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By Gregory M. Rumbaugh, Christopher Mark

"The proliferation of unconventional gas well development in the Northern Appalachian coalfields has raised a number of mine safety concerns. Unconventional wells, which extract gas from deep shale formations, are characterized by gas volumes and pressures that are significantly higher than those observed at many conventional wells. The gas is composed largely of methane as well as other hydrocarbons. Hundreds of planned and actively producing wells penetrate protective coal pillars or barriers within active mine boundaries, including chain pillars located between longwall panels. Gas released from a well damaged by mining-induced ground movements could pose a risk to miners by flowing into the mine atmosphere. The mining-induced ground movements that may cause well damage include conventional subsidence, non-conventional subsidence (e.g., bedding plane slip), pillar failure, and floor instability. This paper describes the known risk factors for each of the four failure mechanisms. It includes a framework that can guide the risk assessment process when mining takes place near gas or oil wells.INTRODUCTIONSouthwestern Pennsylvania has served for centuries as a producer of coal, oil, and natural gas. Coal mines were first developed in the Pittsburgh Coal Seam in the 1760s, with the first recorded mine in 1761 being the Fort Pitt Mine (Edmunds, 2002). Natural gas was introduced to the region when the Haymaker Well in Murrysville, Pennsylvania experienced a blowout on November 3, 1878. Although it was originally drilled prospecting for oil, it produced an estimated 30 million cubic feet per day of natural gas. Without well controls or pipeline infrastructure in place, it burst into flames and lit the night sky for over a year. Soon after, the Penn Fuel Company continued development of the Murrysville gas field and is credited with making Pittsburgh, Pennsylvania the first major city in the U.S. to have natural gas supplied for home and industrial uses. “Natural gas is king in Pittsburgh,” proclaimed an October 18, 1885, article in the New York Times headlined “Value of Natural Gas, Its Use Clarifies the Atmosphere at Pittsburgh” (AOGHS, 2018). By the early 1900s, coal, oil, and natural gas production had reached the southern extents of Pennsylvania in Greene County. The county had first produced oil in 1886, and shortly after began producing natural gas in 1890. By 1906, over 1,300 wells had been drilled (Stone and Clapp, 1906)."

Jan 1, 2019

By Hasan Sevim

A computerized heuristic model for an efficient and economic design of belt haulage networks in underground coal mines is discussed. The model is versatile, easy to use, and is valid for all mining methods singly or in combination. It may be used to design new networks or to analyze existing networks. The input data required are 1. maximum production rates from a section, 2. probabilities of production rates, 3. equipment costs, and 4. data necessary for network coding to represent different cases. The objective function is the "expected minimum cost per ton of coal hauled" while meeting production requirements. The output includes belt width, motor horsepower, bin size etc. and also values of operating parameters for each belt such as belt speed, effective tension, power consumption etc. A detailed account of the cost involved is also provided for each unit as well as for the entire network. Description of the model and an example of the design of a belt network in a mine with two longwall and four development sections are presented.

Jan 1, 1986

By W. F. Kane

Underground geologic mapping is an extremely important aspect of any on- going ground control plan. However, the actual use of data derived from such a program is difficult and often leads to subjective analysis. In this regard, computer software has been developed that utilizes a statistical determination of unstable ground conditions based on geomechanical and operational data and collected by mine personnel on a mine-wide, or regional basis. Categorical variables, such as faulting or joint frequency, are selected from local experience to form the framework of a representative data base. Statistical comparisons between the selected variables and a particular ground control problem are conducted and correlations subsequently made. The probability of encountering unstable conditions in virgin areas is assessed as information from these regions is gathered. This data can be derived from surface mapping, cores, and/or geophysical logs. As mining progresses, new data is merged with the existing data base to form a more comprehensive and extensive unit. The advantages of this approach and the acquisition and maintainence of a large data base include the more accurate representation of existing mining conditions, increased confidence in analyzing future problem areas, and elimination of the difficulties which arise when using ground control theories derived for other, often very different, locales.

Jan 1, 1986

By S. K. Kawatra, T. C. Eisele

Although column flotation is known to be more effective than conventional flotation for cleaning fine coal, little attention has been paid to the considerable sulfur removal potential of this process. Whereas conventional flotation can only with difficulty remove pyritic sulfur from coal, flotation columns can make this separation readily due to their greater selectivity. This project has used a modified flotation column to remove pyrite from fine coal. This column has been shown to be capable of removing 70 to 85 percent of the pyritic sulfur from coal while recovering 80 to 85 percent of the total calorific value. However, the remaining pyrite is too finely disseminated to be readily removed by physical means. Currently, experimentation is in progress using bacterially-catalyzed dissolution of pyrite in acid solution to remove ultrafine pyrite and aid in the removal of coarser pyrite inclusions.

