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By Yi Luo

Bolting the mine roof is one of the noisiest underground mining operations. The main contribution to the noise is the drilling of the roof bolt holes, especially drilling in hard rock. Previous research shows that the specific energy consumed in drilling bolt holes is inversely proportional to the bite depth (i.e., penetration per drill revolution). Less specific energy at a reasonably high bite depth means less energy is wasted in the drilling process for producing heat, bit wear and noise. Therefore, proper control of the drilling operation to achieve a reasonably higher bite depth can reduce drilling noise from its sources as a proactive noise control approach. In order to explore the feasibility and develop the proactive technology for reducing drilling noise, drilling tests have been conducted in laboratory settings. The preliminary results show that significant reduction in noise dose can be achieved by drilling in medium hard rock with uniaxial compressive strength of about 276 bars (4,000 psi) and at a reasonably high bite depth of about 4.6 mm/rev (0.18 in./rev). This paper presents the findings from laboratory experimental studies.

By Ajit Godbole, Ping Chang, Ramakrishna Morla, Purushotham Tukkaraja, Shivakumar Karekal

This paper presents the results of a study on the optimum auxiliary fan location to control air recirculation in dead-end workings where diesel-powered vehicles operate. Investigations were conducted with various secondary fan locations from the dead-end crosscut and with the intake air quantities varied using different auxiliary fans to control air recirculation and diesel particulate matter (DPM).

Jul 1, 2023

By E. H. Cho

Pittsburgh #8 coal cleaned by the conventional froth flotation was oxidized in a 2-liter Parr Stirred Top Bench Reactor. The oxidation time was varied up to 5 hours; the temperature, from 150 to 225°C, the oxygen pressure, from 15 to 500 psi; and coal dosage, from 15 to 60 grams in 600 ml of distilled water. The oxidation of coal was evaluated by measuring total acidic group formed on the coal surface as well as by measuring the adsorption of calcium ion from a solution under standard conditions. It was found that the oxidation increased with increasing oxygen pressure without much leveling-off effect. However, the oxidation of coal increased sharply from 150°C to 175°C and then tended to level off above 175°C. The adsorption of calcium was reached more than 3% on the coal oxidized under favorable conditions. The adsorption of calcium on coal increased sharply with increasing equilibrium pH. The BTU loss was sensitive to oxidation temperature. This study concludes that the optimum oxidation of coal should be conducted at high oxygen pressures around (e.g. 500 psi) 170°C for 3 hours. This study also concludes that the oxidation in an autoclave is far superior to that in a fluidized bed in terms of calcium adsorption, BTU loss and reaction time.

Jan 1, 1994

By B. Seymour

The National Institute for Occupational Safety and Health (NIOSH) is conducting research to develop safe practices for the use of shotcrete as ground support in underground mines, particularly mines operating in weak host rock. As part of this research, tests were conducted with a commercial poly-fiber reinforced shotcrete mix to develop a practical means of measuring shotcrete adhesion strength. Full-scale tests were conducted in a test frame equipped with concrete panels having three distinct surface roughness profiles. Adhesion test fixtures either embedded or epoxied in the shotcrete were overcored into the underlying concrete, and direct tensile tests were conducted to determine the bond strength of the shotcrete cores to the substrate after a selected shotcrete curing interval (1, 3, 7, 14, 28, or 90 days). Measured adhesion strengths typically ranged from 0.5 to 2.0 MPa depending on the curing age of the shotcrete samples. This paper presents the results of these tests, describes the portable test system components, and addresses some of the design issues encountered in the development of a rugged and reliable method for determining shotcrete adhesion strength in underground mines.

Jan 1, 2010

By Clark D. Harrison

This paper compares the ash slagging potential of Illinois No. 6 Seam coal: as raw coal; as commercially cleaned coal processed in a baum-jig plant; and as coal cleaned to a reduced ash specification at the Electric Power Research Institute's Coal Cleaning Test Facility. The comparison is based on: ? ASTM ash fusibility data ? A slagging index ? Gravity fractionation analyses of critical mineral matter compounds ? Comparative pilot combustion tests. The first three grounds of comparison are laboratory data; and the final comparison involves burning approximately 15 tons of each coal at CONOCO's 1.5 MBtu/hr (440 KW) test combustor. The evidence of these .four comparisons indicates that lowering the ash specification of coal before combustion can significantly improve the ash slagging characteristics of Illinois 90. 6 Seam coal.

