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By C. R. Tatman

Failure to achieve the planned production rate at new mines and mine expansions has a major adverse impact on a project's economics. A study of 60 steeply dipping tabular deposit-type underground mines showed that 35% of the mines did not achieve their production goals. An empirical formula based on the geometry of the deposit and expressed as a rate factor is applicable to select a production rate for this type of deposit. The formula is: Annual production rate = Rate factor x Rate multiplier. The appropriate rate multiplier for each category of deposit thickness and the associated risk can be used to select an appropriate production rate.

Jan 1, 2002

By L. G. Austin

Equations are derived to allow for different mean velocities of axial flow for different sizes of particles in fully mixed ball mills. The equations are modified to allow for the exit classification that occurs in grate-discharge autogenous and semiautogenous tumbling mills. An approximate treatment is given that applies for other forms of residence time distribution, provided that the mill contents are close to fully mixed.

Jan 1, 2000

Simulation models were developed at the Julius kruttschnitt Mineral Research Centre to provide accurate estimates of power consumption for a wide range of equipment. With the models, a range of circuits and operating conditions can be compared by simulation for a particular ore type. Accurate models of classification allow for the interaction between classifier efficiency and target product size (e.g., P80 or percent passing 150 /an) to be considered. This paper considers a range of circuit types and overall energy efficiency in the context of case studies where different circuit types were treating similar ore types.

Jan 1, 1999

By Christopher J. Hall

This paper describes the results from computer runs simulating 24 different mine ventilation configurations with the main fan situated first at the top of the upcast shaft and then at the top of the downcast shaft. Real air was used, with evaporation, condensation and heat exchange. The results showed that power requirements for the forcing fan were up to 20% less than for the exhausting fan for equal mass flow rates.

Jan 1, 1989

By M. Karmis

The Virginia Center for Coal and Energy Research is leading an interdisciplinary coalition to identify potential carbon sequestration sinks in unmineable coalseams as part of the U.S. Southeast Regional Carbon Sequestration Partnership. The Virginia Center for Coal and Energy Research and the Eastern Coal Council are leading education efforts for the project, as well as specific outreach efforts in Central Appalachia in order to develop a process for stakeholder education and engagement in sustainable energy.

Jan 1, 2007

By Luis Tavares Ribeiro

Dynamic programming is based on the-, application of a simple property formulated by Bellman in his principle of optimality (Bellman, 1957): "An optimal policy has the property that whatever the initial state and initial decision are, the-remaining decisions must constitute an optimal policy with regard to the state resulting from the first decision". The method is charaterised by: (Dowd, 1979) a) A function defining the total value at each decision time of the system. b) The set of permissible decisions. c) The present state of the system. d) The number of steps remaining before the procedure is terminated.

Jan 1, 1982

By J. Searls

The potash review arrived too late to appear in the June issue. Potash is a general term that includes several water soluble potassium salts: potassium chloride (muriate of potash), potassium sulfate (sulfate of potash), potassium magnesium sulfate (sulfate of potash-magnesia), potassium nitrate (niter) and sometimes potassium carbonate. Potassium carbonate was the original potash when it was leached from wood ashes and dried in large, cast iron pots to black-to-gray crystals (ash) to form "pot ash." "Pearlash" was potash roasted to white crystals. In modern terminology, the great preponderance of "potash" is the mined forms. It is estimated that 95% of the potash mined around the world is used as fertilizer. In 1840, Justus von Liebig demonstrated to the scientific community the importance of potassium to the growth of plants. But there was no low-priced source of potash available at that time. In the winter of 1851-1852, minable potash was discovered near Stassfurt,

Jan 1, 1991

By Marvin Barnes

The Sacaton mine is a relatively new open¬pit copper mine owned by Asarco, Inc., which has been in production only a few years. The mineral deposits consist of two ore zones; a western, near-surface zone minable by open-pit methods, and a deeper eastern zone which will have to be mined underground, probably by block caving. The copper deposits are related to small quartz monzonite intrusives implaced into Precambrian granites. Both rock types act as hosts for the copper mineralization, which has been secondarily enriched sufficiently to constitute ore. In the western zone the enriched supergene chalcocite has been subjected to postenrichment oxidation processes with partial destruction of the chalcocite blanket. The deeper eastern chalcocite zone has not been as severely affected by later supergene processes. Several mineralogical populations are represented in the total copper deposit. Leached capping overlies the chalcocite enriched zone, and in the western ore body there is a very irregular interface between the leached and enriched zone, which is complicated by oxide copper minerals irregularly distributed. Primary lower-grade chalcopyrite mineralization occurs below the enriched zone. When mining commenced near the top of the enriched zone, considerable difficulty was encountered in correlating the actual grade of ore in place with the estimated grade of the mining blocks. The mineralogical complexity and fairly wide spacing of diamond drilling made reliable grade estimation of individual ore blocks a difficult procedure.

