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By Joaquin Marti, Peter A. Cundall

This paper reports on some recent work in which several schemes were developed to model jointed rock under high stress, with particular reference to the phenomenon of "block motion" observed during dynamic loading of underground structures. Three approaches were made, corresponding to an increasing relative importance of internal block deformations as compared to rigid block movements. The first one uses distinct element method and assumes internally rigid blocks, which can break, repeatedly, whenever an empirical crack criterion is met. In the second approach each block is allowed three degrees of freedom to deform internally. The third approach, still in the development stage, permits arbitrary deformation of all blocks, which are internally decomposed into finite-difference zones and automatically rezoned during slip to preserve the calculation accuracy on joints. The last two schemes allow arbitrary constitutive relations for the intact rock, and all three schemes permit the geometrical arrangement of joints to be arbitrarily complex, in contrast to normal Lagrange, finite-difference programs, which are unsuited to model discontinua.

Jan 1, 1979

By R. C. Jr. Babcock, V. S. Znamensky

The Pyke asbestos deposits were discovered by Kennecott Explorations (Australia) Pty. Ltd. in 1969 during the course of base metal exploration on the South Island of New Zealand. Extensive occurrences of chrysotile asbestos were found associated with the Red Mountain ultramafics in the headwaters of the Pyke River, and to the north and south along the ultramafic belt for a distance of 70 km. Surface evaluation and drilling by Kennecott in 1970 and 1971 identified numerous small deposits of good grade fiber in the Little Red Hills between the Pyke and Barrier Rivers. Additional drilling and three adits have been completed by other companies since that time. The property is presently held by Lime and Marble, Ltd., of Nelson, New Zealand, and Kennecott Explorations (Australia) Pty. Ltd. This chapter presents the regional and local setting of the asbestos deposits, including the geology and nature of mineralization. In addition, the exploration methods used by Kennecott in the discovery and evaluation of these deposits are outlined. Subsequent work by other companies is mentioned, but not de- scribed in detail. This subsequent work did not alter Kennecott's conclusions or produce any serious changes in the interpretation of geology and mineralization. The author acknowledges the contribution of the many employees of Kennecott Explorations (Australia) Pty. Ltd. who have been involved in the project. In particular, thanks go to Ramon Farmer, N.G. Corner, and A.W. McConie, who were responsible for completion of field work and reporting on the project. The responsibility for the conclusions and interpretations of this chapter are solely that of the author and result from his involvement in the discovery of the deposits and management of the exploration program. REGIONAL SETTING Ultramafic rocks on the South Island of New Zealand are thought to be Permian in age and occur between crystaIline and metamorphic continental rocks of Precambrian through Cretaceous age in the west, are thought to have once been part of the Antarctic subcontinent, and the extensive geosynclinal graywacke deposits of the Mesozoic New Zealand geosyncline in the east. They consist of the Dun Mountain ultramafics, a 130 km long segment of ultramafic rocks located at the north end of the South Island, and the Red Mountain ul- tramafics that occur in a zone 200 km long in the south half of the South Island as shown in Fig. 1. These two belts, once contiguous, have been offset a distance of 560 km by the still active Al- pine fault, which is analogous in character and offset to the San Andreas fault of the United States. The ultramafic rocks occur within a sequence of Permotriassic volcanic and sedimentary rocks that probably formed at the eastern margin of the continental plate. The ultramafics appear to be tectonically emplaced between Permian lithologies in the Dun Mountain belt (Coleman, 1966), and at the base of or between Permian volcanics and sediments in the Red Mountain belt. The Permotriassic ultramafic volcanic sequence of the Red Mountain ultramafic belt appears to be a typical ophiolite sequence. Ultramafic rocks, mixed mafic intrusive rocks and volcanics, volcanic rocks, and volcanoclastic sediments occur in apparent superposition from east to west in the area of Red Mountain. Farther south, ultramafic rocks are associated with basaltic volcanic rocks and some sediments, and still farther south are emplaced entirely in sediments. These structural compIications of the normal ophiolite sequence have resulted from the coincidence of Permian subduction, early Mesozoic extension and sedimentation, and Cretaceous subduction along the same plate margin (Landis and Bishop, 1972). The general geology in the area of the Red

