Search Documents

The only good news in the exploration sector in 1982-a year plagued by low metal prices and weak demand-was precious metals. Gold in particular remained in the forefront, as it has for at least the past three years. The reason for this is partially due to gold's seeming resilience to conventional supply side factors-such as new production-that normally influence many other metals. Also, with projected production costs of about $6.40-$9.65/g ($200¬$300/oz), modest deposits with average grades can offer an early return on capital investment and good profit potential. Keeping escalating capital costs for new mining ventures within reason has shifted gold exploration efforts in recent years. Many mining companies are seeking relatively low grade, modest tonnage, near-surface gold mineralization. This, of course, leads to lower development costs using open-pit mining methods. Recent refinements in the carbon-in-pulp recovery process also has enhanced the economics of such deposits. Slumping economic conditions certainly played a key role in shaping exploration activity last year. Nearly every major mineral-producing state recorded exploration slowdowns. In Alaska, for example, development expenditures approached the level of exploration spending for the first time in the state's history. This not only reflects major companies' decisions to move toward production but also the economic slowdown. The worldwide recession stopped Nevada's exploration and mining boom "dead in its tracks," said John Schilling, state geologist. The year was one of layoffs and closings for the state's mines and exploration offices, he reported. Similar trends were noted in most other states, especially in the West and Southwest. In the Pacific Northwest, however, exploration appeared to continue at a relatively good pace considering the metals market. In the mining geophysical community, recent advances in telecommunications and microprocessor technology are continuing to provide a positive impact. Many geophysicists have begun using satellite digital communication links to access computer systems from remote sites where using a microcomputer would be difficult. There were also major contributions made in exploration geochemistry last year. Highlights include progress in formulating mineral deposit models, geochemical exploration in glaciated and arid environments, and publication of many informative books. The following state-by-state summary and articles on geophysics and geochemistry provides a detailed view of exploration events throughout the US in 1982.

Jan 5, 1983

By R. D. Lord

This paper deals with the search for the best practical means of storing sulphide bearing tailings, where there is no residual excess of carbonate material. It is the common experience that the sulphide content decomposes, with the aid of bacterial action, and the resulting sulphuric acid escapes, along with any heavy metal solutes, through embankments that are usually porous to some degree. The problem is typified in the tailings of the uranium operations of Elliot Lake, Ontario, where mining started some 20 years ago. The approach to tailings disposal paralleled the practice for other hydrometallurgical plants treating gold and base metal ores. Impoundment areas were designed to retain solids, and a clear and neutral overflow was considered satisfactory practice. Now experience has shown that these areas, some idle for over a dozen years, release acids, in seepage and overflows, to an unacceptable degree. To protect natural water courses neutralizing plants are operated wherever required. Lime slurry is fed continuously into the tailings outflows in a quantity sufficient to raise the pH to 8.5 and precipitate heavy metals that may be in solution. The objection to this procedure is that the plants will require servicing indefinitely, unless a better remedy is found.

Jan 1, 1975

By I. B. Tulu, M. M. Sears

In 2015, 40 longwall mines provided nearly 60% of the US coal production from underground mining methods. This represents a substantial yet gradual increase from just under 50% over the last 5 years. As a result of this increased production share, the percentage of ground-fall-related fatalities in longwall mines has also increased when compared to all US underground coal mines. Additionally, about 80% of ground-fall-related fatalities have occurred in areas where the roof was supported. In an attempt to better understand the status quo of current US longwall support practices, a sample of 25 longwall mines were visited representing nearly 50% of the currently active longwall mines representing all of the major US longwall-producing regions. The resulting data was obtained from a wide variety of overburden depths, geologic conditions, mining heights, ground conditions, support practices, and gateroad configurations. The data collected is reported using both qualitative and quantitative methods. Results from the research update previous efforts in classifying mining accidents and injuries as well as current support practices presented by this author at the 2017 Society for Mining, Metallurgy, & Exploration Annual Meeting. This data provides a necessary background for future research aimed at further reduction of ground fall accidents and injuries.

