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By Peter W. Lipman

Structural and topographic relief in the Sangre de Cristo Mountains of northern New Mexico provides a remarkable cross section through the recently recognized 23-26 m.y.-old Questa caldera and cogenetic volcanic and plutonic rocks. Although largely eroded, remnants of an ash-flow sheet of silicic-alkalic rhyolite and associated more mafic lavas of the Latir volcanic field are preserved as far as 45 km beyond the source caldera. Within the caldera, the tuff ponded to a thickness of 2-3 km and enclosed chaotic megabreccia fragments which slumped from the caldera walls. At the time of ash-flow eruption, the volcanic field was severely deformed along northwest-trending faults related to the Miocene Rio Grande rift, with most intense deformation occurring within the caldera. Strata were steeply tilted and locally overturned along presumably listric faults. Ash- flow tuffs locally underwent secondary flowage over concurrently developing fault scarps and accumulated within structural basins as rheoignimbritic lava flows. Cogenetic batholithic granitic rocks, exposed over an area of 20 x 35 km, range from mesozonal quartz monzonite to epizonal porphyritic granite and aplite, with the shallower and more silicic phases most abundant within the caldera. Compositionally and texturally distinct granitic phases define a highly evolved resurgent intrusion within the caldera, an incomplete ring dike along its southern margin, and a large mass of less fractionated quartz monzonite south of the caldera. A negative Bouguer gravity anomaly is closely confined to the area of ex- posed granitic rocks; it also reflects boundaries of the Questa caldera. The gravity anomaly is interpreted as defining the extent of the underlying batholith, emplaced into lower parts of the volcanic sequence and underlying Precambrian rocks. Paleomagnetic determinations indicate that the granitic rocks were above Curie temperatures at the time of caldera formation and regional listric faulting, yet most are little different in radiometric age from the intensely deformed volcanic rocks. These relations indicate that the batholithic complex represents the source magma body for the volcanic rocks, into which the Questa caldera collapsed, and was largely liquid at the time of regional tectonic disruption. Compositions of the volcanic and plutonic phases changed from early calc-alkaline metaluminous rocks, to weakly peralkaline silicic rhyolite and equivalent afredsonite-acmite granite at the time of the caldera formation, then back to post- caldera calc-riebeckite granitic rocks. Maximum concentrations of alkalis and minor elements such as Rb, Th, U, Nb, Zr, and Y were reached at the time the caldera formed about 25-26 m.y. ago, but the major molybdenum mineralization of the Questa district took place when the late calc-alkaline granitic ring intrusions were emplaced about 23 m.y. ago, along the south margin of the caldera.

Jan 1, 2013

By A. Nieto

This article is a review of previous discussions about underground mining method selection and classification with the purpose to clearly define and classify the two groups of variables (indicators) involved in the mining selection process: key deposit indicators (KDIs) and key mining method indicators (KMIs). This paper provides a simple and clear approach for the classification and selection of a feasible underground mining method based on a predetermined set of favorable deposit characteristics, which are defined as key deposit indictors (KDIs). This article also gives a summary of the key advantages and disadvantages associated with every underground mining method based on their key mining indicators (KMIs). The selection method given in this paper is based on defining field KDIs and comparing them to the KDIs that are favorable to every considered mining method. By cross validating a matrix of favorable KDIs, the paper presents a simple approach to rank several underground mining methods using a scale from favorable to less favorable accordingly to the ore deposit characteristics (KDIs). KMIs are used to further complement KDI rankings by analyzing every method’s KMI performance based on the expected productivity of the mining operation being considered. To further assist the reader through the selection process, this paper gives basic sketches representing each of the primary underground mining methods discussed in this paper. Each method is given using the same 3D isometric view as spatial reference to assist the reader with visual interpretation and comparison between methods.

