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By William X. Chavez

The Mantos Blancos copper-silver district, a major copper-producing area since 1961, is located on the Tropic of Capricorn about 45 kilometers northeast of the northern Chile port city of Antofagasta, as shown in Figure 1. Copper oxide minerals occurring as atacamite (Cu C1(OH)3) and chrysocolla (copper silicate-hydrate) were discovered in the district in the early 1900's (Knobler and Joseph, 1962). The mine is situated in the northern Atacama Desert, one of the most arid regions on earth, and presently receives less than 1 cm per year of precipitation. The extreme aridity of the Atacama Desert is thought to have prevailed since at least Middle Miocene time (Mortimer et al., 1978) when development of important supervene copper enrichment was slowed in many areas of northern Chile (e.g., Chuquicamata, Exotica). Despite the paucity of precipitation, landform development is mature, with large alluvial fans and alluvial-filled valleys covering much of the region. In addition, the aridity and presence of salts have led to the formation of a sub-surface cementing of alluvium and colluvium by halite-rich caliche ranging from a few centimeters to over 3 meters in thickness. These factors, resulting in poor outcrop exposure, make even reconnaissance mapping difficult.

Jan 1, 1983

By LeRoy D. Loy

The coal mining industry must be able to compete with alternate sources of fuel for the utility and industrial customers. If the industry is unable to control transportation costs, either due to government interference, or for other reasons, then mining costs must be kept down. Australia, South Africa, Canada, (and later Colombia) will take larger shares of the export market if mining costs are not kept competitive. The government's environmental regulations must be met without incremental increases in mining costs. Entrepreneurial instincts must be retained by the industry to provide for their investment in the future. What are the Problems with Existing Research? Government funding for coal mining research has been reduced or virtually eliminated. BCR (Bituminous Coal Research) is now a membership- supported organization, but its primary focus has been on health and safety-oriented research. BCR, however, is now attempting to widen its scope and conduct other types of research. There are almost no funds in EPRI's (Electric Power Research Institute) program for coal mining research. Large mining companies do some research for their own purposes and needs, but this is proprietary and therefore results are not shared with the remainder of the industry. The mining industry as a unit is not undertaking productivity (systems) oriented research in any common or cohesive manner.

Jan 1, 1983

By Christopher J. Farrow

This paper describes the grinding circuits installed at two remote sites in northern Canada. One is Cominco's Polaris Project at Little Cornwallis Island; a barge-mounted lead/zinc concentrator. The other is Echo Bay Mines' Lupin Project at Contwoyto Lake, 400 km northeast of Yellowknife, a gold mine, all components of which had to be flown to the site. Logistics and considerations of operating and maintenance presented challenges which were met by innovative design. The evolution of the grinding circuits is discussed. Both plants are operating at design throughput.