Jan 1, 1988

By John O. Marsden

The project development metallurgist is faced with an interesting dilemma: The use of overly conservative metallurgical projections and cost estimates can kill a project that has the potential to provide needed jobs and growth to a company's bottom line. On the other hand if the metallurgist uses a highly aggressive approach by trimming capital and operating cost estimates to the bone and by applying highly optimistic metallurgical projections, there is a risk of creating a project that can never live up to expectations. The metallurgist must walk a tightrope between "sandbagging" and "overoptimism," and this tightrope is fraught with political intrigue and difficulty. This paper takes a some- what lighthearted look at some of the political aspects associated with this issue, and other issues, and offers a few guidelines for walking the "political metallurgical" tightrope.

Jan 1, 2001

By K. J. Stanaway

Environmental pressures on waste disposal are forcing pigment producers to use higher content TiO2 feedstocks with lower levels of trace elements. Despite this, 50% of the worlds TiO2 comes from ilmenite concentrates with only 37 -54 % TiO2 An industry growth rate of 25 % in the next ten years combined with trends to diminishing resources and lower grades for rutile (95 % TiO2) and leucoxenized ilmenite (55 to 90% TiO2) mean that unless new discoveries are made soon, the industry will become even more reliant on ilmenite. A hypothetical ideal feedstock is presented and strategies to obtain it are suggested. Reasons for some of the mineral specifications are given.

Jan 1, 1994

By C. Steiakakis

Over recent years large construction projects have taken place and will be taking place in complex geological environments. In order to reduce costs and increase safety, a detailed geotechnical evaluation of local conditions is very important. This issue has been addressed in much detail for soils and hard rocks but there is a gap in intermediate geomaterials such as soft or altered rocks. In order to overcome this problem geotechnical engineers usually adopt principles and methods meant either for soil or hard rocks. The rock mass classification systems such as RMR, GSI etc. are the ones predominantly used. The users of these systems are of-ten unaware of the theory, limitations or the data behind these systems. The aim of this paper is to demonstrate problems or misuses of rock mass classification systems in intermediate geo-materials. The main focus is on the GSI classification system since it is widely used in Greece. Complex geological environments, altered, weathered or poor rock materials are addressed and suggestions on how they should be evaluated with the use of rock mass classification systems are discussed. Situations where the use of these systems produce erroneous results not due to their limitations but rather due to lack of experience and incorrect use are also discussed. Finally, recommendations are made for better use of these systems in practical problems

Jan 1, 2005

By J. J. Daniels

Advances in borehole geophysical research for mineral assaying and remote detection of mineralization away from the borehole are cited. Nuclear activation measurement research has provided accurate in situ assays of economic metals with neutron-gamma activation, using a high resolution intrinsic-germanium detector. Although nuclear activation analysis is the present "best hope" for obtaining in situ assays for some elements, gamma-gamma and magnetic susceptibility measurements can provide accurate assays for lead-zinc and magnetite, respectively. Borehole optical spectroscopy and X-ray fluorescence are being investigated as possible in situ assaying techniques for some minerals. More laboratory and field calibration research is needed before non-linear complex resistivity (NLCR) can be routinely used as a quantitative assaying tool. Field tests have shown that variations in the local geologic environment can affect the quantitative accuracy of assay values from downhole NLCR measurements. Deeply penetrating borehole geophysical methods are increasingly being used for mineral exploration as drilling costs and exploration have increased. Borehole electrical measurements have been shown to be useful for detecting conductive ore bodies that are not intersected by a drill hole. Hole-to-surface resistivity and surface-to-hole time-domain electromagnetics are demonstrated to be particularly effective for defining mineralized zones in a massive sulfide environment. Borehole gravity meters and three-component magnetometers have been developed and should prove useful for defining geologic anomalies away from the drill hole.

Jan 1, 1987

By Betty L. Gibbs

Microcomputers are becoming more convenient to use at all levels of the business world, including the mining industry and mine offices. The state of the mining industry requires that we become more productive and innovative in our analysis of deposits and operations. With the help of computers, examination of options to increase productivity can be performed quickly and inexpensively. Effective use of the computer for designing underground workings combines the calculation power and speed of a computer with the technical expertise and judgment of the engineer. Computer programs can perform calculations in minutes that could take an engineer several months. The engineer must be on guard when using the computer for any calculation because it is very easy to assume the results produced by a computer program are always correct. The computer is a sophisticated calculator but cannot recognize logical errors nor transposition of numbers. Also some intuitive or obvious decisions made by an engineer are difficult or impossible to program effectively.

