Search Documents

By M. K. Larson

Proper employment of numerical stress analysis design tools is based on the demonstrated ability of a model to capture key elements of the geologic site model and accurately simulate how these elements interact with a mine design. While these tools have progressed markedly, they are, at heart, a gross simplification of the abundant complexity of a natural setting and its response to mining. A generic deep longwall site model was developed that includes aspects of the geology of deep coal mines in the Wasatch Plateau and Book Cliffs coal fields of Utah. The site model contains a set of common features and observations of how these features typically respond to mining. This site model was the basis for evaluating use of empirical, boundary element and volume element stress analysis tools to analyze the distribution of stress around a deep longwall panel. More specifically, this evaluation examined shifting of stress to panel abutments and gob, distribution of stress in the abutment, and deformation and failure of bridging strata. Measurements of abutment stress changes at two sites in the Wasatch Plateau region were used to illustrate model calibration. Overall, these comparisons highlight the considerable differences between methods. Volume element tools can incorporate considerable detail and have fewer underlying assumptions, but this detail carries a considerable computational cost. Boundary element tools are much more efficient. But this efficiency also comes at a cost of added assumptions. These assumptions were challenged by the presence of a strong sandstone unit in the overburden, leading to boundary element results that depart significantly from volume element results. Empirical rules are the simplest, but are even more burdened by assumptions, many of which are implicit in underlying cases. Insight into the nature and impacts of underlying assumptions in each method is essential to proper use of results in mine design. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health

Jan 1, 2009

By D. R. Wilburn

The worldwide budget for nonferrous, nonfuel mineral exploration was expected to increase by 58 percent in 2004 from the 2003 budget, according to Metals Economics Group (MEG) of Halifax, Nova Scotia. The increase comes two years after a five-year period of declining spending for mineral exploration (1998 to2002). Figures suggest a subsequent 27 percent increase in budgeted expenditures from 2002 to 2003. For the second consecutive year, all regional exploration budget estimates were anticipated to increase. The worldwide budget for gold exploration achieved about 50 percent of the total amount budgeted in 2004.This was 68 percent, or US$715 million, higher than the reported 2003 budget. The 2004 worldwide exploration budget estimates for copper increased by 70 percent, orUS$237 million, to US$577 million from the 2003 budget. The budget for nickel exploration increased 52 percent, or US$89 million more than in 2003. The 2004 exploration budget for other mineral targets (primarily cobalt, heavy minerals, industrial minerals and silver) increased114 percent, or US$118 million.

Jan 1, 2005

By N. Loganathan, Tan Boon Tee, Joe O’Carroll, Richard Flanagan

In recent years, tunnelling activities in Singapore have increased considerably with the construction of extensions to the existing sub-surface transport system, a deep tunnel sewerage disposal system, and tunnels for the laying power cables and other utilities. These tunnels are excavated through urban areas, adjacent to high-rise buildings, depressed road structures, beneath other tunnels, and buried services. Earth pressure balance (EPB) tunnel boring machines (TBM) have been used extensively in Singapore with great success. The risk associated with soft ground tunnelling, including tunnelling through Old Alluvium, can be minimized with an understanding of the geology, geotechnical parameters, and the tunnelling-induced behaviour of Old Alluvium (OA The purpose of this paper is to present some design and construction aspects of EPB TBM tunnelling through Old Alluvium.

Jan 1, 2005

By Gennaro Gerald Marino

Vast improvement in methods of design and analysis of the long- term stability of overburden above room and pillar mines is needed. Improved methods are vital for planning and land development and for prediction above existing, presently stable, room and pillar mines. As shown on the flow chart in [Figure 1], the assessment of the long-term stability is an integral part of the site investigation process regarding mitigation of surface damage effects. In Illinois, flat farmlands with subjacent coal reserves cover vast areas. In some of these areas high extraction of the underlying coal layer(s) may not be possible since the resulting surf ace subsidence combined with a pre-existing shallow water table would make the land too wet. Thus recovery of this coal might only be accomplished by room and pillar mining where the ground surface does not subside and the hydraulics of the overburden are not significantly affected.

