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By Wilson Blake

The occurrence of rock bursts in some deep mines throughout the world constitutes a severe operational hazard. In addition to endangering the safety of the miners, the rock-burst problem is a major factor in mining economically in deep mines because of the loss of production and expense owing to cleanup and repairs following a burst. Developing means of controlling or eliminating rock bursts has been the subject of intensive research for over 50 years. While much has been learned about the effects of rock bursts, little is known about their basic causes; hence, control measures have been at best only partially effective--attested to by the number and severity of bursts that continue to occur throughout the world each year. In the Coeur d'Alene mining district of north Idaho, the rock-burst problem continues as the silver and lead veins persist at depth. These veins are presently being mined at greater than 7,000 feet below the surface and will be mined to some 10,000 feet in the future. The majority of rock bursts in this district occur in pillars. While pillar bursting has been essentially eliminated in some deep-mining districts by longwall techniques, modification or application of this technique to the thin, irregular, and near vertically dipping veins of the Coeur d'Alene district has not been found to be practical. The creation of pillars is a consequence of the horizontal cut and fill mining method used. Figure 1 shows a vertical longitudinal projection of the silver vein at the Galena mine, illustrating the mining method. Stoping progresses between raises and is carried upward between levels. A horizontal pillar is created as a stope approaches a mined-out level. Recent broad-band micro seismic monitoring of rock-burst-prone stopes by the Bureau of Mines has shown that potential burst zones could be delineated weeks in advance of a burst and that a definite sequence of events took place prior to the occurrence of a pillar burst (1). Hence, time was available for control measures to be effected when a stope pillar reached a critical burst geometry.

Jan 1, 1971

By V. Karra, G. Beerkircher

Application of the innovative WaterFlush® crushing technology to the processing of gold, copper, and iron ores is presented for retrofit circuits and productivity gain in each case is stated. New operations containing WaterFlush are described in brief.

Jan 1, 1995

By J. H. Heintz

This paper discusses the law as it relates to appraising operational mining properties in the context of a takings claim. Topics include the need for valuation expertise, the differences between de jure and de facto takings, an overview of the law of condemnation, including jurisdictional issues, and defining your strategic options according to the controlling statute. State condemnation law varies by jurisdiction and just compensation can be calculated by comparable sales unit-times-price, before ¬after-valuation, capitalization of income and discounted cash flow methods. Takings under Federal laws are reviewed, as is the necessity of assembling a team including attorneys, valuation experts including a mineral appraiser, a real estate appraiser, economists and geologists.

Jan 1, 2002

By Igor Gonzales G.

Southern Peru Copper Corporation (SPCC) has recently completed the construction of copper leaching, solvent extraction, and electrowinning facilities at their Toquepala and Cuajone plants in Southern Peru. Much of the ore for these new operations is the result of the existing mining operations that have been in existence as early as 1959. At Toquepala, pre-conditioning and bacterial dump leaching of the sulfide ore that was too low in copper content to be processed through the copper concentrator began in 1987. The Cuajone heap leach operation is treating copper oxide ore that has been stockpiled since the Cuajone concentrator began operation in 1976. The pregnant leach solutions from the dump leaching at Toquepala and the permanent pad heap at Cuajone are combined into one plant feed solution. Adjacent to the large dumps at Toquepala, a solvent extraction and electrowinning facility has been constructed. The electrowinning facility has a planned annual production rate of35,000 metric tons per year Grade A cathode copper. Initial production of the cathode copper began in November 1995.

Jan 1, 1996

By Laurel E. Burns

Alaska is in competition with the rest of the world for exploration dollars. Providing a "seed package" of airborne geophysical data for the state's numerous mining districts encourages companies to begin more detailed exploration in more areas than they could have afforded on their own. When data are already available, the initial risk decreases for people involved in exploration. Airborne magnetic and electromagnetic data help ge¬ologists and geophysicists determine what rocks and structures are present under overburden and vegetation. These data form a fundamental package that exploration companies want before intensively exploring most regions. Individual mining companies have conducted their own geophysical surveys during the past several decades. However, these data are not available to other companies. The companies able to afford geophysical surveys have less money for ground exploration after purchasing expensive, private geophysical data. Therefore, they are not able to explore as many places as they might. Additionally, since data are not shared with other exploration companies, the proprietary surveys do not foster intercompany competition to move projects forward. Individual prospectors and small companies can not afford their own geophysical surveys. "It is more often than not the grassroots exploration efforts of the smaller operator that leads to significant discoveries," said Klaus M. Zeitler, senior vice president for development and exploration at Teck Exploration. Acquiring and releasing the geophysical data to the public produces several benefits. The increased explo- [ ]

Jan 1, 1998

By J. A. Rose, A. S. Atkins

Environmental awareness has become a paramount consideration in the issue of planning and licensing arrangements for the disposal of wastes associated with mining operations. In this con- text the disposal of liquid tailings is a difficult and controversial problem with regard to environmental surface disposal. The paper outlines the use of Information Systems for decision support in the safe and environmental disposal of liquid tailings linked to conventional coarse refuse operations. This offers both an economic and an aesthetic approach to a historical perception of waste tipping in the underground coal extraction industry. The paper will demonstrate a prototype system that incorporates multimedia facilities which include data such as; voice comments, site photography, site plans and fluid flow circuits.

