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By Lawrence A. Ph. D. Hansen, J. David Deatherage

Laboratory testing programs were conducted to investigate the performance under compression loading of several types of geomembranes and geotextiles proposed for use in heap and dump leach projects. Synthetic liners of several thicknesses were sandwiched between representative subgrade soils and cover materials, thus modeling in the laboratory the actual installation conditions expected. Performance was evaluated by visual inspection and vacuum testing. Several testing procedures and equipment were used to investigate the effect of these testing parameters on the predicted performance.

Jan 1, 1987

By D. Lelinski, X. Nie, J. D. Miller, J. Hupka, K. Bukka

A preliminary characterization of soil components contaminated at a low level (7 nanocuries per gram) with toxic/radioactive metals has been carried out. Most radioactivity and metals content were present in the minus 100 mesh (<150 µm) size fractions. None of the size fractions examined qualified for uncontrolled disposal at dump sites, thus all material would have to be moved to discharge-controlled landfills. The metal content of the sample was below the limits for economical recovery, therefore eventual processing would be dictated by environmental concerns.

Jan 1, 1992

By Raymond E. Kary, John W. Mcklveen

The four unit Cholla coal fired power station at Joseph City, Arizona, consumes coal from the McKinley mine located in western New Mexico. Since coals may contain relatively high uranium or thorium concentrations and may release quantities of detrimental progeny of these elements to the environs, there is concern that releases may pose an adverse environmental impact or even a health hazard to the workers. Thus, an effort was made to quantify the radionuclide content of the coal and compare the results with radionuclide concentrations already present in the vicinity of the plant. Additionally an attempt was made to assess any potential for significant enhancement of the levels of radioactivity in the environment or to plant personnel. Background gamma radiation measurements at and near the plant ranged from 8 to 12 [µ]R/hr (70 to 105 mR/yr) with a few localized anomolies measuring to 18 [u]R/hr (160 mR/yr). Levels on top of the coal storage piles decreased to ~ 6.5 [u]R/hr (60 mR/yr). Apparently the direct radiation emitted from the coal is less than the background levels in the vicinity of the plant. Measurements performed on top of several coal seams at the mine confirmed low radiation levels emanating from coal, but readings more than doubled when the overburden was monitored. Laboratory gamma spectrometry confirmed the lower amounts of natural radioactivity in the coal when compared against soil and water samples obtained in the vicinity of the plant and the overburden at the mine. In an effort to see if there is biological enhancement, animal feces was sampled. The radiation variations were found to be influenced primarily by naturally occurring potassium-40 which varied from ~ 1 to 18 pCi/gm rather than fluctuations in the uranium and thorium series. The potassium-40 concentrated in the ash were similar to the concentrations in the environs around the disposal ponds while Radium-226 concentrated in the fly ash was ~ 3 times that found in the immediate surroundings. Radon-222 gas concentrations in buildings at or near the plant ranged from 0.5 to 1.8 pCi/l and were generally lower than indoor concentrations measured in the Phoenix area. The burning of coal at the Cholla station does not appear to increase ambient levels of radioactivity found in the surrounding environs or to the workers. However, the use of byproduct fly ash for construction purposes may need to be examined.