Jan 1, 2010

By B. Schimm

Mining of material without blasting and / or selectively becomes more and more important for high quality ROM-products. Surface Miners have been developed especially for this purpose. The cutting technology of these machines has been improved, so that harder material as well as wet and sticky materials can be cut with better results now. Especially the cutting drum design and more precise drum manufacturing process now allow production and equal tool wear over a long period. The better knowledge of rock parameters influencing the cuttability and cutting results allow higher production, less cutting tool wear and therefore reduced production costs.

Jan 1, 1999

By P. I. James, M. R. Baker

Este artículo analiza la nueva producción de cobre a partir de "minerales de desecho" de baja ley usando la tecnología de Blue Planet Strategies DEMET™ (Dynamic Electrode Mining Effluent Treatment, por sus siglas en inglés), que tiene como objetivo salvar la brecha de procesamiento entre la solución débil de lixiviación en operaciones de extracción por solventes/electrowinning (SX/EW), removiendo electroquímicamente los metales a partir de corrientes débiles y a la vez generando productos concentrados en metales objetivo en un análogo funcional de extracción por solventes (SX). Se estudió el tratamiento de la débil solución de lixiviación pregnant (PLS por sus siglas en inglés) y se usó para estimar los impactos económicos y de producción para una hipotética lixiviación en pilas de cobre brownfield y una operación aumentada DEMET usando SX/EW para tratar el "mineral de desecho." Se presenta la remoción de cobre a un 86% de eficiencia en las placas por debajo de 0,1 g/L de cobre con un consumo de energía de 0.55 kWh/lb de cobre y una concentración del producto mayor a 10 g Cu/L. El modelamiento arrojó aproximadamente $2/ lb para la producción total de cobre y costos de tratamiento menores o iguales a $1/lb con un inmediato aumento del margen bruto de operación del 12% para el brownfield incrementado. Se indicó también un aumento de la vida de la mina con un margen bruto promedio de 38% en la producción aumentada de "mineral de desecho" con valores de cobre de $3.25/lb.

Jan 1, 2014

By Earl C. Herkenhoff

Editor's note: The subject of mining on the moon can generate a wide range of strongly held opinion, from those leaning toward the view that, ultimately, such activity is the destiny of mankind to those who believe that all suggestions for moon mining to date are unrealistic, wildly expensive and in the hands of people who 'know nothing.' MINING ENGINEERING herewith publishes some of the basic pros and cons on the subject of moon mining by writers who are among those holding strong views on the subject, with the hope that some of our readers may be interested in joining this debate. Every mineralogist and most mineral industry people were keenly interested in the examinations of the first moon rocks brought back by US astronauts in 1969. Suffice to say that the examinations revealed nothing exotic in the mineral makeup of the very limited rock samples. The rocks were generally of igneous type, dark-colored and contained some common, Earth-type minerals. There was, in Earth terms, above average TiO2 content, but they contained nothing of commercial significance by Earth standards. Therefore, interest in moon minerals rapidly faded. Years later, on Sunday, May 4, 1986, living in Reno, NV, this author was shocked to read a local newspaper article by the Dean of the Mackay School of Mines, University of Nevada, Reno, headlined, "Moon Mining Not Far Off." Considering that the announcement more or less coincided with a slump in our domestic mining industry, the immediate questions in a reader's mind

Jan 1, 1991

By Paul C. Schmall, Arthur B. Corwin, Derek Maishman

Ground freezing occupies a unique and important niche in underground construction, fulfilling a geotechnical need that is difficult, or sometimes impossible, to fulfill through other groundwater control and excavation support methods. Where complete groundwater cut-off and in-built ground support are required, and deep excavation is planned or the work occurs in difficult or disturbed ground, ground freezing offers the assurance critical to safe and timely construction. Compared with other groundwater cut-off or excavation support methods, a frozen wall is easily connected to underlying bedrock and will also adhere to adjoining subsurface installations or obstructions, if necessary, to provide a composite cutoff structure. Ground freezing is effective in all soil and ground conditions and has been used for emergency situations in disturbed, displaced or loose ground, where detailed soil characterization could not practically be performed.