Jan 1, 1986

By Robert L. Virta

An asbestos substitute is any material that replaces asbestos in a commercial product. There are many asbestos substitutes, each with its own unique physical and chemical properties. Substitutes can be inorganic or organic, fibrous or nonfibrous, and natural or synthetic. They also can be used as a direct substitute for asbestos or as a replacement product. Probably in no other field is the diversity of substitute materials so great. The concept of asbestos substitutes is not new. The first major effort to develop asbestos substitutes was undertaken by the federal government. The United States has always been dependent on foreign sources for strategic-grade asbestos, and during World War II, the government was concerned that these supplies would be cut off. Strategic-grade asbestos was critical in many electrical and thermal insulation applications (electrical insulation, battery plate separators, flame-proof boards, insulation for rocket components, etc.). A reliable supply of nonstrategic-grade asbestos also was required for general civilian and military applications, such as in brakes, clutches, and construction materials. The government not only initiated a major search for deposits containing strategic-grade asbestos, it also funded research on synthesizing asbestos in the laboratory and developing products that did not contain strategic- grade asbestos. These efforts, as well as those conducted by the private sector, generally were unsuccessful. In the late 1960s and early 1970s, a second major effort to develop asbestos substitutes began because the general public was concerned about the health threat posed by the release of asbestos fibers during the manufacture, use, repair, and disposal of asbestos-containing products. Strict regulations covering the mining and manufacturing sector already had been enacted because of the issue of occupational exposure. The issue then became environmental exposures. Environmental regulations were enacted, and through time they became more strict. The combination of increasingly strict environmental regulation, maturing of some asbestos markets, and liability issues prompted many manufacturers to discontinue asbestos product lines or search for asbestos substitutes. As a result, asbestos usage dramatically declined from the 1970s to the present (Table 1).

Jan 1, 1994

By Ahmed I. A. Salama

This paper describes the development of computer density control for heavy media cyclone circuit at the Coal Research Laboratories of CANMET. The control objective is to reach and maintain the medium density set point in minimum time. A description of the mechanical components and instrumentation are presented. The control strategy and computer software are discussed. Testing and evaluation of the installed system are presented.

Jan 1, 1989

By J. Allen Hennessy

INTRODUCTION The increasing price of gold and silver over the past 10 years has caused increasing activity in the exploration, evaluation and development of precious metals projects. Many of these deposits are relatively low grade and short lived which makes them economically sensitive to the major project variables such as metal price, capital cost, operating cost and of course, tonnage and grade. These deposits often have a high variability (a coefficient of variation -- o/u -- of 2 to 5) and an intermixing of ore and waste, making ac- curate ore reserve estimation difficult, especially when using traditional estimation techniques. Often, the estimation errors are not the 10-20% that we see in base metal deposits, but the errors in grade and tonnage can be as high as 50%, which can obviously have a very substantial impact on project Recent developments in geostatistics when coupled with a sound geologic under- standing of the deposit can significantly improve reserve estimates of these variable precious metals deposits. Examples will be given of actual deposits where the traditional estimates were significantly different from the mining reality. An attempt will be made to explain the applicable geostatistical tools with a minimum of geostatistical jargon and without complicated formulas. The key to improving the reserve estimates is a clear understanding of the deposit geology and especially the structural controls, the use of local estimation techniques that recognize the intermixing of ore and waste and the effect of selective mining on recoverable reserves, and the use of a global reserve estimation technique to check the results of local estimation. Geologic Controls The vast majority of gold and silver deposits being mined or developed in the western United States would be classified as epithermal deposits. These are formed by hydrothermal fluids (hot water) flowing upward through the rocks and depositing the precious metals as the fluids cool or reach areas of lower pressure or favorable chemical sites. These environments are similar to present day hot springs-type environments with some deposits being clearly associated with surface hot springs such as the Homestake McLaughlin deposit in northern California. These hydrothermal deposits can occur in sedimentary rocks resulting in deposits such as those of the Carlin district or the Jerritt Canyon deposit or the hydrothermal systems can occur in volcanic rocks forming deposits such as Round Mountain, Manhattan or Paradise Peak. The mechanisms of formation were similar in either case with the solution flow controlled by geologic structure and precious metals deposited when the conditions of temperataure, pressure and chemical environment were favorable. The gold and silver hearing solutions travel through permeable faults and fracture systems depositing the metals along these channels. The grades are often highest in the central parts of these conduits (veins) with lower grades in the surrounding rocks. An understanding of the nature, distribution and orientation of these plumbing systems is important to a realistic reserve estimate. The point to be emphasized here is that, good, sound geology in the form of geologic mapping, logging of rotary chip samples and a few carefully logged core holes can signifi- cantly improve an ore reserve estimate.