Jan 1, 1981

By Fred Leighton

INTRODUCTION Dynamic (seismic or microseismic) methods of determining the stability of structures in rock are based on detecting and analyzing the characteristics of seismic energy that has originated from or traveled through the rock mass. This seismic energy can be in the form of naturally occurring rock noise energy resulting from structural adjustments within the rock or can be introduced into the structure by physical means, such as by blasting or impact. In either case, the seismic energy radiating through the rock mass can be detected using standard equipment and can be analyzed by established techniques to reveal a wide variety of information concerning the condition and stability of the rock mass through which the energy has traveled. In the following sections, the basic instrumentation required for seismic and microseismic studies is described, and some of the presently used applications of these methods are discussed to exemplify the state of the art. INSTRUMENTATION Seismic disturbances in a rock structure generate two types of seismic wave radiation, body waves and sometimes surface waves, which radiate outward in all direc¬tions from the source of the disturbance. Underground mining applications are generally concerned only with discerning the characteristics of the resulting body waves, i.e., the compressional (p-wave) and the shear (s-wave) energy. As these two forms of energy travel through the rock structure, the particles of the rock mass are caused to vibrate, and the vibration character¬istics resulting from each of the two types of wave are distinct. Some important differences are: 1) Compressional and shear waves travel at different velocities through the rock structure. 2) The frequency at which each wave causes particles to vibrate is different, and may range from about 50 to 100 000 Hz. 3) The amplitude or energy level of each wave is different, with the shear energy usually being the greatest. These differences form the basis for equipment se¬lection for individual studies and for modern data analysis techniques. The following sections describe the basic equipment necessary to detect and record seismic wave energy data and show several examples of analysis procedures and how these procedures have been used. In principle, seismic equipment is very simple. It consists of a geophone (or geophones) to detect the seismic energy vibration and convert that vibration to an electric signal, an amplification system to increase the level of that signal, and a means of monitoring and/or recording the signals detected. Fig. 1 is a block diagram of a typical system. The following sections offer a very brief discussion of system components and their individual functions. A more complete discussion is given by Blake, Leighton, and Duvall (1974). Geophones The function of the geophone is to detect the vibrations caused by the passing of the seismic wave energy and to convert that vibration into an electrical signal that displays both the amplitude and frequency characteristics of the vibration. Particle motion or vibration can be quantified and measured by measuring displacement, velocity, or acceleration of the particles. Thus, there are three types of geophones: displacement gages, velocity gages, and accelerometers. The choice of gage depends on the characteristic frequencies of the seismic energy to be monitored and the sensitivities of each type of geophone. In general, displacement gages are used for low-frequency monitoring (periods to 1.0 Hz), velocity gages for medium-frequency monitoring (1.0 to 250 Hz), and accelerometers for high-frequency monitoring (250 to 10 000+ Hz). Experience has shown that in underground studies, the choice of which gage to use lies between velocity gages and accelerometers. An easy, accurate method for selection of gage type is discussed by Blake, Leighton, and Duvall (1974). Once the type of geophone has been selected for use, it must be properly installed, and in the installation procedure the most important step is insuring that the gage is firmly attached to a competent portion of the rock structure. Poorly mounted geophones may entirely fail to recognize low-level seismic signals and will distort the information from signals they do see. Amplifiers Seismic events associated with mine structures occur over a very broad range of energy which results in a broad range of geophone output levels. In general, geophone output levels occur in the microvolt to low milli-volt range, and it is necessary to amplify these signals in order to drive recording or monitoring equipment. Because either an accelerometer or a velocity gage might be used as the geophone, the amplification system must

Jan 1, 1982

By S. S. Peng, V. Z. Sun

One of the major concerns of ground control in a coal mine is the prevention of roof, pillar and floor failures of the mine entry. To better design and evaluate the stability of a mine entry within a certain level of confidence, a reliability approach is introduced. The advantage of using the reliability approach, rather than the conventional safety-factor (SF) method, is that it not only takes variability of both rock/coal properties and stress into consideration but also assesses the stability of each component and the mine entry as a whole. Therefore, it is anticipated that by using this approach the current ground-control technology in a coal mine will convey a better sense of confidence. The results of a case study show that there is a significant difference in mine entry stability between the current design method and the reliability approach.

Jan 1, 1999

By Jackson G. Jenkins

Magma Copper Company&apos;s San Manuel SX-EW facility has operated since May, 1986. The original facility had a design capacity of 25,000 tons per year of electrowon copper cathode produced by processing pregnant leach solution from an open pit/heap leach operation. In 1988, the plant was expanded to 50,000 tons per year to incorporate processing in-situ leach solutions. This paper focuses primarily on the heap leaching area with regard to exploration, testing, feasibility, permitting, design and construction, and operating practices. Research utilizing surfactant leaching aids to enhance copper recovery is also discussed.

Jan 1, 1993

By Pieter C. van Aswegen, J. A. Brierley, C. L. Brierley

The bacterial-oxidation (BIOX®) process for the pre-treatment of refractory ores for gold recovery is marketed by BlOMlN Technologies S.A. The process was originally developed by GENMIN who is still providing testwork, design and commissioning assistance to BIOMIN. Since 1986 three BIOX® plants have been commissioned by GENMIN. A further two plants will be commissioned during 1993 and 1994. The commissioning and operational experiences from these plants are described in the paper.

Jan 1, 1993

By J. G. Groppo, J. G. Justice, B. K. Parekh

Removal of particulates and/or metal ions from mineral/coal processing waste water is a necessity from the environmental point of view. This paper describes application of a novel AC- electrocoagulation technique to remove the particulates as well as metal ions using AC power. A series of laboratory tests conducted on a stable black water sample obtained from a sub-bitminous coal operation provided a clear supernatant (-10 NTU) from the suspension. The process also shows promise in removal of up to 90 percent of phosphate ions and other metal ions (copper and nickel) from solution. A preliminary economic evaluation of the process will also be included.

Jan 1, 1992

Exploration for SX-EW copper deposits and plant operation depend largely on the copper and gangue mineralogy inasmuch as? they govern the feasibility of leaching. Mineralogical parameters are pivotal in identifying if an ore is suitable to dump, heap, thin layer, vat or agitated leaching and/or if the ore requires curing, bioleaching or alternate lixiviants. Problems in metallurgical testing, production leaching and recovery forecasting are very often related to lack of mineralogical data. This presentation will illustrate the use of quantitative mineralogical analysis for exploration, acquisition assessment and optimization of copper leach operations.