Jan 1, 1996

By C. D. Buttgereit

A variety of mathematical techniques are available in the pertinent literature concerning the interpretation and reduction of aeromagnetic data. The quantitative methods applicable to this data en¬compass a wide spectrum including filtering, continuation, derivatives, reduction to the poles, spectral analysis, and "undraping" of flight line data. With the aid of the digital computer, the techniques listed, and others, can be computationally performed on a gridded data set. In addition, current sophisticated computer hardware permits the systems analyst greater latitude in the storage and retrieval of data and in the display of resultant naps on a digital x-y plotter than previously available. Although many interpretive techniques concerning magnetic data have been published and computer machinery has been on the market, little has been written incorporating both disciplines into a unified digital processing system. In the present paper, a general purpose system in given which in designed for routine use in the interpretation of aeromagnetic (and other potential field, etc.) maps.

Jan 1, 1970

In some 35 years in the explosive and construction industries, we have probably seen the extremes in drilling and blasting practices. All of you know that it is difficult if not impossible, to separate those two operations, particularly when we are searching for an optimum. Early in my career while doing engineering survey work for a major cross country pipeline construction company, we witnessed some of the wildest blasts imaginable, and they were wild for two reasons. Both the drill hole diameter and the drill pattern were such that when loaded with explosives, the factor in terms of pounds/cu. yd. was extremely high. On the other hand, in 1982 we were in an underground coal mine where just one hole was used to prepare a 20-ft. (6m) wide face. In this coal mine, they brought down 7 yd3 (5.35m3) of coal with just 1 lb. (.454 kg) of explosive. On a pipeline job, the factor may only be .1 yd3 per lb. of explosives. Open pit operations in the same geographical area may have almost the same type of rock, but similarities could end there. The several operators over the years will have installed different size-crushing equipment or variances will exist in other facets such as drilling, excavating, and haulage units. That tells us that if we have 6 operations in that common area, we are faced with a fact that there is an optimum drilling and blasting pattern for each of those six. We start at that point. We will note from Figure No. 2 the simple equations for determining either cu. yds. or tons. For a rock heavier than limestone, it may require only 10 to 11 cu. ft. (.31m3) for 1 ton (.91 metric ton) of rock in place.

Jan 1, 1986

By Charles S. Robinson

The Henderson ore body is east of the Continental Divide in the Front Range of the Colorado Rocky Mountains about 50 miles west of Denver. The ore body is being developed for mining by workings that extend more than 3500 feet below the topographic surface. During construction of the mine workings, ground water in fractures in crystalline rocks has been encountered. From 1969 to 1973, Charles S. Robinson & Associates, Inc., in cooperation with the engineering and geologic staffs of the Climax Molybdenum Company, a division of Amax Inc., studied the ground water geology of the Henderson mine development area. Detailed geologic records of the Henderson mine were available as a result of the exploration, evaluation and development of the mine. Records of the flow, chemical composition and temperature of the ground water at and near the surface, from the entire mine, from portions of the mine, and from exploration holes drilled in the mine, were kept as the mine was developed. Where possible, ground water pressures in drill holes and changes in pressure with time, were recorded. The geologic, hydrologic and chemical data were correlated. The following conclusions were drawn from the correlations: The ground water in the Henderson mine occurs in fractures in Precambrian igneous and metasedimentary rocks and in a series of Tertiary intrusive rocks. Two zones of ground water were recognized; an active zone, in which the fracture systems are recharged and discharged annually into the surface water system, and a passive zone, in which the fractures were filled with water in the geologic past. Discharge from the passive zone is through mine workings that intersect the fracture systems. Discharge from a fracture or fracture system is initially high but decreased with tire!. The rate of decrease in flow (or pressure) is exponential. By measuring the change in flow with time, it is possible to calculate the amount of flow at some given period of time in the future. Based on changes in rate of flow and pressure, and the geology, and assuming rates of mining of the ore, it will be possible to predict the volumes of water that will have to be handled during the life of the mine and the area around the mine that will be drained by the mining operation.