Jan 1, 1987

Underground mining has the potential to be one of the more dangerous industries in the United States and the world. Following recent disasters in Sago, WV; Darby, KY, and Crandall Canyon, UT, the mining industry was reminded of the need for a system to allow trapped miners awaiting rescue to survive following a disaster. To address this need, Battelle has developed a Mine Barrier Survival System (MBSS) that surpasses all current technologies and sets a new standard for keeping miners alive in the event of a fire, flood, explosion or collapse. The MBSS creates a temporary refuge for miners who cannot escape by using inflatable barriers and a post-fire atmosphere scrubbing system to define the ?safe haven? and remove CO2 and CO while replacing oxygen and providing heat. Current personal-protective systems in use are designed to provide breathing air for only a few hours when, realistically, it may take days for rescue teams to reach trapped miners. Battelle?s MBSS is designed to aid up to 15 miners for four days.

Jan 1, 2008

By Susan T. Bagley, Kenneth L. Rubow, David H. Carlson, Bruce K. Cantrell, Winthrop F. Watts

Permissible exposure limits (PELs) have been established for gaseous pollutants, carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO), nitrogen dioxide (NO2), and some gas-phase hydrocarbons emitted in diesel exhaust. There is, as yet, no PEL recommended for diesel exhaust aerosol (DEA), nor is there a standard method for sampling this aerosol. The University of Minnesota and the U.S. Bureau of Mines have collaborated to develop a personal diesel exhaust aerosol sampler (PDEAS) which utilizes size-selective inertial impaction and gravimetric analysis. During the field tests of this sampler, numerous air quality measurements were made in underground coal mines that use diesel equipment. The mine mean DEA concentrations for the five mines surveyed, determined with the PDEAS in the haulageway, was 0.89 mg/m3 with a standard deviation of 0.44 mg/m3. DEA contributed 52 % of the respirable aerosol at this location. In three of the mines filter samples were collected for DEAassociated polynuclear aromatic hydrocarbons (PAHs) and biological activity determinations. Two of the mines were also monitored for the major gaseous constituents found in diesel exhaust. In general, the PAH and biological activity levels were similar for all three mines, and indicate that up to 25 % of the haulageway concentrations may be contributed by outby diesel vehicles. Measured concentrations of CO, C02, NO, NO2, and SO2, were well below regulated levels. INTRODUCTION Diesel exhaust contains pollutant gases, such as carbon monoxide, carbon dioxide, nitric oxide, nitrogen dioxide, and gas-phase hydrocarbons, as well as DEA. Much of the health-related concern focuses on DEA and associated organic compounds (Watts, 1992a). A wide variety of these PAHs have been identified and some are known carcinogens and/or mutagens. The U.S. Mine Safety and Health Administration (MSHA) has proposed new PELs for these and other contaminants (MSHA, 1989). MSHA has also published an advance notice of proposed rulemaking to establish a separate PEL for diesel particulate (MSHA, 1992). The U.S. Bureau of Mines has collaborated with the University of Minnesota to develop and field test a PDEAS. The PDEAS is a three stage sampler based on the MSA' personal respirable dust sampler. It utilizes a respirable cyclone preclassifier followed by a 0.8 µm cut point impactor and afterfilter operating at a flow rate of 2 L/min. Respirable aerosol greater than 0.8, µm in size is collected by the impactor while DEA, less than 0.8 µm in size, is collected by the afterfilter. Hence, gravimetric analysis of the afterfilter permits measurement of DEA concentrations. This development and laboratory evaluation of the PDEAS were described previously by Cantrell (1990) and Rubow (1990). During field tests of the sampler, numerous air quality measurements were made in continuous miner sections of five underground coal mines that use diesel haulage equipment. These air quality measurements included levels of selected PAH and biological activity associated with DEA collected in the intake and haulageway areas of three of the five underground mines, and CO, CO2, NO, and NO2 in two of the mines. The objectives of this paper are to present the DEA and associated pollutant concentrations measured in these mines and to assess the impact of diesel face-haulage equipment on underground mine air quality. MINE DESCRIPTIONS The mines used for the PDEAS evaluation were designated J, K, L, N, and 0. Mines K, N, and 0 are located in the Western United States, while mines J and L are located in the East. Each mine produces high volatile, bituminous coal with shift production levels varying from 500 to 2000 tons/section. Seam heights varied from 1.5 to 3.0 m. Mines K and N use continuous mining to develop longwall panels. The others are strictly room-and-pillar operations using continuous miners. The number and types of diesel-powered vehicles used at these mines were described by Watts (1992b). Mines J, K, N, and 0 use diesel power to assist in a wide range of activities in addition to coal haulage. These included road maintenance, personnel and materials transport, lubrication, and welding. Mine L used only three diesel-powered shuttle cars to haul coal. SAMPLING AND ANALYSIS METHODS Aerosol Measurements Aerosol samples were collected in the mine portal area, the clean air intake to the continuous miner section, the haulageway one crosscut inby from the feeder breaker and belt, in the return airway, and on selected personnel. The haulageway sampling site was located near the point where the diesel-powered shuttle cars turn around to dump their loads. Additional respirable and DEA samples were collected and have been reported by Haney (1990).