Jan 1, 1996

By R. L. Unger

Restricted fields of vision are a common problem with underground mining equipment. Also, when lighting systems are provided, they may be positioned where they cause glare. This restricts the visibility around the machines even further. To help address these problems, the US Bureau of Mines has developed a PC-based software package to aid in the analysis of certain human engineering aspects of mining equipment design. The software is available for use by equipment manufacturers and mining companies for design work on new machines, as well as for evaluating proposed modifications to existing machines.

Jan 1, 1995

By L. A. Hansen, D. L. Buffington, G. H. Beckwith

This paper reviews geotechnical engineering considerations in heap leach pad design, discusses design philosophy and provides design procedures. A brief discussion of surface water hydrology ground- water protection and other design considerations are also presented. Special emphasis is placed on projects in the arid and semiarid regions of the Western United States where annual evaporation exceeds rainfall, and where good foundation conditions are usually present.

Jan 1, 1987

By John F. Martonik

When OSHA came into existence in 1970, it adopted national consensus standards to improve safety and health conditions in work places. Coke oven emissions, which are proven to cause cancer and respiratory diseases, were regulated by the coal tar pitch volatile standard, adopted from the 1969 edition of the Threshold Limit Values for Airborne Contaminants by the American Conference of Governmental Industrial Hygienists. The coal tar pitch standard, based upon the benzene soluble fraction of total particulates, limits the personal exposure to 200 micrograms of the benzene soluble fractions of total particulate per cubic meter of air. This standard can be classified as a performance standard because only general limits are set which allows the employer to choose for themselves the means to comply. Both the United Steelworkers of America and the American Iron and Steel Institute petitioned the Secretary of Labor to write a new standard for coke oven missions, each thinking the coal tar pitch standard unsatisfactory.

Jan 1, 1980

By Ignacio Salazar

Somebody sure gave me the wrong title. I can talk much more freely about the impact of the anti-nuclear movement on the DRILLING industry in New Mexico. In a word, it is being "clobbered." It doesn&apos;t seem like very long ago that my brothers and I were busy trying to find enough new equipment (and trying to talk bankers into lending us enough money) to keep up with drilling work we could get. Seemed like no matter how hard we worked, and how much money we borrowed, we were always one step behind where we wanted to be. We had so many holes to drill that all our crews were working three shifts a day, and over several states. The nation needed energy, and we were ready to help supply it. Exploration and development drilling jobs were all going full-blast. We had trouble keeping up with them. With luck, we figured we&apos;d be able to get all our equipment out of hock before all the necessary uranium mines were developed.

Jan 1, 1979

By Pierre Mousset-Jones, Felipe Calizaya, Malcolm J. McPherson

The algorithm presented in this study determines the combination of fans that provide all working districts of a mine with predefined airflows at the minimum operating cost. It is based on an existing ventilation simulator, VNETPC, and a set of linear equations associating fan pressures and the added resistance of regulators. Two assumptions are undertaken: (1) fan locations are predetermined and (2) the number of working districts is equal to or greater than the number of fans. By means of this algorithm, the optimal solution to an n fan ventilation system may be found after n + 1 simulation runs.

Jan 1, 1987

By K. A. Natarajan

This paper deals with the various electro- and biochemical mechanisms involved in the bioleaching of multisulfide minerals such as those containing copper-lead-zinc and copper-nickel-iron. Galvanic series for sulfide minerals consisting of pyrite, chalcopyrite, galena, sphalerite, pentlundite, and pyrrhotite in an acid bacterial leaching system is illustrated, and the role of relative electrochemical activity on selective dissolution is discussed. Typical leaching results are shown to illustrate the practical applicability of galvanic effects in bioleaching of multisulfides. Attachment of Thiobacillus fewooxidans onto chalcopyrite and sphalerite mineral substrates is illustrated through scanning electron micrographs. The role of high-metal-tolerant, specially adapted strains in the leaching of multimetal concentrates is also outlined.

