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By C. Zhou, B. Whisner, J. Carr

Proximity Detection Systems (PDSs) are used in the mining industry for protecting mine workers from striking, pinning, and crushing injuries when they work in close proximity to heavy machines such as continuous mining machines (CMMs). Currently all Mine Safety and Health Administration (MSHA) approved PDSs are magnetic field based systems which can be influenced by the presence of wire mesh that is commonly used for supporting roof and ribs in underground coal m ines. In this paper, researchers at the National Institute for Occupational Safety and Health (NIOSH) characterize the influence of the mesh on the performance of magnetic PDSs by measuring the magnetic field difference around a CMM caused by the presence of the mesh. The results show that the magnetic fields are generally enhanced by the mesh which causes the PDS detection zones to be increased correspondingly. It was discovered that the fields around the joints of two mesh sections have the greatest enhancement and thus deserve more attention. In addition, it is found that the presence of mesh can also cause a variation in the generator current. The influence of mesh is characterized by the change in the generator current with respect to the distance between the generator and the mesh. It was found that the generator current change caused by the mesh can be significant (on the order of ten) when the mesh is extremely close to the generator (e.g, less than 1 cm) and is negligible when mesh is relatively far (greater than 0.15 m). The findings in this paper can be used to develop guidelines and best practices to mitigate the influence of mesh on PDSs. INTRODUCTION The Mine Safety and Health Administration (MSHA) requires operators of underground coal mines to equip place-changing continuous mining machines (CMMs) with proximity detection systems (PDSs) to protect mine workers from striking, pinning and crushing injuries when they work around these heavy machines. Although a variety of technologies can be implemented for proximity detection, the magnetic-field-based PDS that was originally developed at the National Institute for Occupational Safety and Health (NIOSH) has shown great effectiveness in challenging mining environments and currently all MSHA-approved PDSs are magnetic-field-based systems. As shown in Figure 1, a magnetic PDS typically includes two major components----the magnetic field generator and the Miner Wearable Component (MWC). Magnetic fields are generated by injecting a high electric current into a ferrite-rod antenna sealed in the generator. The magnetic field strength detected by an MWC varies with the distance between the MWC and the generator. In a typical PDS, multiple generators are mounted on different locations of the machine. The relative location/zone of an MWC is determined based on the field strengths from different generators picked by the MWC. Ideally, for a PDS to work properly in the underground, the magnetic fields generated by the different generators should be stable and not vary with the environment, as the system would interpret any variation of the magnetic field as a result of the distance change between the machine and the miner wearing the MWC. In reality, however, this is not always the case since magnetic fields can be altered by a number of environmental factors such as the presence of steel wire mesh that has been widely used in underground coal mines for supporting roof and ribs In this paper, the influence of mesh on the PDS performance is investigated and the magnetic field change caused by the mesh is measured.

