Search Documents

By Donald G. Rogich

The concept of initiating a large action-oriented contract, directed toward inherently safe mining systems, was conceived by the U. S. Bureau of Mines in January 1970. At that time we were in the process of establishing research contracts and grants, about 100 of which were let in FY 71 to deal individually with fairly specific technological areas. These projects in the aggregate covered a wide spectrum of health and safety problems. What appeared to be necessary was the creation of a project or program that would provide a focal point for the demonstration of many of the results of this research and also in the action sense culminate with working hardware and systems that could be tested and demonstrated over a fairly long teen. The concept of working demonstrable systems, rather than just a conceptual study, was, felt to be necessary for two significant reasons. In the development of any new system, the translation from concept to working hardware is usually a costly and time consuming process which acts as a deterrent to implementation. Secondly, many decisions in the mining community to change equipment or systems ,are based on first hand observation of the new system, in operational practice, an attitude which is certainly understandable in view of the high capital costs of equipment. The decision was made to procure a single R&D contract which would be aimed at developing underground coal mining systems which

Jan 1, 1972

By Keith Whiting

The Little Boulder Creek molybdenum deposit is in central Idaho, in the White Cloud Range about 3.2 km (2 miles) northeast of Castle Peak, the highest peak in the range. The elevation of the deposit is about 2591 m (8500 ft). The deposit is accessible only by helicopter or by a 12.9-km (8-mile) trail from the county road along the East Fork of the Salmon River. The nearest towns are Clayton [25.7 km (16 miles) northeast], Stanley [33.8 km (21 miles) northwest], and Ketchum [45 km (28 miles) south-southeast]. The principal known deposit at Little Boulder Creek is called the "North Zone." In this zone, the molybdenite occurs both in stock- work veinlets and disseminated through metamorphosed quartzite of Pennsylvanian age. Pyrite is ubiquitous, averaging perhaps 0.05%. Scheelite and/or powellite are present in trace amounts. An intrusive quartz monzonite stock, probably of Cretaceous age, bounds the deposit on the west. A steep fault which drops Tertiary age Challis volcanics into contact with the mineralization limits the deposit on the east.

Jan 1, 1991

By William R. Groseclose, Kenneth D. Schoeman

The Buckskin Mountains Tunnel is a key link in the Bureau of Reclamation's Central Arizona Project. The 22-foot (6.7-m) diameter tunnel is being bored in a north-northwesterly direction through volcanic rock near Lake Havasu in western Arizona. The 6.9-mile (11-km) conveyance tunnel will carry up to 3,000 cfs (85 cu m per sec) of water through the Buckskin Mountains as part of the Granite Reef Aqueduct. The water for the project will be drawn from Lake Havasu behind Parker Dam on the Colorado River and pumped some 800 feet (244 m) above the lake to the inlet portal of the free flow tunnel where it begins its 190-mile (300-km) journey to Phoenix, Arizona, and beyond into Orme Reservoir (figure 1). Precast concrete segments are being used as a single system initial support and final lining in the tunnel being excavated by a tunnel boring machine specially designed and built for the job by The Robbins Company. J. F. Shea Company, Inc., of Walnut, California, is constructing the tunnel for the Bureau of Reclamation.

Jan 1, 1976

By M. S. Moats, W. C. Hartzell

The stable domestic supply of gallium, indium, and germanium has been identified as a critical need for the United States. Electric arc furnace dusts, processed to recover zinc, produce a residue that could be a potential source of these critical materials. An industrial zinc leach residue was characterized to determine its particle size, chemical composition, and predominant mineral phases. Heated, atmospheric, agitated leaching using sulfuric acid and hydrochloric acid was examined to determine the extractions of gallium, indium, and germanium as a function of concentration and temperature. Extractions of gallium were found to be similar to iron in all experiments. The maximum percentage of Ga, Ge, and In leached into solution were 71%, 63%, and 48%, respectively.