Jan 1, 1987

By Thomas R. Kuesel, Harvey W. Parker

INTRODUCTION This paper describes the use of a shield and compressed air for construction of a short section of a pair of twin single-track tunnels for the Metropolitan Atlanta Rapid Transit Authority (MARTA) transit system. Although only two blocks long, this section posed the greatest difficulties to both engineers and contractors, and is the most expensive section of line construction on the MARTA system. All this derives directly from its setting--these tunnels had to be constructed through mixed-face conditions. SETTING The Broad Street tunnels form a link between the Peachtree Center and Five Points Stations, in the heart of Atlanta&apos;s central business district (Figure 1). Peachtree Center sits atop a solid rock ridge, which inspired the design of a deep rock-mined station, as described in the 1979 RETC. Five Points Station is MARTA&apos;s hub--the intersection of the system&apos;s two main branches. It is located in the old railroad gulch, a filled-in erosional valley at the base of Peachtree Ridge, and was constructed by open-cut methods. The alignment and profile of the Broad Street tunnels were closely constrained by these two adjacent anchors, and in the six-block stretch between them there was very little room for maneuvering. Since the rock ridge petered out about in the middle of the section, it was evident at the outset that there would be about two blocks of rock tunneling at the north end, two blocks of soft ground construction at the south, and two blocks of mixed-face in between. It is this central two-block section that is the focus of this paper.

Jan 1, 1981

By James R. Fahy, Lawrence A. Hansen, J. David Deatherage

A laboratory testing program was con- ducted to investigate the shear strength along specific soil-liner interfaces for five types of liners of varying thicknesses. Results indicated a bilinear relationship between shear stress and applied normal stresses ranging from 276 to 1000 pKa (40 to 145 psi). Friction angles along the soil- liner interface below the break point normal stress (7.5 to 19 degrees) were lower than those recorded above the break point normal stress (14.5 to 39 degrees ).

Jan 1, 1987

By M. B. Díaz Aguado

Traditionally, the practical evaluation of a mining project for a potential investment has been made considering mainly technical aspects. But the concept of sustainable development has introduced significant changes in the factors analyzed to make the final decision. This paper proposes an empirical evaluation of a project considering not only technical, economic and financial parameters, but also associated risks and other intangible aspects, such as political considerations, stability in the legal frame, social factors and environmental issues. The proposed methodology is practical and easy to apply for project management. Among its main advantages, the following could be quoted: using this evaluation two different projects or locations of a same project can be compared, future behaviors could be predicted, the index incorporates a new approach to specific mining projects and this perspective could also be applied to other projects with environmental and social impact, such as civil works or industrial projects.

Jan 1, 2007

By George McArthur

GEOLOGY One of the largest copper resources in North America occurs in the Bingham mining district, located 40 km (25 miles) southwest of Salt Lake City, UT. Anaconda&apos;s present contribution to the development of this resource is the Carr Fork mine. (Fig. 1, Bingham district plan map.) The Carr Fork story began about 300 million years ago when a thick sequence of sedimentary quartzite and limestone was deposited in the Oquirrh Basin. Subsequent earth stresses formed a series of west-northwest-trending overturned anticlines and synclines that were later offset by northwest-striking thrust faults and northeast-trending normal faults. (Fig. 2, Bingham district cross section.) About 38 million years ago the Bingham stock was intruded into some of the folds, resulting in the formation of porphyry ore in the intrusive, and fissure, replacement, and skarn ore deposits in the sediments. The Carr Fork skarns were formed preferentially in two limestone units, called the Yampa and Highland Boy, which average about 46 m (150 ft) in thickness, separated by about 76 m (250 ft) of quartzite. Copper mineralization consists almost entirely of chalcopyrite associated with pyrite and molybdenite in a gangue of garnet, diopside, magnetite, quartz, and carbonate. Molybdenum, gold, and silver are economic byproducts. (Figs. 3 and 4, indicated ore in plan and section.) EXPLORATION HISTORY The West Mountain mining district, of which Carr Fork is a part, was organized in 1863, after leaf-silver ore was discovered in the Carr Fork of Bingham Canyon. However, it was not until 1873, when the Bingham and Camp Floyd railroad to the town of Bingham was completed, that the mining camp flourished. Many small mining companies in the district were reduced, often through consolidation. By 1937 only the National Tunnel and Mines Co. was active in the Carr Fork area. In 1948 it declared bankruptcy, and was later purchased by The Anaconda Co. Anaconda conducted geologic investigations in the Bingham district until 1968, when a concerted diamond drilling program was initiated to fully evaluate the geologic potential of the Carr Fork area. The exploration program commenced with one diamond drill, but was enlarged to three drills following discovery of the first major ore intercept. Near completion of the exploration effort, large oil well rotary drills were used to drill to depths of 762 to 914 m (2500 to 3000 ft), after which the holes were completed by standard diamond drilling techniques. All holes were collared vertically, but considerable deviation occurred because of structure and rock conditions. Wedging and directional drilling were used to keep the holes on target and to provide multiple ore intercepts in the deeper holes. Geophysical surveys, in-

Jan 1, 1982

By V. E. Cole

For the successful execution of a major project, the project team must be thoughtfully organized, manned, instructed and motivated. This is true of both the engineer/constructor team and the mining company team. Then these teams must be carefully related so that they function effectively as one organization on the job. This paper describes the organizing techniques and the human ingredients and know-how of a successful project.

Jan 1, 1980