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By Y. FUJII, E. CHANDA, J. KODAMA, D. FUKUDA, M. NISHIHARA, Y. NAKAYAMA, P. SINKALA

For over 40 years, Mufulira underground copper mine has been recording incidents of rockburst. Laboratory tests and numerical analyses were carried out to understand the rockburst mechanism at the Mufulira mine. Rockburst did not occur in the chain pillars or at the mining face, but mainly in the mining drives along diminishing pillars or ahead of the mining face. RQD suggested that the rock mass in the rockburst areas was relatively intact. Laboratory tests confirmed that the rock at Mufulira mine is very strong and brittle. Elastic stress analyses for the rockburst sites by 3D displacement discontinuity method (DDM) indicated very high stress in the chain pillars and low-stress concentration at the sites of rockburst during the initial mining stages. However, there was no apparent positive correlation between the elastically calculated normal stress values and the occurrences of rockbursts. The 2D elastic FEM analysis was conducted under the concentrated stress by DDM and indicated that some stress increase with face advance for the rockburst in the vicinity of the mining face. However, stress severity indicated almost no increase, and the rockbursts cannot be explained as an instantaneous rock mass failure due to stress increase by mining. Therefore, a creep damage model was proposed to clarify the mechanism of the rockbursts. Cumulative rock damage was evaluated for the edge elements of each sidewall of the mining drives, based on the normal stresses by 3D DDM. The rockburst occurrences were well hindcasted. A method to estimate the volume of the rockburst source was proposed, and a likely result was obtained.

Aug 12, 2022

By L. H. Michaud

A mining company plans to extend its surface coal-mining operations in central Pennsylvania. Although the proposed site contains pyritic material, the results of the acid-base accountings for the site shows an overall Neutralization Potential to Maximum Potential Acidity Ratio (NP:MPA) of 4.26:1 for the entire site. The pyritic material is, however, associated with the lower of the three seams to be mined. If traditional dragline-mining methods are used, this would result in the acidic material being placed at the top of the spoil piles, exposing it to air and water, and therefore to the formation of acid mine drainage (AMD). Further concerns are associated with the fact that the alkaline material is not distributed evenly over the mine site. To prevent the formation of AMD, the company has proposed to mine the area using truck-shovel mining methods. This technique offers a more flexible alternative for cut sequencing and for the selective placement of waste material. Working with the Department of Mineral Engineering at The Pennsylvania State University, amine plan was developed for this site. This plan results in the layering of the alkaline and acidic spoil to achieve an overall net alkalinity in all spoil areas. Therefore, mining this site should not result in the formation of AMD.