Jan 1, 1983

Introduction The art of ripping has been around since the Romans built the Appian Way, but only in the last decade has ripping emerged as a close competitor with drilling and blasting in breaking up heavy rock formations. That is not to say ripping is as effective in every case, or even applicable in all cases, but it does provide a cost efficient option in many situations-if the optimum ripping techniques are used. Originally designed only to loosen hard pan, the ripper has evolved into a powerful tool, its capability increasing as the weight and horsepower of tractors increased. The tractor-mounted ripper extended the range of ripping because of the additional weight it brought to bear on the ripper tooth. Tandem ripping added the weight and power of a second tractor, extending the rippability range even further. Of course, the use of ripping depends on the type of material to be ripped. Not all rock can be ripped. Determination of rippability-an art in itself-is often inconclusive but there are certain universal principles that can be considered in the first step toward optimizing ripping techniques. Each of the three basic rock types, igneous, sedimentary, and metamorphic, exhibits characteristics that bear on rippability. Igneous rocks are the most difficult to rip because they lack the stratification and cleavage planes essential to ripping hard rock. Sedimentary rocks are generally the most easily ripped since they are built of layers differing in material, texture, color, and thickness. Metamorphic rocks vary in rippability with degree of lamination or cleavage caused by transformation from pre-existing rock. The condition of rock also affects its rippability. Although sedimentary rocks offer the best opportunity to rip and igneous and metamorphic the least, decomposed granite and other weathered igneous and metamorphic rock often can be ripped economically. Little or no trouble is encountered with hardpan, clays, shales, or cemented gravel. Likewise, highly stratified or laminated rocks offer good possibilities for ripping. However, thicklybedded rock formations generally must be drilled and blasted. The physical characteristics that favor ripping may be summarized as follows: • Fractures, faults, and planes of weakness of any kind; • Weathering, resulting from temperature and moisture changes; • Brittleness and crystalline nature; • High degree of stratification or lamination; • Large grain size; • Moisture permeated clay, shale, and rock formations; and • Low compressive strength. Ripper Types A second fundamental to optimal ripping is choosing the right equipment for a particular job. There are three types of rippers-the hinge, the parallelogram, and the adjustable parallelogram. In the hinge ripper the linkage carrying the beam and shank pivots on a fixed point at the rear of the tractor. The resulting arc from up and down movement causes up to 30° differential in the tip-ground angle. Thus, the tooth angle changes as it enters and proceeds to ripping depth. The parallelogram ripper's linkage maintains the same tip-ground angle regardless of tooth depth. This type of ripper has advantages over the hinge-type when ripping above maximum depth, but does not provide the aggressive tooth angle necessary for hard-to-penetrate materials. The adjustable parallelogram combines the benefits of both the hinge and the parallelogram rippers. It has the additional benefit of being able to vary the tip angle to the optimum angle of penetration. It can also be adjusted while moving, for the optimum ripping angle in any material. Several other factors that are important in selecting the right ripping equipment are down pressure available at the tip of the ripper, tractor flywheel horsepower, and the tractor's gross weight. Down pressure at the tip determines whether ripper penetration can be obtained and maintained. Flywheel horsepower rating determines whether the tractor has the power to advance the tip. The tractor's gross weight determines whether the tractor will have sufficient- to use the horsepower. The best ripping procedure depends on the job's actual conditions. While conditions, vary, it is still possible to apply certain proven techniques to a typical ripping situation. Caterpillar Tractor Co.'s Handbook on Ripping says optimum ripping efficiency can be realized if-before actual ripping begins-these questions and answers are considered.

Jan 1, 1983

By Scott G. Britton

This chapter discusses the necessary construction techniques for installing coal mine ventilation devices. Included in the discussion are the major air controlling devices called over- casts, regulators, stoppings, and doors. Under-casts, although a valid device, are used infrequently in coal mining and are not discussed here. Typically, coal mines require a great many ventilation devices to control the air movement. Post-I969 mines have had to design their air systems to comply with the Federal Coal Mine Health and Safety Act (CMHSA) as discussed in Chap. 1. Pre- 1969 mines have had to redesign major portions of their systems to comply with the basic components of the law such as separation of air courses, single unit split ventilation, and minimum air quantities. It is not uncommon, therefore, to find a large mine (2.0 Mt/a) requiring several hundred overcast installations (permanent, as well as repeat construction), plus doors and regulators placed among a thousand or more stoppings. When each of these devices is subject to leakage from installation and weathering defects, the importance of effective construction becomes evident. An historic rule of thumb for average mine ventilation says that about 70% of all the air pressure generated by the mine fan is lost between the portal and the working faces. Of course, this rule is subject to many factors, but the message is clear: there is a tremendous inefficiency in controlling leakage through common air devices. This chapter strives to present a standard approach and design alternatives which can go a long way in reducing this leakage, and hence, ventilation costs. Historically, mine ventilation has progressed from natural, or draft ventilation, to fire-induced ventilation (Fig. l), furnace-fired centrifugal fans and finally, to today's modem mine fans. Underground controlling devices have been in use in the coal mines since the late 1600s, but the CMHSA of 1969 was the real turning point for mine ventilation. Minimum quantities and velocities of fresh air were required for mining, forcing coal operators and engineers to reevaluate and improve their systems. As a consequence, the cost for ventilating air increased. Today, companies face a variety of choices among design alternatives, materials, labor, and costs of ventilating devices for their mines. The best approach for any individual company or mine is determined by (1) the needs of the mine, and (2) the local design parameters. In my discussions of ventilation construction I shall be fairly general in terms of device installation steps, where specifics are warranted for clarification, I will include this information.