Jan 1, 2005

By Dean R. Gehring

Creating projects to reach a goal is not new to American industry. In fact, all major construction projects, from skyscrapers to bridges, are completed using similar project management techniques. However, modern project management is relatively new. It was not formalized until 1962, when NASA and the US Department of Defense recognized the need to develop uniform project management procedures throughout the aerospace industry (Moder, Phillips and Davis, 1983). This management method was not introduced to the mining industry until the early 1970s (Britton, 1983). Project management typically follows an organized, four-stage process —definition, planning, implementation and control.

Jan 1, 1996

By Wallace N. Thomas

The present interest in large diameter grinding mills and the rapidly rising cost of the drive in proportion to the cost of the mill establishes a need to explore the drive system in detail. The drive for a seven to eight thousand horsepower mill will cost from 1350 thousand to $600 thousand which represents nearly half the total cost of the mill package, and requires as much building space as the mill proper. Some of the drive components require a longer time to manufacture and the installation time and costs are equal to those for the mill. It is apparent that the drive has become a dominant factor in the overall mill design consideration. A new plant requires a tremendous investment in both time and money. With the high degree of competition in the mining industry, low capital cost is an exceedingly important factor in the development of a project. It is just as important, however, to insure that the equipment is going to perform satisfactorily for the anticipated life of the project without adding unplanned operating, maintenance and replacement costs. This is the position in which the engineer or designer usually finds himself and is really one of his primary functions -- establishing a realistic compromise between cost and performance.

Jan 1, 1969

By F. G. Crack, R. V. Ramani, R. L. Frantz

Management for mine construction and development differs from that needed for routine mine production and maintenance. An integrated approach to managing mine development projects must consider contract documents; management organization of a project; the project manager's role and the field supervisor's responsibility; and the use of scientific techniques for planning, scheduling, executing, and controlling projects. Professional project management encompasses the following: • Preparing contract documents that establish technical and financial schedules, and detail the responsibility for the physical work commitment. • Developing a project's organizational structure, to clearly define the roles of the project manager and the field supervisors. • Establishing project management and field supervisor relationships, to avoid ambiguity in assigning responsibility and to ensure desired project progress. • Using management science techniques, particularly networking techniques such as the critical path method for planning scheduling, executing, and controlling projects. Project Versus Production Management Project management differs from routine production management in the following ways: • Uniqueness: A project is unique. Production operations tend to be repetitive. The magnitude of one-time capital expenditures for many facets of mine development warrant special skills and attention. These professional project development skills must already be available by prior experience in the management team. • Personnel: In projects, personnel are usually assigned on a specialty basis and frequently change with the project activity. On the other hand, production personnel work together, more or less permanently. • Management Structure: In a project there may be several staff-line relationships that are not clearly defined and change with changing project activities. In a production situation, the lines of communication and authority are usually well defined. • Time Frame: A difference between project and routine production management is that project activities have comparatively less well defined durations and often tend to be relatively short-term. Production usually has both long-term and short-term plans and well defined long-term and shor-term goals. In project management, formal, critical, short-term reviews are frequently required. In production management, five year plans can be formally adjusted quarterly and annually. Short-term weekly or daily reviews can be informal. • Response to Delays: Delays in a development project may occur without anyone being immediately aware of their existence or suspecting the magnitude of consequence. In contrast, any delays in the production process can be easily identified from prior results comparison. Additionally, the response is quick, usually in a set routine. This can be traced back to the management structure and personnel. • Control Techniques: Measurements of project progress for control are not easily made due to the variety of activities that are carried on at the same time by different work groups. The yard-sticks of performance measurement for individual activities, let alone for the total project, are not easily established. However, due to the difficulty in detecting project delays, a workable control system is vitally important to a project manager. To apply a scientific project control technique such as "management by exception" requires specific planning and monitoring from the project manager for each activity in the project. Production and productivity are quick and effective yard-sticks of measuring performance in a routine operation. Control techniques required in production management usually revolve around these measures. Construction Contracts The construction contract is an important document that establishes contract scope, technical and financial details of the work, and achievement deadlines. It may also serve as the contract document to pay for work done and to verify field progress with planned progress. In practice, it is a good idea to develop a job-specific contract. This whole area is replete with legal precedence and procedures, and it is not the intent here to deal with the intricacies of establishing a contract document. But it is necessary to have an understanding of major contract types. Construction contracts are extremely important legal documents. They may vary in work specifications and enforcement of the provisions. Due to their nature, they must be composed with legal help and will take some time to compile. Even with all the precautions and provisions, it is not uncommon to find owner and contractor disagreeing. Therefore, it is important to include a way to resolve any difference quickly and to incorporate aspects of the contract as part of an overall management control tool for efficient project management.