Jan 1, 1996

By Alice S. Allen, James Paone

SURFACE SUBSIDENCE IN MINING The consequences of subsidence are becoming progressively more serious as the consumption of an ever- increasing quantity of minerals conflicts with the needs of an expanding population for surface land area. The inevitable result will be an increase in the amount of land area on which undermining is restricted because surface subsidence must be prevented. Designation of land areas that may be undermined, provided that subsidence is controlled and kept within specified limits, also will increase. The decisions as to which land is to be used for urban, agricultural, or other purposes clearly involve considerations that go far beyond the scope of mining technology. Under the authority assigned to the US Bureau of Mines (USBM) by the Organic Act (May 16, 1910) and its succeeding amendments and pursuant regulations (30 U.S.C. 1-1 1 ), the Bureau conducts scientific and technologic investigations concerning mining and its related problems. Subsidence-control demonstrations that have been conducted under this authority include projects in Wyoming, West Virginia, Illinois, and the Pennsylvania anthracite region. The problenls for technology arc to devise methods for extracting minerals with controlled subsidence in varying geologic settings and for calculating or predicting the amount, extent, and characteristics of the subsidence that accompanies the extraction of our principal minerals mined by high-tonnage methods so that logical choices can be made from the possible alternative approaches. Where underground minerals and fuels are mined and removed, the voids that are created underground generate strong imbalanced stresses in the surrounding and overlying rock strata. The resulting readjustments in the rock masses may cause subsidence of the ground surface. Subsidence implies vertical collapse, because the most conspicuous component of movement is downward. However, the downward component is accompanied by differential horizontal strains that may be more damaging to man-made surface structure.; than the more apparent vertical displacements. SUBSIDENCE CONTROL The most widespread method of alleviating potential subsidence problems in undermined areas has been to backfill mine voids with mine refuse or some other in- expensive material that provides lateral support to the remaining mine pillars and vertical support to the mine roof and overburden. Most USBM backfilling work has been conducted jointly with the Pennsylvania Department of Environmental Resources in the anthracite region of northeastern Pennsylvania. These joint projects were conducted under the authority of the Anthracite Mine Drainage Control Act of July 15, 1955 (Public Law 84-162, as amended), and the Appalachian Regional Development Act of 1965 (Public Law 89-4. as amended). In addition to the Appalachian and mine-drainage projects, the Bureau has either conducted or participated in demonstration projects to develop the "pumped- slurry" method of backfilling mine voids. Three of these projects were conducted in Rock Springs, WY. The first was a field test of the pumped-slurry technique, conducted in 1970 under the combined participation of the City of Rock Springs, the US Department of Housing and Urban Development, the Dowell Div. of the Dow Chemical Co., and USBM (Candeub, Fleissig, 1971). The objective was to demonstrate that a large quantity of sand could be hydraulically injected under pressure through a single borehole, and that filling of the mine voids would be essentially complete. In the earlier "blind-flushing" methods, involving sluicing material through boreholes by gravity, quantities per injection hole ranged from 15 to 765 m3 (20 to 1000 cu yd), and the mine voids were only partially filled. In the first test of the pumped-slurry method, approximately 14 900 m (19,500 cu yd) of sand were injected success- fully through a single borehole. Subsequent information obtained through 43 monitoring boreholes indicated that mine voids below 11 330 m2 (2.8 acres) had been filled. As a result of the successful initial test of the pumped-slurry process, USBM conducted additional backfilling demonstration projects using the new technique. The first full-scale demonstration was carried out in the Green Ridge section of Scranton, PA, between 1972 and 1974. This project proved the feasibility of using the new hydraulic-injection technique to back- fill dry mine voids, as well as flooded voids, and it demonstrated that crushed anthracite refuse could be used as easily as sand in the process. Stabilization was pro- vided for about 202 300 m2 (50 acres) of Scranton, having a population of approximately 1000. Additional demonstration projects at Rock Springs, WY, between 1973 and 1975, resulted in the stabilization of about 364 200 m2 (90 acres). The work was necessary to preserve the physical and economic well- being of the city, because there have been numerous occurrences of subsidence during recent years. A demonstration project completed in 1976 in Rock Springs brought the total stabilized area in that city to 647 500 m2 (160 acres). At a cost of about $3,000,000, a population estimated at 7000 persons and property values exceeding $18,000,000 were protected. Presently. USBM is participating in subsidence- control projects involving backfilling in Pennsylvania, Illinois, and West Virginia. Eleven demonstration projects were in progress by USBM in 1977-eight in the Pennsylvania anthracite region and three in bituminous areas of West Virginia (one) and Illinois (two). The estimated total property value is over $100,500,000, and the total cost of the projects is expected to be nearly $20,000,000. The demonstration projects are designed to adapt the pumped-slurry technique to a variety of subsurface conditions, to increase efficiency, and to reduce costs.

Jan 1, 1982

By A. O. Drysdale

From a mining point of view the Portland Cement Industry falls logically into the Industrial Minerals Division. Portland Cement manufacture requires four principal materials, lime, silica, alumina and iron. The usual source of lime is limestone. Silica sources include clay, shale, quartz, sandstone and sand. Alumina is usually provided by selecting a silica source with a suitable alumina content such as clay and shale. "Cement Rock" is occasionally found in which all four ingredients are found in natural combination or sufficiently close that only minor adjustments are required. In the absence of iron oxides a white cement can be produced. All raw materials used in Canada contain some iron and in most plants further minor quantities of iron are added to promote fluxing, hence the typical grey colour of Portland cement. The modern period in cement manufacturing started in 1824 when Joseph Aspdin of England patented a process for the manufacture of a modified hydraulic cement which he called "Portland Cement". Hydraulic cements are cements that harden under water. Although natural cements, made by calcining and grinding natural argillaceous limestone were produced in Canada as early as the 1830's, Portland cement was not produced in Canada until 1890, about 18 years after it was first made in the United States.