By Harley G. Pyles

Rotary Percussion drilling has shown great improvement over rotary drilling, when hard roof is encountered. In addition, Rotary Percussion drills have eliminated the need for air drills in many applications. Improved drilling rates have been achieved but roof bolting is still a bottleneck in many operations and the demand for further improvement will continue. Drilling rates beyond current performance is limited by the capabilities of existing drill steels and bits to resist increased horsepower input. The most apparent immediate solution to improved drilling is to increase the strength and rigidity of the drill steels. Drilling experience indicates that a l-1/2" diameter or 1-5/8" diameter hole can be drilled as rapidly or 'more rapidly than the standard 1-3/8" diameter hole. Greater torque and thrust capacities can be achieved through the use of larger O. D. and I. D, steels, however, this is only possible if the larger hole sizes can be made allowable. Large diameter anchorage shells can be made available at a slight extra cost.

Jan 1, 1965

By Lawrence Adler

The design of an underground opening involves the coincidence of two highly complex and poorly specified components. First, the structural or mechanical characteristics of a geologic rock mass are not only extremely variable but are also very difficult to evaluate. Second, the general lay¬out of mine workings contains a large degree of indeterminancy as to the structure itself as a result of the indefiniteness of the mining process, and also because of the inherent redundancies associated with bulky and weighty structures. Even for the relatively simple problem of tunneling this complexity is well recognized to be "without question that to which the study of geo¬logy (for the Engineer) can most fitly and usefully be applied".1 It can, therefore, be appreciated that the comprehensive opening design problem involves a complicated assemblage of component structures made up of a sketchily defined, or sometimes even an undefined material and acted upon by largely unknown tectonic forces.

Jan 1, 1968

By Jon T. Langstaff

The microseismic method of detecting instability and high-stress zones in underground mines was first developed in this country by the US Bureau of Mines in the early 1940's (Obert and Duvall, 1957). Early laboratory experiments showed that when competent rocks are stressed in a testing machine, the rock noise rate (number of rock noises per unit time) increases with increasing applied stress. This increase is more pronounced as the ultimate strength of the rock is approached. Subsequent testing of rock noises in underground mines confirmed this laboratory experience and much effort has been directed in recent years to make use of this property to develop a practical method of predicting rock failure. Investigations conducted in the Coeur d'Alene district mines have pointed out a definite relationship between the stress buildup in a rock mass caused by mining activity and the emission of audible and subaudible seismic activity (microseisms). In 1968, a concentrated joint effort by USBM Denver Mining Research Center and American Smelting and Refining Co. at Asarco's Galena mine was undertaken to verify several theories regarding the generation of microseisms (Blake, 1971; Blake, Leighton, and Duvall, 1974; and Kovacs, 1973). Findings indicate that (1) rocks under stress emit detectable seismic energy; (2) the energy source can be located using a triangulation method involving travel time differences to various receiving stations; (3) the rate of release of seismic energy increases with increasing stress; and (4) this increase in noise generally precedes a major rock failure (rock burst).

Jan 1, 1979

By T. A. Vivian

The use of heavy media organic solvents to recover coal from its attendant gangue is hardly new. DuPont built a pilot plant using pentachloroethane in 1936 at Weston Coal Company, Weston Breaker, Shenandoah, Pennsylvania. That's almost half a century ago. Since that time, it has become common practice to utilize similar classes of chemicals in laboratory separations of coal samples. It is the objective of this paper to discuss some specific separations on both pilot and laboratory scale on samples representing different classifications of coal. These separations have been carried out on coarse (+4 M), middling (4 x 20 M), and fine (-20 M) coal samples. The coal samples tested include Pennsylvania anthracite; Pennsylvania, Indiana and Colorado bituminous; Wyoming sub-bituminous; and Texas lignite. Other chlorinated solvents were used to vary the specific gravity of separation.

Jan 1, 1984

By Roland Froidevaux

The potential use of geostatistics for quantitative ore reserve reporting is shown using a simple gold case study as an example. The need of defining quantitative class limits is stressed, and a possible approach to this problem is suggested.