Jan 1, 1984

By H. N. Dougherty

"The National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) ventilation gallery was used to study methane-air flows around a continuous miner mockup with water sprays and a scrubber fan. Methane gas was released from pipes located at the face to simulate face gas emissions. Methane concentrations and air velocities were measured while varying parameters such as airflow quantity, entry width (sump or slab cut), and face ventilation configuration (blowing or exhausting curtain). Test data showed a similar pattern of methane concentrations at both low and high airflow quantities, but a difference in the distribution of methane concentrations between narrow and wide entry widths. Most tests showed that blowing face ventilation was more efficient in diluting methane than exhausting ventilation, similar to observations made in previous empty gallery studies. The patterns of airflow and methane concentrations observed in this testing can further improve the understanding of airflow in and around the CM and face, promoting effective use of face ventilation to improve the health and safety of miners. INTRODUCTION Attaining an accurate understanding of airflow distribution at the continuous miner face is instrumental in maintaining a safe mining environment. US mining regulations require that sufficient airflow must be directed to the deepest penetration of the face and render harmless contaminant gases, as verified by the Mine Safety and Health Administration (MSHA). Currently, continuous miner face air readings can be taken in the last open crosscut and at the inby end of the curtain mouth. By measuring adequate airflow in a pre-determined area it is accepted that a sufficient quantity of that air exists to sweep the face of harmful dust and gasses. Unfortunately, due to the location inaccessibility, precise face velocity readings cannot be measured in situ. Face velocities may be estimated through computer-simulated programs based on laboratory models. Improving upon previous empty gallery testing and to more effectively determine representative face methane readings, a mockup of a continuous miner with water sprays and a scrubber fan was used in the current study to further refine face airflow conditions that would be closer to actual mining conditions."

Jan 1, 2016

Editor's note: Biographical information about Ihor Kunasz, president, Newmont Uzbekistan, can be found in the February 1998 issue of ME, page 94 and in the May 1996 issue, page 92. Your personal assessment of the minerals business. Gosh! When I think about what has happened to the minerals industry over the past 27 years that I have been a member of SME! There have been fundamental structural changes in the industry. And I think that SME has been quite successful in coping with these changes as well. There has been a reorientation in how the minerals industry does business. It used to be called rationalization. Today we call it reengineering. In addition, the minerals industry has become more complex and more global. Shareholders have become more vocal and demanding in the management of the business, asking for protection of their shareholders' value. In the 1980s, a fundamental change was precipitated by a merger and acquisition fever in all industries, including the minerals industry. Raiders such as T. Boone Pickens put enormous demands on companies that, in turn, had to spend substantial management time to fend off the raiders. This resulted in a major restructuring of the mining houses. Today, for example, Anaconda, Kennecott and Amax are only historical names.

Jan 1, 1998

By S. G. Hardcastle, C. K. Kocsis

Ventilation is an expensive prerequisite for underground mining. Current mining trends, including increasing depth and mechanization and more stringent health regulations would generally dictate that more air volume is required in order to provide good working conditions underground. However, any increase in the mine’s intake airflow can produce a disproportionate increase in power consumption and hence operating costs due to the cubic relationship between the sup-plied air power and the airflow (Power a Flow3). Furthermore, forecasts of significant increase in energy prices and new commitments with regard to reductions of greenhouse gas(GHG) emissions, determined the mining industry to look into developing new concepts, design tools and incorporate the latest mining technologies in order to lower capital and operating costs while meeting commitments regarding GHG emissions. The advances in computing power and modelling software now make it possible to design, model and schedule a mine from opening to closure. A developing trend is to design and plan the mine by means of orebody modelling software, followed by using discrete-event simulation techniques to predict production rates and evaluate various operating scenarios throughout the life of the mine. The authors are currently evaluating how such process simulators could be adapted in order to forecast the need for materials or a specific resource, and one of these would be the mine’s “life-cycle” airflow demand as a function of scheduled production rates and mine operating characteristics. Further to this, based upon the mine’s life-cycle airflow demand schedule, the ventilation system could then be designed using a mine ventilation simulator. This new design approach would integrate in parallel the development of the ventilation system with the current mining conditions, therefore, heading towards “develop-as-you-go” as opposed to developing the system for final requirements with high upfront costs. This new ventilation system design criteria would also incorporate the use of the “ventilation-on-demand” technology, which will further lower development and production costs and implicitly, the mines’ GHG emissions.