Jan 1, 1964

By José Maria Silva, Eugênio Oliveira, Ruberlan Silva, Thiago Souza, Lucas Reis, Lorena Guimarães, Matheus Bianchetti

Copper mine operations consistently generate a large quantity of tailings after their concentration processing. These tailings are either piled up or stored in a dam, where both alternatives of disposal lead to environmental impacts. The dam copper tailings have a huge potential for by-product production thus improving sustainability and profitability in industrial operations. This paper describes a study aiming at producing a magnetite pellet feed as a by-product from a dam chalcopyrite flotation tailings and generating free magnetite non-magnetic rougher tailings. The chemical assay and mineralogy analysis of dam copper flotation tailings indicate low Fe grade (6.34 wt%), high SiO2 grade (63.14 wt%), low magnetite (3.6 wt%), and high iron silicates content (22.72 wt%). The complex mineralogy of these tailings leads to the need of grinding the rougher magnetite pellet feed as fine as 80% of particles smaller than 20 μm ( P80) aiming at improving magnetite liberation. The proposed process route comprises a scalping screen, low field rougher, and cleaner magnetic separations using a drum magnetic separator (80 kA/m or 1000 Gauss), followed by silicates reverse cationic flotation as a recleaner step. With this process route, it was possible to produce a high-quality magnetite pellet feed reaching 68.00 wt% of Fe, 2.13 wt% of SiO2, 0.51 wt% of Al2O3, and 95.1 wt% of magnetite. The Blaine specific surface area was 2300 cm2/ g, being in the range recommended for pelletizing (1900 up to 3000 cm2/ g). The total mass, Fe, SiO2, Al2O3, and magnetite recoveries were 2.77%, 29.71%, 0.09%, 0.12%, and 73.17%, respectively. Most of the magnetite losses, around 20% of total magnetite fed, occurred in the oversize of the scalping screen. Additionally, it generated non-magnetic rougher tailings with less than 1.0 wt% of magnetite that could be used as by-products and reduced the amount of tailings disposal in a dam. This study contributes toward the sustainability of operation, minimizing tailings disposal.

Sep 28, 2022

By B. W. Cavender

Capital investments are made for a variety of reasons, ranging from providing incremental capacity at existing operations to developing and implementing new technologies intended to radically improve a company's capabilities. These projects generate very different business opportunities and create value in distinctive ways. For incremental improvements, the capital budgeting process assures at least a loose fit between short-term goals and readily available resources. However, the criteria used to evaluate capital projects often prevent a company from committing to more aggressive goals, which lie beyond the firm's current abilities or resources. Such projects may not have clearly identifiable future cash flows, and the degree of interaction with other projects and the nature of the risk incurred may be difficult to estimate. Additionally, by focusing only on quantifiable benefits, the budgeting process often fails to recognize "soft" improvements such as increased operating flexibility or new knowledge generated by such projects. By rejecting these projects, the capital budgeting process may actually harm the company's future competitive position.

Jan 1, 1999

By Edward Holloway

The basis for the selection of the ultimate pit for an open-pit mining operation is generally opaque. Some form of value-based analysis will generally guide the final decision; however, the value will often gradually plateau while the ultimate pit size continues to increase. There is no established framework to guide specialists in the selection of the ultimate pit, with such decisions regularly made on a somewhat arbitrary basis. The key component that is missing from the analyses typically used to select the size of the ultimate pit is risk. Once risk is quantified within the analysis framework, the decision-mak-ing range is significantly reduced and the process for select-ing the ultimate pit becomes more consistent, replicable and defensible. The technique outlined in this paper provides an approach to including risk in the process used to select the ultimate pit.

