Search Documents

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 L. J. Buter, D. J. Collins

Introduction FMC's Paradise Peak gold mine was discovered by staff geologists in July 1983. Located south of Gabbs, in western Nevada, the deposit contains about 11 Mt (12 million st) of ore grading at 3.6 g/t (0.105 oz per st) of gold and 129 g/t (3.75 oz per st) silver. It is estimated that the ore contains 34 t (1.1 million oz) of recoverable gold and 933 t (30 million oz) of recoverable silver. The 3.6 kt/d (4000 stpd) mill began operation April 14, 1986, just 18 months after Davy McKee completed a feasibility study and construction, and two-and-a-months ahead of schedule. It also came in about 10% under budget at a cost of about $100 million. Crushing Run-of-mine ore is delivered from the mine in 45-t (50-st) haul trucks to a 272-kt (300,000-st) capacity open air stockpile. Ore is reclaimed using 5 m3 (7 cu yd) front-end loaders that feed a 91-t (100-st) hopper equipped with a 610- x 610-mm (24- x 24-in.) grizzly. A 1.4- x 11-m (54-in. x 35-ft) apron feeder delivers ore from the hopper by way of a vibrating grizzly screen with 127 mm (5 in.) openings to a 1- x 1.3-m (43- x 51-in.) Rexnord jaw crusher. Crushed material is conveyed to a 1.8- x 4-m (6- x 14-ft) Link Belt vibrating screen equipped with a 50-mm (2-in.) manganese grizzly bar deck. Screen oversize is fed to a 1.7/0.6-m (5.5 ft) Rexnord standard cone crusher. Product from this crusher joins the -50 mm (-2 in.) screen undersize and is conveyed to a 136-t (150-st) surge bin. Three hydraulically driven belt feeders deliver ore from the ore bin to three 2 x 6 m (7 x 20 ft) Link Belt single-deck tertiary screens fitted with 6 x 25 mm (0.25 x 1 in.) slotted polyethylene screens. Screen undersize - -6 mm (-0.25 in.) rock - is conveyed to a 3.6-kt (4000-st) ore storage bin. Screen oversize is delivered by way of a conveyor to a 91-t (100-st) surge bin. From this bin, two belt feeders feed ore to two 1.7 m (66 in.) Rexnord Gyradisc crushers, which are in closed circuit with the tertiary screens. Design features include magnetic protection for tramp iron removal and sloping floors and pump sumps for ease of clean up. Dust scrubbers keep the working environment clean and in compliance with state dust emission regulations. Grinding Two 1 x 4.5 m (3.5 x 15 ft) belt feeders deliver ore from the fine ore bin to a conveyor belt that feeds it to the 5 x 7 m (16 x 22 ft) Allis-Chalmers ball mill. The conveyor belt is equipped with a Merrick weightometer. This controls feed rate to the ball mill by speed control on the hydraulic motors driving the feeders. The 2.6 MW (3500 hp) powered mill grinds 3.6 kt/a (4000 stpd) to an average grind of 85% -75 µm (-200 mesh). The mill is in closed circuit with four 660 mm (26 in.) Krebs cyclones. Three of these are normally in operation while one is a standby. Warman pumps feed the cyclones through a cyclone distribution manifold. The cyclone underflow returns to the ball mill, which has a 300% average circulating load. Mill discharge pH is 11, and that is obtained through pebble lime addition to the feed belt. Cyclone overflow is sampled using a Heath & Sherwood two-stage sampler. It then flows to a 27-m-diam (90-ft-diam) Eimco thickener. Thickener overflow is returned to the grinding circuit, while underflow at 50% solids is pumped to the leaching circuit. Grinding-circuit design features include a steeply sloped floor for ease of clean up, an open area over the pumps for maintenance accessibility, and a ball hopper with a self discharge bottom to speed ball addition. Other features include a mill liner handler and an air clutch that connects the mill motor to the mill.