Jan 1, 1987

By J. A. Brierley, C. L. Brierley, R. C. II Blake, S. McGinness

A principal long-term goal of this laboratory is to achieve a detailed understanding at the molecular level of the microbial-dependent solubilization of minerals. Three recent advances in this research are summarized. (i) An in situ electrolytic procedure is described whereby large quantities of autotrophic iron-oxidizing organisms may be achieved for fundamental or applied studies. Over 600 grams wet weight of Thiobacillus ferrooxidans were harvested from a single 55-gallon growth vessel. (ii) A basis is presented for classifying some 70 different iron-oxidizing bacteria into one of 4 categories, depending on the type of redox-active electron transport proteins expressed during aerobic respiration on reduced iron. Comparative spectroscopic analyses indicated that different electron transport mechanisms exist in different genera and species of acidophilic bacteria that respire on iron. (iii) A method is introduced to investigate the binding interaction between bacteria and minerals, based on changes in the electrokinetic properties of the two species. Preliminary experiments indicated that the electrophoretic mobilities of pyrite and Thiobacillus ferrooxidans were both altered when the two colloid particles were mixed prior to the actual electrokinetic measurement. The need for more basic information regarding all aspects of the microbial-dependent solubilization of minerals is evident.

Jan 1, 1993

By Jon C. Yingling

A control system for reducing peak loads on mine conveyor networks is proposed. The system involves continuous monitoring of flows into the conveyor network and section feeders with variable discharge capability. The control strategy uses differences in material transit times from various production units to the transfer points in the network to forecast load levels that will be intersected by the discharge of the controlled feeders over future time intervals. Feeder setpoint adjustments are made to prevent excessive peaks in the combined flows at the transfer points, while maintaining adequate feeder throughflow to avoid production bottlenecks.

Jan 1, 1992

By Keith G. Wallace, Malcolm J. McPherson

In order to model accurately a mine ventilation system in an existing mine, it is necessary to determine the resistance to airflow in all main airways. This is accomplished by measuring the airflow and pressure differential in each airway. Gauge and tube methods have been used to determine pressure drops in ramps and level airways. However, it has rarely been used in evaluating the frictional pressure drop in shafts. Because shafts commonly have the highest pressure loss in mines, it is critical that the resistance of these airways be determined accurately. This paper describes the theory and practice of using the gauge and tube method for determining the pressure drop in shafts. The pros and cons of using this method are discussed as well as a comparison between the gauge and tube and barometer measurement techniques. Case studies showing the accuracy of shaft gauge and tube measurements are also presented.

Jan 1, 1991

By Roland C. Walker

Traditional headed rebar has existed in the mining industry as a ground support product for many years. The head of a rebar bolt is most commonly produced by hot upset die forging. Upset die forging produces a rugged, simple head that performs well. Certain elements of the head must comply with regulatory standards, such as ASTM F432-95, which offers a standard test procedure to ensure quality of the product. The head style produced by all major manufacturers has been optimized to reduce manufacturing costs, provide greater miner safety and provide an excellent performing product. Observations were made in some mines of heads failing under in-situ loading. These observations could not be replicated according to the ASTM testing method. This paper highlights the problem and how a solution was developed. The development includes pictures of in-situ failures from the underground operations, laboratory replication tests indicating how this loading occurs, and then the use of this calibrated test method to validate the new design created.

Jan 1, 2009

By Y. L. Su

This paper describes a case study where solutions were sought to the truck queuing that occurred at a central processing plant. Ore from three production shafts at Falconbridge Limited's Sudbury Opera¬tions is hauled by three trucking contractors to Strathcona Mill. On return trips, the classified mill tailing is carried back to the mines for backfilling. The ore feeder at the mill handles three times the tonnage designed for and the situation is not expected to improve. Excessive truck queuing and consequent mine production interruptions are therefore of great concern. During the study, stochastic models were formulated and programmed for the IBM/AT personal computer. Basic information sought from the models were truck waiting time and ore production interruptions. The existing system was tested, not only to verify the validity of the models, but also to understand the causes of the problem. Several alternatives were simulated and a simple solution selected for implementation.

Jan 1, 1986

All coal preparation unit operations in which fine coal is handled depend to some extent on wettability of coal surface by water. The wetting results from interactions between the coal surface and water molecules that are determined by the composition of coal matrix (interrelated with coal rank) and heterogeneous constituents such as oxygen functional groups, mineral impurities and pores. The contact angle of water on an unoxidized, homogeneous coal hydrocarbon matrix is calculated to be 100o, and much lower values measured on real coal specimens result from contributions from the heterogeneous constituents. While the effect of wettability is critical in flotation and oil agglomeration, suppression of respirable dust, and coal water fuels, it has been shown to play a significant role also in coal flocculation with semi-hydrophobic and totally hydrophobic flocculants.