Jan 1, 2019

By Robert B. Fulton

The objective of this chapter is to discuss the interrelationship between industrial minerals and chemical manufacturing. It is intended to supplement rather than duplicate the commodity chapters. Particular emphasis is given to the pertinent chemical element and to market factors. Condensing this broad subject into a few pages of this handbook permits treating only the most important elements derived from industrial minerals. Hydrocarbons, which quantitatively dominate as raw materials for the chemical industry, are omitted, as are the metallic elements and the minerals covered in other "use" chapters such as phosphorous, potassium, and nitrogen for fertilizers, and titanium dioxide for pigments. The remaining six elements of major importance are: boron, bromine, chlorine, fluorine, sodium, and sulfur. These elements are treated individually under separate headings. [Table 1] affords an overview of the main industrial minerals, the chemical products derived from them, and end uses of the products. Salt brines have particular importance as raw material sources for the chemical industry. Table 2 is a chart of the chemical compounds derived from four types of brines: (1) Owens Lake-type brines, which are sources of boron and sodium compounds; (2) Midland-type brines, from which bromine, iodine, and chlorides of calcium, magnesium, potassium, and sodium are derived; (3) Searles Lake-type brines, yielding boron, bromine, lithium, magnesium, potassium, and sodium compounds; and (4) Silver Peak- type brines, produced mainly for lithium. MARKET ATTRIBUTES Some of the important market traits common to industrial minerals used by the chemical industry are: 1. They are international commodities, such as fluorspar and sulfur, which largely move to foreign consumers. 2. Grade, and freedom from deleterious elements are important factors affecting their usability in chemical processes. An example is salt (NaCl) used in electrolysis where ultrapure evaporated salt is required to meet rigid specifications. 3. Purified products take on the characteristics of specialty items and command a distinctly higher price than the basic commodity from which they are derived. 4. In practically all cases, chemical users require some sort of cleaning or beneficiation of the naturally-occurring mineral to bring it to specification, and individual specifications may vary from user to user for essentially the same use. 5. In some instances it is necessary to strike a balance between what the vendor can supply and what the buyer requires, with the result that specifications have to be eased to afford the needed materials in marginal cases. 6. Because they tend to be bulk commodities, low cost for handling and transportation are important and such costs may limit the area from which a chemical user can draw his supply. 7. Shipments are usually in bulk and frequently in multiple-car, full-trainload or full-shipload lots to reduce transport costs, which in turn may require large terminal investment facilities. 8. Purchases are generally by contract of one year or longer term, with spot buying playing only a minor role. 9. Contract prices are usually fixed in short term commitments, but may vary according to assay, with premiums and penalties for content above or below the norm; however, general practice is for specifications to be fixed in the contract with minimums being set for the desired material and maximums for undesired elements. In longer term contracts, prices are often escalated on labor, fuel, and other vendor processing costs. 10. Suppliers of individual commodities to the chemical industry tend to be limited in number and are generally medium- to large-size producers that supply a few major consumers. 11. The bulk of the mineral volume is for basic chemical uses, sulfur suppliers to sulfuric acid producers and fluorspar for hydrofluoric acid producers being typical examples. These basic chemical products then are used for the production of other products. 12. Shortage of a supply of adequate quality leads consumers to seek substitutes. In the case of fluorspar, much work is being done on recovery of fluorine from phosphate rock. Success in the form of fluorosilicic acid and/or hydrofluoric acid production could, in time, affect the hydrofluoric acid chemical industry. 13. Markets tend to be characterized by cycles of shortage followed by oversupply, with attendant wide price fluctuations. 14. Baniers to trade can have an adverse effect on the necessary movement of industrial minerals used by the chemical industry in international trade. Antidumping laws, quotas, and tariffs can disrupt or dislocate normal markets. 15. Chemical industry consumers may back-integrate for security of supply or for favorable economics, sometimes by joint ownership and often with experienced mining partners.

Jan 1, 1994

By C. M. Marquardt

The materials handling systems in the large concentrating plants have required the employment of a considerable number of workmen, many of whom had very little to do except to act as watchmen to avoid bad spills at belt junctions and to operate tripper cars, shuttle belts, etc. Much time also was spent in watching bins to make sure they were properly filled. Approximately four and one-half years ago the author, Yin coopera¬tion with the engineering and supervisory personnel of The Anaconda Company at Anaconda, Montana, began to give this problem serious consideration. Prior to this the author had developed, at the request of The Anaconda Company, a transistorized resistance-sensitive probe relay system for detecting the level of ore in bins. With this system cables or chains were suspended from insulators above the bins and were of suitable length to determine the elevation of the ore in the bins.

Jan 1, 1962

By James J. Olson

INTRODUCTION The need for Government-sponsored research and development to increase excavation rates and lower costs for tunneling and mining operations in a variety of rock types has been emphasized in a wide range of publications from advisory panels, symposiums on rapid excavation, and individuals. In response to the predicted demands for mining and construction-oriented underground excavations for the next two decades (1970-1989), a comprehensive 10-year, $200-million research program in rapid excavation was proposed by the National Academy of Sciences in 1968 (1). Although the large program recommended by the Academy has not been funded, substantial Government-sponsored research in rapid excavation has been conducted during the past several years. This paper reviews some of the significant research accomplishments obtained under a three-year, $6.6-million research program in rock mechanics and rapid excavation sponsored by the Defense Department's Advanced Research Projects Agency (ARPA) and managed by the Bureau of Mines. In addition to the rock mechanics research, five major phases of excavation; systems analysis, geologic prediction, rock disintegration, ground support, and materials handling were represented by the projects funded under the ARPA program. The brief outline below recapitulates the major research areas and some of the projects summarized by this paper: Excavation Process Modeling by Computer Geologic Prediction Geologic Reconnaissance for Site Selection Longhole Probe Drilling for Hazard Detection