Jan 12, 1986

By Thomas B. Borak, Keith J. Schiager, Janet A. Johnson

OBJECTIVES OF RADIATION MONITORING Monitoring is a tool used in the practice of radiation protection. The primary reasons for monitoring are to reduce radiation exposures to levels that are as low as reasonably achievable and to assure that no individual receives a dose exceeding the maximum individual dose limit. The documentation of radiation doses for legal, medical, or epidemiological reasons is a subordinate function of any monitoring program. The investment in radiation monitoring programs should be guided by four criteria: (1) the detection and avoidance of unnecessary exposures, (2) the magnitude of potential health risks, (3) the determination of combined doses and risks with adequate confidence, and (4) the verification of compliance with established limits. FIRST CRITERION: DOSE REDUCTION - DETECT AND CORRECT UNNECESSARY EXPOSURES The system of dose limitation advocated by the International Commission on Radiological Protection (ICRP, 1977), and subscribed to in a broad sense by various regulatory agencies, is comprised of three essential ingredients: (1) [justification] of any practice that produces radiation doses by some commensurate net benefit, (2) [optimization] of radiation control measures by reducing doses to levels that are as low as reasonably achievable, and (3) [limitation] of individual doses to preclude inequities and [moldistribution] of risks. All too often, only the third criterion - the limitation of individual doses to prescribed regulatory limits - is explicitly addressed in everyday radiation protection programs. The emphasis of most exposure control and monitoring efforts appears to be directed toward limiting and documenting individual doses that might approach the legal limit. The first two criteria, i.e. justification and optimization, should contribute to a rationale for allocating monitoring efforts. When applied to individuals, these criteria mean the detection and elimination of unnecessary exposures. This should be a high priority of any monitoring program. Measurements should be directed toward detecting inoperative or ineffective control measures, whether or not there is a risk of exceeding the individual dose limits. The ICRP recommends a procedure that can be used effectively to reduce unnecessary exposures. A n investigation level should be established at an exposure rate substantially lower than the regulatory limit, e.g. 30% of the limit (ICRP 26, 1977, p.33). Measurements obtained during routine monitoring that exceed the investigation level are evaluated with respect to cause and potential reduction. To be effective, the evaluation results should be formally recorded and conveyed both to management and to the workers involved. Although the investigation level recommended by the ICRP is based on a fixed exposure rate or derived air concentration, an equally effective evaluation program may be based on the investigation of a percentage of all measurements. For example, one might investigate the highest 5% or a random selection of all measurements. In any case, the objective is to detect and correct situations that are producing unnecessary exposures. SECOND CRITERION: MONITOR IN PROPORTION TO THE MAGNITUDE OF RISK The ICRP criteria apply generally to all radiation exposures. However, a second priority for monitoring programs should be established on the basis of the nature of the exposures and the magnitude of the health risks involved. Current practices in radiation protection are based on dose limits to specific organs and assessment of individual exposure pathways, with little consideration of the combined doses from various pathways. Although the intent of the ICRP recommendations was to limit the total dose to each critical organ, combined doses from external and internal sources are rarely determined. The recent recommendations of the ICRP (Publ. 26, 1977) are based on the limitation of total health risk from occupational radiation exposures. Implementation of this concept would necessarily require the measurement, calculation and summation of doses and concomitant risks to all organs of the body from all exposure pathways. The U.S. Environmental Protection Agency has taken the first step toward translating the ICRP recommendations into regulations. The proposed recommendations for Federal Radiation Protection Guidance for Occupational Exposures (USEPA, 1981) include provisions for summing the risk-weighted organ doses to determine compliance with an effective whole-body dose equivalent limit. Whether or not the proposed guidance is modified before final adoption, it seems clear that some version of dose summation and combined risk limitation will be included in future regulations. With this

Jan 1, 1981

By John G. Hall

Everyone forms his own mental picture when the subject of copper is mentioned. To an architect, copper is a warm, enduring metal with a quiet beauty; to the historian, man's first metal; to the product engineer, the best electrical and thermal conductor of all commercial metals; to the investor, a volatile stock; to the speculator, the daily price quotation; to those in the mining industry, the challenge of producing copper for rising needs in the face of rising costs and lower grades of ore. At this meeting, we will look upon copper as a key raw material in industry, in national defense, in technology, in world trade, and as a principal commodity in the economies of several developing countries. As miners, and most of us here are miners, we are prone to view our role as suppliers of copper. We locate, mine, smelt and refine the metal. In the complexities of today's world, however, following a period of the longest domestic copper strike in history which caused critical world-wide shortages and widely fluctuating prices; it becomes necessary for all of us to concern ourselves with the whole spectrum of copper affairs -"from mine to consumer " But first we need to look at the miner's side of the picture -- capacity and production. We will examine these functions in terms of the whole world -- not simply the free world. Nature did not endow all regions of the earth equally, and copper in world trade has a way of ignoring political boundaries. Science and technology, as well, know no national boundaries. It is said that the "Engineering & Mining Journal" has as many readers in the Communist World as in the Free World. Nor is this a one-way street. We presently have available to us in the. U.S., cover-to-cover translations of many Communist World mining and metallurgical journals.