Jan 1, 1993

By A. G. Journel

The regionalization of tungsten grades at the deposit represents an ideal case for anisotropic hole-effect variogram modelling. The modelling technique is presented step-by-step and the consequences of the model on block kriging are indicated.

Jan 1, 1982

By Alex Harrison, K. Payne

Computer generated magnetic field reference signa- tures of steel cord belt splices are used to evaluate lay-up and fabrication irregularities of splices in operating conveyors. Used as a quality inspection tool, magnetic signature analysis is useful in auditing data collected by general non-destructive testing (NDT) consultants. The evaluation can detect irregularities that weaken a splice, as well as detecting signature changes that can be indicative of adhesion loss. The evaluation can be applied to any NDT data available from a variety of commercial sources, which means that independent review of critical splice data is possible.

Jan 1, 1996

By P. Albert Carpenter, Wallace B. Howe, Michael N. Greeley, E. C. Bingler, Gilbert R. Eakins, Christy Bell, John Callahan, Gary B. Glass, T. J. Crabs

Although gold's market price dropped considerably from 1980's all time high, exploration for the precious metal remained a particularly bright spot last year, especially in the western US. For example, in Nevada-the nation's largest gold producer-further exploratory drilling at Louisiana Land & Explorations Co.'s deposit at Round Mountain and Newmont Mining Corp.'s find near Carlin resulted in sharp boosts in estimated reserves at both sites. Louisiana Land said its deposit is well on the way to being one of the largest gold reserves in the US. Based on further drilling, Newmont said its Gold Quarry property near Carlin could now produce 4.7-6.2 t/a (150,000-200,000 oz/ year). Reserves at Newmont's two properties near Carlin and a third property in southeast California are reportedly at least 218 t (7 million oz), up from the previously announced 128 t (4.1 million oz). Gold exploration activities were brisk in many other states, including a noticeable effort to explore and reopen dormant properties. Although the return on investments didn't appear as favorable last year as they did in 1980, the gold price was apparently sufficient to spur healthy exploration activity. Outside precious metals, market conditions, and subsequent exploration activity, appeared much more bleak. In the molybdenum market, for example, prices continued to slide, and Amax Inc. tightened its exploration budget. (Amax supplies 60% of the domestic market and 45% of the world demand for molybdenum.) The company spent 16% less on exploration during the first six months in 1981, compared to the same period in 1980. Copper and many other base metal producers appeared in similar straits throughout the year. Uranium exploration activities continued to suffer last year also due to depressed market conditions. Among others, Gulf Minerals Resources and Amoco Minerals Co. suspended uranium exploration activities in the West. Despite current unfavorable conditions, some companies continue uranium searches, confident that market conditions will rebound. On a brighter note, interest in exploring for some industrial and strategic minerals appeared on the upswing last year. Minerals used for oil and gas drilling, such as barite and special sands, were especially noteworthy. In geophysical activity, significant developments were achieved for electromagnetic techniques in both frequency-domain and time-domain systems. Geophysical logging activity declined due to decreased uranium exploration, and computer hardware continued to impact the way mining geophysical data are being acquired. Many presentations and papers were given last year to help exploration geochemists develop new techniques to locate concealed ore bodies. Among techniques described were statistical and computer modeling for enhancing anomalies over blind deposits.