Jan 7, 1982

By Tuncel M. Yegulalp, Anuta Belova

This paper expands on the ZECA (Zero Emission Coal Alliance) technology, which is aimed at making coal a sustainable source of clean energy in the near future. The technology proposed immediate capture of carbon dioxide and other pollutants upon generation, thus alleviating their negative effects in the Earth’s atmosphere. ZECA proposes using chemical energy of coal to produce hydrogen; the latter is then used to produce electricity via fuel cells or Hyrogen-Oxygen turbines. In this study, a chemical engineering package, AspenPlus 12.1, is used to simulate the reactor (reformer) in which hydrogen is produced from methane water and lime as part of the zero emission power plant. Thermodynamic conditions, pressure and temperature, are optimized with respect to molar hydrogen production. Under the proposed conditions, molar conversion efficiency, carbon to hydrogen, of 95% is achieved. Further studies are required to model the complete power plant and to optimize it for efficiency.

Jan 1, 2005

By M. Menéndez

Enhanced gravity separation appears to be one of the most promising methods for processing all types of <200-µm coal feeds and tailings. Systems based on this technology are reviewed, and the results of investigations based on C900 Multi-Gravity Separator tests conducted to assess the treatment of <200-µm, extremely difficult-to-wash coal settling pond tailings are presented. Multi-Gravity Separator processing tests of ultra-fine tailings with a high clay particle size content (22.6% <10 µm and 60.1% <40 µm) and a 69.56% ash content show that this material can be effectively treated after desliming (<10 µm) of clay-size particles to produce a coal with a 20.6% ash at a separator combustible material recovery of 69.3%. Desliming is shown to be critical in reducing coal ash content and combustible material recovery. Similar improvements are anticipated in the recovery and separation pro-cesses for other enhanced gravity separation systems from the desliming of feeds. Although not a conventional form of treating Multi-Gravity Separator data, the existence of well-defined polynomial relationships based on the product of drum shake amplitude and shake frequency relative to product coal recovery, product ash content and yields at varying wash water flows is demonstrated. Low-amplitude and intermediate- to high-frequency bed agitation are shown to produce optimum ash reduction results.