Jan 1, 1968

By D. Murray

"The Mine Improvement and New Emergency Response (MINER) Act included the need for improved chemical technologies to address respiratory protective device inadequacies and refuge alternative development. The National Institute for Occupational Safety and Health’s (NIOSH) National Personal Protective Technology Laboratory (NPPTL) invests in research and development to improve the carbon dioxide (CO2) scrubbing technologies built into these mine safety systems. Testing at NIOSH NPPTL is performed using a custom-designed test system containing a chemical reactor and sensors in a constant flow of simulated expired breath to evaluate chemical performance for the scrubber materials. Current testing procedures focus on device duration or capacity, but do not report criteria needed to effectively optimize chemical performance. In this presentation, testing results which identify the chemical performance roles for CO2 scrubber components will be reported, and specific component chemical activities will be linked to both duration and CO2 absorption capacities. Chemical components being evaluated include hydroxyl, superoxides, metal, and amine active sites, distributed in salts, zeolites, metal-organic frameworks, and microporous materials. INTRODUCTION CO2 absorbents and oxygen sources are at the heart of closed circuit breathing air supply systems used in mining escape and rescue operations. CO2 absorbent technology was first developed for diving rebreathers and has been in use for over a century. Typically these devices include a soda lime formulation of pellets in the 8-12 mesh range. Larger 4-8 mesh particles are used in medical grade “low-flow” applications, since these particles present a lower flow resistance regime more amenable for use with resting individuals. Potassium superoxide and lithium hydroxide formulations are also used, where in each case the formulations involve bulk solid pellets or materials affixed to surfaces. CO2 capture technologies are now under intensive study in the energy and automotive industries, where the pursuit of optimal combustion processes has led to the development of new materials to capture, convert and store CO2, oxygen and carbon monoxide gases. Recent advances in nano-structured and high surface area catalysis have produced novel materials demonstrating chemical performance improvements in these industries, and these improvements may now also be adapted to enhance chemical efficiency and performance in escape and rescue devices. Higher surface area materials offer promise for improving the efficiency, or decreasing the burdens associated with the use of closed circuit respiratory protective devices containing CO2 absorbents. Novel chemicals that display advantages in chemical performance or decreased burden will be examined for inclusion in developing systems such as the next-generation closed-circuit mining escape respirator or refuge alternatives."

Jan 1, 2018

By Warren D. Stanford

The Alligator Ridge mine is a near-surface gold mine located in a remote area 113 km (70 miles) northwest of Ely, NV. The deposit was discovered in 1976 by a lone prospector working under a grubstake contract for Amselco Minerals Inc. Evaluation of mine potential proceeded quickly. Favorable drilling results led to feasibility and mine design studies by the end of 1978. Mine construction began in early 1980. By September of that year, the process plant was fully operational. The first gold was poured a few months later. Alligator Ridge is designed to produce 1.9 t (60,000 oz) of gold each year. The projected mine life, based on proven reserves, is to mid-1988. However, Amselco is actively conducting exploration nearby for additional reserves to extend the mine's life. Amselco, a subsidiary of the British Petroleum Co., is based in Denver, CO. The company is mine operator and jointly owns the project with Nerco Minerals Inc., a wholly-owned subsidiary of Pacific Power and Light. Alligator Ridge is Amselco's first US mining operation. Geology Alligator Ridge, so named because it appears in outline to be an alligator at rest, contains disseminated micron gold embedded in iron-streaked siltstones. Although definitive conclusions have not been drawn on age and origin, the gold ore bodies are probably young by geological standards. They were formed in a recent volcanic period still evidenced in parts of Nevada by geysers and hot springs. As these superheated solutions rose through the permeable siltstones, they deposited minerals in the rock and formed the present gold ore bodies. During 1977, an extensive soil geochemical sampling program with additional geologic mapping and outcrop sampling were conducted. The results generated several drill targets. Initial drilling was performed in November and December 1977, and ore grade mineralization was encountered in the first drill hole. The Alligator Ridge mine is unusual in relation to other and more recent western US mineral discoveries in that it occupies an area that had no previous mining history. The ore deposits are hosted in upper Paleozoic sedimentary rocks that consist predominantly of a thick carbonate sequence. The main ore host is the Devonian-Mississippian Pilot shale, which occurs locally as a sequence of thin bedded calcareous, carbonaceous siltstones and claystones. The maximum observed thickness of the Pilot section in the mine area is about 140 m (460 ft). Rocks in the Alligator Ridge area have been folded into a series of low amplitude anticlines and synclines that strike north-south and plunge to the south at about 20°, with limbs that dip nearly 20°. The folds have been truncated and deformed by later high-angle faults that generally strike northwest. Although multiple stages of movement are evident on the fault systems, the youngest period of activity is along the major northeast trend. The predominant structural pattern in the area is of the basin- and range-type high angle normal faults. Alligator Ridge is actually a horst block between two basin and range faults. Vantage Ore Deposits There are three principal ore deposits within the Vantage Basin and several smaller satellite mineralized areas. The three Vantage deposits are encompassed in a mineralized zone that covers an area 915 m (3,000 ft) long and 305 m (1,000 ft) wide. All mineralized zones have been outlined by more than 600 rotary drill holes, with an average depth of 150 m (500 ft). Mineralization occurs in both carbonaceous and oxidized rocks. The carbonaceous gold-bearing material is not amenable to current heap leaching practice. Therefore, only oxidized ores are now treated. The carbonaceous gold-bearing material is segregated and stockpiled as it is encountered during mining. The three ore bodies occur along a north-northeast strike, with mineralization becoming progressively deeper from north to south. The ore block dimen-

