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By B. A. Slaker, T. Miller, M. M. Murphy

An underground limestone mine in eastern Ohio was experiencing significant floor heave and roof falls, attributed to high horizontal stresses. Areas of the mine showing floor heave were monitored with roof-to-floor extensometers and photogrammetry surveys to determine the rate and magnitude of heave. Extensometer data were recorded hourly at four locations across adjacent entries while photogrammetry surveys of the floor were performed at the same locations every two to five weeks. A final survey was performed using an I-Site 8200 laser scanner. Following instrumentation, floor heave up to 10.1 cm (4 in.) was measured by the extensometers, photogrammetric reconstructions and laser scanner over a six-month period. The extensometers were biased by the location where they were placed, failing to consistently capture the location and extent of floor heave and cracking. The photogrammetry surveys were not precise enough to capture small magnitude movements. Mining in the area was halted and within several months the floor movement and incidence of roof falls were significantly lessened.

Jan 1, 2018

By Bernard F. Anderson

INTRODUCTION In this chapter, the term "down-the-hole drill" (DTH drill) is used as a generic name that encompasses the various trade names and other references such as "downhole drill," "in-the-hole drill," etc. This chapter is limited to a description of DTH drills used in stoping large underground ore bodies. DTH drills differ from conventional drills by virtue of the placement of the drill in the drill string. The DTH drill follows immediately behind the bit into the hole, rather than remaining on the feed as with ordinary drifters. Thus, no energy is dissipated through the steel or couplings, and the penetration rate is nearly constant, regardless of the depth of the hole. Since the drill must operate on compressed air and tolerates only small amounts of water, cuttings are flushed either by air with water-mist injection or by standard mine air with a dust collector at the collar. HISTORICAL DEVELOPMENT Mine managers have long known the economies enjoyed by quarry and open-pit operators in producing large quantities of ore. The savings are due primarily to the availability of massive equipment, capable of drilling large blastholes to reduce the amount of drilling, increase the fragmentation, reduce secondary blasting, and im¬prove the flow of the product. In an attempt to reduce underground mining costs, various methods are used for long-hole drilling, includ¬ing standard pneumatic percussion drifters and diamond drills. These systems have their shortcomings; percus¬sion drills are limited to small hole sizes and they ex¬perience excessive deviation and significant loss of energy with increased depth. The diamond drills provide deeper and straighter holes, but only at high cost. Both systems suffer from high noise levels, low penetration rates, and poor explosives distribution, among other problems. When the mining companies approached the drill manufacturers for a compact and portable large-hole jumbo for underground use, they specified not more than 1 % deviation on 60 m (200 ft) of vertical hole and a penetration rate of 15 m/h (50 fph). On Dec. 23, 1960, a test unit was placed in service in Montana and met the performance criteria. Though lacking the so¬phisticated features available today, the economies of surface blasting were brought underground. Unfortunately, the first system did not gain immedi¬ate acceptance in the industry. Among the factors con¬tributing to its demise were resistance to change, the need to alter development methods for the ore bodies, and a lack of flexibility in moving the rig from setup to setup and from level to level. In 1972, the mining industry again challenged the drill manufacturers to provide a workable jumbo that would combine compactness, ease of maintenance, relia¬bility, and efficiency, all on a self-propelled chassis. The manufacturers responded by providing improved jumbos, which have been accepted with enthusiasm throughout the mining industry. Today's DTH jumbos are capable of drilling from 100 to 200 mm (4 to 8 in.) diam holes that can be reamed to even larger diameters. The holes can be drilled to depths of 150 m (500 ft), depending upon ground conditions and the capability of the jumbo to retrieve the steel and drill. Fig. 1 illustrates a typical DTH jumbo. APPLICATIONS The uses to which DTH drill jumbos have been put are quite numerous, with new uses being found regularly. For convenience, these uses may be classified as primary blastholes and nonblasting holes. Primary Blastholes The original purpose for the development of the DTH jumbo was for drilling primary blastholes that could be mined by open-stope methods. Prior to the advent of the DTH jumbo, extensive development was required before production drilling could begin. Sub¬levels were required to allow access for column-and-arm stopers or ring/fan jumbos, to the extent necessary based on the effective penetration of the chosen machine. With the DTH jumbo, the mine engineer is able to reduce preproduction time and development costs. How¬ever, the most significant saving results from an im¬proved cost per ton of broken ore in the production phase. To utilize a DTH system, only a top heading and drawpoints are necessary. The top heading can be the width of the ore body with a 3.7-m (12-ft) back. A drop-raise pattern is drilled and shot to begin the stoping operation, providing a free face for subsequent blasting. A typical layout is illustrated in Fig. 2. The advantages of this system include: 1) Drilling and blasting are independent operations, and blasting can be performed at a rate congruous with the mine's ton-per-day capacity. 2) The development layout is simplified. 3) Good explosive distribution is achieved, provid¬ing more uniform fragmentation. 4) Environmental conditions for operators are im¬proved, including improved safety with all work directed downward (not overhead), lower noise levels, little fog, and a reduced dust count. 5) Improved production per manshift. 6) Simplified and easier operator work cycles. 7) Reduced cost per ton of product. 8) Fewer holes lost due to ground shifts. Nonblasting Holes With the introduction of the compact DTH jumbos, other practical uses became apparent, including the drilling of: 1) Holes for sand fill, from level to level and from level to stope. 2) Drain and dewatering holes. 3) Power and communications cable holes.