Jan 1, 2007

Many states rely upon the Pennsylvania 1957 “Gas Well Pillar Study” to evaluate the coal barrier surrounding gas wells (Commonwealth of Pennsylvania, 1957). The study included 77 gas well failure cases that occurred in the Pittsburgh and Freeport coal seams over a 25-year span. At the time, coal was mined using the room-and-pillar mining method with full or partial pillar recovery, and square or rectangle pillars surrounding the gas wells were left to protect the wells. The study provided guidelines for pillar sizes under different overburden depths up to 700 ft. The 1957 study has also been used to determine gas well pillar sizes in longwall mines since longwall mining began in the 1970s. The original study was developed for room-and-pillar mining and could be applied to gas wells in longwall chain pillars under shallow cover. However, under deep cover, severe deformations in gas wells have occurred in longwall chain pillars. Presently, with a better understanding of coal pillar mechanics, new insight into subsidence movements induced by retreat mining, and advances in numerical modeling, it has become both critically important and feasible to evaluate the adequacy of the 1957 study for longwall gas well pillars. In this paper, the data from the 1957 study is analyzed from a new perspective by considering various factors, including overburden depth, failure location, failure time, pillar safety factor (SF), and floor pressure. The pillar SF and floor pressure are calculated by considering abutment pressure induced by full pillar recovery. A statistical analysis is performed to find correlations between various factors and helps identify the most significant factors for the stability of gas wells influenced by retreat mining. Through analyzing the data from the 1957 study, the guidelines for gas well pillars in the 1957 study are evaluated for their adequacy for room-and-pillar mining and their applicability to longwall mining. Numerical modeling is used to model the stability of gas wells by quantifying the mining-induced stresses in gas well casings. Results of this study indicate that the guidelines in the 1957 study may be appropriate for pillars protecting conventional gas wells in both room-and-pillar mining and longwall mining under overburden depths up to 700 ft but may not be sufficient for protective pillars under deep cover. The current evaluation of the 1957 study provides not only insights about potential gas well failures caused by retreat mining but also implications for what critical considerations should be considered to protect gas wells in longwall mining.

Jul 28, 2020

By Grover Wallace

At is important for today?s mining executives and leaders not to underestimate the fact that, while the recent downturn in the economy did take its toll on balance sheets and productivity, factors such as emerging countries, aging workforces, globalization and individual knowledge growth did not lay dormant while the economy was in a lull. It is key for mining leaders to be proactive in their talent strategies. Successful mining companies are developing a clear, concise and communicated strategy and placing a high priority on recruiting the right talent in global markets that parallels their business strategy. They are focused on placing the right people in the right jobs.

Jan 1, 2011

By S. Krukowski

Iodine is a bluish-black, crystalline solid with sub-metallic luster, and has a specific gravity of 4.93. It volatilizes (sublimates) at ordinary temperatures into a blue-violet gas that has an irritating odor. Iodine is the least active of the halogens, all of which readily displace it. Only slightly soluble in water, iodine also dissolves in carbon disulfide, carbon tetrachloride and chloroform, giving a deep violet solution. The primary sources for iodine production are sub-surface brines associated with petroleum and natural gas deposits, and as a byproduct from nitrate deposits in Chilean desert caliche. The largest source of iodine is seawater which contains 0.05 ppm, or about 31 Mt (34 million st). Seaweed of the family Laminaria can extract and accumulate up to 0.45 percent iodine on a dry basis. Seaweed was an important source of iodine prior to 1959. However, it remains a significant source of iodine in the diets of many populations throughout the world.

Jan 1, 2005

By P. Zhang

Previous studies have shown that separation of clay minerals from non-clay minerals is the key to economic recovery of the phosphate from the waste phosphatic clays (slime) which represent about 20- 300/0 of the phosphate mined. Small hydrocyclones of different sizes (4" and 6") were tested for sizing the slime at +10 microns in order to remove most of the clay minerals. The effect of design variables and operating parameters were evaluated. Multi-stage cycloning and the effect of dispersant were also investigated. Chemical and mineralogical analyses of different size fractions of both the underflow and overflow samples indicated satisfactorily separation efficiency.

Jan 1, 1998

By John W. Sweeney

Florida is usually thought of as a vacation State, not a mining State, yet Florida has been the leading producer of phosphate rock in the United States for 85 consecutive years and in 1978 supplied over 80 percent of the national output and over 30 percent of the world&apos;s output. It is estimated that the Central and South Florida phosphates contain 412,800 short tons (374,000 metric tons) of U308, that 115,000 short tons (104,000 metric tons) of U308 will be contained in the wet-process phosphoric" acid procsssed in the United States through the year 2000, and that 54,000 short tons (49,000 metric tons) of U308 will be available from Florida. In 1978, two companies in Florida and one in Louisiana went on-stream recovering uranium oxide from wet-process phosphoric acid and three others started construction of U308 extraction facilities. These six companies will have the capacity to recover 2,137 short tons (1,900 metric tons) of U308 annually in 1980, which will account for about 15 percent of our domestic requirements.