Jan 6, 1984

By R. Gray

"Experience from Australia has identified what is referred to as non-conventional surface subsidence behaviour. This occurs under irregular surface topography, resulting in valley closure, valley floor uplift or “upsidence”, and far-field horizontal movements – even occurring beyond conventional “angle of draw” limits. This paper discusses such behaviour recently observed in Pennsylvania and focuses on the 2005 case of Duke Lake Dam in Ryerson Station State Park. In July 2005, there was a significant increase in water leakage through a number of growing cracks in the dam leading to the dam being breached to avoid an uncontrolled failure. An underground longwall mine was located approximately 900ft to the north, mining at depths of 330 – 720ft. Investigations (including a subsequent ground movement monitoring program) found a range of evidence in the vicinity suggesting that valley closure and far-field horizontal movements may have occurred resulting from the adjacent mining. The paper discusses the phenomenon of non-conventional subsidence behaviour and the Ryerson State Park case study, including an assessment of mining, geology and subsidence impacts and suggested ground behavioural mechanisms. INTRODUCTION Non-Conventional Subsidence The conventional understanding of coal mine subsidence on which most current subsidence understanding and prediction techniques are based, includes the concept of angle of draw which effectively limits the lateral extent of subsidence effects and impacts. Within this zone – above and marginally beyond the boundary of mining – downward vertical subsidence is the dominant component, together with localised horizontal movements towards the mined region, with related tilts and strains. However, more recent experience from Australia over the last two or three decades has identified what is referred to as non-conventional surface subsidence behaviour. This is found to occur in areas of irregular surface topography or variable terrain, and is characterised by phenomena such as valley closure, valley floor uplift or upsidence, and far-field horizontal movements, all of which can occur beyond the conventional angle of draw limits. NSW Department of Planning (2008) defined the conditions for both conventional and non-conventional subsidence behaviour as follows: “The conventional or general model of surface subsidence, which finds worldwide acceptance, is based on assuming the following site conditions:"

Jan 1, 2015

By Aaron Jones, Guy Reed, Russell Frith

"In 2017, one of the international authorities on coal bursts, Dr. Chris Mark, published a paper entitled “Coal Bursts that Occur during Development: A Rock Mechanics Enigma,” in which several relevant technical issues were identified, the most pertinent being:i.whilst development coal bursts are commonly associated with geological faults, understanding which specific faults result in burst-prone development mining conditions and why, remains undefined.ii.conventional wisdom in relation to strong roof and floor geology of the coal seam might be limiting, based on certain burst examples in Colorado.iii. development coal bursts can occur without the local ground stresses being substantially elevated from their in situ levels.This paper outlines what is considered to be a credible, first-principles, mechanistic explanation for these three current development coal burst conundrums by reference to early published coal testing work examining the significance of a lack of “constraint” to coal stability and an understanding of how very specific structural geology and other geological features can logically cause this to occur in situ, albeit on a statistically very rare basis. This basic model is examined by reference to published information pertaining to the development coal-burst that occurred at the Austar Coal Mine in New South Wales, Australia, in 2014 and from the Sunnyside District in Utah, USA.The “cause and effect” model for development coal bursts presented also offers a meaningful explanation for the statistical improbability for what are nonetheless potentially highly-destructive events, being able to explain the statistical rarity being just as important to the credibility of the model as explaining the local conditions associated with burst events.The model could also form the basis for a robust, risk-based approach utilising a “hierarchy of controls” to the operational management of the development coal burst threat. Specifically, these include the use of pre-mining predictions for likely burst-prone and non-burst-prone areas, the use of the mine layout to avoid or at least minimise mining within burst-prone areas if appropriate, and finally the development of an operational Trigger Action Response Plan that reduces the likelihood of inadvertent roadway development into a burst-prone area without suitable safety controls already being in place."

Jan 1, 2019

By John M. Hill

Automation technology has many facets, some well tested and proven, some yet to be put to the acid test of economic reality. In this paper, we will limit our purview to the former. Consider, if you will, an automated handling system combining high-speed conveyors and automatic devices on-line which not only provide signals for routing and sorting, but also format those signals for the production of manufacturing, inventory, shipping and billing paperwork. This is not futuristic, but practical and a realistic accomplishment. Therefore, the following discussions will address today's challenges not with tomorrow's solutions, but rather, with an established technology which is playing an increasingly prominent role in materials handling systems. Until recently, relatively modest importance has been attached to the timeliness of information feedback from the production or assembly line, warehouse or distribution center. Thus, initial applications of automatic identification equipment focused almost exclusively upon the control of materials flow - that is, routing, sorting, etc. However, these systems have performed successfully and quietly established an enviable track record as reliable materials control tools.