Jan 1, 1982

By James S. Browning

In 1975 bituminous coal and lignite production in the United States reached an all-time high of 637 million tons, an increase of 6 percent over production in 1974. The output, valued at $11.9 billion f.o.b. mines, was produced at 5,100 mines in 24 states (6). Coal mining is the largest mining industry in Alabama. Production from Alabama's mines in 1975 was over 21 million tons, and present projections forecast a steady increase in production, with tonnages almost doubling by 1985 (5). Of the total quantity of coal produced, about 16 million tons were consumed in electric power generation and the remainder was used for metallurgical coke production, extraction of chemicals and petroleum based products, and power for industry. The fact that 75 percent of Alabama's power is generated by burning coal attests to the importance of this fossil fuel to the State. Approximately 14 million tons of coal were produced by strip-mining methods in Alabama during 1975 and about 7 million tons were produced by underground mining during the same period. Surface mining is expected to continue at about 14 million tons per year, but by 1980 underground coal mining is expected to increase to about 25 million tons (3). About 7 million tons of surface-mined coal in Alabama is subjected to some means of washing or cleaning. The methods used are screening accompanied by heavy media separation, jigging, tabling and flotation. Some of the simpler approaches employ screening and jigging, or tabling. Except where flotation is used, the screen undersize fraction (finer than 0.25 inch) is rejected, with the result that 10 to 15 percent of the coal is lost. Thus, in the State of Alabama an aggregate of about 1 million tons of coal is wasted annually in the fines which are impounded from treatment of surface-mined coal. The use of the Humphreys spiral to concentrate fine coal was practiced as early as 1947. At that time the Hudson Coal Company (1) used Humphreys spirals to concentrate anthracite fines. In 1950, the use of spirals to treat fine-size

Jan 1, 1977

By J. Baz-Dresch

A custom-designed shotcrete system, consisting of an 8-m3 (10-cu-yd) transit mixer and a shotcrete spray boon carrier, is used by a two-man crew to transport and place up to 25 m3 (32 cu-yd) of steel fiber reinforced, dry, silica fume shotcrete per 11-hour shift. Shotcrete is custom blended by a local supplier and delivered predampened. Mix design and quality control are performed with a computer program that develops and graphs a properly balanced mix based upon the materials sieve analyses.

Jan 1, 1992

By Cliff Holloway

The past year has been difficult for Canada's primary industries. The mining, oil and forestry industries have been hit by low prices and a reduced demand for natural resources. Foreign competition, militant environmentalists, the breakdown of the Asian and European economies and Canada's shrinking dollar have all put additional pressures on the commodity purchaser to buy smarter. It is easy to appreciate why operations and maintenance supervisors want the best performing product. It makes good sense. The challenge is to source that quality product while staying within the budget. The bottom line (price), however, often becomes the control- ling factor, usually at the expense of quality and performance. This is short-term thinking, often with expensive consequences.