Jan 1, 1995

By Michel Dagbert

The determination of the precision of reserve estimates (tonnage, grade, quantity of metal) for an entire deposit or a large block in a deposit has received some attention in the early developments of geostatistics. A general formula to derive the estimation variance of any linear combination of a large number of sample values can be found in any geostatistical textbook like David (1977) or Journel and Huijbregts (1978). A particular case of this general formula is of course the kriging of the entire deposit. However, besides the technical difficulty of dealing with many samples the application of this formula necessitates the knowledge of the covariance between any two samples in the deposit. This is quite unrealistic in the usual case of limited stationarity where the assumption of a covariance or a variogram just function of the distance vector between two samples is only valid for samples within the same area of restricted size.

Jan 1, 1982

By George E. Niewiadomski

The exposure of miners to radon gas and its airborne daughter products is a serious health problem which has long been recognized in the uranium mining industry. The association of high exposure to alpha particle emitters with incidence of lung cancer is well established. There continues to be a pressing need to reduce and eventually eliminate the high incidence of occupational lung cancer among uranium miners through the development of new and improved measurement and control technologies. This paper highlights the current efforts of the Bureau of Mines radiation hazards research program. It is aimed at obtaining a fundamental understanding of the behavior and transport of radon and radon daughters, developing more accurate and reliable instruments and measurement methods and developing cost-effective control techniques. Also discussed are the most recent accomplishments and the future research plans of the program.

Jan 1, 1981

By Fathi Habashi

METALS COMMONLY leached may come from one of the following sources: 1) Occurring in nature in the native state, e.g., gold, silver, platinum metals, copper. 2) Produced as by-product of a metallurgical process, e.g., gold, silver, platinum metals, selenium. 3) Produced by reduction of an oxide ore, e.g., copper, nickel. GOLD AND SILVER Cyanidation According to Mellor (1923) the alchemists of the eighteenth century knew that gold was soluble in aqueous solution of potassium cyanide, and the early jewelers probably utilized this fact in gilding. He also mentions that Scheele in 1783 and later Bagration in 1843 noted the solvent action of aqueous solutions of alkali cyanides on gold. Yet it was not until 1887 that the value of this observation was recognized, when MacArthur and Forrest (1887) made use of it in leaching gold from its ores. Since then, the process has spread to every gold and silver mining district in the world.

Jan 1, 1970

By William M. Greenslade

As the search for minerals leads to deeper mines the need to control water inflow into mine shafts and mine workings will grow. As shal¬lower more readily available minerals are exploited, ore bodies which were previously uneconomic be cause of their depth will now become attractive targets. In known mining districts new ore bodies are being discovered down dip of existing ones. In the west many metal deposits are being developed in rocks of the mountain front pediments, frequently covered by several hundred feet of saturated alluvium. Greater depth often means that workings are developed well below existing water tables, creating high hydrostatic heads adjacent to mine workings. The purpose of this paper is to review some of the methods available for determining if water control will be necessary and to present some of the techniques for locating water bearing zones and the amount of water to be expected. The paper will concentrate on problems associated with water control in mine shaft development, although many of the exploratory techniques are similar to those needed for assessing overall mine water inflow problems. A brief case history on water control problems in mine shafts in the Grants mineral belt of northwestern New Mexico is presented. Water control during shaft sinking presents some unique features. First, the problem is a relatively short term one, since water control is often necessary only while the shaft is being sunk. Control measures may be necessary only while the shaft is open into the water bearing zone and the lining installed and cemented. Secondly, limited working space within the shaft area presents difficulties in handling large amounts of water inflow. The presence of water in the shaft working area increases sinking time and the potential hazard to miners. Finally, there is the economics of shaft sinking. While the shaft is being sunk no ore is being produced and there is every incentive to minimize costs.

Jan 1, 1979

By G. Davey

High speed stirred milling is a relatively new method of grinding in the metalliferous process industries. However it has been it has been in wide spread use in the industrial mineral field for over 30 years for various minerals. Many existing metallurgical operations are looking to maximize economic return from existing deposits, requiring new thinking and technologies. The operating experience of two existing copper operations will be covered to show the effect of the introduction of the Metso Stirred Media Detritor (SMD) a new type of high speed stirred mill. Both operations have derived significant metallurgical benefits from the introduction of this new technology. The benefits and process difficulties are covered and explained.

Jan 1, 2003