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By Daniel D. Sweeney

The United States coal mining industry has traditionally experienced difficulty in controlling dust levels below the occupational exposure limit. While improvements in face ventilation and water spray nozzles have decreased dust exposures, approximately eight percent of experienced coal miners are still developing Coal Worker?s Pneumoconiosis. This investigation tested the feasibility of enhancing existing engineering dust controls by mounting a simple barrier on a longwall shearer that separated the operators from the cutting drums. The barrier was constructed and tested above ground at the National Institute for Occupational Safety and Health Pittsburgh Research Laboratory longwall gallery test facility. A 96-percent reduction of respirable dust occurred at the headgate sampling position when tested at 2.4 m/sec (480 ft/min). The average dust level decreased from 39 mg/m3 to 1.5 mg/m3 by utilizing the barrier.

Jan 1, 2009

By George Rice

VENTILATION of underground workings to fur-nish air of good quality to workers is now the accepted practice for all kinds of mining; but in coal mining it is also a requirement vital for safety to have systematic coursing of the air to all parts of a mine so that fire damp can be diluted and carried away. These two basic needs are recognized in the codes of every country or State where coal is mined, and each has its own system of ventilation requirements. With the same fundamental requirements, varying in degree but not in kind, the surprising thing is that these and other features of regulatory codes should vary so-wide-ly that their provisions on the same subject bear hardly any resemblance to one another. This was strikingly brought out in the paper given before this institute in 1926, on "State Coal-Mining Laws Concerning Ventila-tion1. The explanation ordinarily is that the geologic forma-tions and the mining conditions and methods differ in the various coal fields. Although that is true, in most countries and States the variations in the differ-ent mining districts within each country or state vary widely, and the respective codes must be made to apply by special provisions to meet the variations in thickness of coal, depth,. dip, character of roof, and presence or absence of gas. Evidently the great diversity in codes is due to the method of formulating them. Some are prepared by political commissions in which partisan interests are a factor; others originated in the early days of mining with meager outlines and were so amended by legisla-tive acts or administrative orders from year to year as to become complicated and ambiguous, and pro-visions in different parts of a single law are often contradictory. Such laws have therefore been difficult to interpret and to enforce adequately.

Jan 5, 1928

Silver is one of the three major metals produced from the Broken Hill mines. The accurate determination of the silver in these ores, therefore, is of economic importance.With due appreciation of the divergence of opinion of many who are interested in the subject of the determination of silver, the writer has been prompted to present the results of some recent experiments on silver losses during cupellation and conclusions from these experiments in the present paper. The losses of silver in the fire assay for this metal are due to silver retained in the slag during the fusion or scorification of the ore, and to silver volatilized from, and absorbed by the cupel during the process of cupellation.The literature describing the results of experimental work on silver losses due to the above causes is extensive, and the general conclusion of these experiments is that the silver lost in the slag is small, but that lost by cupellation is larger and more variable.The term cupellation loss in this paper refers to the total cupellation loss, no distinction being made between the absorption and volatilization losses.Volatilization loss is shown by King to be 0.5% of the total cupellation loss and, as it is generally accepted among assayers as being only a small fraction of the cupellation loss (3) (5), it will not receive further consideration in this paper.The factors causing the loss of silver by cupellation and the precautions to be obs~rved to reduce the loss in this operation are described in (1), (2), (3), (4) and (5). The...

Jan 1, 1940

By Mingju Liu

The coal and gas outburst accident on May 20, 2007 at Sihe Coal Mine is unique in that there was no or very little soft coal in the coal seam and that the coal strength was very high. The outburst also showed that there was a very high gas content of 20-30 m3/t in the coal seam nearby the outburst site. Based on the field test and observations, together with laboratory experiments, detailed analysis was conducted on the controlling factors of coal and gas outburst potential at Sihe Coal Mine. Stress data available from Sihe Coal Mine, northern China, and other parts of the world, were also taken into account to facilitate the analysis. The results shows that the stress level was not abnormal compared to other coal fields in China prone to outbursts, and that gas contained in the coal seam was the main factor that triggered the outburst. All these factors were essentially controlled by the tectonic evolution features in Qinshui Coal Basin, to the Southeast of which Sihe coal field is located. Based on the analysis, assessment of coal seam outburst potential was carried out by measurements of coal seam gas contents, observation, and detection of soft coal layers in the coal seam. The results show that outbursts are limited to only a small part of the whole coal seam and that the eastern part of coal field is not prone to outbursts.