Jan 1, 1974

By Jasinder S. Jaspal, Bradley J. Bourquin

Introduction Operation is underway at the Dutch Creek No. 1 mine of the first US longwall panel to be mined under the cooperative agreement between the US Bu¬reau of Mines and Mid-Continent Resources. The 244-m (800-ft) wide longwall face is part of a multilift longwall demonstration. A 3-m (10-ft) top slice is being extracted from the 8.5-m (28-ft) coal seam. This occurs in an area of the property where the Coal Basin A and Coal Basin B beds have come together to form one seam. This face, longest ever operated in the US, is being worked on an advancing longwall system. During the first months of its operation, this longwall face has been very productive and safe. Mid-Continent Resources operates two coal mines in the Coal Basin, located in the White River National Forest near Carbondale, CO. The Colorado Fuel and Iron Co. originally opened this property in 1895, and conducted a small mining operation for 10 years on the north rim of the basin and then abruptly shut down. Mid-Continent began operations in 1956, after the Coal Basin fields had lain idle for about 60 years. Operations commenced at the outcrop of the Coal Basin B bed situated at the 3-km (10,000-ft) elevation. At this time, coal was produced from Coal Basin A and Coal Basin B seams in the area. Since 1981, operations have been centralized at two mines, the Dutch Creek No. 1 and the Dutch Creek No. 2, both located in the center of the basin. Since 1981, Mid-Continent has shifted its emphasis to longwall mining as the primary method of production, and each of these mines is equipped with state-of-the-art longwalls using shields as the method of roof support. A 4-km (13,000-ft) long twin-bore rock tunnel is being driven at a lower elevation of 2.4 km (8,000 ft) to intersect the coal seams at depth, as they dip 12° in a westerly direction. This tunnel will enable the company to reduce costs by replacing trucks with conveyor belt haulage (Fig. 1). Mid-Continent began longwall operations in May 1976 with the US's first modern, mechanized advancing longwall face, using chocks. In August 1978, a second advancing longwall face was started. Results from two faces showed that the mining system could be used effectively to manage the difficult conditions encountered in both the Dutch Creek No. 1 and the L. S. Wood No. 3 mines. Unfortunately, low productivity and high costs plagued the company's advancing faces. The problems resulted principally from major equipment failures, poorly designed chocks and face conveyors, and the lack of an efficient, cost effective system for building packwalls. Flushing of rock between chocks and roof control were also major problems. In Sept. 1979, Mid-Continent and the US Bureau of Mines entered into a cooperative agreement to demonstrate the feasibility of mining thick coal seams using the multilift longwall mining method. Two lifts are to be used to mine the 8.5-m (28-ft) thick coal seam in Dutch Creek No. 1 mine. The Bureau provided mining equipment for 180 m (600 ft) of longwall face. This included the shields, face conveyor and drive units, shearing machines, panel belt, and stageloader. As a result of previous experience in advancing longwall mining, Mid-Continent purchased an additional 60 m (200 ft) of face, including roof supports and an additional face conveyor. Design The Dutch Creek No. 1 is a slope mine located on the flank of a plunging anticlinal structure that

Jan 1, 1984

By G. R. Laurer, J. W. Neton, C. Pomroy, N. Cohen, M. Eisenbud

INTRODUCTION In uranium miners, a causal relationship between exposure of the lung to high levels of alpha radiation and the consequential induction of bronchial carcinoma is now well-established (Wagoner, et al., 1965). Quantitation of this cause-effect association presents considerable difficulty, however, as the result of various confounding factors such as the contributing effects of smoking and/or arsenic exposure (Archer, Gillam, and Wagoner, 1976), normal metabolic variability and, perhaps most important of all, the absence of accurate radon/radon daughter exposure data. Estimates of cumulative lung exposures suffer from inaccuracy due to critical factors such as 1) unknown ventilation rates; 2) difficulties in obtaining representative mine air samples; 3) the variable character and magnitudes of the exposure sources; and 4) specific differences in metabolism and job histories that exist among miners. It was with considerable enthusiasm, therefore, that investigators readily embraced the idea of using skeletal burdens of the relatively longlived descendants of radon and its short-lived daughters, i.e., 210 Pb and 210Po (Archer, et al., 1968), to provide a measure of cumulative past exposure wherein the body acts as an integrating dosimeter. Early studies considered excretion rates of 210Pb and 210Po in urine, blood and hair (Sultzer and Hursh, 1954; Black, et al., 1968; Jaworowski, 1965; Bell and Gilliland, 1964) as well as their concentrations in bone samples, if and when they became available (Blanchard, Archer, and Saccomanno, 1969). These methods were ultimately complemented by in vivo, whole-body counting techniques using low background, NaI-Csl(T1) detectors (Eisenbud, et al., 1969). By this latter method, it would be possible to measure the skeletal burden of 210Pb directly, thereby avoiding the many difficulties associated with the relation between nuclide excretion rates and body burden. The rationale was simple; by knowing the skeletal burden of 210Pb it should be possible, by the judicious use of an applicable metabolic model, to estimate the cumulative lung exposure to alpha-emitting radon daughters (Fig. 1). Various models that were consequently constructed, however (Fisher, 1969), all suffered from the same limitation, i.e., the assumption that the source of 210 Pb in the skeleton and the source of lung exposure to the short-lived radon daughters were simply related and, if not, were at [ ] least not too variable (Raabe, 1970). By now, the difficulty with this assumption has been recognized and more sophisticated modeling techniques have been attempted which presumably present a more realistic picture of exposure conditions (Holtzman and Rundo, 1981). There is, nevertheless, the pessimistic view that due to the variety and variability (in time as well as in character) of sources that may exist for the origin of 210Pb in bone, it may [never] be possible to estimate past lung exposures accurately by an indirect, predictive model. For example, the origin of 210 Pb in the skeleton may include such sources as: 1) the decay of short-lived 222Rn daughters, inhaled and ingested; 2) the decay of 222Rn dissolved in body fluids and tissues; 3) directly from 210 Pb present in air, inhaled and ingested; and 4) 210Pb from non-occupational sources, e.g., food, water, smoking and endogenous 226Ra. The contribution of each of these sources may vary depending upon specific site conditions such as ventilation and mining operation. On the other hand, empirical evidence seems to indicate a trend reflecting the simplest of direct