Jan 1, 1979

By Paul H. Madsen, Victor S. Romero

The Tren Urbano project in Puerto Rico includes a 19 m diameter tunnel constructed by the stacked drift method, which involves installation of a pre-supported concrete arch using multiple tunnels. Geotechnical conditions consisted of weak rock and highly weathered, unstable alluvial soils. Due to low cover, reinforcement of the arch was required. Ground behavior ranged from firm ground to mixed-face to raveling and flowing ground. Consequently, construction of the individual drifts involved many different soft-ground techniques such as steel set supports, shotcrete support, shield tunneling, forepoling, and consolidation grouting. During construction, the design was modified to improve constructability. Although settlement was experienced during excavation of the drifts, arch movements were within predicted limits and minimal surface settlement was observed upon excavation of the interior.

Jan 1, 2001

By J. O. Stephens

During the late 1940&apos;s and early 1950?s, the Westinghouse Combustion Turbine Division built and demonstrated a residual oil-burning locomotive on six eastern railroads. Plans were made to convert to burning pulverized coal, and a single combustor was operated at a full-pressure condition in the laboratory for about two years. During the mid-1960&apos;s to mid-1970&apos;s, there was considerable interest in coal-burning MHD and a combustor was developed which would also be applicable to combustion turbines. In the early 19801s, the BCR National Laboratory (BCRNL) became affiliated with the University of Pittsburgh, and a program was begun, supported by the Stare of Pennsylvania, to develop an all-purpose combustor for use with industrial and utility boilers and eventually with combustion turbines. In this paper, we review the work of almost 40 years, indicate our present position, and propose steps to be taken leading to efficient and environmentally acceptable power generation from coal, and specifically to coal-burning locomotives.

Jan 1, 1986

By J. -G. Swanson

Dust control in longwall coal mining depends primarily on the prevention of dust at the source and secondarily on the suppression of airborne dust. One of the primary methods for the prevention of dust is the wetting of the coal face prior to extraction, which can be achieved with water spray systems installed on the shield supports. The spray droplets must travel across the airway to the longwall face, where high ventilation air speeds can entrain water droplets and prevent them from reaching the face thus minimizing the dust control at the source. Through an evaluation of spray plume characteristics in a wind tunnel, the droplet size and droplet drift behavior was determined. This drift behavior was examined by evaluating the spray plume concentration drop and the droplet size shift near the nozzle exit at varying air speeds. Based on these evaluations, CFD modeling was applied to simulate the spray behavior for varying geometries. These results led to the selection of appropriate spray nozzles capable of carrying water droplets to the face at higher air speeds, resulting in an adequate wetting of the coal face and reduced dust generation.

Jan 1, 2012

The schlieren technique describes an optical analysis method designed to enhance light distortions caused by air movement. The ability to visualize air flow has significant implications for analyzing underground mine ventilation systems, including the enhancement of surveys and models. Currently, traditional schlieren methods are impractical underground. Background oriented schlieren (BOS) provides a solution to this problem. BOS requires two primary components, a professional quality digital camera and a schlieren background. A schlieren background is composed of a varying contrast repetitive pattern, such as black and white stripes. This background allows the camera?s sensor to capture minor light diffractions, such as those caused by air flow. Although BOS shows great potential for ventilation analysis, sensitivity is an issue. This paper seeks to validate the BOS technique for imaging flow through a regulator by comparing BOS images with traditional schlieren images. This paper also outlines initial experimental efforts used for the validation.

Jan 1, 2011