Jun 1, 2024

By Greg Sanders, Bill Lueck, Michael Gilbert, Mahmood Khwaja

"The city of Minneapolis contracted with CDM Smith to update and provide a conceptual design for improvements to mitigate surcharge flooding in the Central City Storm Water Tunnel System (CCSTS). As a part of the project, CDM Smith conducted a field survey and condition assessment of the existing tunnel system. Information from the survey was then used to update the existing XPSWMM model and develop system wide alternatives.The CCSTS provides storm-water runoff drainage for nearly the entire area of the city’s downtown commercial district. The system consists of deep storm-water tunnels constructed in the St. Peter Sandstone, approximately 21 m (70 ft) below the street’s surface. The primary tunnels comprising the Central City storm water tunnel system are located below Hennepin Avenue, Nicollet Mall, Lesalle Avenue, Marquette Avenue South, 2nd Avenue South, South 5th Street, Washington Avenue South, Portland Avenue South, 2nd Street South, and Chicago Avenue South, as shown in Fig. 1. This network of tunnels conveys the runoff from a 305-acre tributary area that is generally bound by Hennepin Avenue and 1st Avenue North to the east, 12th Street to the south, 4th Avenue South and 7th Avenue South to the west, and 2nd Street South. These tunnels were constructed between 1936 and 1940, except for the Marquette Avenue South tunnel, which was constructed between 1963 and 1964.The CCSTS operates as a gravity flow system. These tunnels were constructed within the St. Peter Sandstone layer of bedrock and emerge from the bedrock at the Mississippi River below St. Anthony Falls. The Central City and the adjacent Chicago Avenue tunnel system converge into a single outfall at the Mississippi River. The runoff discharges from the converged outfall to a side channel of the Mississippi River, called a tailrace, located near the Guthrie Theater. The Minneapolis Division of Surface Water and Sewers provided 32 historic plats detailing the plan and profile of the tunnel system.The tunnel plans show nine different cross-section configurations. Eight configurations within the overall system generally show the same geometric “cathedral” shape with the inside dimensions varying from 1.2 to 1.8 m (4 to 6 ft) in width and 1.8 to 2.4 m (6 to 8 ft) in height. For analysis, these eight configurations were reduced to three configurations with regards to tunnel liner, cross-sectional area and support. For simplicity, the three configurations are described according to the three types of tunnel support used during construction: none required, light timber and heavy timber"

Jun 1, 2019

By D. L. Boreck

With increasing land development, the potential of fatalities from abandoned mine shafts increases. To minimize potential liability, shaft closure should be a critical part of mined land reclamation. The Bureau of Mines is conducting research into using lightweight foam concrete in sealing abandoned coal mine shafts. A demonstration seal consisted of a 3m thick foam concrete plug to provide lateral stability inside the shaft. A high density concrete cap provided load-bearing capacity for a 100-year service life. The USBM has also completed research into changes in foam concrete when it is pumped or dropped from different heights. It is concluded from the research that foam concrete can undergo significant air loss with pumping or dropping. This foretells significant changes in the characteristics of the concrete as well as an increase in the weight and cost of the in-place concrete seal. When using foam concrete to seal abandoned mine shafts, care must be taken to minimize air loss during placement.

Jan 1, 1994

By Lynn B. Hales

Unfortunately, the term "control" has a negative connotation in the minds of many of our operating plant personnel. Whereas the opposite is true of those associated with research and technical centers in our industry. The magnitude of this difference in opinion and actual experience has often proved to be a major factor influencing the success or failure of process control applications. Through the years, many plant people have endured a number of unsuccessful attempts by "outside" people to "optimize" their plants; and these experiences have proved to have had quite a callousing effect on them. On the other hand, in many plants, successful process control efforts have made firm allies of the operating personnel, and have increased the number of metallurgical people who are well qualified and experienced in process control. The instrumentation industry, computer industry, and the mining industry's ability to quantify what is really happening in our processes have grown and developed rapidly since the first control efforts were made in the 1930's (1). Because of this-,: new control opportunities are becoming increasingly more feasible and older well established ones are becoming even more practical and necessary with regard to the economic s of our industry.