Jan 1, 2009

By L. Yan, C. Zhou, M. Reyes

"The MINER Act requires the installation of post-accident, two-way communications and electronic tracking systems for all coal mines. One communication system which can satisfy this requirement is an electrode-based, through-the-earth (TTE) communication system, which sends signal directly through the overburden of a mine. The performance of these types of systems relies on several controlling factors such as earth conductivity, overburden depth, operating frequency, TX/RX antenna length, TX/RX offset, TX/RX orientation angle and TX current. In an effort to estimate attenuation through the earth, NIOSH researchers developed an analytic solution for the electrical field distribution of an electrode-based TTE communication system for the extremely low-frequency (ELF) range (< 30 Hz) or DC excitation source. The analytic model was then validated using test data measured at an operating coal mine. The validated model can be used to optimize the operating frequency, estimate the required transmitting current, choose appropriate TX/RX orientation, and predict the performance of an electrode-based TTE system at a coal mine. INTRODUCTION One of the requirements of the Mine Improvement and New Emergency Response Act (MINER Act) of 2006 is the installation of post-accident, two-way communications and electronic tracking systems for all underground coal mines. As one of the through-the-earth (TTE) wireless communication methods available for the mining industry, the electrode-based, or linear, TTE systems establish communication by inducing a current within the earth medium by use of a pair of current probes. The resultant current is detected as a voltage by a similar set of distant probes. These probes could be an insulated piece of wire tied to two electrodes grounded at distant ends, or the grounded ends could be rails, roof bolts, or grounded electric rods. The analytical solution developed in a homogenous half-space, for this form for various transmitter/receiver (TX/RX) configurations, will be presented in this paper. The communication signals can be sent either from underground to surface (uplink) or from surface to underground (downlink). In order to achieve a successful communication link, it is necessary to understand the electric fields within the earth so that the appropriate size of transmitting antenna, TX/RX relative orientation, and operating frequency can be chosen. Hill and Wait gave the explicit forms of partial magnetic fields and partial electric fields of electrode-based TTE downlink communication with finite cable length [1]. In prior research, the E-fields of electric line transmitter were obtained for a static TX current [2] [3]. In this paper, the general and explicit forms for electrode-based TTE electric fields are developed and presented. The solutions for the extremely low-frequency (ELF) range (< 30 Hz) or DC excitation source obtained from these forms are presented. Also, factors that affect the E-field strength at RX are discussed."

Jan 1, 2017

By Donald W. Mitchell, John Nagy, Edwin M. Murphy

In 1957 research was initiated in the U.S. Bureau of Mines experimental coal mine near Pittsburgh, Pa., to study factors affecting foam generation and transport, to evaluate the effectiveness of high-expansion foam for controlling mine fires, and to develop techniques for applying the method under U.S. mining conditions. These investigations showed that high-expansion foam containing at least 0.2 oz of water per cu ft of foam is effective in controlling experimental underground fires burning coal, wood, and oil. Sometimes the fire was completely extinguished, but more often, it was brought under sufficient control to permit either a direct attack on the fire with a stream of water or loading of the hot material into cars. A progress report prepared in July 1958 summarized the initial achievements of the USBM experiments. Since then other phases of the foam-plug method for attacking fires have been studied in the laboratory and in the mine. Previous studies by British engineers of the foam-plug method for fighting mine fires indicated that high-expansion foam was effective in controlling experimental timber fires in an underground passageway. Their subsequent work pertained to the practical aspects of fighting large fires within a mining area with a foam-plug.