Jan 1, 1983

By L. U. Spellman

Atlantic Cement Company's new multimillion dollar, 10,000,000 barrel per year cement plant went into full operation in February, 1962, bringing into reality a new concept in the distribution of Portland cement. The Cerro and Newmont Mining Corporations, well established in the mineral extraction and dressing industry, backed the venture. To take advantage of the, economics inherent in single production units of large capacity, it was necessary to first find a market' capable of absorbing such large quantities. Cement can be economically shipped by rail and truck about 200 miles. Beyond' that radius from the producing facility the freight costs become prohibitive. No single marker area within that radius exists which could absorb such a large volume of cement. However, water transportation provides a relatively inexpensive method of transporting bulk products many times over such a distance. Thus, it was decided to locate the producing facility near a deep water port which had ready access both to the Atlantic Ocean and, just as important, a good source of raw material. An extensive feasibility study was made and the site at Ravena, New York on the Hudson River near Albany was chosen. Here, vast quantities of limestone in the foothills of the Catskill Mountains are found within a short distance of-the deep-water Hudson River.

Jan 1, 1964

By L. R. Chirinos

The Tintaya mine of BHP Copper, located in Southern Peru, includes a copper oxide deposit hosted in a mineralized skarn zone. The ore contains large amounts of clays and high acid consuming species resulting in low heap leaching performance. A treatment scheme was proposed that included a wet screening separation. The coarse fraction would be treated by heap and the fines by agitation leaching. The dissolved copper would then be recovered through solvent extraction and electrowinning (SXEW). Testwork determined the optimum heap leaching conditions to treat the oxide in on/off pads of 3 meter height with an initial acid cure followed by variable acid strength during irrigation. The method resulted in a reduced acid consumption and good copper recoveries.

Jan 1, 1997

By D. M. Conner

An innovative patented process has been developed to convert high volume wastes--fly ash from coal-fired power plants, municipal solid waste (MSW) ash from incineration, solids from waste water treatment and paper mill sludge into a high value and environmentally benign product in the form of a lightweight aggregate. Lightweight Aggregate is widely used in the building construction industry in the United States, Europe and some Asian countries. This paper will present the development of the process, the process itself and details on the first commercial scale plant. The commercial plant is owned and operated by Wisconsin Electric Power (WEPCO).

Jan 1, 1997

By Eugene F. Casey

An immersed tube tunnel is one which is composed of elements that are prefabricated in a dry dock or on shipways, usually away from the actual tunnel site, floated into position and then lowered into a preexcavated and graded trench below a body of water. The elements or segments are then connected to each other under water, and the entire immersed tube tunnel covered with a protective blanket. Because water is essential, this method of construction offers advantages in a relatively limited field. By the very nature of the method, lowering elements to the bottom of an underwater trench, immersed tube tunnels are primarily used for crossing bodies of water, such as rivers, bays, straits, canals, etc. Although this method of construction was first used for a subaqueous railway crossing under the Detroit River in 1906-1910 and again in 1912-1915, for a four track subway tunnel under the Harlem River in New York, the reason immersed tube tunnels construction has not been used more extensively is simply a matter of economics. Bridges, compressed air tunnels and similar structures could be constructed at a lower cost.

Jan 1, 1970

By R. L. Bullock

For many years, the combined efforts of machinery manufacturers and mine operators have endeavored to achieve greater productivity from the men involved and the machinery and capital invested, by developing methods to drill blast holes more effectively. Obviously, this means much more than simply developing a drill that will drill a single hole faster. Considerable attention over these years has also been given to methods of carrying and positioning the drilling machine on versatile jumbos, whereby the man's time can he better utilized by the faster drilling machines. Likewise, the art of blasting to utilize the holes that were drilled to achieve the maximum amount of fragmented ore and the methods of moving the broken ore have also progressed. But each phase of the production cycle just described must be made to balance with the other phases of the work. Obviously, major breakthroughs in only one phase don't always generate more "rock in the box" per manshift. Yet, through the persistent effort of the machinery developers and the researchers, the progressive attitudes of mine managers, backed by corporate capital investments, and battle after battle at the operating level, progress is made. Then, if the innovated system is good enough to "stick", in a few years it becomes the system that the newer method must replace, after the same repeated struggle. This is the situation that many mine operators find themselves in today, Looking at their production cycle, which is assumed to be efficient and balanced between drilling, blasting and materials moving capabilities, they tend to guard any visable disruption of the balance of that day's production, and many would prefer to maintain the status quo indefinitely. Yet, if history repeats itself, we can expect any major breakthrough in the cycle to trigger other innovations in the