Feb 1, 2023

By Utku Gumus, Ertan Bostanci, Hanifi Copur, Ahmet Rüfai Bilgin, Ugur Altay

"Field observations on replacements of 12-inch constant cross-section double disc cutters in Tuzla Wastewater Tunnel excavated by an EPB TBM with 3.151 mm excavation diameter excavating hard rock are summarized. Cutter life is correlated to rock’s uniaxial compressive strength and Cerchar abrasivity index, and TBM operational parameters. Number of cutter replacements, average cutter replacement rates and types of cutter damages are summarized. The relationships between cutter life and rock properties and TBM operational parameters are analyzed by single variable regression method. Detailed analysis between chainages 1+200 and 1+982 km indicates that average cutter consumption rate is 35.7 m3/replacement (4.6 m/replacement). Cerchar abrasivity index and uniaxial compressive strength does not indicate any meaningful relationship with cutter life. Penetration per revolution and field specific energy might be used for predicting lives of constant cross-section double disc cutters. However, additional data is required to generalize the findings of this study. INTRODUCTION Cutter life / replacement and/or consumption rates in terms of cutter cost and replacement time loses is one of the most important parameters affecting excavation performance of mechanical excavators, especially of TBMs used very widely and equipped with usually disc cutters. Predicting cutter cost is a very important task in especially feasibility stage of tunneling projects. Basic parameters affecting cutter life can be classified into 3 general groups as geological and geotechnical, excavation machine (TBM) related, and operational parameters (Bilgin et al., 2013). The geological and geotechnical parameters are the most dominant ones among them. The machine related parameters should be arranged in accordance with the expected geological and geotechnical conditions for the best TBM excavation performance and minimum cost."

Jan 1, 2016

By J. G. Asbury

Broadly conceived, the demand for electricity depends upon three sets of variables: (i) the growths of the many individual demands for energy services; (ii) the competitiveness of electrically driven technologies in meeting these demands; and (iii) the energy-conversion efficiencies of installed electrical technologies. The first set of variables establishes the size of the potential market; the second, the market penetration of electrical equipment; and the third, the quantity of electricity required to operate the equipment. All forecasts of electricity consumption ultimately depend upon inferred or assumed relationships to describe the future behavior of these variables. This partitioning of the demand-forecasting problem is conceptually useful and will guide the discussion presented in this paper. However, it is also something of an oversimplification. Examined in more detail, the electricity fore-casting problem is exceedingly complex. The variables mentioned above are, in turn, found to depend upon more fundamental sets of demographic technological, resource, and policy variables. The demand projections developed by the major forecasting services are usually developed in terms of these underlying variables, which themselves must be independently forecast.

Jan 1, 1985

By James C. Cobb

Middle Pennsylvanian (Desmoinesian) coals of certain areas of the Illinois and Forest City Basins contain epigenetic sphalerite and associated minerals in veins, clastic dikes, cleat, and other small-scale structural features. The presence of sphalerite in these coals records information about the geology of coals and coal basins, and represents a potential source for zinc as a byproduct of coal production. Origin of Sphalerite in Coal The origin of sphalerite in coal suggested by Cobb (1) involves sphalerite precipitation from zinc-bearing ?Na-Ca-Cl brines upon contact with sources of sulfur in the coal bed, e.g., pyrite, H2S, and organic sulfur. These brines were essentially at the temperature of the host coals as determined by fluid-inclusion thermometry and vitrinite-reflectance studies. The migration of these brines into coal beds may have been caused by compaction of sediments due to continued sediment loading of the coal basins. Zones of high permeability such as sandstones and the coals themselves presumably acted as conduits for the movement of the brines. The open spaces where sphalerite was deposited resulted from minor deformation associated with differential compaction and cleat formation enhanced by volume shrinkage during coalification.