Jan 1, 1983

By Harry E. Holzschuh

The two Agrico Chemical Company self unloading Phosphate Rock barges put into service in 1976 operate at over their design carrying capacity. Each barge now carries 26,000 short ton instead of the planned 25,000 short ton at 32 foot of draft. They are in service between Agrico's Tampa, Florida Terminal and the Donaldsonville, Louisiana Fertilizer Complex, moving a total of 2,500,000 short tons each year. This was the first use of the Parascrew design for a marine application. The barges, with their 3,000 STPH unloading and matching loading rate is the vital link in this total transportation and handling system. Rock is moved from the Pierce, Florida Mines through the Tampa Big Bend Terminal, across the Gulf of Mexico, and up the Mississippi to the Agrico Faustina Phosphoric Acid Plant 30 miles below Bacon Rouge, Louisiana. The trip from the terminal to the plant is 600 miles and the turnaround time is just about six days. Seven years operating experience has proved that the system works. Fittingly, the two barges are named the "Faustina" and the "Pierce". They have a beam of 85-feet and are 495 feet long. folded depth is 43 feet, with a ballasted light draft of 19 feet and a typical loaded draft of 32 feet. There are four separated holds with the machinery room located forward of 101 hold. Each hold is 51 feet wide at the coamings with an 18 foot straight section on the side, and a 24 foot long, 600 slope sheet for a 23 foot clear reclaim width at the bottom. The Parascrew in each of the holds is 37 feet long between the bearings and is supported on a 14 inch diameter hollow shaft. The screw pitch varies and the diameter of the flights step up from l'-9" diameter to 2'-6" diameter on the discharge end. By sloping the centerline, a minimum four inch bottom clearance is maintained across the hold. Some bending of the tube does take place.

Jan 1, 1983

By Robert H. Robinson, Levent Ozdemir, Russell J. Miller

The paper summarizes an investigation into the applicability of mechanical excavation to oil shale mining; identifies available machine types that are best suited to various aspects of the mining operation; presents preliminary comments on the configuration of an "IDEAL" oil shale mining machine; and establishes the background information necessary for conceptualizing and evaluating new mining methods using mechanical excavation equipment. Conclusions are also presented as to the best currently available systems, as well as potential future systems.

Jan 1, 1983

By Howard J. Handewith

Long used in mine development in England, Europe and Russia, roadheaders are growing in size, features, productivity and application. Beginning with the basics, this paper covers the economic and the technical aspects of the new roadheaders in both mine production and development. The author explains how to choose and integrate roadheaders into ongoing operations as another step in the inexorable march from labor to capital intensive mining. Innovations now on the drawing boards are covered that are the challenge of the future.

Jan 1, 1983

By R. M. Schuster, F. M. Benavides

Samuel G. Bonasso The article by Benavides and Schuster provides an in-depth study of three transportation alternatives for a four-mine complex in western Kentucky. The examination of aerial tramways was not undertaken as an alternative solution. We feel this is an oversight since industrial ropeways are competitive with both belt conveyance and overland truck hauling. In fact, there are aerial tramway systems, operational today, which are 100 years old and operating with some original components. Maybe unfortunately, there are no fixed rules or guidelines whereby the most cost-effective means of transporting and handling material for a given situation may be selected. Each situation must be evaluated so the variables that influence the selection of the desired alternative can be clearly defined. However, there are in-place industrial ropeway systems that have proven economically feasible over a range of 1.6-50 km (1-31 miles). The more difficult the terrain, the greater the cost efficiency.

Jan 1, 1983

By William E. Lamont

The Mineral Resources Institute (MRI) of the School of Mines and Energy Development (SOMED), University of Alabama conducted studies to determine the potential for upgrading the Eastern Devonian shales by flotation. Results of those studies indicate that flotation concentrates containing 150 liters of oil/t (36 gal/t) can be produced from shale containing 50 liters of oil/t (12 gal/t) as determined by Fischer Assay with good recovery of the kerogen. Organic carbon and trace elements such as molybdenum, vanadium and uranium also are concentrated with the kerogen. Kerogen concentration was found to be a function of the size of grind.

