetry. Testing has shown the system can operate maintenance- free for several months.

Jan 1, 1992

By Clarence O. Babcock

Model pillars of limestone, marble, sandstone, and granite, with length-to-diameter ratios of 3, 2, 1, 0.5, and 0.25 (0.286 for granite), were broken in axial compression to determine to what extent an increase in end constraint increased compressive strength. Radial end constraints of 13 to 23 percent of the average axial stress in the pillar, produced by solid steel rings bonded with epoxy to the ends of dogbone-shaped specimens, increased compressive strength somewhat above that of cylindrical pillars without ring constraint. However, when the results were compared with those obtained by other investigators for straight specimens of several rock types taken collectively, with L/D ratios greater than 0.5, the resulting strengths were not significantly different. Thus, the amount of end constraint produced by the solid steel rings was about the same as that produced by the friction from the steel end plates. In other tests a radial prestress of 3,000 psi or 5,000 psi was applied prior to axial loading by adjustable hardened steel rings to increase the constraint above that obtained for the solid rings. The average radial constraint stress, expressed as a percentage of the average axial pillar stress at failure for the 3,000 psi prestress, was 54.3 percent for limestone, 40.3 percent for marble, 44.7 percent for sandstone, and 23.4 percent for granite. The average radial constraint stress, expressed as a percentage of the average axial pillar stress at failure for the 5,000 psi prestress, was 74.2 percent for limestone, 51.2 percent for marble, 61.6 percent for sandstone, and 29.7 percent for granite. These constraints increased the compressive strength significantly above the strength of straight specimens and solid-ring constrained specimens. These results suggest that large horizontal stresses in orebodies mined by the room and pillar method should increase the strength of the pillars and allow an increase in ore recovery by a reduction of pillar size when major structural defects are absent.

Jan 1, 1969

By Ron Robinson, Trevor Harrison

The planning, installation and commissioning of the first scheme of controlled recirculation of air flow in a section of coal mine in Great Britain is described, together with the proposals for a second installation. The work updates a previous paper (Robinson and Harrison, l986) on the subject. The special problems of ventilating the increasingly distant faces of the undersea mines in the North East Area of the British Coal Corporation are discussed and the alternative solutions stated. The advantages of using a system of controlled recirculation of air are proposed together with the safety features considered necessary. Design and installation details of the recirculation fans and a new booster fan are described.

Jan 1, 1987

By Jaroslav Briancin, Katarína Gáborová, María Florencia Márquez-Zavalía, Marcela Achimovičová, Ol’ga Šestinová, Pavel Škácha

Naumannite (Ag,Se), a silver selenide mineral, was first discovered in 1828. This study investigates the structure, morphology, chemical composition, and leaching kinetics of naumannite. Mechanical activation in a planetary ball mill increased its specific surface area, enhancing the leaching rate of silver in nitric acid (HNO3). The study found that mechanical activation significantly improves silver recovery.

Jul 1, 2023

By T. R. Ley

"INTRODUCTION Brutally honest mining executives will tell you that “safety is job #1 but.. dollars are also extremely important”. When economic times are tough, as they are now in mining, it can feel like you need to choose between safety and cost control. Leading edge companies know that it is excellence at both that provides the best performance. FLUID POWER SYSTEMS Fluid power systems are ubiquitous in mining – longwall systems, continuous miners, drills, haul trucks and excavators, etc. And fluid power systems are getting more powerful and using higher pressures to move greater volumes and achieve higher productivity. Average operating pressures in mobile equipment has been rising to 450 bar (6,500 psi) over the last decade. With increased system pressure comes ever increasing levels of stored energy. Stored energy that, if released in an uncontrolled fashion, can do tremendous harm to people and things.Fluid power systems are composed of pipe, flexible hoses, pumps, valves and actuators. They are filled with fluid (mineral oil or fire-resistant) to transmit power to where it’s needed for performing work. With time and use fittings can loosen, component performance diminishes and hoses wear and tear. In hostile environments, like coal mining, hydraulic hoses can fail in as little as 2 years according to DGUV (umbrella association of German Accident Insurers), maybe sooner in some particularly challenging environments. FLUID POWER SYSTEM SAFETY While appearing simple and benign on the surface, fluid power systems, particularly such systems on mobile equipment, have many potential hazards. Hazards that most workers aren’t aware of – particularly young, new hires. And those hazards that can quickly turn deadly. During the past couple of years, including at last year’s SME Conference, I talked to a wide variety of mining people about high pressure fluid injection injuries. Some people, often with little or no field experience, never heard of it. But, people with mine operations / maintenance experience were almost always aware of such injuries.Some had even seen it happen right in front of them. But most claimed it didn’t happen all that often. It just wasn’t seen as a problem!"