Jan 1, 1982

By Richard L. Bullock

At the beginning of the previous chapter, variation in the types of room-and-pillar stopes were briefly identified so that the reader could begin to understand the extensive application of this mining system. These same variations will be reviewed and elaborated upon in this chapter while discussing the methods by which the material is extracted. FULL-FACE SLICING BY DRILLING AND BLASTING When the entire mineralized thickness is taken in one pass of mining, it is known as full-face slicing. There is no mineral of economic value intentionally left either in the floor or the back. Theoretically, there is no limit as to how high the face could be in a single pass. But there are practical limitations to equipment size, pillar stability, and control of local loose slabs on the face, roof, and pillars that dictate current practices. The range of face height of the 15 typical room- and-pillar mines covered in Table 8 (Sec. 1, Subsec. 7) from the Dravo report, 1974 was 1.7 m (5.5 ft) to 9.8 m (32.1 ft), the average being 5.2 m (17.1 ft). In the Gaspe copper mine, Murduchville, Que., the drill jumbos were constructed with an extendable tower for full-face mining up to 15.2 m (49.9 ft) if necessary. However, a more common practice at that mine is to take the ore in multiple slices (Hall, 1959). In many metal mines the normal practice when starting stoping is to drive a single development drift into the ore zone a distance that will allow at least four or five rooms to be opened on each side of the initial drift. Since this opening will probably serve as the main haulage drift, it should be kept as straight and as level as possible. As to the other criteria for the stope developments, it might be well at this point for the mine planner to review the remarks presented earlier (Sec. 1, Subsec. 7) on drifts, entries, and crosscuts for production. After the initial drift is driven, it should be slabbed to the full room width if it is not that wide already. Next, the future pillars should be marked on the ribs and the rooms driven between them. If the ore extends beyond the length of the initial drift and is to be mined in the normal sequence of mining, care should be taken in a random room-and-pillar system to see that the extension of the initial roadway remains straight. If pillar "spotting" is left to the shift foreman or to the miners, they probably will not realize the importance of maintaining a uniform pillar line next to the roadway, and of keeping the line straight. Invariably, a pillar will end up in the middle of the future drift extension resulting in a "dogleg" in a possible main haul- age road. While this error is not catastrophic, too much weaving in and out of pillars will certainly slow down future production haulage and needlessly increase costs. Face or Breast Drilling and Blasting Practices To drill and blast the initial advances into the rock, usually some form of cut pattern must be used. In room-and-pillar mining, when a pattern is drilled in a face and that face is the only exposed surface to which all of the rock must be broken, the pattern is known as a "face round" or "swing." The face to which the rock must be broken is referred to as a "free face." Thus the most common way to advance a room into virgin rock with only one free face is by drilling swings. If, after breaking around a pillar, taking down back, or taking up bottom, there is a second (or third) face exposed, a group of holes drilled nearly parallel to a free face and breaking to it is known as a "slab round" or "slabbing." In some mining districts it is also known as "slashing." Obviously, because two faces exposed offer less resistance to fragmentation than a single face, slabbing requires less drilling and fewer explosives than required to break the same tonnage with the same degree of fragmentation with swings. Therefore, it behooves the driller (or supervisor) to plan the combination of

Jan 1, 1982

By A. E. Hall, K. R. Mutama

The wind tunnel has been used extensively for mine ventilation research and continues to be a valuable tool. The advent of the powerful personal computer has reduced the use of wind tunnels because several flow problems car be simulated and investigated quickly. This paper describes the recent design and construction of a wind tunnel which is now being used for mine ventilation aerodynamic research and teaching purposes. The wind tunnel has a square cross section measuring 900 by 900 mm and is 8485 mm long from the entrance to where it joins the fan. The tunnel was designed as an open circuit suction type and is attached to a 7.5 kW variable pitch axial flow fan capable of producing over 6 m3/s of airflow. The entire length of the wind tunnel can be used for flow investigations and all activities are visible since the sides are made of plexiglass. Results are presented from the test program to show that even without honeycombs and screens air flow symmetry is achieved.

Jan 1, 1993

By Hassan Madani

Kushk lead-zinc mine is located in central part of IRAN. The mine is owned by Bafgh Mines Co., which is a nationalized company. Exploration results show that ore occurs in the area that extends for 800m length and 180m depth. The approved, probable and possible reserves of the mine is 900,000 tons, 1,120,000, tons and 1,450,000 tons respectively with average grade of 17.7% zinc and 4.3% lead. The total annual output of the mine all was by underground mining, is in the order of 100. 000 tons. The main entry to the mine is via an inclined shaft with a cross-sectional arp of 8 m2, length of 263m which dips at 20°. The ore is mined mostly by sublevel stopinq method. The major difficulty in ventilating the mine was that related to spontaneous combustion of pyrite, which was more serious in some parts of the mine than others. In order to reduce this risk, a new ventilation system for the mine was designed, using 4 exhusting fans.