Jan 1, 1983

By Pramod C. Thakur

Methane drainage by cross-measure boreholes on retreat longwall faces can be a viable alternative to the vertical gob degas boreholes under favorable circumstances. The research was done in a mine working Pittsburgh Coal seam in Northern West Virginia under U.S.B.M. Co-operative Agreement No. 14-09-0050-3252. The study was the first application of this technique to Pittsburgh coal seam. A total of fourteen, small diameter, inclined boreholes were drilled over a retreat longwall panel from gate roads, to intersect the overlying coal seams. All boreholes were manifolded to a pipeline and the gob gas was extracted by an exhaust fan on surface. The methane capture ratio was poor at 7 to 18% at various stages of the longwall panel. A vertical gob degas borehole captured an additional 20% gas. Poor results were due to premature failures of the cross-measure boreholes leading to air leakage. For better performance the boreholes should be drilled from a point 30 to 45 m from longwall pillar over the largest chain pillar, the standpipe should be grouted for at least 6 m, and the entry containing boreholes and the pipeline must be supported to ensure access for maintenance, and optimization of methane capture. Coursing the ventilation air around longwall such that it forces methane-migration towards cross-measure boreholes can further improve methane capture. The optimum vertical inclination is 45° ± 10°.

Jan 1, 1983

By Carlton H. Baab

In June, 1981 the Electric Power Research Institute (EPRI) issued a report titled "Control Systems in Coal Preparation Plants" to determine the status of instrumentation and automation systems in the coal preparation industry. EPRI concluded that the control systems presently being employed in the U.S. coal preparation plants "are relatively primitive compared with those in other mineral processing industries; and analytical instrumentation is virtually non-existent". Until recently, clean coal has had a low selling price and satisfying the purchasers' specifications required only minimum cleaning. However, it is becoming more apparent that the increases in coalfired utility power plants forced outage rates are relative to the deterioration in the quality of fired coal. Utility companies are becoming aware of the economic value of reducing the variability of ash, moisture and sulfur in steam coal purchase orders. New contracts are currently being negotiated between electric utilities and coal producers that include provisions for increased penalties if the product does not meet specifications. With tighter specifications on the quality of steam coal, interest is increasing in more sophisticated control systems. One type of device that is currently assisting the preparation plant operator optimize and control the coal cleaning process is nuclear based instrumentation. Nuclear instrumentation includes methods for measuring weight, level, and density as well as for performing elemental analysis on coal. This paper discusses the various types and applications of nuclear instrumentation currently in use in the coal preparation industry.

Jan 1, 1983

By William C. McBee

A sulfur concrete technology has been developed by the U.S. Department of the Interior, Bureau of Mines, in which chemically modified sulfur is utilized with suitable mineral aggregates to produce construction materials which are resistant to corrosion by acids and salts. This report presents a summary of the basic technology and results of testing the materials under actual operating conditions in 50 corrosive environments in 40 commercial plants. After 4 years of testing, there was essentially no evidence of material degradation or loss of strength. Regular concrete materials were attacked and in some cases completely destroyed under the same conditions. Testing is continuing to establish ultimate longevity and durability of the sulfur concretes. The materials are finding widespread applications in metallurgical, chemical, and fertilizer processing plants.

Jan 1, 1983

By H. C. Lautenschlaeger

Let's start with a bit of History. Before the advent of woven wire screen cloth or perforated plate as we know it today, screens or sieves, as they were called, were probably made by the Greeks or Romans around the year 150 B.C. Coarse openings were made from bamboo or other woven reeds or with holes punched in leather hides, while fine openings may have been made using hair from the long tails of horses woven with small openings. The first metallic woven wire screens were probably produced by the Germans in the 15th Century. All of these screening devices were, of course, hand operated. The first records of mechanically driven shaking screens are found in "John Smeathon's Diary of His Journey to the Low-Country" in 1775. He was the English Civil Engineer who built the famous Eddystone Light House and discovered the formula for making hydraulic cements. He described a screen the Dutch were using as a wooden frame on which woven wire was mounted. This box was inclined at an angle and hinged on the lower end. The upper or feed end was equipped with a pulley so they could raise it up, say 5" or 6", and then let it drop abruptly onto a sill or stop plate, thus jarring the material deposited on the woven wire through the openings. Material that was passed over the deck was scooped up and redeposited on the woven wire for rescreening. This was an early form of what is today known as a recirculating load.