Jan 1, 1979

By Chris C. Sundberg, Ronald E. Heuer, Stanley L. Paul, Peter M. Douglass

Use of prestressed concrete cylinder pipe (PCCP) for pressure tunnel liners is gaining popularity with contractors, engineers, and owners. This paper presents loading considerations and a beam-spring computer model approach to tunnel liner analysis, together with ultimate strength (US) and service load (SL) procedures for liner design. The US procedure is best suited to check for adequate liner strength under extreme loading conditions. The SL procedure, based on conventional pipeline design practice, is considered more appropriate when addressing crack control and serviceability under normal working load conditions. Other design and construction considerations are discussed and a design example is presented.

Jan 1, 1987

By Thomas A. Thorson

Bentonite is a common name applied to a variety of clays that develope swelling properties when associated with water. Useful bentonite deposits occur in many Western and Southern states. Their origins may consist of the alteration of volcanic sediments or the decomposition of shallow lake deposits. The specific type of bentonite that will be discussed in this review will be only the Western or high swelling sodium type bentonite that is mined primarily in Wyoming. Wyoming bentonite first entered the market in the late 1880's when it was used as an oil absorbing cosmetic. In the 1920's it was discovered that superior binding properties were present which created new opportunities in pharmaceutical, animal feed, and steel foundries. The swelling properties that were exhibited by the high swelling Wyoming bentonites soon led to its use in oil exploration when the rotary drilling process developed a need for multipurpose fluids. Bentonites in general and Wyoming bentonite in particular have fascinated chemists and process development specialists since the 1920's. There exists a long list of industrial uses that has led to hundreds of patents and extensive literature reviews. The binding and swelling properties are developed as a result of large surface areas and high cation exchange properties. Water, being a di polar molecule, attaches to the ionic vacancies and forms a network of tightly held water particles which in turn produces an impermeable seal or a binding characteristic in unconsolidated powder. Newer uses for Wyoming bentonite that once again utilized the binding and swelling properties include the pelletizing of iron ore and a vast array of civil engineering applications including slurry trenching, lagoon sealing, and garbage landfill sealing.

Jan 1, 1983

By Tim O’Neil

Big and getting bigger. Barrick Gold Corp., the third-largest gold producer in the world, began production in September — ahead of schedule — at its Meikle Mine. At a scheduled full production rate of 12.4 t/a (400,000oz/year), it will be the largest producing underground gold mine in the United States. The $180-million Meikle Mine is located on Barrick’s Goldstrike property in Nevada and has 205 t(6.6 million oz) of gold reserves. The compact Meikle deposit has an average ore grade of 23 g/t (0.68 oz/st), making it one of the highest-grade mines in the country.

Jan 1, 1996

By E. F. Divers, R. A. Jankowski

In response to a request from the Mine Safety and Health Administration (MSHA), the US Bureau of Mines completed a respirable dust survey of 18 US coal preparation plants. Of these, three were essentially free of dust problems. Respirable dust exposure to workers in the remaining plants depended on the time spent in the dusty areas. In five of the plants surveyed, Bureau tests showed that in some areas worker exposures could exceed Federal dust limits in less than two hours. Cooperative studies were arranged with coal preparation plants using three different dust control techniques. These included a standard baghouse-type dust collector, two types of scrubbers, and an electrostatic precipitator. Results of these evaluations are presented. Various types of ventilation systems used during summer and winter conditions were also evaluated. Results showed that appropriate ventilation can provide a highly cost-effective method for controlling coal preparation plant dust.

Jan 1, 1987

By Robert D. Gibson, E. Donald McKay, Paul B. DuMontelle

Subsidence of the land surface in some parts of Illinois is caused by underground coal mining. The U.S. Bureau of Mines is backfilling abandoned mines at selected sites in southwestern Illinois in an attempt to support failing mine openings. The Illinois State Geological Survey assists the Bureau by developing geologic and engineering information. As part of this investigation, television probes of fifteen injection borings in Belleville augmented conventional methods of study. The television probes of uncased sections of borings revealed several phenomena. Water erosion caused shale beds to slough, which partially filled some borings. Fractures caused by subsidence were identified, and excellent views of underground mine workings provided documentation of the mining method. The condition of mine timber was evaluated. Pack walls supported some openings. Both floor heave and roof fall were observed to be causes of failure in the mines.

Jan 1, 1982

By G. T. Lineberry, R. Q. Honaker

Coal extraction typically results in the recovery of pure rock that ranges from small to very large quantities depending on seam thickness and other characteristics. The removal of pure rock may allow the recovery of three times the amount in middling coal particles, which has significant economical benefits. In an industrial example, a 150% increase in revenue was realized from deshaling a low-ash, run-of-mine coal and blending with a processed clean coal product. Deshaling is the process of removing pure rock from coal, which normally involves a high-density separation in a gravity-based process. The removal of the relatively pure rock near the point of extraction has the potential to further enhance the economics of an operation due to reduced materials handling and refuse storage costs.