Jan 1, 1981

By W. T. Robertson

My charge is to review briefly "Coal In The Electric Utility Industry - Present and Future." Thus, I will not dwell on the overall energy picture, other than to express what most others involved in the energy picture know - we're in trouble! Several years ago, speaking to another engineering society, I said, "Much has been and yet will be said and written about the energy situation in our Country." What an understatement! The energy question has reached crisis proportions and is a top priority item at the highest level of government, Unfortunately, it will be in that situation for some time to come. Many factors created this complex problem, and we all share some of the blame. But I am perplexed when I read in the popular press that environmental factors are unrelated to the energy crisis when I know this to be untrue. In the recent past all forms of energy have been cast in the role of villain, particularly coal with its problems of surface mining, mine safety, acid water drainage, sulfur content, and a multitude of other adverse factors relating to the environment in one way or another. As you know, the sulfur situation has led to the closing of numerous mines, resulting in the lessening of our mining capacity. Today, along the Eastern Seaboard, 60 to 70 million tons of coal are displaced by imported oil, primarily to meet air standards. Even in the Midwest, utilities sitting on enormous coal reserves are converting to other fuels or hauling low sulfur coal thousands of miles from the western Mountain States. [We will hear more about this coal from another speaker on the program this morning.]

Jan 1, 1973

By Cheryl Lee Vatter

The Lupin mine consists of a gold mining, milling, and refining complex located 400 km (250 miles) northeast of Yellowknife and 100 km (60 miles) south of the Arctic Circle on the southwest shore of Contwoyto Lake in Canada's Northwest Territories. (Fig.1). The mine was commissioned in 1982 and is presently producing 6 t/a (193,000 oz per year) of gold from 612 kt (675,000 st) of ore. The success of this operation is due to such factors as the continuity and grade of the ore body, the competency of the host rock, low mining costs, efficient milling, the transportation of people and materials to and from the mine site, and the unique work schedule resulting in a stable workforce. Echo Bay Mines operated a silver mine at Port Radium on Great Bear Lake, Northwest Territories, from 1965 to 1982. The company first obtained an option on the Lupin property from Inco in February 1979 and completed an underground exploration program in 1979-1980. Topographic relief is low and vegetation is sparse in the continental subarctic climatic zone, consisting mainly of moss and lichens. Temperature extremes are from 24°C to - 45°C (+75°F to -49°F) with an annual mean of -12°C (+54°F). Permafrost extends from near surface to 500 m (1640 ft) in the ore zone. Its remote location and harsh climate presented some challenging design and logistical problems. Construction began at the Lupin mine site in 1980. Before construction, a 1.5-km (5000-ft) gravel landing strip was prepared, suitable for landing a C 130 Hercules. The entire Lupin project took 20 months to build. All of the men and materials were transported to the site with some 1100 Hercules flights and several hundred Convair 640 flights. The Convairs transported construction crews, which numbered 400 at their peak, and also carried 3.2 kt (3535 st) of supplies during construction. The facilities were constructed and commissioned for a total cost of C$135 million. The operation was originally designed to throughput 860 t/d (950 stpd). Expansion in 1983, circuit refinements, and some capital projects brought the daily throughput to 1.7 kt/d (1850 stpd). The underground mine delivers 612 kt/a (675,000 stpy) of ore to the mill at an average head grade of 8.46 g/t (0.3 oz per st). The ore is nonrefractory and is processed in a conventional cyanide leach using the Merrill Crowe process. Gold recovery is about 95.0%. The average production cost is $US5.85/g ($US 182 per oz) based on 1987 figures. Mining at Lupin – Geology The Lupin deposit occurs in amphibolite grade iron formation overlain by mudstones (phyllites) and underlain by graywacke (quartzites). Contacts between the wallrock units and the iron formation are well defined. It has been folded and tilted into a megascopic antiform-synform-antiform structure (Fig. 2). Gold occurs primarily within the sulfide rich iron formation, with some minor occurrences in sulfide poor iron formation. The distinction between sulfide rich and sulfide poor iron formation is based on a visual cutoff of 5% total sulfide content. Mining widths are determined by an assay cutoff of 4.2 g/t (0.15 oz per st) gold. There are few tons between 1.7 and 4.2 g/t (0.06 and 0.15 oz per st). The amphibolitic iron formation at the mine ranges from 1.5 to 20 m (5 to 65 ft) wide and has been followed over a strike length exceeding 1.7 km (5600 ft). The wider portions of the ore body tend to occur at its north extent and south nose. The gold-bearing iron formation appears on plan as a Z-shaped structure made up of three zones: the West, Center, and East. The West and Center zones dip steeply to the East (75° to 90°). Each of the ore zones plunge at an angle of about 65°. Total strike length of the three zones is more than 610 m (2000 ft). The zones are confirmed at a depth of 650 m (2130 ft) below surface. The Center zone is the widest and varies from 4.5 to 20 m (15 to 65 ft) while the West is the narrowest, averaging 1.5 m ( 5 ft). The footwall is comprised of quartzites that are strongly jointed and locally grades into phyllite, which comprises the hanging wall. The hanging wall and footwall are reversed in the West zone. Mineralogy of the ore at Lupin consists of amphibole minerals (hornblende, cummingtonite, and grunerite), feldspars, quartz, occasionally garnet, pyrrhotite, arsenopyrite, minor pyrite, and trace chalcopyrite. Also found in minor amounts are scheelite, apatite, epidote, calcite, tourmaline, and some arsenides (notable loellingite). Quartz