Jan 1, 1999

Within the research project "Mine Development" funded by the "Austrian Fonds zur Forderung der wissenschaftlichen Forschung (FWF) " (funds for scientific research) between 1991 and 1993 150 underground hardrock mines in Europe, Northern America, Australia and Japan have been visited to analyze their general design and layout. The main aim of the project was to develop strategies for accessing new underground hardrock mines and to establish a mine planning database. The investigation included mines in high developed countries only, with a comparable labor cost situation. This paper presents the results of one part of the project, which deals with investigations into the influence of different parameters on the design of the primary access for a mine.

Jan 1, 1995

By Charles A. Beasley

Coal conversion to electricity or to substitute natural gas requires a significant quantity of natural and human resources including, in addition to the coal resource base, land, water and the construction and operating labor force. Each method of coal conversion has its advantages and disadvantages relative to conversion efficiency, preferred method of resultant energy transportation, resources consumed, and impact on the environment. Regulations which have been passed in recent years to maintain or restore the pre-project environment can add significantly to the capital and operating costs of both a conversion facility and its associated mine.

Jan 1, 1983

By J. M. Dean

With the continued downward pressure on coal selling prices, mine management must make its operations as efficient as possible. The problem is the same one throughout the mineral industries, streamlining operations to maintain competitive mining costs (Born, 1991). There has been a great deal of research into better using production manpower. But the story is different for operations support personnel. Traditionally, planning man-power requirements are done annually, with modifications to the operating plan occurring generally quarterly. On the other hand, the demands on manpower are often dynamic, being responsive to changing productivity levels ,mine conditions (including water influx, bad roof, poor floor)and unanticipated project requirements (responses to machine breakdowns or a new section setup requirement because of a drop in coal quality in another area). Such changes may impact the manpower structure significantly. At times they may cause serious labor relations problems concurrently. Realignments and the generation of instability in the workforce because of active job switching (bidding) are a result. Most responses by coal operators are reactive rather than proactive, a situation that could be mollified by more accurate and detailed planning of predictable manpower requirements. A manpower planning tool is needed that takes into consideration such things as changing productivity levels and conditions as manhour requirements for different work areas are planned, rather than blindly allocated through traditional staffing modes.

Jan 1, 1995

Reaction kinetics for gold dissolution in acid thiourea solutions were investigated using formamidine disulfide as an oxidant. For the conditions studied it appears that a surface reaction limits the rate of gold dissolution. The rate was found to be first order with respect to thiourea concentration and half order with respect to the concentration of formamidine disulfide; the apparent activation energy for the reaction was 10.40 kcal/mol (43.40 kJ/mol); and the reaction rate was independent of pH for the pH range 1.0 to 3.0.

Jan 1, 1999

Production reporting is a natural computer application and is often one of the first applications implemented by new computer users. Automation of a manual reporting system is a good place for new computer users to gain computing experience because generation of basic reports - is fairly straightforward, and automation can often be justified easily on the basis of clerical cost savings. Computers are particularly well-suited for reporting applications which generally satisfy the criteria for effective computerization. Three characteristics must be present to effectively utilize a computerized system: 1) The potential application must be precisely definable. If an algorithm for data processing cannot be developed, data cannot be processed. 2) The operation to be performed must be repetitive. If a particular function is only going to be performed once, computerized systems development is probably not justified. 3) The volume of the data to be processed must be relatively large. If only a few items of data must be manipulated, manual methods are probably adequate. Although a computer can perform only a few functions (it can compute; it can make comparisons; it can rearrange data), it can perform these functions much faster and more accurately than a human being can. The ability to classify and reclassify data in a variety of ways and the ability to summarize data make the computer an ideal tool for production reporting. Production reports can be classified into three major categories, depending on their purpose. Reports can be used for (1) informative, (2) analytical, and (3) control purposes.