Jan 1, 2004

By J. T. Tanner

The research activities of the Minerals Research Laboratory, which is a part of North Carolina State University, is normally confined to solving beneficiation problems, and developing flotation processes for the mining industry. In recent years the laboratory has veered from its main purpose somewhat and has placed some emphasis on the manufacture of products from mineral concentrates. This has been the result of requests for help from industry. One such request came to the MRL from a talc producer in North Carolina who was having a difficult time competing with foreign imports of steel marking crayons. He felt that if a process could be developed whereby a satisfactory crayon could be produced from powdered talc at a low cost that he could compete.

Jan 1, 1986

By Paul Cameron Gilmour

Geologically, as distinct from economically, "porphyry copper (molybdenum, gold, silver, etc.) deposits" might be defined as large, disseminated and/or stock-work occurrences of copper-minerals, generally averaging less than 1 per cent cop-per. They are normally associated with small plutons which range in composition from granite to diorite, although, typically, they consist of quartz monzonite or granodiorite. Circumstantial evidence indicates that these "minor" granitic intrusions may represent the intrusive phases of post-orogenic, calc-alkaline volcanism, this conclusion being suggested by: 1. Texture and grain size. 2. Prevalence of intrusive breccias. 3. Relationship to unconformities and estimated depth of emplacement. 4. Spatial distribution in relation to orogenic zones. 5. Age of mineralization and igneous episodes

Jan 1, 1972

By Zhibiao Guo, Jinglin You, Dongshan Yang, Yuanxin Zhao, Yuhui Li, Jingwei Gao

By utilizing collapsed gangue to create gob ribs, roof cutting and roadway maintenance (RCRM) technology enables coal pillar-free mining, presenting a novel approach. Due to their inherent structure, faults, which are common geological formations, can lead to various hazards, including fault sliding and significant deformation of roadways. In this study, a selfdesigned underground engineering simulation test device is utilized to imitate the cross-fault mining of the 11,101 working face in the Qipanjing Coal Mine (East). The objective is to examine the behavior of the surrounding rock and stress evolution. Generally, the experimental findings demonstrate that compared to the return air roadway, the RCRM roadway experiences a 3.3% decrease in maximum coal rib stress. This suggests that the implementation of this technique can effectively alleviate the stress on the surrounding rock of the roadway. The maximum coal rib stress, lateral pressure of the gob rib, and maximum deformation of the roof near the fault of the RCRM roadway are 11.3%, 25.6%, and 86.1% greater than those of the conventional geological conditions, respectively. The roadway deformation is negatively impacted by the fault structure. Based on experimental data and field measurements, a discrepancy in the maximum roof deformation between the test and field monitoring results under typical geological conditions is 8%. This indicates a favorable alignment between the test results and the real-life scenario. In conclusion, the proposed targeted control technique is implemented in the field by integrating the mining invariant equation and gangue volume expansion equation. This not only validates the effectiveness of the technology but also offers valuable insights for the future utilization of RCRM technology under comparable circumstances.