Jan 1, 1991

By William J. Ferguson

At Henderson Operations the 24-kilometer conveyor system consists of three main conveyors with lengths of 1.2 km, 16.7 km and 6 km. Upon commissioning of the conveyor system, the Henderson maintenance department was challenged with the inspection and monitoring of over 50,000 idlers. To take a proactive approach to idler maintenance, an idler tracking database system was developed. Using the idler tracking program, the Henderson Crush & Convey department now has the ability to provide data for engineering solutions to idler problems and to manage thousands of idlers for priority replacement work and warranty purposes. Recognizing the potential for injury to Henderson employees in the process of idler handling, Henderson approached idler replacement as a material handling process. Material handling solutions have resulted in failed idlers being replaced and discarded from the underground environment without ever touching a human hand. This paper will detail how Henderson tracks idlers in all primary conveyor belts and how an innovative idler handling system can result in reduced risks to conveyor maintenance employees.

Jan 1, 2004

By S. J. Knoll, D. F. Scott, T. J. Williams

Highly stressed rock in stopes continues to be a primary safety risk for miners in underground mines because it can result in failures of ground that lead to both injuries and death. Spokane Research Laboratory personnel investigated electromagnetic (EM) emissions in a deep under-ground mine in an effort to determine if these emissions could be used as indicators of impending catastrophic ground failure. Results suggest that (1) there is no increase in the number of EM emissions prior to recorded seismic activity, (2) some EM signals are generated during blasting, (3) interference from mine electrical sources mask seismic-generated EM signals, (4) EM emissions do not give enough warning (compared to seismic monitoring) to permit miners to leave a stope, (5) the distance an EM signal can travel in the rock is between 17.7 and 39.6 m (58 and 130 ft), and (6) current data acquisition systems do not differentiate between EM signals generated from seismic activity and random mine electrical noise. These results preclude monitoring EM emissions as precursors of impending catastrophic ground failure.

Jan 1, 2004

By L. D. Gehi, A. W. Khair, M. Ahmad

This paper presents an analysis of the dynamics of bit wear on the productivity of continuous miners. Two field surveys were carried out. The first survey assessed the impact of bit wear on productivity and production cost. The second survey studied the wear characteristics of the cutting tool (i.e., magnitude, forms, and mechanisms of bit wear, Primary factors affecting bit wear were identified. Laboratory experiments were carried out to study in detail the effect of some of these primary factors on wear. Results indicate, that bit wear has a significant effect on the productivity a continuous miners. Furthermore, under severe geologic conditions (i.e. cutting rock partings in roof and floor) bit wear not only hampers the productivity, but also increase the production cost due to a higher consumption of bits. This study also indicated that beyond 20% of the conical height loss (which corresponds to 7% of the weight loss) the rate a bit wear accelerates. This increased rate of wear is an indication of higher abrasion between bit body and cutting material, resulting in a dustier environment.

Jan 1, 1995

By E. Rubenstein, V. Gangrade, K. V. Raj, M. L. Harris

Underground stone mine ventilation is characterized by large openings with low resistances. These mines primarily face three challenges: moving adequate volumes of air, controlling and directing the airflow, and planning ventilation systems that work well with production requirements. Given these challenges, this paper examines the data collected by the Mine Safety and Health Administration (MSHA) to determine the extent to which respirable crystalline silica (RCS) and diesel particulate matter (DPM) are an issue in underground stone mines. Out of 522 sampled mines, there were 108 personal samples exceeding the RCS Permissible Exposure Limit (PEL) during 2000–2020. DPM were more prevalent than RCS in these mines with 382 personal samples exceeding the DPM PEL out of the 929 mines sampled during 2002–2020. Dilution of DPM is usually the defining parameter for design of mine ventilation systems in largeopening underground stone mines. With this knowledge, focused attention can be directed to these mines so that appropriate prevention and mitigation techniques can be utilized to prevent stone miners’ exposure to RCS and DPM and subsequent respiratory diseases.