Jan 1, 1975

By R. J. Heath

Potash, the general term for potassium salts used as fertilizers, is one of the essential growth nutrients (together with nitrogen and phosphates) required by all living things. Total world consumption of potash for fertilizer use - almost all of it in the form of potassium chloride - amounted to an estimated 47 million short tons in the 1979/80 fertilizer year*. While there is some limited demand for potash for a variety of industrial applications, this amounts to only 3 or 4 per cent of total world demand, and the potash business can be viewed as essentially a fertilizer business. Total available world potash production in the 1979/80 fertilizer year also amounted to approximately 47 million tons. There are two large potash producing countries - Canada and Russia - and a number of other countries where production is significant - East Germany, West Germany, the U.S.A., France, Israel and Spain. Production volumes are shown in Table 1.

Jan 1, 1980

By R. D. Schmidt, M. J. Friedel

Unsaturated permeability and flow capacity exist where copper mineralization is disseminated in segmented, very-low-permeability ore blocks. The US Bureau of Mines (USBM) investigated this condition for application to in situ, copper-leach mining at the Cyprus Casa Grande mine site. Moisture retention properties are derived and combined with scanning-electron-microprobe data to characterize the host rock's mineralogy, texture, pore size, distribution and permeability. Finite element modeling is used to estimate saturated permeability and the ambient degree of saturation and to gain insight into appropriate in situ leach design. Recommended design modifications for optimized solution distribution and maximum recovery from the Casa Grande ore require: • well pressure injection exceeding 1500 psi and recovery wells operating in a suction mode, or • secondary, permeability enhancement by explosive rubblization. In the former, the lack of conditioning and the use of lesser pressures will result in leach solutions confined to the macrofractures. With the latter requirement, pressures can be reduced to 500 psi, with improved recovery and solutions containment.

Jan 1, 1993

By E. H. Cho, Q. Luo

Pittsburgh No. 8 coal, cleaned by conventional froth flotation, was oxidized in a 2-L Parr stirred bench-top autoclave. Autoclave tests were carried out for up to 5 hrs under the following conditions: 150 to 225ºC, 60 to 500 psi 02 and 15 to 60 g of coal per 600 mL of distilled water. The oxidation of coal was evaluated by measuring the total acidic group formed on the surface of the coal and by measuring the adsorption (under standard conditions) of calcium ion from a solution. The degree of oxidation of the coal increased continuously, without much leveling off, with increasing oxygen pressure. With increasing temperature, the oxidation of the coal increased sharply between 150 to 175ºC and then leveled off above 175 °C. The adsorption of calcium was >3% on coal oxidized under the most favorable conditions. The adsorption of calcium on coal increased sharply with increasing equilibrium pH. The loss in Btu was found to be sensitive to oxidation temperature. This study concluded that the optimum oxidation of coal is achieved over 3 hrs at high oxygen pressures (e.g., 500 psi) at ~170ºC. This study also concluded that, when measured in terms of calcium adsorption, Btu loss and reaction time, the oxidation achieved in an autoclave is far superior to that achieved in a fluidized bed.