Feb 20, 2024

By Laszlo Valentyik

Heavy media separation (HMS) is one of the most widely used gravity methods in the mineral industry. The feed is separated, according to the specific gravities, into two products; float (light) and sink (heavy) particles. The universal acceptance of the process is due to simplicity, efficiency and robustness for ease of control. However, if optimum separation is desired during the operation of heavy media plants, a delicate balance of a number of variables is essential. Among the variables, the two which are generally the most frequently checked and controlled are specific gravity and consistency of the medium. The latter is a function of the settling rate of the media. The medium is generally made up of finely ground ferrosilicon, magnetite, galena, shale, quartz sand, clay contaminants and water. The frequently present clay in the medium acts as a stabilizing agent, since the coarse heavy medium solids (called media) would quickly settle if they were mixed only in water. Clay concentration of the medium varies between 3-7% by height (1,2). Although clay is essential for reasonable media stability, clay concentration greater than 7-8% imparts too high a viscosity to the medium, and the feed cannot accurately stratify and therefore separate into the required products. To be on the safe side, plant operators clean the medium from most of the clays, and would rather work at a lower stability than have a very viscous medium on their hands. The most recent advance in the area of consistency control rlas made by the introduction of atomized (spherical) ferrosilicon (3). This extended the upper limit of the use of ground ferrosilicon from 3.3 to approximately 3.6, broadening the range of the optimum operating conditions. A viscosity control method was also worked out by the use of low cost additives which lower viscosity while retaining a favorable low setting rate (4). Recently (5) polymers have been successfully used in oil well drilling muds then the requirements were mainly to suspend and transport cuttings during the periodic shutdowns and dril1ings respectively. The rheological properties of these polymer suspensions are such that they present an infinite viscosity to

Jan 1, 1971

By Andrew Chegwidden, Tara Wilk

Construction of Shaft 17B-1, a part of The New York City water supply system, required an excavation of approximately 38 m (123 ft) through water-bearing overburden soil and more than 152 m (500 ft) of gneiss bedrock to make a connection to Water Tunnel No. 3. Ground freezing was the specified method to provide temporary earth support and ground water control for the overburden material. The ground freezing process relied on a supplemental geotechnical investigation and comprehensive laboratory testing of the frozen soil to evaluate the potential long-term creep behavior of the soil and the elimination of a temporary lining system. This paper describes that process as well as the drilling and installation methods of the ground freezing system. Additionally, the methodical system of excavation and insulation is discussed that permitted a safe and timely excavation followed by the installation of the permanent concrete liner.

Jun 13, 2023

By Liming Yuan, A. C. Smith

Barometric pressure changes affect air density, leading to change in the mass of the gas in the gob. When the barometric pressure decreases, the volume of gas in the gob expands, while the volume of gas contracts when the barometric pressure increases, a process which causes the gob to “breathe” out and in. Although the concept of gob “breathing” is simple, its effect on spontaneous heating of coal in the gob area is not clear. In this study, computational fluid dynamic (CFD) simulations were conducted to model the spontaneous heating of coal in the longwall gob area under measured barometric pressure changes. A single longwall panel using a bleederless ventilation system was simulated. If there is no barometric pressure change, the intake airflow rate is equal to the return airflow rate. When the barometric pressure changes, these two airflow rates are no longer equal, and the difference between the two airflow rates represents the airflow rate the gob breathes in and out. The effect of inflow and outflow of gas on the potential spontaneous heating in the gob was investigated using the CFD model developed in our previous study. The effect of barometric pressure changes on the spontaneous heating was found to be dependent on the gob permeability and the coal oxidation rate. The effect of barometric pressure changes on oxygen concentrations in the gob was also examined.

Jan 1, 2010

By A. J. Kwitowski

Remote control for mining machines ordinarily means the operator is not seated on the machine, but is located within direct view of the machine and work area Thus, remote control operators are exposed to the hazards of roof/rib falls and dust/methane explosions. The U.S. Bureau of Mines has developed a method to disassociate remote operators from these hazards. Off-board, computer-based "tele-operational" systems are utilized that station the operators one-hundred meters or more distant from the working faces. Details are provided for tele-operated systems for thin-seam extraction and haulage equipment in highwall and deep, room-and-pillar coal mines.

Jan 1, 1992

By V. R. Degner

The trend in both the metallic and non-metallic mining industry is toward processing increasing y higher tonnages of lower grade ores, thereby resulting in a growing interest in progressively larger volume individual machines in the flotation circuit. Because of the relatively high cost of large flotation machine development and evaluation, it is important to establish a rational basis by which the existing smaller flotation machine experience can be extrapolated to establish the configuration of the next larger family of flotation machines with a minimum of development modification in the field. This paper reviews the R&D approach used in translating smaller flotation machine experience to establish the configuration of a 1000 cu ft (2B.3 cu m) induced air machine. Internal cell hydrodynamic principles, which governed this extrapolation, and cell (liquid) surface and froth management considerations will be reviewed, and prototype machine mill tests will be summarized.