Jan 5, 1982

By D. J. Hutchinson, S. Nickson

Cable bolts are used as a means of rock support around underground excavations in many mines across Canada and around the world. A substantial body of research on cable bolting was conducted at a number of Canadian universities and mines from the mid-1980s through the 1990s. Since then, research into selected areas of cable bolting practice has continued in Canada. The research has focussed on cable bolt instrumentation and on the inclusion of cable bolts in empirical stope design techniques. A review of cable bolting practice is now warranted at many mines. It has been five years since the completion of the previous substantial body of Canadian academic research and the associated advancement in understanding of cable bolt design, implementation and verification practice. Attempts were made at that time to transfer the new design procedures and performance assessment technologies to mine-site personnel. In some cases, this was effective, and ground control personnel continue to improve on their cable bolting practice at each specific mine site. However, at other sites, experienced people have moved on, and the new, less experienced personnel do not have access to the training or technical resources required to improve their understanding of the subject. In other cases, the technology was not transferred effectively to practitioners, with the result that substantial improvements can be made to the cable bolting practice at those mines. Guidelines for auditing cable bolting practice are provided in this paper. The guidelines include a discussion of the objectives of the audit, suggestions for audit procedure and a summary of the possible outcomes of a cable bolt audit. The objectives of an audit might include assessing the reasons for unexpected cable bolt failures, evaluating the quality of the installation procedures, quantifying the efficiency of the cable bolt system and assessing training requirements and procedures. A cable bolt audit should include consideration of all aspects of the cable bolting cycle, including the design, implementation and verification phases of the operation. At the end of the audit, a ranking should be assigned to the components of the cycle. The ranking system can then be used to identify items that require immediate attention, others that could be improved and others that are adequate. Following completion of a cable bolt audit, increased confidence in the support system and its application is generally, found, along with the potential for cost savings in many cases.

Jan 1, 2002

By Theodore H. Budd, Douglas J. Heinz

This report concerns the successful construction of Contract No. 287 of the Northeast Side Relief Sewer System for the Metropolitan Sewerage District of the County of Milwaukee. The contract involved the construction of approximately 3316 meters (10,880 feet) of tunnel concrete lined to 1.83 meters (72 inch) internal diameter; 30.48 meters (100 feet) of 1.83 meters (72 inch) reinforced concrete pipe jacked-in-place; a river crossing of approximately 107 meters (350 feet); 197 meters (647 feet) of 1.83 meters (72 inch) reinforced concrete pipe in open-cut; several diversion and flow monitoring structures; and miscellaneous manholes and appurtenances. The contract proposal, which was extremely prescriptive, did allow alternative methods of primary support consisting of precast reinforced concrete segments, steel liner plates, steel ribs with wood lagging, and combinations thereof in designated areas. The specifications required the contractor to designate which support scheme it intended to use. The specifications also required compressed air as a means of ground water control for approximately 2316 meters (7600 feet) of tunnel. The alternative selected in the bid proposal was the support method consisting of steel ribs and wood lagging for 2263 meters (7425 feet) of tunnel and steel liner plates for the remaining section. Shaft supports, by specification, were designed to be steel liner plate with steel ribs varying in size from 4.27 meters to 6.10 meters (14 foot O.D. to 20 foot O.D. ).