Jan 1, 1986

By Jorgen Elbrond

The capacity calculation of complex transportation systems involving variable activity times such as encountered in the mining industry are often worked out by means of simulation, which reconstructs waiting times and cycle times. The queuing theory, which mathematically calculates waiting times, has been used mainly to describe the, phenomena. This is due partly to the difficulties encountered in modelling complex systems and partly to the difficulty of reconciling the required time distribution laws with the real phenomena by means of the queuing theory. It is, however, obvious that formulas for capacity calculations would be preferable to simulation procedures because of their higher calculation speed, shorter and more flexible programs and shorter programming work. The calculation procedure presented in this paper is composed of some rather simple models, which are based on the queuing theory, and on some probabilistic and some deterministic considerations. The models are supported by observations, and to some extent by simulations. It has been attempted to find all the components of the cycle time and to include them in a comprehensive model. It is the intention to demonstrate that even quite complex mine transportation systems can be treated by means of the queuing theory with the advantages mentionned above and, without sacrificing the precision of the estimates. The speed of calculation of a wide range of parameter combinations is such that the procedure can be used extensively by a project engineer in the search for optimal modifications of the entire transportation system.

Jan 1, 1979

By J. Luxford

The last decade has seen an enormous increase in the use of contractors right across the Australian mining industry. So much so that contractors now operate 33 of the 68 underground metalliferous mines around Australia and are making significant inroads into iron ore in the west and coal in the east. Safety used to be a low priority for many contractors. The picture has changed dramatically in recent years as most contractors take a far more professional approach to safety management. This paper examines the changes that have occurred and the requirements for effectively managing safety in a contracting environment.

Jan 1, 2000

By G. Bylapudi, A. Bhagwat, K. Mondal, A. J. S. (Sam) Spearing

Minimizing the effects of corrosion improves the long-term performance of the rock anchors and ground control systems in underground mines, which is fundamental for safe operation over the design period. The primary objective of this study is to explain the problems due to stress corrosion cracking (SCC), strain-induced corrosion cracking (SICC) and other forms of corrosion, and why the mining industry’s ground control professionals should take this into serious consideration. It is important to clearly determine the kind of SCC mechanisms that causes roof bolt failures in order to suggest the necessary action plan to mitigate or eliminate the possibility of the cause. Pertinent literature and studies around the globe on this complicated subject are reviewed. The secondary objective is to encourage the use of corrosion-resistant ground control products in the underground mining industry in areas of high corrosion potential. Characteristics of SCC on high strength steel are also reviewed. The literature and preliminary studies to date indicate that research work is necessary in United States.

Jan 1, 2015

By Robert C. Horton

The Getchell Mine is located on the east flank of the Osgood Mountain Range in the Potosi Mining District, Humboldt County, NV. Mining in the area first began in 1883 for copper, lead and silver in skarn-related deposits. Tungsten was discovered in the skarns in 1916 and was mined sporadically until 1957. The first major discovery was made in 1933 when two Winnemucca prospectors, Edward Knight and Emmett Chase, found gold at the present site of the Getchell gold mine. In 1934, after a small amount of preliminary prospecting, the claims were purchased by Noble H. Getchell of Midas, NV. The Getchell Mine Inc. was organized and exploration and development work began on a broad scale. Major funding was provided by George Wingfield and investors he assembled. Laxalt described Wingfield’s immediate history prior to his financing of Getchell as follows.

Jan 1, 1999

By T. Veneroso

Comminution is the process by which rock or ore is reduced to a size where the liberation of the minerals is maximized without changing the chemical or physical properties of the rock. Comminution accounts for about 50% of all energy that mines use (Klein et al., 2018). Growing demands from stakeholders and shareholders for sustainable development and CO2 reduction will increase the need for energy-efficient comminution. Ores with different mineralogical characteristics, textures, strengths, apparent stiffness, and mass-specific fracture energies need to be processed with a specific, new, and efficient comminution technology to increase the production and profitability of mining companies. The adoption of crusher wear parts built with new materials, such as non-Hadfield manganese steel or synthetic materials or traditional manganese with wear-resistant components, could improve the efficiency of the crushers, reduce downtime, increase production, improve the desired P80 (the aperture through which 80% of the product will pass) product size distribution, and enhance mine safety.