Jan 9, 1960

By Rachel Bauer, Jacob Henderson, Dr. Catherine Johnson

Capital Quarries in Owensville, Missouri faces several challenges when designing a blast that allows for ease of movement while maintaining controlled throw and compliant air over pressure. The primary challenge is the nearest non-owned structure (NNOS) is a residential home located 250 feet from the quarry. Another challenge is a production bench which is 100 feet tall and separated from the NNOS by Pennsylvanian fire clay that filters out high frequency waves from the blast. Material from the blast must also be less than 5 inches in order to be processed by the crusher in the quarry. To provide as much relief as possible, production shots will consist of a single row with the minimum required burden. To design the shot, signature hole analysis was used to determine the optimal timing between powder columns. Electronic detonators provided an accurately timed shot to minimize the amplitude of the vibrations while maximizing the frequencies. Boretraking and 3D profiling with Renishaw laser profiler and Strayos drone photogrammetry provided an accurate burden measurement. Powder factor was kept at 1.3 tons/lb using bulk emulsion. The boreholes were split into 5 powder columns with the top of the hole firing first in order to blast to floor grade. The resulting shot produced good fragmentation and shot to floor grade. Seismograph readings showed air over pressure vibrations within legal limits. Due to this success, multiple shots will be designed using the process described.

Feb 6, 2023

By Richard C. Enochs

In order to clearly understand our process control system it is necessary to briefly discuss the various process control systems that were considered and why we chose our particular configuration. We considered Analog Systems, Computer Supervisory Systems, Computer Setpoint Systems, Direct Digital Systems and Direct Digital with Backup Systems. Our concept of these systems is illustrated in Figure 1 through Figure 5. We chose Direct Digital Control with Manual Backup because it had the greatest flexibility, ease of implementation and cost no more than a pure Analog Control System for one control concept. There would be no increase for a Direct Digital Control with Manual Backup System if the control concept were changed, while there could be considerable additional cost with an Analog System, if the control concept were changed.

Jan 1, 1975

By Steve Kral

The third edition of the Underground Construction Association of SME?s (UCA) Cut-ting Edge series of conferences focused on a challenge every underground construction and tunneling project faces: controlling ground water. The conference, held in New York City in November, is a partnership between the UCA and The North American Tunneling Journal. It featured more than 20 technical presentations by professionals from around the world. Each described specific challenges unique to their projects and the solutions employed. More than 175 professionals attended the two-day conference that included an exhibition featuring 17 companies. In addition to the technical program, the Cutting Edge conference featured a site visit to the $10.4 billion East Side Access Project. Sponsors of the meeting included Soil Freeze, Traylor Bros., Kiewit, Skanska, Moretrench, Aecom and The Robbins Co.

By Rob Domotor

This paper tells the story of using controlled surface and underground blasting methods to excavate hard rock in three areas on Australia’s largest road infrastructure project; the Airportlink Project in Brisbane; worth a total value of AUD $4.8 billion. The project used blasting methods including design, modelling, drilling and loading of the explosives that had never been used before in Australia, some of these were probably unique in the world.

Jan 1, 2012

By K. C. Vories

Surface mining and reclamation has the potential to at least temporarily increase surface runoff and resultant erosion and gully development. This increase in erosion is due in part to compaction of the soil surface with heavy equipment, creation of large relatively unvegetated watersheds, and elimination of natural dendritic ephemeral drainage patterns. Methods for stabilizing gully channels which may develop prior to establishment of sufficient vegetation to control erosion are analyzed. Utilization of various sizes of riprap for channel lining, the use of riprap check dams, reinforcement of riprap check dams, and the relation- ship of type of control structure to area of watershed and resultant flow velocities are discussed.

Jan 1, 1986

By Pengfu Tan

Xstrata Copper at Mount Isa in Australia has operated one copper Isasmelt furnace and four P-S converters. The phenomena of foaming occur in above 10% of converter operations. A thermodynamic model of copper P-S converter and a viscosity model of converter slag have been developed to simulate the slag blow and copper blow. The model predicts the chemistry and viscosity of copper skims during copper blow. The effects of oxygen potential, charge of dirty materials, slag carry-over, under-blowing, over-blowing, and temperature on the foaming and viscosity of copper skims have been discussed. Some improvements of the industrial operations have been presented.

Jan 1, 2006

By Mohammad A. Pasha, John T. Atkins

Utah International&apos;s Shirley Basin Mine is located in the Southeastern High Plains of Wyoming at an elevation of 7100 ft. The Shirley Basin area is a gently rolling semi-arid land. The uranium ore zone occurs at depths ranging from 270-350 ft below the surface. Overburden consists of poorly consolidated sandstones, siltstones and clays. Underground mining was begun in 1960. Conditions were made difficult by high rates of water inflow and ground support problems. Development of a solution mining or in-situ leaching technique allowed underground operation to be abandoned in 1964. Solution mining provided limited production from 1963 to July 1970. In January, 1969, large scale development of open-pit mining was begun. A 1200 tpd mill went on-stream in March, 1971.