Jan 1, 1979

By Mehdi Noori, Atefeh Azizitorghabeh, Fereshteh Rashchi, Ataollah Babakhani, Sarah Mahmoudi

The focus of this research was to evaluate the synergistic effect of bis(2,4,4-trimethylpentyl) phosphinic acid (CYANEX 272) and di-(2-ethylhexyl) phosphoric acid (D2EHPA), diluted in kerosene, on the extraction and separation of Co(II) and Li(I) from synthetic sulfate solution. The results indicated that using a mixture of CYANEX 272 and D2EHPA was efficient in extracting and separating Co(II) from Li(I). The optimum ratio of CYANEX 272/D2EHPA was found to be 5:1, in which the highest separation factor was obtained (5973.23), and ΔpH0.5 was 4.10. Adding tributyl phosphate (TBP) as a modifier and increasing the temperature improved the metals’ separation rate and extraction efficiency. Thermodynamic studies were also carried out, and ΔH, ΔS, and ΔG values were computed, revealing the endothermic nature of Co(II) and Li(I) extraction by CYANEX 272/D2EHPA mixture. The conducted experiments for the McCabe–Thiele diagram showed the possibility of using two stages to extract over 99% of Co(II) and Li(I). Slope analysis and Fourier transform infrared spectroscopy (FT-IR) were employed to comprehend the Co(II) and Li(I) extraction mechanism using a mixture of CYANEX 272 and D2EHPA.

Jan 17, 2022

By Robert L. Russell

The Bunker Hill Mine, located in the Coeur d'Alene Mining District at Kellogg, Idaho, has been a major producer of lead-silver-zinc ores since its discovery in 1887. The mine has produced over 29 million tons of ore from some 20 to 25 veins and ore zones, and now covers an area approximately one mile in length and one-half mile in width. The active section of the mine extends from 2500 ft above sea level to 1600 ft below sea level. Production is presently at the rate of about 1700 tons of ore per day. A two-mile adit, the Kellogg Tunnel, at the 2500 elevation, provides access to the main shaft area. Ore is hoisted to the adit level through a 5000-ft, 500-inclined shaft, extending to the lowermost haulage level 1200 ft below sea level. Primary shaft service for men and materials is supplied by three major internal, inclined shafts equipped with double-drum hoists. Present production requires ten levels to serve for mainline track haulage. These range up to 5000 ft in length and are either 200 or 400 vertical feet apart. Also, many intermediate levels exist throughout the mine. The conventional and autoloader mechanized square-set and cut-and-fill mining methods used throughout the mine have been the subject of a recent paper(l). One-third of current production is from vein-type ore bodies which are long distances from main shaft areas. Such veins generally dip about 450, have relatively narrow widths of from 3 to 20 ft, and usually contain less than 500,000 tons of ore. For many years, ore bodies thus situated have been developed by means of a separate inclined, timbered service shaft-raise connecting two or more main haulage levels. These commonly range from 400 to 1000 ft in vertical extent and are equipped with 25 to 50 hp electric, single-drum hoists. Intermediate levels are driven as conventional track drifts at 100-ft vertical intervals between the haulage levels. Ore and waste from the intermediate levels are trammed to orepasses for delivery to the lowermost haulage level servicing an ore body. The final result may be visualized as a number of small mines within a large mine. The problems of high development costs and high total development time, and the large amount and high cost of providing materials handl ing and ore haulage service while producing from this isolated type of stope block, made it desirable to consider totally new approaches in developing and mining a number of similar areas.

Jan 1, 1971

By I. Chatterjee

The application of microwaves has a demonstrated potential for the ultimate removal of water from fine coal. The principle of microwave drying of fine coal is based on the selective absorption of microwaves by water. Coal is a poor absorber of microwaves. As a result, water can be removed from fine coal by selectively heating water molecules. One of the difficult problems drilling microwave heating is the exact determination of temperature in the core of the materials. The electromagnetic energy absorption in coal/water mixtures during microwave drying is controlled by several factors including the dielectric properties of the constituents. In this paper the dielectric properties of various ranks of coal are presented as a function of frequency and moisture content. The measured dielectric data are incorporated into electromagnetic and thermal models of coal which predict the energy absorption and temperature distribution during microwave heating.