Jan 1, 1973

By Randall Morris

After years of steadily declining employment and production, the U.S. coal industry is having a moment. In 2016, when Donald Trump was running for U.S. President, he cast a spotlight on coal mining in his campaign speeches, promising to end the “War on Coal.” Fast forward to 2025. On the first day of his second term, President Trump signed the National Energy Emergency Act, which emphasizes domestic energy production as a matter of national security and focuses on incentivizing domestic energy resources. Then on April 8, President Trump issued an executive order opening federal land to coal mining to reinvigorate “America’s beautiful clean coal industry.” As the nation seeks to identify reliable solutions to meet its ever-growing energy needs, the administration is going all in on proven, reliable and readily available natural resources, including coal. This means the coal industry is positioned to play a pivotal role in the administration’s stated energy policy, and highwall mining could be an integral factor in helping the industry optimize the extraction of ore to make the most of this moment. The White House noted in a statement that the United States’ “abundance of energy and natural resources … have historically powered our Nation’s economic prosperity” and vowed to remove regulations that have hindered developing these resources — regulations that resulted in job reductions and higher energy costs for U.S. consumers, while weakening national security. “There has been an increase in electricity prices in the United States of over 30 percent in the past four years,” said Rich Nolan, president and chief executive officer of the National Mining Association (NMA). “This administration wants to focus on that, inflation and on increasing electricity availability to help lower the price over time by incentivizing energy policy. Coal is definitely a high priority for this administration.” Part of the White House’s strategy is to facilitate investment in coal-fired plants. The shift comes at a time when the reliance of coal-powered energy plants has been waning. According to the U.S. Energy Information Administration, 7.5 GW of electrical capacity from coal-fired plants was retired in 2024, following the retirement of 22.3 GW of electric generating power the two years prior.

Jun 1, 2025

By G. J. Schneider

The higher stress zone adjacent to an underground opening causes a velocity anomaly that can be mapped in favorable conditions with an acoustic cross-borehole logging system. Bureau personnel used a specialized system at the Colorado School of Mines test site near Idaho Springs, Colorado, to locate the Edgar Mine tunnel and its associated stress anomaly. Data from the logging system' were processed with a tomographic image reconstruction algorithm to map the opening and the location of the high velocity zone around the opening. The velocity imagery from tomographic analysis compared favorably with predictions from numerical modelling of the location of the stress anomaly.

Jan 1, 1988

By W. R. Hail

A proactive design and construct approach was used to remediate the Warm Springs Ponds Complex near Anaconda, Montana under "Superfund". The pond complex is used for treatment/settlement of heavy metals and is a repository for 19,000,000 cubic yards of tailings, precipitates and associated sediments. Remediation has resulted in treatment/settling capacity for flows up to the 100-year flood (3,300 cfs); expansion from 5 to 11 ponds in series requiring 12.5 miles of new or improved embankments with associated hydraulic structures; flood protection for the 0.5 Probable Maximum -Flood (PMF) (70,000 cfs); and closure of exposed tailings along with aquatic and terrestrial habitat enhancement.