Jan 6, 1973

By John T. Atkins

Utah International&apos;s Shirley Basin Mine is located in the Southeastern High Plains of Wyoming at an elevation of about 7,100 feet. The Shirley Basin area is a gently rolling semi-arid land. The uranium ore zone occurs at depths ranging from 270 to 350 feet below the surface. Overburden consists of poorly consolidated sandstones, siltstones, and clays. Underground mining was begun in 1960. Conditions were made difficult by high rates of water inflow and ground support problems. The development of a solution mining I or in-situ leaching technique allowed underground operation to be abandoned in 1964. Solution mining provided limited production from 1963 to July 1970. In January, 1969, large scale development of open-pit mining was begun. A 1,200 ton per day mill went "on stream" in March, 1971.

Jan 1, 1973

By Kaushik Dey

Bord and pillar is the most predominant method of wining of coal in Indian underground coal mines. Development heading in coal mines often encounters roof stability problem and results in roof overbreak. Research on this reveals that the blast-induced ground vibration may have significant contribution in roof overbreak, especially, when solid blasting is carried out in the bord and pillar method. Solid blasting, in general, is associated with higher charge confinement due to lack of free face and generates higher ground vibration, which in turn results in excess overbreak.

Jan 1, 2008

By Balakrishnan Nanthakumar, Marek Pawlik, Dennis Grimm

"The anionic flotation of a high-iron phosphate ore from Agrium - Kapuskasing Phosphate Operations was investigated through batch flotation tests in the presence of soda ash. The flotation data were supplemented by titration of the flotation pulp with soda ash, analysis of process water chemistry, and determination of the mineralogical composition of the ore. The results of lab tests were applied to the flotation circuit design allowing the flotation plant to efficiently process problematic ores. Process control measures (pH, conductivity) were also developed.Calcium cations and sulfate anions were identified as the dominant ions present in the process water when the difficult-to-process ores are beneficiated in the flotation plant. The concentrations of calcium and sulfate ions were consistent with the presence of a small amount of a calcium sulfate mineral in the ore although an oxidation/weathering process of iron sulfide minerals present in the ore could also be responsible for the observed water chemistry and subsequent flotation problems with the ores. The latter possibility suggests that the long-term stockpiling of such ores may have a highly negative impact on the flotation process.The role of soda ash in the flotation circuit is to precipitate metal cations from the pulp thus allowing the tall oil-based collector to selectively interact with the phosphate components.INTRODUCTIONPhosphorus minerals are the main source of this element for the production of fertilizers, and the froth flotation process is the most important technology for beneficiating phosphate ores. The flotation concentrate from Agrium-Kapuskasing Phosphate Operations (KPO) is transported to Redwater Fertilizer Operations in Alberta (also operated by Agrium) where the phosphate concentrate is converted into a phosphate fertilizer and other important chemical products. The KPO phosphate ores differ widely in mineralogy and phosphate grades, and are broadly divided on-site into three classes. The easy-to-float A-type ores do not pose any major flotation problems, but the B-type and “marginal” ores, which are quite common in the KPO igneous phosphate deposit, are not always readily-floatable using the current reagent suites and process parameters (pulp density, feed particle size, pH). In fact, marginal ores are presently considered impossible to process by flotation. A-type ores contain normally more than 15% P2O5 and less than 8% ferric oxide equivalent (Fe2O3). B-type ores are approximately of the same P2O5 grades as A-type ores but their iron content may reach 30% Fe2O3. Any material containing less than 15% P2O5 is rejected as waste rock."