Jan 1, 1979

By Kwadwo Osseo‑Asare, Isehaq Al‑Nafai

The hydrometallurgical processing of bastnasite is a well-known process that is used to extract rare earth metals. However, more accurate measures are required to enhance the efficiency of extracting and recycling rare earths. In this work, Pourbaix (Eh–pH) diagrams for La-, Nd-, and Pr-(F)-(CO3)-(SO4)-(Cl)-(NO3)-(C2O4)-H2O systems were theoretically derived to investigate the stability relations during the hydrometallurgical processing of bastnasite. The diagrams for RE-H2O systems show similar trends to the original ones drown by Pourbaix. The stability domains of RE carbonates were presented by RE-CO3-H2O systems with pH range of 4.5–11. In contrast, the diagrams for RE fluorides showed a large stability region of insoluble REF3 (pH ~ − 1.7–12). The decomposition behaviors of REFCO3 were studied by constructing Eh–pH diagrams for RE-F-CO3-H2O system. The stability regions of bastnasite species extend from nearly neutral to basic media (pH ~ 6.5–12). The acid treatment (using H2SO4, HCl, and HNO3) of bastnasite was investigated by constructing Eh–pH diagrams for REF- CO3-(SO4)-(Cl)-(NO3)-H2O systems. According to these systems, REFCO3 can be decomposed at pH ~ 6.5 when treated with H2SO4 and at pH ~ 1.7 when treated with HCl and HNO3 acids. On the other hand, the alkaline treatment of REFCO3 converts it to RE(OH)3 at pH ~ 11. The recovery of rare earths ions was studied with the aid of RE-C2O4-H2O systems which shows a wide stability region for RE oxalates in pH range of − 2–11. This theoretical approach explained the aqueous relations in the hydrometallurgical processing of bastnasite ore and it can improve the practical hydrometallurgical processing of such ores.

Feb 9, 2024

By William F. Stowasser

The organization and operations of the information gathering system, and examples of the products prepared for the commodity phosphate rock by the Division of Nonmetallic Minerals, U.S. Bureau of Mines, are used to describe the Bureau's commodity program. Selected examples from publications about phosphate rock are used to illustrate the program. The Commodity Divisions reporting to the Office of the Assistant Director-¬Metals, Minerals and Materials, have the responsibility in the Bureau of Mines to maintain commodity records, understand the present supply and demand status of the commodity, and forecast future supply, demand, and problems. Within the Divisions, commodity specialists have the broad charter of acquiring as much information about a commodity as is necessary to characterize its history, current status, and future. This information and understanding are the base for the development of mineral policies. To accomplish these objectives, the commodity specialists acquire data and information about each commodity and produce a number of standard publications each year. In addition, as circumstances dictate, each specialist will prepare or participate in the preparation of special documents for specific purposes or problems associated with his commodity. In the preparation of reports and publi¬cations, he may communicate with industrial organizations and other Government agencies.

Jan 1, 1975

By Güldane Atesoglu, İsmail Atilgan

The changes in the elemental contents and the structural properties of chalcopyrite concentrate when roasted were studied, and the main reactions contributing to the leaching process revisited. Firstly, TG/DTA measurements were performed to identify the roasting temperatures that influenced the type of species reacting with sulphuric acid leaching liquor. The temperatures of main reactions, whose output may affect the subsequent leaching process, were analysed for the concentrate at hand, and concluded to be generally lower than those reported in literature. Secondly, the obtained results were confirmed by images and XRD measurements on the roasted concentrate at temperatures in between 350 and 600 °C with increments of 50 °C. Finally, the leaching behaviour of the roasted specimens in a stirred sulphuric acid solution examined and the Cu/ Fe selectivity investigated that the maximum Cu/Fe ratio in the pregnant solution would nearly be achieved for the roasting temperatures lower than 500 °C, since the oxidation temperature of iron sulphate is found lower than that of copper sulphate.