Jan 1, 1976

By D. L. Petersen, C. R. Nelson, P. M. Bergson, B. K. Nelson

Membrane waterproofing systems in large tunnels cause the partial decoupling of the concrete liner from the rockbolted and shotcreted reinforced rockmass. This decoupling leads to a loose fit of the liner in the excavation when shrinkage from cooling and moisture loss occurs. This increases tensile stresses which require either the addition of reinforcing steel in excess of common European practice or the potential for liner cracking. Hot weather concrete placement and cold weather service conditions increase the magnitude of the problem, while creep of the rockmass reduces it. Contact grouting also reduces, but does not eliminate, the problem.

Jan 1, 1991

Mining steeply dipping coal seams is a difficult task in the mining industry. Prior to 1996, fully mechanized longwall mining methods along the seam strike direction were tried in China and other countries. Due to its larger coal reserve in steep seams, China made more but still limited progresses on mining in such seams than the other major coal-mining countries. In the last two decades, accelerated research efforts have been made to improve the mining technology in steeply dipping coal seams. Based on these works, a dynamic model of ?R-S-F? system under asymmetrical constrains in mining steep seam is established and the theory of strata control and hazard prevention begin to be formed. The key technologies for mining steep coal seams include: global and regional strata control methods in longwall face, methods for the longwall face machines to sustain static and dynamic loads, and flexible protection technology. These theory and technologies have been successfully applied to mining of steep coal seams of varying thickness and hardness, with hard and soft roof and floor, and with high potential of spontaneous combustion in China. In the recent years, the technology has been introduced to Russia, India, Uzbekistan and other countries where steep coal seams are mined.

Jan 1, 2012

By R. C. Richardson

Barite Worldwide barite production for 1985 decreased 1.3%, while US barite production increased 1.4%, according to US Bureau of Mines statistics. The increase in US production is attributed to heavy demand for oil and gas drilling during the first quarter and an unrealized heavy expected demand in oil and gas markets for the last quarter. Nevada accounted for 82.1% of the 807 kt (890,000 st) of barite produced in the US last year, according to the Bureau. Other producing states were California, Georgia, Illinois, Missouri, Montana, Tennessee, and Washington. In 1985, the US imported 1.8 Mt (2 million st) of crude barite and 64 kt (71,000 st) of ground barite. China led the way with 43.3% of the total. Imports from India accounted for 21.6%; Morocco, 15.5%; and Thailand, 5.6%. The 1.8 Mt (2 million st) of crude barite imported is an 18.8% increase over 1984. Apparent consumption of barite for 1985 was about 2.6 Mt (2.9 million st), a 15.7% increase from 1984. Due to very low drilling rig activity during the last quarter of 1985, actual consumption is probably less as crude barite inventories at mines and plants increased. According to the Bureau, 90% of barite consumed in 1985 was for the oil and gas market. Paints, rubber, glass, and other chemical uses consumed the other 10%. With the price of oil falling dramatically early in 1986, the outlook for oil and gas drilling looks to be significantly lower than 1985. This lower demand for barite, coupled with the high year-end inventories, should lower both imports and domestic production. Significant lower prices on imported barite are expected, especially from China, Morocco, and India. This also could further lower US production of barite this year.

Jan 5, 1986

By Dinah O. Shumway

California's annual production of >11 million tons of cement, at a value of over $640 million, comes from eight companies, which operate 11 plants. Cement is California's second most important mineral commodity, representing 25% of its total annual mineral production. Although most of the cement produced is consumed within the state, current export locales include the Pacific Northwest, Nevada, Arizona, Utah, and New Mexico. An enumeration of the components required to produce cement is deceptively simple: calcium oxide (65%), silica (20%), alumina (4-5%), iron (3-4%), and calcium sulfate (4%) as a retardant admixture. The last, and most expensive, ingredient in cement manufacture is energy. Detrimental materials in cement mixes include excess .magnesium, alkalis, heavy metals, sulfur, and other volatiles. Each of the 11 cement plants in California requires a unique chemical solution of combined raw materials to produce a uniform product: portland cement. The geologist proposing solutions for the additive raw materials in cement manufacture must have a thorough knowledge of a particular cement plant's needs. In the California cement market, keeping the costs of additive raw materials down is one way to also stay competitive, and using a combination of natural and waste materials as additive raw materials allows cement producers to stay competitive.