Mar 2, 2022

By Frank Florez

INTRODUCTION The Magma mine, located at Superior, AZ, some 100 km (60 miles) east of Phoenix, was discovered in 1875, and was originally mined for silver. The property was acquired by W. B. Thompson who formed the Magma Copper Co. in 1910. Prior to 1965, square-set mining and cut-and-fill methods were used to mine steeply dipping veins at Magma. Ore was moved to the chute by gravity in the square-set stopes and by slusher in the cut-and-fill stopes. The stopes were gobbed with waste from the surface and development headings in the mine. The original square-set method of mining was modi¬fied in order to extract replacement ore bodies in limestones that dipped at 0.52 rad (30°) and varied in thick¬ness from 4.6 to 38 m (15 to 125 ft). Mining of these ore bodies was done by starting at the upper lateral ex¬tremities and retreating to the access openings. The timber square sets and cribbing were used as temporary support, the ground being allowed to cave as the mining retreated. It was found, however, that mining in such a manner was very inefficient; safety hazards increased be¬cause of the blocky and fractured characteristics of the ore and the weakness of the hanging wall. GENERAL DESCRIPTION The undercut-and-fill method of mining is now the primary stoping method used at Magma, and no pillars are left for later extraction. Four ore bodies are pres¬ently being mined. These ore bodies (see Fig. 1) dip conformably at 0.52 rad (30°) to the east with the host limestone and shale sediments, their average strike length is about 122 m (400 ft), and their thickness varies from 9 to 38 m (30 to 125 ft). The ore bodies are separated by varying thicknesses of barren rock. Three of them come together at various elevations primarily in the area of the main feeder fault, but there is an apparent horizontal displacement of about 23 m (75 ft) on the main feeder fault which complicates stope layout. The method as originally applied has been modified in order to mine more efficiently ore bodies that are 9 m (30 ft) or more in thickness. The modification was made to mine all the ore at a given elevation before dropping down for the cut below. The advantage of this is that mining is done on a horizontal plane and there¬fore muck removal can be mechanized. Also multiple faces are made available, thereby improving overall min¬ing efficiency. Another major change made was to carry a 6.7-m (22-ft) face when mining the top sill and a 6.4-m (21-ft) face when mining under fill rather than the former standard 3.35-m (11-ft) high face. This change lengthens the mining cycle and cuts mat prepa¬ration costs in half. Stopes are laid out (see Fig. 2) so that maximum mining panels are available and yet one stope crew will not tie up too much of the ore reserve. One stope might consist of as many as 20 panels, and these panels are divided evenly on opposite sides of the extraction cross¬cut. The stope layout is planned so that the maximum tramming distance to the orepass will not exceed 30.5 m (100 ft) on the crosscut and 38 m (125 ft) in the panel. Stope panel distances are sometimes exceeded when min¬ing to the extremity of the ore body. Tramming distance limits are determined by the efficiency of the com

Jan 1, 1982

By William T. Ingram

Early in the 60's the author served as Chairman of the Engineering Foundation's Coordinating Committee on Air Pollution Research. One of our objectives was the development of a study on the measurement of stack emissions. Three publications of the Foundation resulted from these efforts to focus attention on the stack sampling problem.1,2,3 Two of these were annotated bibliographies covering 197 references. The third reported the results of a workshop meeting at which some 21 individuals from research institutes, industry and government discussed the possible and probable areas of research that would add to or increase the ease, precision and utility of sampling gaseous and particulate matter emitted from stacks. The American Society of Mechanical Engineers has had in its Power Test Codes a Standard Code for Determining the Dust Concentration in a Gas stream4 since 1941, The American Industrial Hygiene Association has published, in its Air Pollution Manual,5 a Section on Stack Sampling. Industry and regulatory agency requirements for stack sampling have utilized some modification of the alternatives in methodology. There has been ho single guide to stack sampling that met the needs of those who have the need to know.