Jan 1, 1989

By Dick Lewis

The Misima deposit is on Misima Island in the Lousaide Archipelago, 240 km east-southeast of the Papua New Guinea mainland, and 600 km east of Port Morseby. Misima is a narrow mountainous island 40 km long and up to 10 km wide. The highest point is 1035 m above sea level. Gold mineralization is restricted to the eastern and less rugged third of the island. The Melanesian population lives in coastal villages. Subsistence agriculture is the main activity, although copra and cocoa are grown in plantations on the eastern and southern coasts. Prior to 1950, mining was important in the economy of the island. Climate is tropical, with little seasonal variation in temperature or rainfall. Tropical cyclones occur about every 10 years (Fig. 1).

Jan 1, 1990

By D. Lynn, D. Arthur

Infrastructures continue to age and drinking water supplies are becoming scarce in the San Fernando Valley of Los Angeles, California. Frontier-Kemper Constructors, Inc. (FKCI) was engaged by the Los Angeles Department of Water and Power (LADWP) to complete the River Supply Conduit Improvement Upper Reach—Unit 7 Project (RSC7). Two tunnel sections were bored using a 2.64 meter diameter Microtunnel Boring Machine (MTBM) and a 4.12 meter diameter Earth Pressure Balance Tunnel Boring Machine (EPBTBM) to excavate approximately 3,733 meters (3.7 km) of tunnels through highly abrasive late-Pleistocene-age Quaternary alluvial deposits (Old Alluvium) and Holocene age Young Alluvium deposits above the water table. This paper discusses the challenges encountered managing the TBM’s equipment degradation, use of soil conditioners, cutterhead wear, torque and advance rates while maintaining the necessary face-pressures and parameters to limit over excavation and ground settlement.

Jun 13, 2021

By E Marambio, R Brändle, G Fischer, G von Rickenbach, L Burgos, R Luis Fonseca

Ground support systems must provide safe and effective designs for underground excavations under high stress conditions. These systems must be capable to resist dynamic impacts and yielding during the loading process. In this context dynamic testing of the reinforcement and retaining elements that compose the ground support system are required to study and improve the behaviour of these elements under dynamic load events. During the last years, Geobrugg has been working on the improvement of retaining products by testing them in a large-scale impact test facility located at Walenstadt, Switzerland. The test facility is composed of a double level platform with a square-shaped pyramidal trunk geometry, in the upper level housing a loading mass that drop from a height up to 5m. The loading mass is guided by one central steel pipe, and the impact occurs in the sample to be tested located at the lower level in a slab with an area of 3.6m × 3.6m where the ground support system is installed. During the last years, this innovative facility has been used to test several configurations of ground support systems. The results of these tests have enabled to improve the understating of the behaviour of ground support systems under dynamic loads. In this manuscript, the arrangement, measurement, results, and the preliminary analysis of a single impact dynamic test performed during 2021 of a ground support system with a high-tensile steel wire mesh MINAX 80-4.6 is presented.