Jan 1, 1978

By Zhiyuan Ma, ZUI WANG, Xincheng Hu, Jianwei Cheng, Junhong Si, Yi Qin, Gao Ke

The harmfulness and destructiveness of mine gas explosion is quite serious, which is the first of all kinds of coal mine disasters. Once the gas explosion occurs, it could instantly generate explosion shock waves, high temperature airflows, and disaster gases, which cause the destruction of underground ventilation structures, disruption of airflow direction in a mine ventilation network, and miners’ deaths by asphyxiation. As an important barrier to prevent the spread of accidents caused by the gas explosion, the safety and reliability of the mine seal affects the mine’s production and the health of workers. Due to the demands of coal mine production and transportation, a large number of longitudinal and horizontal roadway networks have been developed underground. There are not only many flat and straight roadways in the complex roadway network structure, but also a large number of different types of bifurcations and bends. Once a gas explosion occurs, the impact of the blast waves on the mine seal after passing through the complex path is difficult to determine. Therefore, this paper establishes a numerical model of bifurcated and cornered roadways and studies how the impact of gas explosion shock waves on the structure of sandwich mine seal after passing through different types of bifurcated and cornered roadways. The damage state of sandwich mine seal is analyzed. The researching finding could prevent and manage the spread of gas explosion disaster, and improve the disaster mitigation of mine explosion accident.

Jul 11, 2023

By D. D. Xu

A novel system for the depression of pyrite and the ash-forming minerals has been developed. A metal ion, including but not restricted to Fe+2, is added to form a hydroxide coating on the pyrite or ash-forming mineral. A polymeric depressant is then added to attach to this re-surfaced mineral. Nearly 200 flotation tests with a 11 different coals indicate the effectiveness of this system. Many of the important process variables such as the coal source, frother-collector system, grind size and procedure, pH, metal ion, and depressant type and concentration have been studied.

Jan 1, 1994

By E. R. Bauer

In response to the mandates in the MINER Act of 2006, the National Institute for Occupational Safety and Health (NIOSH) conducted refuge alternatives research that included characterizing the utility, practicality and survivability of refuge chambers and outby safe havens. NIOSH also prepared and delivered a report to Congress in late December 2007 that summarized the findings of the re-search, included recommendations concerning the design and performance specifications for refuge alternatives, and focused on specific information that could inform the regulatory process on refuge alternatives. This paper highlights NIOSH?s research and recommendations concerning refuge alternatives, survivability evaluations of refuge chambers and presents a brief review of the current deployment of refuge chambers in underground coal mines in the U.S. The research has lead to the conclusion that refuge alternatives have the potential for saving the lives of mine workers if they are part of a comprehensive escape and rescue plan and if appropriate training is provided.

Jan 1, 2009

By David R. Maneval

In 1956 the Legislature of the Commonwealth of Pennsylvania created a "Coal Research Board" in the Department of Mines and Mineral Industries. Over the years through amendments to the original legislation, the scope of authority for research has been expanded from the narrow area of improving and increasing the utilization of coal to covering all aspects of coal technology and any other area of interest which would be of value to the coal industry. In January of 1964, the Board commenced a vigorous program using appropriated funds and funds donated by the coal industry to finance a research program devoted to seeking solutions to the mine drainage problem. A review of published literature on the treatment of mine drainage indicated that much work done up to that point in time concerned only the mechanism of mine drainage formation and theoretical chemistry. Very few applied, developmental, or engineering studies had been devoted to finding practical solutions to the problem of polluted waters being discharged from active or abandoned mines. Projects were therefore undertaken on a wide variety of more utilitarian approaches. This paper will discuss briefly some of the pollution abatement approaches which have been funded by the Coal Research Board of this State, and will describe in some detail a multistage flash evaporator treatment plant now under construction.

Jan 1, 1970