Jan 1, 1970

By A. L. Hinde

Ideally, mill circuits should be controlled so that excessive random disturbances are reduced in frequency and amplitude. It is difficult to derive an objective measure of the effectiveness of any chosen control strategy. Often, the response of the circuit to pulse or sinusoidal disturbances is used as a measure of the effectiveness of control, but this is not adequate in many circumstances because such disturbances bear little resemblance to those that occur in practice, and such an approach cannot be easily related to the profitability of the reduction process. A superior approach appears to be the application of the theory of stochastic processes. This theory permits both real process disturbances to be modelled accurately, and useful objective functions for control to be derived. A test of the usefulness of stochastic theory in mill control was made on the gold ore milling circuit shown in Figure 1. This circuit was fed with an ore which had a liberation characteristic such as that shown in Figure 2. It is simple to show that, for such a liberation characteristic, the recovery of valuable mineral will vary as the standard deviation of the particle mass-size distribution varies even though the mean particle mass-size is kept constant. Similarly it may be shown that excessive perturbations in the circulating load in a milling circuit such as that shown in Figure 1 can affect liberation. Figure 3 shows how, as the cyclone feed density increases and the sump water addition decreases at constant sump level, the cyclone operation becomes unstable and the discharge "ropes? with a consequent catastrophic coarsening in product size. By minimising the variance of the circulating load it is possible to reduce the probability of initiating instabilities of this nature.

Jan 1, 1977

The Mesquite mine is being operated by Gold Fields Operating Co.-Mesquite, a subsidiary of Gold Fields Mining Corp. The mine Is located in southeastern California about 56 km (35 miles) east of the farming community of Brawley, California. The mine has been in commercial production since early 1986 and Is a conventional open pit mine developed on 6.1 m (20 foot) benches. The gold is recovered by heap leach using permanent heaps built in multiple 6.1 m (20 foot) lifts. This year's gold production will be in the range of 5,600 kg (180,000 troy ounces). Current ore production is about 18,140 tonnes (20,000 tons) per day while the total tons mined Is averaging 65,000 tonnes (72,000 tons) per day. The climate at the mine is extremely arid with rainfall of 7.6 cm (3 inches) per year. From early May until late October daytime temperatures generally exceed 37.8 degrees Celsius (100 degrees Fahrenheit) and can be as high as 37.9 degrees Celsius (120 degrees Fahrenheit).

Jan 1, 1989

By E. M. Hill, D. E. Walsh, J. T. Hollow, H. K. Lin

Fairbanks Gold Mining, Inc. (FGMI) began blending and processing True North ore at their Fort Knox mill on April 12, 2001.Gold extraction subsequently dropped from 88% to 71% during the last week of April 2001. 25% of the gold values remaining in the leach tailings were gravity recoverable free gold. Significant quantities of stibnite and arsenopyrite were also identified in the tailings. In laboratory bottle roll tests, the gold extraction from a composite of leach circuit feed collected during the same period was 72.6%, when leached at an average NaCN concentration of 0.16 g/kg. The extraction increased to 82.4% and 91.7% with 0.5 g/kg NaCN, and 0.5g/kg NaCN plus 0.075 g/kg Pb(NO3)2, respectively. A passivating layer surrounding liberated gold particles and resulting from sulfide mineral dissolution, likely contributes to reduced gold recovery, which can be substantially increased by the addition of lead nitrate. Lead species remain in the solid residues after leaching and were not mobilized using Meteoric Water Mobility Procedure.

Jan 1, 2003

By Frederik P. Agterberg

Mineral exploration consists of the acquisition of data and their interpretation to ascertain the presence or absence of uncertain events. In general, the amount of uncertainty decreases during exploration when targets become increasingly well defined. Decisions on further exploration and whether or not mining should be commenced are based on new information using both objective facts and subjective reasoning. Computers play an important role during all stages of exploration. Three recent books (References 1-3) on decision-making in exploration and mineral-resources evaluation provide additional background supplementing the papers in this volume and articles in scientific journals or other conference proceedings (e.g., References 4 and 5) dealing with the subject. Other new developments to be considered are that microcomputers are becoming increasingly important in the earth sciences (Reference 6), and so are applications of artificial intelligence (Reference 7). Microcomputer- based technology allows rapid communication between field parties and main office. Expert systems are becoming increasingly sophisticated aids for mineral exploration an can now contain objective rules based on statistical theory (Reference 8).

Jan 1, 1989