Jan 1, 1983

By R. C. Dunne, C. T. O'Connor

Flotation practice on eighteen South African flotation plants is described. The plants are categorized as those treating reclaimed tailings, those treating material which has already been subjected to cyanidation or uranium leaching, and those treating milled ore. The similarities and differences are highlighted.

Jan 1, 1998

By Thomas Schwind, Elmar Feigl, Gerald Skalla, Angelos Gakis

Cedarvale station was constructed as part of the Eglinton Crosstown Light Rail Line, under the operational Yonge-University Line Subway box of Toronto Transit Commission (TTC). The station was constructed as an open-cut, which necessitated the underpinning of the existing TTC box to minimize the impact on the Subway and allow its unhindered operation. Six mined galleries, 4 m wide by 2.75 m high, were excavated sequentially (SEM) immediately under the existing box, to provide the required space for the installation of the main underpinning beams. This novel solution was executed successfully providing quick access for the main excavation works to commence.

Dec 1, 2022

By Ivan Caetano Machado

Good morning ladies and gentleman. During 1995 Prof. R. P. King (University of Utah Comminution Center) presented 2 papers on new horizons in comminution: "Comminution Research in the United States " was presented at the 1995 Meeting of the National Mining Association, while "Comminution: Meeting the Needs of Fundamental Research in the Mineral Industry" was presented at the 2nd SME Research Forum - 1995. In both papers a very interesting graph named "Energy usage for various comminution schemes" illustrated some poignant issues proposed by Prof. King. We do think that some of Prof. King's ideas might very well serve as "warm-ups" for this Comminution Panel Discussion, which are ultimately the goals to be reached by the 3-minute presentations. Thus, we shall be addressing in the sequence Prof. King's most relevant ideas (as well as introducing his graph), intending therefore show how important creative and state-of-the-art Mill Modeling is, if it is to become a Tool to Effective Cost-Saving Optimization Strategies.

Jan 1, 1996

By Clement K. Chase, J. A. Eisele, Paul D. Chamberlain, Terry Laverty, Lee Rice, Larry Sevenker, Albert G. Law, Daryl Tweeton, John Peters

"Name your poison," wrote Forbes, Jan. 3, 1983, in an article describing the plight of much of the mineral industry as it entered the new year. "To ask which (mining) segment is better these days is almost like asking which of several stones would make a better life preserver." "The scene has seldom seemed darker or apparently less promising," said the Mining Journal in June 1982. And the Northern Miner described the year as the third in a "3-year drought which has completely dried up (company) coffers." Thus, 1982 became the worst year for much of the mining industry since the Great Depression. Low prices, commodity surpluses, output reductions, layoffs, temporary and permanent closures, and financial losses made headlines as the general recession continued to hurl blows at an industry facing strong foreign competition, increased government regulations, and plummeting market demand. At fault were tight US monetary policies and the resulting high interest rates that, while forcing inflation to slow, also threw the economic wheels of the country into reverse gear. Automobile production, housing starts, consumer durable sales, and capital spending all fell dramatically. US industrial production fell about 8.5% in 1982, with the GNP dropping by 1.7%. Production Value Not a single mineral escaped this recession. According to the US Bureau of Mines, US nonfuel production value dropped for all but four out of 21 metals and 14 out of 44 nonmetals. Production quantities increased for only gold, lead, and zirconium among metals and for only six nonmetals. Total nonfuel mineral production value dropped a whopping 21% from 1981 levels, the largest decline since 1938 and the first since 1971. Production value was estimated at $20 billion. Metal commodities showed heavier losses than nonmetals-37% vs. 12%-because of their link to depressed automobile and construction industries. Prices From peaks in early 1980, prices of precious and base metals, ferrous and nonferrous metals, and virtually every mineral dropped to 30-month lows in June 1982. Gold dropped to $9.64/g ($300/oz) compared to a high of $27/g ($850/ oz). Silver was quoted below 164/g ($5/oz) versus a $1.61/g ($50/oz) high. Copper was offered at a five-year low of $1.22/kg (55.5¢/lb) compared with a high of $3.30/kg ($1.50/lb). Lead went for 53¢/kg (24¢/lb) versus $1.21 (554). Nickel begged for buyers at $4.19/kg ($1.90/lb) compared to a high price of $7.72/kg ($3.50/lb). Molybdenum was available at or below $8.82/kg ($4/lb), down from a high of $44/kg ($20/lb). Cobalt went for $11/kg ($5/lb) versus $55/kg ($25/lb). Adjusted for inflation, increased currency costs, and currency devaluation, many of these prices are the lowest reached in decades. Financial Profits & Losses Low prices severely impacted companies' earnings, turning profits into sometimes disastrous or fatal losses. Robert Norton, director of the US Bureau of Mines, noting there has been a recession in the mineral industry for years, said, "Profit rates as related to invested capital have been considerably lower (for mining) than those of other industries. Mineral industry profits have been subject to greater cyclical swings and debt equity ratios have been significantly greater than