Jan 1, 1990

By Clifford R. Porter

A 200 pound per hour Magnex Pilot Plant was designed and constructed. A non-compliance Eastern Coal which would generate more than 2.0 lb of SOZ per million Btu upon burning was brought into compliance (less than 1.2 lb of S02 per million Btu) during continuous operation of the pilot plant. Approximately 85 percent of the pyritic sulfur was removed while recovering 86 percent of the Btu of the feed coal. Pilot plant operation is summarized and preliminary economics presented. Present status of the Magnex Program is reviewed.

Jan 1, 1977

By S. Shankar

The phenomenon of re-entrainment is seen in many environments, such as sand dune formation, soil erosion, fugitive dust emission, spread of radio-nuclides from accidents involving nuclear weapons, etc. A thorough review of existing literature reveals that work on re-entrainment of dust in mine atmospheres is scant. The present study was undertaken as a part of on-going research in the Respirable Dust Center on the prediction of ambient dust concentrations in mine atmospheres (Ramani, 1983) to identify the contribution of dust re-entrainment to the spatial and temporal concentration in mine airways and included wind tunnel and in-mine studies. A set of seven experiments was performed in the Lake Lynn Laboratory Mine of the U.S. Bureau of Mines under controlled conditions. Two types of source coal dust, anthracite and bituminous, were subjected to airflow with a range of air velocities and walking by two different walkers. Six sets of instruments were used along the test section for sampling the airborne particles. The average air velocity just above the coal dust bed varied between 2.1 to 3.2 m/s. Due to re-entrainment as a result of the airflow conditions, the average respirable dust concentration in the center of the mine airway increased to 0.09 mg/m3 (standard deviation = 0.03 mg/m3) from an initial value of 0.02 mg/m3. The concentration of all (i.e., total) airborne dust increased to 0.17 mg/m' (standard deviation = 0.10 mg/m') from an initial value of 0.02 mg/m'. The action of personnel walking, however, caused higher amounts of re-entrainment. Average concentration of respirable and total dust at the center of the mine airway increased to values of 0.28 mg/m' (standard deviation = 0.12 mg/m3) and 1.53 mg/m3 (standard deviation = 1.0 mg/m3), from initial values of 0.03 mg/m3 and 0.05 mg/m3, respectively. It was observed that the dust concentrations were much higher near the floor, immediately at the end of the coal dust bed. Depending on the level of activity and the amount of dust deposited in mine airways, re-entrainment may become an important source of airborne dust away from the point of actual mining.

Jan 1, 1994

By A. J. Naldrett

Over the past six or seven years important new ideas have been developed concerning the origin of nickel sulfide deposits. To a large extent these have been stimulated by the major nickel discoveries of the Eastern Goldfields area of Western Australia (Woodall and Travis, 1969; Ewers and Hudson, 1972). Prior to these finds, the most important nickel camps were regarded as being associated exclusively with intrusive rocks such as the Nickel Irruptive at Sudbury or the intrusive peridotites at Thompson, rocks that were thought to have no close association with volcanism. Study of the Australian discoveries, coupled with work in South Africa (Viljoen and Viljoen, 1969) and Canada (Naldrett and Mason, 1968; Pyke, Naldrett and Eckstrand, 1973), has shown that volcanic rocks with true ultramafic compositions and extrusion temperatures of 1400 to 1600°C were a common feature during the Archean. Under certain circumstances economic concentrations of nickel sulfides have formed from these rocks, either settling to the base of their associated flows or accumulating in shallow intrusive feeders to the flows. The aim of this article is to show how these ultramafic rocks can be recognized, how the nickel deposits, if present, are likely to occur within them, and what special features characterize ore-bearing examples of the rocks.