Jan 1, 1995

By Alice S. Allen, James Paone

SURFACE SUBSIDENCE IN MINING The consequences of subsidence are becoming progressively more serious as the consumption of an ever- increasing quantity of minerals conflicts with the needs of an expanding population for surface land area. The inevitable result will be an increase in the amount of land area on which undermining is restricted because surface subsidence must be prevented. Designation of land areas that may be undermined, provided that subsidence is controlled and kept within specified limits, also will increase. The decisions as to which land is to be used for urban, agricultural, or other purposes clearly involve considerations that go far beyond the scope of mining technology. Under the authority assigned to the US Bureau of Mines (USBM) by the Organic Act (May 16, 1910) and its succeeding amendments and pursuant regulations (30 U.S.C. 1-1 1 ), the Bureau conducts scientific and technologic investigations concerning mining and its related problems. Subsidence-control demonstrations that have been conducted under this authority include projects in Wyoming, West Virginia, Illinois, and the Pennsylvania anthracite region. The problenls for technology arc to devise methods for extracting minerals with controlled subsidence in varying geologic settings and for calculating or predicting the amount, extent, and characteristics of the subsidence that accompanies the extraction of our principal minerals mined by high-tonnage methods so that logical choices can be made from the possible alternative approaches. Where underground minerals and fuels are mined and removed, the voids that are created underground generate strong imbalanced stresses in the surrounding and overlying rock strata. The resulting readjustments in the rock masses may cause subsidence of the ground surface. Subsidence implies vertical collapse, because the most conspicuous component of movement is downward. However, the downward component is accompanied by differential horizontal strains that may be more damaging to man-made surface structure.; than the more apparent vertical displacements. SUBSIDENCE CONTROL The most widespread method of alleviating potential subsidence problems in undermined areas has been to backfill mine voids with mine refuse or some other in- expensive material that provides lateral support to the remaining mine pillars and vertical support to the mine roof and overburden. Most USBM backfilling work has been conducted jointly with the Pennsylvania Department of Environmental Resources in the anthracite region of northeastern Pennsylvania. These joint projects were conducted under the authority of the Anthracite Mine Drainage Control Act of July 15, 1955 (Public Law 84-162, as amended), and the Appalachian Regional Development Act of 1965 (Public Law 89-4. as amended). In addition to the Appalachian and mine-drainage projects, the Bureau has either conducted or participated in demonstration projects to develop the "pumped- slurry" method of backfilling mine voids. Three of these projects were conducted in Rock Springs, WY. The first was a field test of the pumped-slurry technique, conducted in 1970 under the combined participation of the City of Rock Springs, the US Department of Housing and Urban Development, the Dowell Div. of the Dow Chemical Co., and USBM (Candeub, Fleissig, 1971). The objective was to demonstrate that a large quantity of sand could be hydraulically injected under pressure through a single borehole, and that filling of the mine voids would be essentially complete. In the earlier "blind-flushing" methods, involving sluicing material through boreholes by gravity, quantities per injection hole ranged from 15 to 765 m3 (20 to 1000 cu yd), and the mine voids were only partially filled. In the first test of the pumped-slurry method, approximately 14 900 m (19,500 cu yd) of sand were injected success- fully through a single borehole. Subsequent information obtained through 43 monitoring boreholes indicated that mine voids below 11 330 m2 (2.8 acres) had been filled. As a result of the successful initial test of the pumped-slurry process, USBM conducted additional backfilling demonstration projects using the new technique. The first full-scale demonstration was carried out in the Green Ridge section of Scranton, PA, between 1972 and 1974. This project proved the feasibility of using the new hydraulic-injection technique to back- fill dry mine voids, as well as flooded voids, and it demonstrated that crushed anthracite refuse could be used as easily as sand in the process. Stabilization was pro- vided for about 202 300 m2 (50 acres) of Scranton, having a population of approximately 1000. Additional demonstration projects at Rock Springs, WY, between 1973 and 1975, resulted in the stabilization of about 364 200 m2 (90 acres). The work was necessary to preserve the physical and economic well- being of the city, because there have been numerous occurrences of subsidence during recent years. A demonstration project completed in 1976 in Rock Springs brought the total stabilized area in that city to 647 500 m2 (160 acres). At a cost of about $3,000,000, a population estimated at 7000 persons and property values exceeding $18,000,000 were protected. Presently. USBM is participating in subsidence- control projects involving backfilling in Pennsylvania, Illinois, and West Virginia. Eleven demonstration projects were in progress by USBM in 1977-eight in the Pennsylvania anthracite region and three in bituminous areas of West Virginia (one) and Illinois (two). The estimated total property value is over $100,500,000, and the total cost of the projects is expected to be nearly $20,000,000. The demonstration projects are designed to adapt the pumped-slurry technique to a variety of subsurface conditions, to increase efficiency, and to reduce costs.

Jan 1, 1982

By Richard L. Gordon, William A. Vogely

ENERGY POI.ICY-PRINCIPLES AND THEIR PRACTICE Persistently, at least since the end of World War 11, governments have intervened broadly, deeply, and incoherently in major energy markets. If we take a broad definition of energy that encompasses gas distribution and electric power, we can observe regulations of even older vintage. This trend, of course, is not unique to energy. Expansion of government controls has occurred in many areas. The relevant basic question about energy regulation, therefore, is not why is energy special, but whether any general principles exist to explain the wisdom of existing regulations. This review takes place at a time, the middle 1980s, in which a massive onslaught is being undertaken against government regulation. However, the present chapter is influenced primarily by my observations of the failures of energy regulations and not by any inspiration from those ideologically opposed to government intervention. Several subquestions arise in policy appraisal. A primary need is to establish clear objectives and determine the consistency between these goals and the policies imposed. Thus, the first step is to set objectives. The next is to outline ways to attain these goals. However, it should be recognized that many apparently distinct options are economically equivalent. When the goal is to charge producers or consumers for something, it is possible to attain the same result through either government ownership or taxing private transactions. The tax can raise the price to the level the government would have charged if it were the owner. Creation of a Department of Energy is not necessarily any different from having separate energy agencies well coordinated by some small supervisory body. Thus, a distinction should be made between substance and form in policymaking. The critical substance concerns such matters as whether the government imposes financial penalties, incentives, or rules to attain a goal. Then, there can be many equivalent ways to implement the basic policy form. The second prior illustration suggests that one favorite question is how to attain proper integration of policy. At various times, voices on either (or even both) sides of the Atlantic have called for a coordinated energy policy. The U.S. Paley Commission made this a primary goal for future policy. The western European governments that were the founding members of the Coal and Steel, Economic, and Atomic Energy Communities spent much time in the middle fifties and much of the sixties trying futilely to agree on an energy policy. (See Gordon, 1970 for an annotated review). The energy price rises of the 1970s rekindled United States interest in coordination. However, astute observers of the problem such as O. C. Herfindahl of the United States and Maurice Allais (1 962) in France warned the discussions confused form with substance. The crucial issues were what were the goals and what were the best types of policies to attain such goals. Policy suffered, not from poor organization, but from discord about the goals and how to attain them. All this suggests that we need principles to guide policy appraisal. The branch of economic theory known as welfare economics concentrates on providing guidance about the problems of policymaking. The theory examines both what