Jan 5, 1983

By Richard J. Adams

Coal jigs have played a predominant role in U. S. coal preparation for fifty years. Recently, an improved fine coal jig has been used to prepare the middle size range coal. These efficient machines are changing the historical thinking about jigs and is consistent with trends in coal preparation throughout the world. The performance achieved and operating cost savings are causing a change in fine coal cleaning strategy. With the exception of a handful of operators, fine coal jigs are generally not well understood by the industry. The objective of this paper is to provide some insight into the past use of fine coal jigs and their potential in the future. Improved Fine Coal Jig Since the mid 701s, an improved fine coal jig has been employed to an important niche in preparation, the 19 mm x 100 M range of cleaning. Several factors due to mining and liberation considerations have caused an expansion of this middle range of coal resulting in a host of challenges for coal preparation engineers. Fine coal jigs have been commissioned in several installations in North America to handle these important applications as shown in Table No. 1.

Jan 1, 1988

By Christian Jeger

After recalling the principles underlying fire-damp flow in coal and the essential part played by permeability (Darcy's law) in the intensity of flow, a few theoretical and experimental results showing the possible causes and range of variation of coal seam permeability are presented. The study of firedamp flow into gate roads and of residual gas concentrations in coals as a function of the gate road distance, shows that, in French mines, coal seams in a virgin zone have a very low permeability, but they become permeable when destressed by mine workings, in particular overlying workings. This is the case not only in the fractured zone round a mine excavation in which the gas is released, but also beyond the limit of the zone degassed by the excavation. In the floor of flat seams, upward boreholes can be used for predegassing seams that have been relaxed but not degassed, as the result of an overlying coal face. In this respect we shall describe the predrainage experiment carried out in the Marienau district of the Lorraine coalfield. Predrainage can contribute considerably to the reduction of methane emission in the ventilation of newly opened longwall faces. But to be efficient and useful predrainage should meet certain conditions.