Apr 26, 2022

By Richard L. Nielsen

Early Models In 1906, Daniel Jackling demonstrated that relatively low-grade disseminated copper deposits could be mined profitably using mass mining technology. The ensuing years saw a gradual increase in activity aimed at defining ore targets for large reserves of disseminated supergene enriched copper ores. Prominent organizations, such as Calumet and Hecla, Phelps Dodge, and Asarco, established teams of geologists. They focused on interpreting oxidized and leached outcrops over supergene chalcocite ore bodies. Techniques to evaluate oxidized cappings and predict the presence of underlying supergene chalcocite enrichment ores were developed and put to practical use by the late 1920s and early 1930s (Locke, 1926; Blanchard 1939, 1968). Oxidized capping evaluation centered on recognizing oxidation products derived from the various sulfide minerals found in disseminated deposits. Chalcopyrite, for example, oxidizes to a characteristic reddish pitch limonite that exhibits characteristic boxworks. Chalcocite is recognized by earthy, powdery, indigenous, hematite-rich limonite. Pyrite weathers to characteristic cavities and yellowish jarositic limonites. Evaluation of cappings is a systematic effort of noting and estimating the preoxidation sulfide mineral content and copper grade in an oxidized outcrop using mineral composition and morphology of oxidation products. Several complications were noted early in this technology's development. For example, the associated pyrite content of protore greatly influences mobility of copper and iron during oxidation. High-pyrite disseminated sulfide assemblages, upon oxidation, mobilize iron as well as copper. This results in oxidized rock with many leached cavities, poorly developed boxworks, and poorly developed indigenous limonites. This effect was noted and used in a general way to identify possible development of supergene chalcocite. Indeed, strongly leached outcrops could be present over enriched ore. A second complication is the manner in which associated gangue minerals influence the products of sulfide oxidation. Reactive gangue minerals, such as carbonates, neutralize acids formed by sulfide oxidation. Thus, copper cannot be moved from oxidized outcrops. Relatively nonreactive gangue, such as quartz-sericite-altered schist or porphyry, neutralizes supergene acid very slowly. This allows copper to move out of the oxidized outcrop. Recognizing these features was closely allied to an early understanding of the processes involved in oxidation supergene enrichment of disseminated ores. Field observations and mineralogic mapping of oxidized cappings were important in discovering many important porphyry copper ore bodies during the 1920s. These include Silver Bell, Miami-Inspiration, and Morenci in Arizona; Tyrone, NM; and Ely, NV. Capping interpretation like-wise led to discoveries at Mineral Park and Esperanza in Arizona during the exploration surge that accompanied high copper prices in the 1950s. In the 1960s, Kennecott research geologists refined and quantified some aspects of oxide capping appraisal (Anderson, 1982). The ratio of jarosite plus hematite to the total limonite assemblage was shown to be proportional to amount of copper leached from the oxidized outcrop. Thus, if the limonite assemblege in an oxidized capping consists of 40% goethite, 20% jarosite, and 40% hematite, 60% of the original copper is leached. The amount of copper remaining in the capping, together with the limonite mineralogy, can then be used to estimate original copper grade in the outcrop, amount of leaching, and chalcocite enrichment grade (in feet/% copper) in the underlying supergene chalcocite zone (Anderson, 1982). Evaluation of oxidized cappings and prediction of chalcocite blanket ore targets were successfully used in the western US and South America through the 1950s. Discovery of new porphyry copper provinces in other regions during the 1950s and 1960s, however, underscored some limitations of capping evaluation technology. Porphyry copper systems in Australia generally oxidize and weather to hematitic cappings. Presumably, the semiarid monsoon environment and the long time that the sulfide systems have been exposed to oxidation on that continent lead to development of relatively stable hematite. It is now recognized that jarosite and goethite persist metastably in the limonite assemblage in all areas once sulfide oxidation is complete and acid generation ceases (Brown, 1971). The assemblage eventually converts to hematite. But, climatic conditions in arid southwest US allows metastable limonites to persist for a long time, thus providing information on former sulfide assemblages. Another problem occurs when applying capping evaluation techniques in extremely humid re-