Jan 1, 2004

By R. J. Snow, S. N. Bhattacharya, D. D. Patil

Electrokinetics involves the movement of charged particles or water molecules in an applied dc field. Applications in particle fluid systems include the dewatering of soils, the densification of mill tailings and the treatment of coal wastes. In this paper, a novel application of this technique is discussed, wherein an electric field is applied to a coal-water slurry flowing through a pipe, resulting in lower pressure losses in the system. A unique experimental setup was designed and built to study the effect of an electric field (dc) on the wall shear stress for the flow of coal-water slurry through the pipe. The effect of solids concentration, current strength and pH on drag reduction across the system was quantified.

Jan 1, 2002

By P. Riveros, A. Pratt, G. Deschênes

The effect of pyrite, pyrrhotite, chalcopyrite, realgar and arsenopyrite on gold dissolution in cyanide media was investigated. The cyanidation of synthetic gold ores, in the presence of various concentrations of sulphides, was studied under constant experimental conditions. A mineralogical analysis of the minerals was performed. The leaching kinetics were determined. The negative effect of sulphides on the gold dissolution rate varies with the sulphide mineral, and decreases according to the following order: realgar > pyrrhotite > chalcopyrite > pyrite > arsenopyrite. The chemical characterization of gold and sulphide minerals surfaces using X-ray photoelectron spectroscopy (XPS) was undertaken to identify the mechanisms involved. XPS analysis showed that a passivation layer of sulphides, arsenic or iron compounds may form on the gold surface as a result of the dissolution of the sulphide minerals.

Jan 1, 2002

By Christopher Newman, David Newman

The ability to assess, address, and predict mining-induced stress distribution is paramount in maintaining a safe and efficient underground operation as coal mines continue to develop at deeper depths and in more geologically complex reserves. This is especially true for longwall mining operations given their limited flexibility in panel layout and orientation. This paper focuses on ground behaviors and conditions observed at two deep-cover, steeply dipping longwall mining operations in Utah’s Unita coal basin. This region is susceptible to coal pillar bump/bounce events as a result of high depth of cover, high-extraction mining, and the close proximity of a thick massive stiff sandstone stratum to active mineworks. The successful prediction of mining-induced coal bump events for Mine A and Mine B operating in the Unita basin has prompted mine management to develop a rock mechanics testing database for reserve calculations. The database is applicable to mine planning as well as the development of multiple numerical models to proactively identify and address adverse ground conditions using input parameters calibrated to site-specific behaviors and conditions. For both Mine A and Mine B, the most critical question relates to longwall development and recovery for “extreme” deep-cover longwall panels at overburden depths greater than 600 m. This paper highlights the impact of high-stress concentrations associated with deep-cover longwall mining as well as the methods applied to mitigate stress impacts on miner safety and longwall production.

Jul 1, 2023

By B. C. Bhowmick, B. B. Dhar

Central system of ventilation, adopted almost universally in coal mines of India and elsewhere in the world, has often proved deficent in providing a cost effective solution to the acute ventilation problems of remote workings in many mines. Loss of air due to leakage through a number of stoppings, doors etc. and accumulation of heat and moisture by intake air on its way to a working through long and circuitous route are the main unavoidable reasons for low efficiency of the system, sluggish and oppressive ventilation of workings. Multi-zonal ventilation system using large diameter bore holes for feeding fresh air in the mine close to a working has been proposed as a viable economic alternative. The method promises to provide congenial environment at working faces without resorting to air conditioning or use of booster fan. Optimum location and diameter of bore holes as well as general design procedure have been dealt in the paper. Finally, the technical as well as economic advantages of the method over the conventional design have been highlighted with the help of a case study where ventilation system of an extensive shallow mine in Central India has been redesigned according to the old and the new concepts. The methodology is general enough for adoption elsewhere in other mines under similar circumstances.

Jan 1, 1993

By M. Dale Slade, Gordon S. Bird, Robert S. Kelly

Gallium scrap is obtained from many different sources, therefore each lot received has to be evaluated and then processed accordingly. Some of the problem areas are separating small amounts of gallium from large concentrations of iron, eliminating trace amounts of gold, silver, copper, germanium, tin, and zinc from gallium, and having the flexibility to process each lot of scrap individually Following gallium from the raw scrap material to the final seven nines pure product requires stringent quality control and excellent analytical capabilities.

Jan 1, 1983

By G. J. Lindenburg, T. L. Wilson

The Velvet uranium mine is located in the Big Indian district of the Colorado Plateau. The uranium ore body lies within the lower Triassic Chinle Formation, and the ore is associated with west-south-westerly trending fluvial sand systems. Exploration and mining are directed by longhole drilling and radiometric sampling. Results of the gamma probing, face scanning, and geologic mapping guide mining decisions and planning. Three people are directly involved with the geologic procedures: two geologists and a mine supervisor. The two geologists map, do rib scans, and direct longhole drilling. The third man involved, the mine supervisor, has last minute directive action based on shot hole probe data.

Jan 1, 1992