Jan 1, 1996

By George H. K. Schenck

INTRODUCTION Boom-type miners mechanize the cutting and loading of a solid face of rock having a compressive strength as high as 124 MPa (18,000 psi). These machines differ from continuous miners in that they can cut much harder rock for any given cutter-motor power. In addi¬tion, a boom miner is more flexible, selectively cutting any cross-sectional configuration from circular to square arched faces, 1.57-rad (90°) turns, and mixed faces. The basic operational concept of these machines, utilizing a rotary cutterhead mounted on a slewing boom, gained importance in Europe during the 1960s, where, due to their specialized use in roadway development in coal mines, they were called roadheaders. Along with continuous miners, boom miners share the ability to fully mechanize the cutting and loading of rock, while eliminating the need for explosives and the shattering and overbreaking of roof and rib rock that is normal with conventional mining methods. The machines are crawler-mounted and most have a gathering-arm load¬ing system that, moves the cut rock onto an internal chain conveyor, subsequently discharging the rock into a transport device such as a shuttle car or a bridge conveyor. Light- to medium-weight boom miners are cutting softer rocks and minerals successfully, including coal, shale, rock salt, potash, phosphate, weak sandstones (e.g., those associated with uranium ore), and other softer ores such as iron. Heavy third-generation ma¬chines have extended rock cutting to much harder ores such as borate, oil shale, and almost all rock associated with coal seams, except for the harder sandstones and limestones. The mention herein of specific manufacturers, brand names, or models is made by way of example only and does not constitute endorsement by the author or The Pennsylvania State University. All costs cited herein are in 1977 US dollars. TYPES OF BOOM MINERS All boom miners utilize drag bits fixed on a rotary cutterhead that is powered by an electric motor mounted in the slewing and elevating cutter boom. The cutter¬head is either a ripping or a milling type, and the machines have evolved through three generations (Boldt, 1977). As shown in Fig. 1, only one boom miner cur¬rently produced can use both ripping and milling cutter¬heads on one machine. Table 1 lists boom-miner models built in large num¬bers and/or successfully used or marketed in North America. Table I excludes machines of which only a few have been produced and none sold in North America, such as those manufactured by Demag, Eick¬hoff, Paurat, and Thyssen-Rheinstahl. The only Ameri¬can boom miners are the F-16 and Super ROC¬MINER"', manufactured by AEC, Inc., State College, PA. Machine Generations Three generations of boom miners can be distin¬guished according to their times of introduction, their rock-cutting abilities, and their weight classifications. Fig. 2 illustrates typical best-practice production rates possible from boom miners for selected cutter-motor power sizes (other power figures can be interpolated). Productivity is related directly to the energy applied to the cutterhead and indirectly to machine weight; higher

Jan 1, 1982

By Bruce Johnson

This paper is not written to "break new ground" in computer applications; it is just a treatment of how an operating metal mine utilizes a mainframe computer for planning, analyzing, and reporting on the ventilation and cooling systems. The Unisys mainframe computer at the mine site is used in programs that analyze the ventilation network, keep records on various ventilation installations, calculate the results of measurements and produce reports on ventilation conditions in the working places and on the main air distribution, and plan and analyze the cooling system. All the programs are interactive to terminals. There are a series of data files that are generated by some programs which may be used by other programs. Most of these programs have been developed in-house. The computer is also used as a word processor via a vendor-supplied text editing program to produce memos, letters, and to keep up-to-date lists of equipment used.

Jan 1, 1989

By Allan Gebhard

The purpose of this paper is to summarize the role of water resource monitoring in mining activities and to discuss the considerations that go into designing and implementing a monitoring program. The design of a monitoring program is invariably based on sound engineering and scientific judgement since no design formulas exist that can be universlly applied to the monitoring of all activities. As discussed in this paper, however, a methodology of designing a water resource monitoring program does exist. In order to cost-effectively monitor the water resource impacts of mining activities, the following three monitoring related items should be understood: 1. the role of water resource monitoring in the planning, construction, and operational stages of mine development, 2. the available water resources monitoring methods and the proper role of each method in the various scages of mine development, and 3. the strategies that should be followed in designing and implementing a water resource monitoring program.

Jan 1, 1976

By John C. Nixon

In 1959, The Australasian Institute of Mining and Metallurgy (Aus. I.M.M.) was asked by the Federal Government of Australia and the State Government of South Australia to join in the formation and management of a new contract research organization which was subsequently named The Australian Mineral Development Laboratories (Arndel) ? This body was formerly the Research and Development Branch of the South Australian Department of Mines which had been set up to develop the Radium Hill uranium deposit. It had then gone into contract R&D and the State felt that it would be more appropriate for the Branch to become a separate national organization. The Aus. I.M.M. decided that a professional institute could not participate directly in Arndel and, as there was no other suitable industry group to do so, it formed the. Australian Mineral Industries Research Association Limited (AMIRA). AMIRA held its first Annual General Meeting in September 1959 when the first Council was elected and the Memorandum and Articles of Association were adopted. The initial task of AMIRA was to raise guarantees of work or cash from its members to underwrite Arndel for the first five years of operation. The Federal and State Governments also provided guarantees and Arndel commenced operations in January 1960.

Jan 1, 1977