Jan 12, 1984

By Roy M. Fleming, Christine B. New

The federal standard for limiting exposures to miners from radon daughters was reduced from 12 working level months (WLM) per year to 4 WLM per year in 1971. However, even at that time some researchers were concerned that the new limit would eventually be shown to result in an excess risk for lung cancer mortality in miners. The National Institute for Occupational Safety and Health (NIOSH) is now engaged in a comprehensive review of this topic. As the lead agency in this project, NIOSH has developed a work plan and established a work group to implement this plan. The procedure and specific considerations are outlined in the work plan for developing a comprehensive ionizing radiation standard recommendation for all miners, underground and surface. Such a recommendation will not only include estimates of health risks at various levels of exposure, but also appropriate recommendations for medical monitoring, sampling and analytical methods, sampling strategies, posting, engineering controls, personal protective equipment and recordkeeping. The work group has twenty-four members. Eleven members are NIOSH personnel representing six divisions of the Institute. The remaining thirteen members represent other federal agencies, specifically the Bureau of Mines of the Department of the Interior, the Mine Safety and Health Administration and the Occupational Safety and Health Administration of the Department of Labor, the Office of Radiation Protection of the Environmental Protection Agency, and the Bureau of Radiological Health of the Food and Drug Administration, Department of Health and Human Services. Several factors contributed to the decision to initiate this project. First, the efficacy of the current standard was considered. An initial study group was formed in the spring of 1980 by NIOSH to identify and evaluate articles that contained information on lung cancer mortality risks at and below the present permissible exposure limit. The conclusion drawn from their evaluation was that a two-fold excess risk of lung cancer mortality at and below 120 cumulative working level months (CWLM) of exposure to radon daughters is evident. This composite indication from selected studies was of sufficient magnitude to justify further evaluation. The study group, however, recognized that other studies and information must also be considered in a quantitative risk assessment which would form the basis for recommending an acceptable and feasible permissible exposure limit. A second factor in the decision to pursue further evaluation was the gaps in the current standard that had previously been identified by the Mine Safety and Health Administration (MSHA). These included lack of medical monitoring of underground miners and absence of regulations for surface miners. The seriousness of the health hazard relative to other hazards in mining was also considered. Along with exposures to silica and asbestos fibers, radiation was judged to be one of the major health hazards in mining, These combined factors constituted the justification to develop criteria and recommendations for improved mandatory health standards. The development process begins with a survey and review of the available world-wide information on the topic, including data and information developed by NIOSH. The end product of this review is to be a document that will contain an evaluation of the collected information and support for any recommendations that are made. To develop this document, the present work group has been divided into five task groups with the following emphases: Health Effects, Medical Aspects, Monitoring, Environmental Exposures, and Engineering Controls and Work Practices. The Health Effects task group is to evaluate the evidence from epidemiologic and animal studies of adverse health effects associated with all forms of ionizing radiation encountered in mining and milling operations. The "weight-of-evidence" of the results of all relevant and useful studies will be summarized, with the reasons for emphasizing the cited studies. The critical cells or tissues and the factors that should be considered in estimating the dose to these areas from various types of radiation will be identified. An evaluation will be made of the possible impacts of smoking and exposure to diesel exhaust on the determination of health effects related to radiation. The implications of biologically redundant dose in terms of the time between tumor initiation and death will also be analyzed. The Medical Aspects task group is to review the generally-accepted and the state-of-the-art medical technology for the detection of adverse health effects from ionizing radiation exposure. An evaluation will be made of the accuracy of urine and fecal analysis, wholebody counting, chromosome analysis and nose blows, as well as their usefulness for early detection of adverse health effects. Early detection is of little utility to the affected individual unless subsequent medical care can improve the prognosis. Recommendations for screening tests will be made after carefully considering the accuracy of the diagnostic procedures and the usefulness of early detection. Required recordkeeping and transfer rights will also be addressed. The Monitoring task group is to consider the state-of-the-art technology for the monitoring of occupational radiation exposures. Instrumentation, sampling strategies and analytical procedures will be reviewed for both personal and area sampling. The implications of the associated levels of confidence for non-compliance decisions will be evaluated. The discussion will also include an evaluation of the feasibility of replacing present monitoring systems with recent technology and the impact that a possible lower permissible exposure limit would have on monitoring requirements. The Environmental Exposure task group is to investigate the field procedures and mathematical methodologies which have been used to quantitate exposure levels to the various kinds of ionizing radiation. The magnitude and direction of the possible biases in past exposure assessments will be estimated. Specific attention will be given to the controversies concerning the quantification of the biological dose equivalent and the feasibility of recommending standards for mixed radiation exposures which use "rem" as the unit of measurement. The Engineering Controls and Work Practices task group will analyze the advantages and limitations of

Jan 1, 1981

By M. L. Leming

The mechanisms of Alkali-Silica Reactivity (ASR) are briefly reviewed, test methods are examined, and typical specifications are discussed. In addition, views on responsibility of the aggregate supplier regarding specifications are presented.