Jan 1, 1983

By Om P. Garg

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

Jan 1, 1983

By Jurgen Weissflog

Why, where and since when using shiftable conveyors? Advantages of this equipment The ever increasing demand for bulk materials such as ore, coal, lignite, oilsand, oilshale and bauxite requires mainly an opencast operation. To exploit these materials huge amounts of overburden and partings must be transportes by means of conveyors, trucks or trains. When analyzing the various opencast mines it can be established that there exist only two basic types of mining systems, i. e., the discontinuous strip mining system as used in the USA (Fig. 1) and the continuous mining system as is commonly applied in Europe. The reason why these two mining methods have been developed parallel to and independently of each other to such a high technical standard results from the varying geological conditions of the mineral deposits.

Jan 1, 1983

By Joseph M. Zigich

The Anaconda Minerals Company operates a molybdenite and copper producing mine and mill facility near Tonopah, Nevada. Included with the milling facility is a ferric chloride leach plant for removal of copper mineralization from the molybdenite concentrates. Discussed are the engineering and construction schedules associated with the leach plant. The chemistry associated with the process along with a description of the process flow, equipment, and operating parameters are contained in the paper.

Jan 1, 1983

By Bobby J. Timmons

Luck; blind, beginner's, fisherman's, or whatever type, plays an important role in romance, racing, football, gambling, and mineral exploration. However, for each of these; education, training, technique, and experience are necessary for a long, continuous, successful relationship. Success, no matter how obtained, is easier to defend than almost success, regardless of the education or the degree of refinement of the seeker. Similarly, investment dollars are more readily available to a successful, uneducated and unscientific practitioner than to his beginning or unlucky professional counterpart.

Jan 1, 1983

By M. Grun, A. C. Marlowe, I. Littleford

SYNOPSIS A Wirth tunnel borer owned by Anglo American Corporation completed a 1150m long tunnel some years ago and was subsequently extensively modified by Technical Development Services. In 1982 this borer provided new and particularly interesting information In the field of hard rock boring. The abrasive quartzltes traversed proved to be a challenge to the cutter manufacturer and the project team. This paper examines the problems faced, the solutions found and the lessons learnt.

Jan 1, 1983

By D. S. Choi, D. L. McCain

INTRODUCTION Coal is forecast to be an increasingly important and economical source of energy for the future as the supply of oil and gas declines relative to overall energy demand and perhaps in absolute quantities produced. With the decline in productivity, especially in underground mining, in the early seventies coinciding with the need to produce greater quantities of coal for market, a gradual change from room-and-pillar mining to longwall mining has been taking place in the United States. Consolidation Coal Company (Consul) produces about 50 million tons of coal per year with approximately 66% being from underground mines. Most of the mines are located in the Appalachian Region in the States of Pennsylvania, West Virginia and Virginia, and in Ohio and Illinois. Coal is produced by the room-and-pillar mining method with continuous mining machines in addition to an increasing number of longwall mining faces. Continuous mining machines will continue to be used for driving longwall development entries as well as in areas where partial extraction must be practiced in order to support the overburden rock because of surface structures or in areas that cannot be subsided, or where unfavorable geologic conditions limit the application of the longwall mining methods. ROOM-AND-PILLAR MINING METHOD Some background in the room-and-pillar mining method may be helpful to provide perspective. This method has been widely practiced since the beginning of coal mining in the region. It is a flexible system because it can provide either partial or nearly complete extraction, and coal pillars can be left where needed to support surface structures or oil or gas wells or because of unfavorable geologic conditions (Choi, Dahl and McCain, 1980).

Jan 1, 1983