Jan 1, 2016

By M. P. A. Hames, D. R. Beaumont

INTRODUCTION Legend has it that when Isembard Kingdom Brunel was confronted with the cost and consequences of one of his bridges having failed, he responded cheerfully that the event had saved investors and taxpayers a fortune because it prevented him from repeating the same design at several other locations. To meet the demands of rejuvenating and expanding the transportation system in an era of industrial growth Brunel and his contemporaries introduced bold designs and many innovations. Great advances in design and construction techniques resulted, yet these too had their practical limits as the story tells. In the gold mining industry today we face the same challenge of expansion, yet designers must respond mindful of economic restraints. Is innovation the answer? It has two meanings; to bring in novelties and to make changes. Distinguishing between improvement and novelties, or simply recognizing the benefits and limitations of new ideas over proven technology is part of good design. This paper will illustrate the practical aspects of selecting appropriate solutions to a design problem by examining a variety of examples common throughout the industry. Since a variety of engineering disciplines contribute to the design of a gold processing plant, and each has some old wisdom to impart or new development to boast this paper is divided into the different areas of expertise involved.

Jan 1, 1987

By Cem Şensöğüt, Özer Ören, Yaşar Kasap

The mining sector is one of the leading sectors where work accidents are most intense because of the constant change of work environment and heavy working conditions. The losses and the halt of production after the accident negatively affect productivity and production efficiency. It has been found that there are very few studies on the use of Data Envelopment Analysis (DEA), which is one of the nonparametric efficiency analysis methods, in the evaluation of mining sector occupational accidents. According to parametric activity measurement methods, it has been tried to show that the DEA can also offer the opportunity to interpret work accidents by taking advantage of its advantages. Due to the application of open-pit mining methods along with underground working techniques which increase the risk factors with respect to accidents at work that occurred between 2012 and 2018 of Western Lignite Corporation (WLC) were tried to be analyzed in the present work. As a result of the analytical work using Data Envelopment Analysis (DEA) for the years 2014, 2015, 2016, 2017, and 2018, inefficiency has been determined in both underground and surface operations. According to the results obtained, it was determined that WLC could not produce enough production in both the underground and surface coal mining operation, despite the accidents that occurred, while it had the opportunity to produce more. In addition, it was found that the increase in accidents occurred more than the increase in the amount of production during the years studied.

Jul 4, 2021

By G. R. Harrod

Effective mine operation demands that the right people have the right information at the right time. Caterpillar's Mining and Earthmoving Technology System (METS) meets this demand by providing "real-time" information transfer between the mine offices and machines equipped with the Caterpillar Computer Aided Earthmoving System (CAES). Transfers of mine plans from the mine planning software to CAES-equipped machines give operators access to current mine plans within minutes of their creation. Additionally, office personnel have access to a current digital terrain model (DTM) of the mine site as it is updated in "real-time" by CAES-equipped machines. METS provides mine personnel in operations, planning, and management the information they need when they need it.