Jan 1, 2008

By T Howard, J E. Everett

BHP Billiton Iron Ore has replaced the conventional product quality control batch system at Yandi with the Continuous Stockpile Management System (CSMS) centred on a fully integrated æcontinuousÆ stockpile flow from mine planning through to port reclaiming. With increasing tonnage rates, tight operational coupling associated with the original batch system caused production interference which achieved final product quality but in an increasingly inefficient manner. This innovative approach places a continuous emphasis on product grade control and takes full advantage of the most appropriate blending opportunities of the mine to port planning and production system in order to reduce the natural variability of the ore to an acceptable level. To implement continuous control, product variability throughout the process is classified as long-term and short-term. Long-term variability is best controlled through the monthly mine planning process which determines monthly grade targets while taking into account optimum mine development. In the past, attempts to control long-term variability were made at the port through selective stockpiling and reclaiming which reduced operational efficiency. Short-term variability is best controlled around the monthly mine grade target by daily mine production scheduling, train sequencing, stacking into port stockpiles of appropriate size and systematical stockpile reclaiming. The implementation of the new system has maintained customer accepted shipping grades and has provided significant improvements in resource utilisation, operational efficiencies and costs.

Jan 1, 2002

By B. M. Larsen

IN endeavoring to put the art of the steelmaker on a more scientific basis, as a means of securing closer control of the product, we must be severely critical of the basis of any theory we use. In particular, we must be careful to distinguish between factors that are primary and those of only secondary importance. The concentration relations that determine the slag-metal equilibria, which are usually more or less closely attained, are of course of primary significance, but a clear picture of the whole process requires that the actual rates of the several reactions be taken properly into account. At the high temperature of the steelmaking furnace, all reactions might be thought to be very rapid, but some of them in fact are not; the essential causes of this condition are important to a proper understanding of the process. This paper aims to present, and to justify, the viewpoint that the most significant reaction is the oxidation of carbon in the metal, the progress of which determines the oxygen pressure levels in slag and metal and produces stirring effects, all of which influence the course of the process as a whole. REACTION RATES AT STEELMAKING TEMPERATURES General experience in reaction rates makes it almost certain that at steelmaking temperatures equilibrium is attained practically instantaneously when the reactants are well distributed in a single liquid phase -that is, in the so-called homogeneous reactions. The actual slowness of some of the reactions in the open-hearth furnace must therefore be attributed to a relatively slow rate of diffusion within the slag or metal phase, which limits the rate at which the reactants can meet each other in the liquid steel or at its surface. That the reactions can be made to go with great rapidity, by proper mixing and stirring of the reacting phases, is indicated by the following illustrations: I. In the Bessemer process there is intimate contact between air and the whole mass of metal, and the reactions are complete in a few minutes. 2. Perrin1 has demonstrated that by pouring liquid steel into slag contained in a deep ladle, and thereby producing almost a slag-metal emulsion, the phosphorus or oxygen content of the steel is adjusted immediately. 3. Barret, Holbrook and Woods observed a quite rapid rate of desulphurization when powdered calcium carbide was stirred vigorously into liquid iron. 4. When a spoonful of liquid steel is poured into a mold containing aluminum wire, the formation and precipitation of alumina occurs in the fraction of a second required to freeze the surface layer of the tiny ingot. The first three examples all show that any means of increasing the effective surface between slag and metal and promoting intimate mixture of the reacting phases, thereby obviating the limitation imposed by diffusion, will enhance the speed of the steelmaking process.

Jan 1, 1941

As mining operations in the United States (US) have become more productive, controlling the dust exposure of mine workers has become more challenging. In response, US mining operations are applying basic controls at elevated levels and are looking to emerging control tech­nologies in an effort to better control airborne respirable dust levels. The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) conducts research to develop and/or improve control technologies that reduce the respirable dust exposure of workers in underground coal mines. The goals of this research involve optimizing the use of water sprays and ventilating air, as well as, evaluating emerging control tech­nologies. An overview of dust controls typically utilized in underground US coal mines will be provided. An update on ongoing PRL research efforts that are evaluating new control technologies will also be presented.

Jan 1, 2008

By W. C. Smith

Even with conservative mine planning, rib instability can progress from a nuisance to a major safety hazard. This Bureau of Mines paper examines the mechanisms of progressive rib failure in high mine openings and discusses techniques to control rib slabbing. A field test site in a longwall mine was instrumented to investigate rib behavior during mining. While data analysis showed minor pillar dilation. sporadic zones of progressive rib instability were detected that culminated in eventual rib failure. The failure occurred despite conservative pillar dimensions and shallow depth. Models were used to demonstrate the mechanisms of rib failure and then evaluate the influence of support and other mine-related parameters on rib behavior.

Jan 1, 1991