Jan 1, 1980

By Hans Ehdwall

INTRODUCTION Investigations of radon and radon daughter concentrations in Swedish [non-uranium] mines started in the late 1960's. The first screening measurements showed that the average annual exposure to radon and radon daughter products was 4.7 WLM. The main reason for high radon and radon daughter concentrations was inefficient ventilation and radonrich water entering the mine. In the radon regulations worked out later it was stated that no miner should be exposed to more than 60 000 pCi h/1 equilibrium equivalent concentration of radon annual exposure, corresponding to 3.6 WLM. Now, 1981 the situation has changed considerably. From the average annual exposure of 4.7 WLM in 1970 it is now only 0.7 WLM. Sweden has up to now had only one [uranium] mine and the work there has only been investigative. However, there are plans for a commercial uranium mine in another part of Sweden. The radon problems in these mines are widely different depending on the mineralogy. NON-URANIUM MINES The radiation problems in Swedish mines were not recognised until the late 60's. The first radon and radon daughter measurements were made in some sulphide ore mines in 1967 (1). The radon and radon daughter concentrations were surprisingly high for non-uranium mines. In order to have a complete picture of the radon situation in Swedish mines the National Institute of Radiation Protection (NIRP) decided to make measurements in all, at that time about 60 mines (2). To get results as fast as possible measurements on radon gas seemed most appropriate to start with. Sampling was made by mailing a number of evacuated 4.8 litre conventional propane containers from NIRP to each mine. The containers were then opened at the place of interest. After sampling the containers were sealed and then mailed back to the institute for measurement. The measurements were made in ionization chambers. This method only gave the radon concentration and the radon daughter concentration was estimated by multiplying the radon concentration by an assumed equilibrium factor. The equilibrium factor is defined as the ratio of the total potential alpha energy for the given daughter concentration to the total potential alpha energy of the daughters if they are in equilibrium with the given radon concentration. The results of this first preliminary survey indicated that a great many of the Swedish miners probably had an annual radon daughter exposure of more than 3.6 WLM. As the radiation exposure in non-uranium mines was not regulated in either the Swedish Radiation Protection Act or the Swedish Labour Protection Act work was started on special radon regulations. A lung cancer mortality study was also started. To check the results of the first survey and to get experience and knowledge of radon problems in mines, it was decided that personnel from the NIRP should visit each mine for a detailed investigation of radon and radon daughter concentrations starting with the ones with the highest radon concentrations. The main reasons for these so-called "basic measurements" were: 1. To estimate the doses received by Swedish miners 2. To find the sources of the high radon and radon daughter concentrations 3. To find appropriate counter-measures 4. To determine the most typical equilibrium factor for each mine. Unlike most uranium mines the reason for high radon concentrations in non-uranium mines is seldom the occurrence of highly radioactive minerals. The main sources were found to be waste-rock and radon-rich water. In order to filter and warm up the inlet air, especially in winter time, it was very common at that time to suck the air through broken wasterock. By doing so the air was contaminated with radon from the waste-rock and radon-rich water in it. It is noteworthy that the radium and uranium concentration in the waste-rock is relatively low. The uranium concentration is only of the order of 15 - 20 ppm. The action to prevent this contamination of the inlet air was to change the direction of the ventilation and in the case of radon-rich water entering the mine the action was to prevent the air coming into contact with the water. The first calculation of the radon daughter exposure of Swedish miners was based on radon gas measurements. The radon daughter concentration was estimated by using an assumed equilibrium factor of 0.5. Later when the mines were visited by institute staff it was possible to compare the assumed equilibrium factor with the measured ones. It was found that the factor varied from 0.15 at the air inlet to 1.0 at the air outlet and the average equilibrium factor on workplaces for almost all mines was between 0.4 and 0.6. The result of the exposure calculation in 1970 showed that more than 40 % of the miners had an annual radon daughter exposure of more than 3.6 WLM. The overall average was 4.7 WLM and the maximum annual expo-

Jan 1, 1981

By Richard Keith Corbin

Canadian junior mining companies whose gold exploration and exploitation programs take them across the border into the western United States should be prepared to deal with the myriad of title issues involved in acquiring unpatented gold mining claims. The purpose of this paper is to serve as an introductory outline for Canadian junior mining companies to mining laws of the United States, as well as to relevant laws of some of the western gold mining states. Topics will include the five w's (who, where, what, why and when) of Canadian junior mining companies1 rights and responsibilities in acquiring interests in U.S. gold mining properties by claim staking, lease or purchase. Historic terms of common parlance among U.S. miners, such as "claimjumping" are defined and discussed. Various legal doctrines, such as "pedis possessio" and "good faith" in the location of claims are covered as well. Controversial subjects of contemporary interest are addressed in some detail, such as whether to locate a bulk-mineable disseminated gold deposit with placer claims or lode claims, and whether lodes may be staked over placers. By thus heightening the awareness of Canadian junior mining companies, it is hoped that they can be properly prepared to avoid title disputes, and to win lawsuits when they are unavoidable.

Jan 1, 1988