Jan 1, 1995

By D. L. Kuck

Water ice pillars far underground mine roof support can be frozen and/or maintained and/or melted on demand. The system to do this consists of a refrigeration brine chiller, brine circulation system and disposable plastic containers. Fusion expansion, resilience to dynamic loads, plastic deformation under stress, and non-contamination of coal or ore are unique properties of ice. Lower labor and material costs are economic advantages of ice far mine structural support. Ice brattices can become ice pillars on retreat. For safety, ice pillars can be placed (by remote control, if necessary) in hazardous sites without human entry.

Jan 1, 1988

By Michael Traylor, Michael Jatczak, Brett Robinson

The Detroit River Outfall No. 2. is an effluent water conveyance system linking the Detroit Metropolitan Wastewater Treatment Plant to the Detroit River. The 6.4m (21ft) finished diameter tunnel extends 1,890m (6,200ft) east from the bottom of a 91m(300ft) deep, 9.2m (30ft) diameter drop shaft. At the eastern terminus of the tunnel, six Riser Shafts connect the tunnel to diffuser heads on the riverbed. The tunnel runs through a highly fractured Limestone formation capable of producing high levels of groundwater in?ows and Hydrogen Sul?de gas. Control of this water and gas was a theme which ran through the entire Project’s design and construction. This paper will provide an overview of each portion of the Project’s construction, including the Entrance Shaft, Precast Concrete Segments, TBM Tunnel, Pre-Excavation Grouting Methods, and the Riser Shafts.

Jan 1, 2003

By S. A. Jeric

In-pit crushing and conveying of waste has been utilized in the mining industry for over 30 years. In recent years, innovations in crushing, conveying, and particularly waste and leach stacking technology have sparked a renewed interest in continuous haulage systems for large-scale open pit applications. A review of the advantages/disadvantages and operating techniques of crushers, feeders, conveyors, and stacking systems currently available is made. The paper examines some operations that are currently using large scale continuous haulage systems. Finally, a case study is presented that evaluates the application of a continuous waste haulage system in a large open pit mine in the Western United States, The case study includes a economic comparison with the existing truck haulage system.

Jan 1, 1997

By M. Robson

Water & Earth Technologies, Inc. (WET), Habitat Management, Inc. (HMI) and Chevron Mining, Inc. (CMI) together developed a solution for reclaiming steep southwest facing slopes in mining Area 12C that have historically been prone to excessive erosion, low vegetation establishment and continuing maintenance. Area 12C is located in the east wing of the Chevron McKinley Coal Mine, 27 miles northwest of Gallup, New Mexico, on Navajo Nation land administered by the Office of Surface Mining (OSM). Mining in this area was completed in May of 2007. Challenges encountered for this reclamation project included the need to reclaim graded material on a slope of 18-35% with southwest facing aspect, the presence of undisturbed rock outcropping that needed to be avoided during reclamation, the operational need to limit bulldozer pushes and the inability to import or export additional materials for construction. Two different reclamation alternatives were considered for Area 12C. The first alternative would use a traditional reclamation approach including three levels of draining terraces designed to convey water on a 3% slope to a single riprapped down drain. Terracing and down drains have been used to reclaim areas with similar terrain conditions elsewhere at the McKinely Mine and have failed to adequately control erosion (Williamson 2006). Terrace overtopping and down drain blowouts have been issues in maintenance and functionality for the mine. Maintenance routines consist of cleaning out terraces where they have filled in with sediment and repairing damaged or blown out terraces and down drains.

Jan 1, 2010

By Young C. Kim

Because of the high cost of obtaining coal washability samples, it has been difficult to obtain washability variograms in the past. As a result. It could not be determined if geostatistical prediction tool known as kriging can be applied to predict in-situ coal washability characteristics.

Jan 1, 1988

By Gill G. Geesey, Michael R. Hankins, Paul L. Wichlacz, Anita Gianotto, John G. Jolley, Randy B. Wright

Thin films of copper [2.0 nm on germanium internal reflection elements (IREs) and 3.4 nm on germanium discs] were exposed to 10% gum arabic (aqueous solution) , 2% alginic acid (aqueous solution), 1% bacterial culture supernatant (BCS, simulated seawater solution) and 0.5% Pseudomonas atlantica exopolymer (simulated seawater solution). The IRES were monitored in situ, in real time using fourier transform infrared/cylindrical internal reflection/attenuated total reflection spectroscopy as a function of time at ambient conditions. The discs were characterized (pre- and post-exposure) by X-ray photoelectron and Auger electron spectroscopies. Ancillary graphite furnace atomic absorption spectroscopy was used to monitor the removal process of the copper thin film from the germanium substrates. Results indicate that Cu was oxidized by gum arabic, alginic acid and BCS. Furthermore, Cu was removed from the Cu/Ge interface by all four polymers. The Cu was found associated with the polymer solutions.

Jan 1, 1989