Aug 11, 2022

By Matthew Geary, Stephen J. Marino, Jordan A. Schreiner

"INTRODUCTION Project Overview The Southeast Collector (SeC) is a new 15km long 3.0m internal diameter wastewater tunnel designed by Hatch Mott MacDonald (HMM) that twins the existing 2.6m diameter York-Durham Sewage System (YDSS) tunnel. Both sewage tunnels are located north of the City of Toronto in Ontario, Canada. The SeC provides much needed conveyance capacity for the rapidly growing York Region population, supporting development until 2036 and increasing sewage system security (Hatch Mott MacDonald and AECOM 2011). Construction of the SeC will also permit flows of the twinned section of the YDSS to be bypassed in order to clean, inspect and carry out any essential maintenance within the YDSS tunnel. Although owned and operated by York Region, the SeC spans two regional municipalities beginning upstream from the intersection of Ninth Line and Rouge Bank Drive in the City of Markham in York Region to the downstream Finch Avenue and Valley Farm Road intersection in the City of Pickering in Durham Region. See Figure 1 for the SeC and YDSS alignment. The project includes 19 shafts and chambers with depths ranging from 8 to 48m in addition to seven facilities supporting the operation and maintenance of the sewer. The construction contract was awarded to Strabag Inc. in July 2011 for $291M CAD. Construction Management services were provided by a joint venture team of Hatch Mott MacDonald and AECOM. Existing York-Durham Sewage System The YDSS tunnel was completed in 1979 and was constructed using an open shielded TBM with ribs and lagging temporary support, followed by installation of a 380mm thick unreinforced cast-in-place (CIP) concrete final lining. The YDSS sewer system has numerous connections that accumulate flows from various urban areas within York Region. The section of the YDSS twinned by the SeC flows under gravity conditions and had been putting a strain on the municipality’s potential for population and development growth having reached its maximum capacity of 420 ML/d. According to the York Region’s Water and Wastewater Master Plan, the existing YDSS would not have been able to handle wet weather flows past 2016 (Genivar and XCG Consultants 2009). The dependability of this section of the YDSS is also of concern because it is the main and critical connection between the sewer systems upstream and the downstream Duffin Creek Water Pollution Control Plant (WPCP)."

Jan 1, 2016

By R. J. Sheets

In 2009, the Gold Quarry openpit mine experienced multiple large-scale slope failures of the upper east highwall that reduced gold ore extraction for nearly 18 months. The slope failures occurred within a weak, consolidated sedimentary sequence that exhibits strength characteristics that are transitional between soil and rock. Instability initiated as mining exposed the lower, high plasticity subunits of the Carlin Formation. This deformation created preferential flow paths that allowed ground water from the upper sandy subunits to infiltrate low-permeability, clay-rich subunits, thereby enhancing deformation of the slope toe, which, in turn, destabilized the upper portion of the highwall. The outcome was a 160 m high slope failure that had a lateral run-out of 850 m. The effort to return the pit to ore production required geotechnical and hydrogeological investigations and the preliminary remediation mining activity to be concurrent. This required the development of detailed safety procedures and a requirement to modify the remediation design as new results were obtained. An initial challenge was to mitigate a near vertical, 90 m headscarp with localized, blast-induced slope failures. Back-analyses with numerical modeling software indicated that the failure surface could be shallower, which contradicted the initial failure interpretations. Eventually, drilling results confirmed this alternative failure geometry. The final remediation design incorporated shallower slope geometries and an approximately 3 Mt buttress along the base of the Carlin Formation and bedrock contact to reinforce the subunits with residual strength properties. The results are a stable highwall within the Carlin Formation following nearly 10 years of repeated slope failures, and an example of the necessity to conduct appropriate geotechnical and hydrogeological studies during the early stages of a new layback evaluation or new openpit development.

By Catherine C. Kilgore

The Bureau of Mines investigated the availability of fluorspar from 35 domestic and 50 foreign, mines and deposits in 13 countries. Only 6 domestic properties are considered to be economic reserves, as 29 domestic deposits were found to have an average total cost of production that was uneconomical at a breakeven (0 pct) DCFROR. The 50 foreign properties evaluated were selected to represent at least 85 pct of the known demonstrated fluorspar resources located in market economy countries and China. All evaluated foreign operations were found to be economic to marginally economic in January 1984 dollars. World demonstrated ore reserves of 344 million metric tons (mt) containing 123 million mt of CaF2 were evaluated for the 56 operations. Average total costs needed to cover all costs over the life of each operation were determined for all recoverable fluorspar products. Comparisons of mining, beneficiation, and transportation costs per mt of fluorspar concentrate illustrate advantages between countries. Of the three largest producing countries, China, with its high-grade, low-cost operations had the lowest weighted average total cost of production ($38/mt concentrate). Mexico was next at $54/mt concentrate, and South Africa needed an average of $90/mt of concentrate to cover all costs of production for its low grade deposits.