Jan 1, 1985

By C. A. Rowland

Introduction Rod mills are horizontal, cylindrical, rotating, tumbling mills in which steel rods, that are usually about 6 in. shorter than the length of the grinding chamber, are used for grinding media. Fig. 33 shows a cutaway view of a rod mill. Rod mills were first used around 1910 because of their ability to grind in open circuit, consistently produce a uniformly sized prod¬uct, give greater continuous availability, and give lower maintenance costs. They have basically replaced roll crushers and coarse grinding ball mills in comminution flowsheets. The present 20-ft limit on rod length, based on rod manufacturing methods, and the pulp flow char¬acteristics, that influence mill capacity, have established the maximum rod mill sizes' of 15 x 21 Vs ft using 20-ft rods and drawing from 2,200 to 2,300 hp. Rod Mill Uses. The principal uses for rod mills are: preparing feed for ball or pebble mills, grinding gravel or aggregates to the size analysis required for making concrete sand, preparing coarse agitator feed for leaching operations, and for primary grinding circuits, particularly in industrial mineral applications. Wet grinding is the most frequently used grinding process for rod milling. There are a few special cases where dry rod milling is used. Preparing feed for ball or pebble mills is the most common use for rod mills. In ferrous and nonferrous ore concentrators, wet open-circuit grinding is used to prepare ball-mill feed. Figs. 34 thru 37 show the four basic grinding circuits used in these concentrators. In rod mill-ball mill grinding circuits, where the rod-mill discharge contains 25% or more of the grinding circuit product-size material, the rod-mill discharge can be fed to the ball- or pebble-mill classifier as shown in Fig. 34. This is the most frequently used rod mill-ball mill circuit in the nonferrous ore concentrators. In a few concentrators such as Anaconda's Weed concentrator,55 the rod mill discharges to one classification stage which makes the same or a slightly coarser particle-size cut as the classifiers used to close the ball- or pebble¬mill circuits, as shown in Fig. 35. In concentrators where rod mill-ball mill circuits are used to grind low grade magnetic iron ores such as Reserve Mining Co., Silver Bay, Minn.; Erie Mining Co., Hoyt Lakes, Minn.; Eveleth Taconite Co., Forbes, Minn.; US Steel, Mt. Iron, Minn. and Atlantic City, Wyo.; Inland Steel-Jackson County Iron Co., Black River Falls, Wis.; and The Cleveland-Cliffs Iron Co., Adams mine, Kirkland Lake, Ont., the rod mills discharge to rougher magnetic separators (cobbers), the concentrates from which are fed to a ball milling stage as shown in Fig. 36. The same basic circuit is also used with gravity concentra¬tion methods such as spirals (Hanna Mining Co., Groveland, Mich.), tables (St. Joe Minerals, Bonne Terre, Mo.), and jigs. When the rod-mill discharge contains less than 25% of the grind¬ing circuit product size, this indicates an ore that does not readily produce the fines needed to help carry the coarse feed into the ball charge. When this occurs, the fines in the rod-mill discharge are needed in the ball mill or pebble mill so the rod-mill discharge flows direct to the second-stage mills as shown in Fig. 37. Rod mills are used to make feed for open-circuit ball mills such as those used in wet grinding cement raw material (American Cement, Brennan Ave¬nue plant, Detroit, Mich., and Port Huron, Mich., plant, and at the South Dakota State Cement plant, Rapid City, S. Dak.). Grinding gravel or aggregates to the size analysis required for making concrete sand is used in areas where natural sand of the proper particle size gradation required to make concrete is not availa¬ble. Three-quarter inch crushed aggregate is ground to 4 mesh using center peripheral-discharge rod mills (Fig. 38) operating in open circuit. US Corps of Engineers specifications state that the sand product be 93-100% passing 4 mesh and contain no more than 3-7% passing 200 mesh. It may be necessary to classify the rod-mill discharge to remove any excess -200 mesh sand produced in the rod mill. Particu¬larly when processing aggregate with high abrasion indices, center peripheral-discharge rod mills are used instead of hammer mills, fine bowl crushers, and crushing rolls for the production of specification sand. If the -4 mesh size fraction of the rod-mill feed is removed

Jan 1, 1985

By Yuanhong Qi, Xun Fu Wang, Tao Fu, Kunkun Cui, Yingyi Zhang, Jie Wang, Junmao Qie

With the sharp decrease of sulfide nickel resources, the nickel laterite is becoming more attractive as nickel oxide, nickel matte, and nickel-iron. This study investigated the mineral phase structure, chemical analysis, thermal properties, and element distribution characteristics of the rotten rock layer deposited in the Southeast Sulawesi Ophiolite Belt. The results show that the nickel laterite deposited in Southeast Sulawesi Island, Indonesia, belongs to the typical high-nickel and low-iron garnierite-type laterite. The concentrations of nickel and iron of the nickel laterite are 1.99 wt% and 17.55 wt%, respectively. The serpentine, olivine, clay, chlorite, hematite, and magnetite are the major minerals, and the pyroxene, actinolite, limonite, and chromite are the minor minerals in the nickel laterite in Southeast Sulawesi, Indonesia. Serpentine and olivine are the main nickel minerals with an average nickel concentration of 3.65 wt% and 1.73 wt%, respectively. The Fe and Ni have homogeneity and symbiosis in the serpentine and olivine, and their concentrations are often positively correlated.