Jan 1, 1999

By J. A. Rusnak, M. M. Gadde, S. S. Peng

In situ stresses are one of the key inputs to a successful underground excavation design. Because of the complex mechanisms involved in arriving at the current state of stress at a point in the Earth’s crust, often the only reliable way of estimating in situ stresses is by actual measurement. In the United States coal mines, overcoring relief method is by far the most popular technique used for estimating the virgin stress field. Typically, for stress measurement with overcoring, a vertical borehole is drilled into the roof or floor of an underground coal mine opening to a certain distance and change in borehole diameter is monitored at multiple points along the length of the hole when this borehole is overcored. For the measured stresses to represent the pre-mining stress field, the measurement points should be located beyond the influence zone of the mine opening. Actual data from several US coal mines have been collected to check if the measured stresses by overcoring represent true in situ stresses. The data indicate that most of the stress measurements were within the excavation influence zone. A three-dimensional numerical modeling methodology was applied to one of the collected cases to correct the measured stresses for the excavation influence. The modeling approach demonstrated the usefulness of integrating numerical modeling into a stress measurement program to estimate ‘true’ in situ stresses.

Jan 1, 2006

By D. S. Ramey

In-situ leaching of the oxidized copper mineral resource at the San Manuel mine has proven to be a technically and economically viable method of copper extraction. Although this leaching method has been modeled to predict future production capabilities, the expected magnitude of the ultimate recovery from any portion of the present mine is not fully understood. A closely controlled test has been designed, constructed, and is now operating to determine the rate and magnitude of copper recovery. The test, initiated in June 1992, is scheduled to operate for approximately 18 months. This paper presents an overview of the test design and current results.

Jan 1, 1993

By M. R. Yalamanchili

The in-situ FTIR/IRS technique has been used to spectroscopically characterize interfacial water near a hydrophilic surface. Interfacial water was examined spectroscopically over known distances from the surface of a silicon single crystal by appropriate design of the geometry and optics of the internal reflection system. The in-situ FTIR/IRS spectra of interfacial water were examined by consideration of the 0 -H stretching region (3000 -3800 cm-1) associated with the vibrational spectra of water. The broad peak: in this region which describes the interfacial water structure was deconvoluted in order to isolate the overlapping spectral features of the interfacial water. Preliminary spectral results indicate the prevalence of an ice-like water structure (-3200 cm-!) at the silicon surface. Importantly, it appears that the interfacial water structure may extend a considerable distance (several tens of molecular layers) from the surface as established from the spectroscopic depth profile measurements which show that the free OH stretch at 3600 cm-1 becomes very significant at distances from the surface exceeding 400 nm.

Jan 1, 1995

By P. Tsang

The stability of longwall chain pillars depends not only on the mechanical properties of coal and surrounding rocks, but also geological and mining conditions. In order to evaluate the effects of each, variable, the orthogonal experiment design was employed in this study for significance analysis. The study concluded that the stability of longwall chain pillars is mainly controlled by the ratio of pillar stress to pillar strength, the ratio of Young's moduluds of the roof to coal and floor to coal, entry width, pillar width and the internal friction angle of coal. Additionally, horizontal stress, panel width and mining height also play a significant role.

Jan 1, 1994

By Gary S. Brierley, John W. Critchfield

This paper is a case history of a subsurface exploration program conducted for a system of sewer tunnels in upstate New York. The focus of the discussion is a non-technical outline of how the exploration process was organized to efficiently produce a large body of geological and geotechnical data. A brief description of the project and geological setting is provided, the scope of the exploration program is summarized, the logistics of collecting, processing and reporting subsurface data is outlined, and recommendations for management of explorations applicable to any rock tunnel are provided.

Jan 1, 1983

By Steve Skelhorn

Over the recent years, major advances have been made in design of precast concrete segmental tunnel liner. Starting from basic, parallel sided rings, we now have state of the art, universal rings incorporating custom tapers to suit individual requirements. At planning stage, the ring diameter is normally fixed and the ring geometry is one of the first items to be assessed. Obvious factors such as TBM layout and curve radius can constrain geometry; however, there others factors that should be considered in order to optimize production. This paper takes a look at the history of the segmental rings and criteria for ring selection, including: general ring geometry;; individual segment geometry; ring taper, and ring width. This paper also explores optimization of ring with a focus on constructability.

By A. P. Chaves, A. Gomes

The cyanidation and adsorption processes at Fazenda Brasileiro mine were studied with the aim of increasing hydrometallurgical recovery. Technical evaluation of the processes consisted of (i) quantitative mineralogy of ore samples collected in different points of the circuit, and (ii) comparison of plant performance in the original (designed CIP) and in the modified (current CIP/CIL) circuits. An empirical correlation between process variables and gold grades in the cyanidation tailings was established. The suggested modifications in the circuit and in the operation conditions led to an increase in gold recovery, from 91 to 93.5%. Annual revenue is expected to show an increase of approximately US$ 1 million.

Jan 1, 1998