Jan 1, 1985

By S. Shankar

Available literature on the effect of re-entrainment on overall airborne dust concentration in mine airways or the fundamental mechanisms of coal dust re-entrainment in mine atmosphere is scant. Therefore, as part of the Respirable Dust Center's ongoing research, a three part study was envisaged: study of the re-entrainment phenomena of anthracite and bituminous coal dust particles in a wind tunnel under the influence of varying air velocities; study of the same in the Lake Lynn Laboratory Mine of the USBM with both airflow and walking by personnel causing re-entrainment; and mathematical modeling and computer simulation of the re-entrainment phenomenon. In this paper, results from the re-entrainment studies in the wind tunnel and the Lake Lynn Laboratory Mine are presented. Further, the results from the wind tunnel studies are compared with the results from in-mine studies conducted at the Lake Lynn Laboratory Mine of the USBM. Comparing the results from the two studies it was observed that increasing air velocity increased the rate of re-entrainment, but increased time of exposure decreased the airborne dust concentration. Compared to same size particles, a mixture of sizes created more airborne dust concentration when re-entrained. It was also observed that contribution of airborne dust concentration due to airflow was negligible compared to the contribution due to walking.

Jan 1, 1995

By W. D. Monaghan

One of the major ignition sources of fires and explosions in underground U.S. coal mines is flame cutting and welding. On May 20, 2006, a flame-cutting operation at the Darby Mine No. 1 led to an explosion that resulted in five fatalities. On Jan. 22, 2003, another explosion caused by flame cutting at the McElroy Mine resulted in three fatalities and three serious injuries. On June 22, 1999, a flame-cutting and welding operation at the Loveridge Mine caused a fire that required sealing the mine for an extended period. On March 19, 1992, an explosion initiated by welding at the Blacksville No. 1 Mine resulted in four fatalities. These examples of mine incidents demonstrate the need to conduct research to develop best practices for safely conducting flame cutting and welding in underground coal mines. The National Institute for Occupational Safety and Health (NIOSH) conducted a study on fires and explosions in underground U.S. coal mines that were caused by flame-cutting and welding operations to determine the root causes of these types of incidents. The methodology included interviewing mining personnel who perform flame-cutting or welding operations in underground U.S. coal mines and visiting mines to observe these operations. In addition, MSHA reports of investigations and accidents statistics were analyzed. The findings were used to identify and compare differences between flame-cutting and welding practices and techniques in small and large mines, eastern and western mines, low-seam and high-seam mines, room-and-pillar and longwall mines, and between experienced miners and new miners. As a result of this study, best practices were developed to reduce the number of ?res and explosions caused by flame cutting and welding. This paper provides a summary of this research.

Jun 1, 2010

By James J. Scott

I welcome this opportunity to speak before the Coal Division of the AIME in such an attractive setting as the Pacific Northwest. With the development of the Centralia project, the Pacific Northwest will have its first major coal-fired thermal electric generating plant. This State has a long history of coal mining that diminished with the passage of coal-fired steamships and locomotives but is now reviving with the growth of electrical power demand. Because this 1,400 row plant is to be supplied with surface-mined coal, it is particularly appropriate that this area be the setting for a talk on factors influencing the growth of surface coal mining in the West. During the course of my talk, I will touch on a number of factors including electric power demand, coal resources, production trends, environmental considerations and trends in State and Federal activities that I feel will influence surface coal mining in the West. Total electric power consumption by the year 2000 is expected to reach 9.4 trillion kilowatt-hours. Predictions of total coal consumption for electric power generation by that year range from a low of 845 million tons to a high of 1,520 million tons, or 2.6 to 4.7 times the amount used for this purpose in 1970.

Jan 1, 1971

By LeRoy D. Loy

Would you believe me if I told you the constant battle between Government regulatory agencies and industry could be won by both sides? No, I'm not crazy, nor have I been soaking up any of that fine Kentucky whitelightning. But I have recently been a participant in a battle where both sides won. Actually, I'm using the term "battle" loosely because, in reality, it wasn't a battle at all - despite the fact that all the ingredients were there for a monumental struggle; i.e.. government, industry, special interest groups and a controversial issue - the development of effluent limitations. I'd like to tell you about it. Historically, on one side of the battle, government has always been ac¬cused of adopting regulations with limited evaluation of existing technologies; and then with seemingly no regard for the economic consequences. On the other side, industry gets punished by government's harsh actions because of their past "do-nothing" attitude toward pollution control. Recently, this battle seems to be losing steam, because both government and industry are beginning to realize that, ultimately, they both will lose. Even more important is the fact that both sides are, or should be, working for industrial expansion compatible with environmental protection.

Jan 1, 1977