By James L. Kelley

The Twin Buttes Mine, one of the more recently developed large copper mines in the United States, is in the Pima Mining District about 25 miles south of Tucson (Figure 1). Other copper producing mines in the district are the Esperanza-Sierrita mining operations, five miles to the southwest and the Pima and Mission Mines, seven miles to the north. Copper metal production from the Pima District in 1974 totaled 276,728 tons and the Twin Buttes Mine's share was 46,473 tons or about 17%.' The district's copper production was 31% of Arizona State's production and nearly 17% of the production from the United states in 1974. The Pima District thus ranks as one of the major copper producing areas in this country.

Jan 1, 1976

By Basar Arioglu, Jaeung Kim, Mehmet Öztürk, Jinmoo Lee, Dongho Lee, Taek-Kon Kim

"Istanbul Strait Road Tube Crossing Project (Eurasia Tunnel) includes 3.34 km of a bored double-deck tunnel under the Bosphorus Strait, at a maximum depth of 106 m from the sea level, and 1 km of twin NATM tunnels on the Asian side. The region’s variable geology, hydrology and propensity for seismic activity, combined with high water pressure and large-diameter/double-deck tunnel configuration, make the Eurasia Tunnel one of today’s most challenging and complex projects under construction. Due to the site’s proximity to the active North Anatolian Fault, the tunnel is designed to withstand a 7.5 magnitude earthquake. The tunnel penetrates through both the Trakya bedrock (on both European and Asian sides) and the alluvial sediments at the bottom of the channel. The tunnel is designed to accommodate differential displacements by introducing seismic/flexible joints at proper locations at the transition zones between rock and soft soils. Tunnel fire is also a significant design consideration for undersea tunnel due to that the rubber protecting it in close proximity of the seismic joint should resist a fire for long term safety and durability. This paper mainly focuses on the design for method of tunnel response analysis in transverse and longitudinal direction against seismic demands relating with the seismic joints. INTRODUCTION Istanbul Strait Road Tube Crossing Project (Eurasia Tunnel) will build and operate a roadway tunnel under the Borphorus connecting Kazlicesme on the European side and Goztepe on the Asian side, to provide additional road-access across the Strait and consist of three main parts as shown in Figure 1."

Jan 1, 2016

By P. K. Kankar, Manoj Khandelwal, Ramesht Shukla

One of the utmost severe mining catastrophes in underground hard rock mines is rock burst phenomena. It can lead to damage to mine openings and equipment as well as trigger accidents or even threat to life as well. Due to this, a number of researchers are forced to study some easy-to-use alternative methods to predict the rock burst occurrence. Nevertheless, due to the extremely multifaceted relation between mechanical, geological and geometric factors of the mines, the conventional prediction methods are not able to produce accurate results. With the expansion of machine learning methods, a revolution in the rock burst occurrence has become imaginable. In present study, three machine learning methods, namely XGBoost, decision tree and support vector machine, are utilized to predict the occurrence of rock burst in various underground projects. A total of 134 rock burst events were gathered together from various published literatures comprising maximum tangential stress (MTS), elastic energy index (EEI), uniaxial compressive strength and uniaxial tensile stress (UTS) that have been used to develop various machine learning models. The performance of machine learning methods is evaluated based on the accuracy, sensitivity and specificity of the rock burst prediction.

Mar 17, 2021

By R. W. Lake

The decision to develop an ore body can lead to multi-million dollar profits, or equally substantial losses. Accordingly, the effort required to adapt a valuation model to the specific proposal at hand, or even the development of a new model from basic principles, is clearly warranted. In the formulation of a model of this nature, one is faced with some major questions. For example, with the long term obligations that it implies, on what basis should a decision to initiate mining operations be made? Furthermore, how can the vagaries of inflation and the uncertainties that shroud the future be accommodated? Beyond the general principles by which mineral deposits are evaluated, specific cost behaviour is a function of the geology of the deposit, and of the mine design. Moreover, mine design, during the life of the mine, must be a continuing process somewhat akin to dynamic programming. An initial, apparently optimal, design is selected and mining commences. With production, a continual process of information updating leads to revisions. Thus if the maximum value is to be obtained, the mine design must be adjusted to conform to the changed conditions.

Jan 1, 1977