Jan 1, 1998

By K. A. Natarajan, M. R. Sabari Prakasan

"Biodegradation of sodium isopropyl xanthate using two types of bacterial strains, Paenibacillus polymyxa and Pseudomonas putida, is demonstrated. At concentrations higher than 50 mg/L, the presence of xanthate in the growth medium resulted in bacterial toxicity, retarding growth kinetics. Adaptation through serial subculturing in the presence of higher xanthate concentrations resulted in the development of xanthate-tolerant bacterial strains. Stress proteins secreted by bacterial cells grown in the presence of xanthate were isolated. Bacterial cells could utilize xanthate as a growth substrate, degrading xanthate species in the process. Acidic metabolic products generated by bacterial metabolism promoted efficient xanthate decomposition. Probable mechanisms for the biodegradation of isopropyl xanthate are illustrated.IntroductionDifferent types of alkyl xanthates (ethyl, isopropyl, amyl, etc.) have been used as flotation collectors in the concentration of sulfidic ores for several decades. Large quantities of waste water and xanthate-containing effluents are generated by ore flotation processes, posing considerable environmental challenges. Billions of cubic meters of such process waste waters are produced annually across the world, most of which are discharged to the environment, often without any treatment. Leakages and accidental release of xanthate reagents from manufacturing plants and during transportation and storage can also contaminate the environment. Residual concentrations of xanthate reagents are encountered in waste effluent, which are found to be toxic to aquatic life and unfit for human consumption (Harris, 1984; Okibe and Johnson, 2002). Further, direct recycling of such waste waters for plant operations can compromise water quality standards required for process operations. The presence of residual xanthate in recycled waters from flotation plants deleteriously influences flotation processes. Xanthate can be easily decomposed at low pH values; however, CS2, which is more toxic, will be produced by the acidification of neutral and mildly alkaline xanthate-containing solutions. Physico-chemical methods such as flocculation, chemical oxidation and decomposition and physical adsorption used to remove residual collector reagents from mill process waters are often expensive and not environment-friendly (Oliveira and Rubio, 2009; Cheng et al., 2012; Molina et al., 2013,)."

Jan 1, 2015

By Anil K. Ray

Roof falls are one of the greatest hazards in underground coal mines worldwide. Due to stringent safety measures and extensive support system development, roof falls have been reduced significantly but they still persist in many underground coal mines. Some of the roof falls initiate with cutter roof or guttering. In the past, many factors have been identified as being responsible for the development of cutters and roof fall. These responsible factors can be broadly classified as stress related or non-stress related. In this paper the finer details of mining technique have been taken into consideration for better understanding of cutter roof and roof fall problems. Three dimensional finite difference modeling has been used to explain the mechanism of cutter development. Strain softening material behavior has been used to realistically simulate the cutter formation, and common cutting sequences as implemented in the field have been simulated. This was done with an objective to determine whether the cutting sequence has really any significant control over cutter formation or not. In addition to cutting sequences, the effect of cut length is also studied. The effect of step cutting and turning of crosscut into and away from major and minor horizontal stresses is also examined to see its influence on cutter development.

Jan 1, 2009

By R. W. Brann, R. C. Freas

Franklin Industrial Minerals operates several mines/quarries, including two room and pillar underground mines. Both of these mines are operated as multiple level room and pillar including heading and bench operations on one or both of the levels. This paper focuses on Franklin’s Crab Orchard, Tennessee mine, which produces both high purity chemical grade limestone and crushed stone for construction applications. The high purity chemical specifications for the chemical grade limestone and filler/extender applications are inconsistent with the non-chemical rock being produced to supply the crushed stone market. As a consequence Franklin has developed a unique mine plan and operation to maintain both product balance and a safe and stable working environment.

Jan 1, 2003

By P. Croney

Environmental monitoring requires major effort and expense but management of data receives less attention. A modem database system can manage hydrochemistry, water levels, meteorology, geology and downhole geophysics data and is flexible to allow the storage of ad hoc data. Reports can be customized by the user and derived data generated from input values. The production of high quality maps with contours and hydrochemical diagrams is an essential part of the reporting process. These maps integrate directly with the current site survey information. These facilities are best provided by storing the data in an industry standard database such as Oracle or Access to which customized AutoCAD and Microsoft Office routines make direct SQL calls.

Jan 1, 1997

By Om P. Garg

The purpose of this paper is: 1) To summarize the capabilities and some of the limitations of the existing mine planning software. 2) To provide some guidelines for acquiring the software. 3) To identify problems and challenges in terms of how to justify increased use of computers (particularly the 32-bit microprocessor based super micro computers), for various activities related to a mining operation No attempt has been made to review the contents of available software packages in detail. Also the scope of this paper is limited to mine planning related computer applications. Applications related to accounting, inventory control, preventive maintenance, equipment scheduling, etc. have not been covered.

Jan 1, 1983