Jan 1, 1975

By Robert E. Frey

Regardless of the mechanical design features of a particular air classifier certain basic principles apply. Specifically , there are two forces at work: 1. An air drag force 2. An inertial or centrifugal force. The air drag force has an increasing influence as particles become smaller. A very small low mass particle is easily carried along with an air stream even when turning a corner. Thus, fine particles follow the air away from the classifying zone. Inertial forces increase as the mass of a particle gets larger. Thus oversize particles tend to obey Newton's laws and respond to centrifugal forces or simply continue in a straight path when the airflow changes direction.

Jan 1, 1985

By R. W. Sayers

The Duval Corporation porphyry copper deposits at Copper Canyon and Copper Basin, though widely separated, form an economic unit requiring integrated exploitation. Contrasts in mineralization, host rocks, and mode of occurrence present unique mining and milling problems. Mixed oxide-sulfide ore is treated in extensive dump leaching facilities in both areas. Complex copper-gold-silver ore is treated in a 4,000 tpd mill at Copper Canyon. In both areas, hypogene metallization occurs within large aureoles of metamorphism and hydrothermal alteration related to quartz monzonite intrusions of mid-Tertiary age. Supergene processes further altered the rocks and enriched the hypogene protore. At Copper Canyon, hypogene copper and iron sulfides with gold and silver occur in fractures, as partial replacement of favorable beds, and as disseminations in Paleozoic sedimentary rocks. The lower part of the Pennsylvanian Battle Formation was a particularly favorable host. Metallization occurs to a lesser extent in quartz monzonite. Metal zoning is well developed. The deposits at Copper Basin consist principally of supergene copper minerals in arenites of the Cambrian Harmony Formation. Oxidation of hypogene copper and iron sulfides in tactite zones has formed at least two commercial deposits; intersections of fractures with favorable beds exerted important ore controls.

Jan 1, 1968

By Ahmet Tezcan, Zeki M. Dogan, Yalçin Kaytaz

Autogenous grinding in Turkey was first applied to quartzite where the mill is grate discharge type with an internal diameter of 2.99 m, having a length of 3.20 m and a capacity of as to 11.0 tons per hour. The second autogenous grinding was applied to a copper ore at Murgul Cakmakkaya Flotation plant of (KBI) Black Sea Copper Works having three mills 26 feet in diameter and 10 feet in length in close circuit with hydrocyclones. Recently, alterations were made in grinding circust by adding pebble mills. Furthermore, rubber liners and lifter bars were introduced pebble extractor and classifier were new features in the primary mills and circulating load was reduced by 20-50 tons per hour. At the end of these charges, capacity of each mill line was increased to 48 tons per hour with a full capacity of more than 9000 tons per day. Thirdly, autogenous grinding has been executed successfully on the slags of Samsun Smelting Plant of (KBI) Black Sea Copper Works with a mill of 20 feet in diameter and 6 feet on length having pebble mill following autogenous grinding.

Jan 1, 1992

By K. C. Nathsarma

An attempt was made to extract niobium oxide from ~98.5% Nb2O5 using solvent extraction processes. Nb2O5 is used as the feed material in carbothermic reduction processes aimed at producing high-homogeneity, super-conductor-grade niobium on a laboratory scale. The Nb metal used for superconductor applications requires a residual resistivity ratio (RRR) > 300, which in turn needs a stringent purity of Nb and allows impurities (substitutional and interstitial) in ppm levels only. In this paper, solvent extraction of niobium was studied under various experimental conditions, such as effect of different extractants, concentration of methyl isobutyl ketone (MIBK) in the organic phase and concentration of various acids. The concentrate was digested with hydrofluoric acid, with ammonium fluoride (NH4F) as a stripping agent. The extraction of niobium from low hydrofluoric- (HF-) bearing solution was found to be low. Thus, various concentrations of hydrofluoric acid and sulfuric acid, as well as hydrofluoric acid and hydrochloric acid, were investigated towards obtaining a maximum amount of niobium in the filtrate and a minimum amount of niobium in the residue. A McCabe - Thiele plot for extraction of niobium from the aqueous phase, HF-bearing solution using HCl with 85% MIBK in kerosene has been constructed to determine the O:A ratio and the number of stages of the process.

Jan 1, 2011