Feb 1, 2023

By Yves St-Amour, Vince Luongo

This paper will discuss one of the largest construction projects the City of Portland has undertaken. This phase of the Willamette River Combined Sewer Overflow (CSO)project consists of approximately 18,500 ft of tunnel in soft ground, requiring the construction of six deep shafts and jet grout ground improvement. The purpose of the project is to reduce volume of combined sewerage overflows from the drainage areas on the west side of the Willamette River. Bencor-Petrifond-Pacchiosi Joint Venture was awarded a contract to design and construct six deep circular shafts, jet grout ground improvement for three bridges and jet grout ground improvement break-in/outs for some shafts. Of the six shafts the Pumping Station Shaft was the deepest and largest, requiring a permanent ground support system with a deep jet grout ground water cut-off to 335-ft deep. The joint venture used state of the art methods and equipment to achieve its objectives and build the structures through some very difficult alluvial soils to great depths next to the Willamette River. The paper will provide a general discussion of the shaft construction and jet grout ground improvement installed for this phase of the project. It will also discuss some of the technical challenges encountered while effectively managing risk and costs, resulting in a successful project completed in a timely manner.

Jan 1, 2005

By A. Juganda, F. WILSON, H. PINHEIRO, N. SANDOVAL, J. F. Brune, G. E. Bogin Jr.

To evaluate methane explosion hazards in longwall coal mines, a CFD model was developed along with a 1/40th-scale, optically accessible model of an underground longwall coal mining section. In this project, CFD models assisted in the design of the physical model to ensure specifications were met for accurately representing the scaling physics as well as to assist in narrowing the experimental matrix and identifying key locations for sensor placement to measure velocity, pressure, and gas concentrations. This research will help develop strategies for methane monitoring that prevent methane ignitions and explosions in longwall coal operations.

Aug 15, 2022

By Garry Keizer

The Cortez gold mine is located in Lander County, NR, about 130 km (80 miles) southwest of Elko. Cortez Gold Mines (CGM) is a joint venture between Placer Dome US Inc. (60% operator) and Kennecott Corp. (40%). The claims that supply oxide and refractory ore feed to the Cortez milling facility are located in both Lander and Eureka counties. These include the Cortez and Horse Canyon deposits, all operated by the joint venture. Other deposits outside the CGM claim area include Fire Creek, Buckhorn, Gold Bar and Tonkin Springs. These deposits all occur along the Battle Mountain-Eureka Trend. History Mining in the Cortez district began in 1862 with the discovery of high-grade silver ores. Grades in the hundreds of ounces per ton occurred in an area 7 km (4.5 miles) southeast of the current CGM mill site. Underground mining through the Garrison and Arctic tunnels provided the bulk of the ore production between 1864 and 1895. To a lesser extent, the Mill Canyon area also supplied ore until 1930.

Jan 1, 1993

By Verya Nasri, Heather M. Ivory, Kevin Clarke, Eric Cole

Development of the New York City Water Supply System The New York City water supply system serves a population of almost nine million, including residents in neighboring counties. Peak day demands on the system are currently running at about 70 m3/sec (about 1,600 mgd), which is significantly lower than in the 1990s. This trend of reducing demands over the past 25 years, which has been experienced in other major urban centers in the US, is mainly the result of conservation measures and increased cost consciousness on the part of water users. In the long term, demands are expected to once again follow an increasing trend with population growth, so that by the end of the planning horizon of these studies, the year2045, the peak day demand is expected to increase to about 85 m3/sec (2,000 mgd).The system is served largely by surface water sources, regulated by a system of 19reservoirs and three controlled lakes, which are connected to the City by a series of aqueducts, the longest of which is about 87 km (54 miles). The total storage in the sys-tem amounts to about 560 billion gallons, providing a system firm yield of about1300 mgd. The Delaware system provides about 50% of the City’s water, the Catskill about 40%, with the remaining 10% provided by the Croton. The system as a whole, which is shown on Figure 1, has been built up over the past 150 years, and is truly a marvel of engineering. The Catskill and Delaware aqueducts both discharge into Kensico Reservoir, which is a daily balancing reservoir located in Westchester County about 24 km(15 miles) north of the New York City line. The two aqueducts extend south for a further 14 miles to combine again at Hillview Reservoir in the Bronx, which provides hourly balancing storage for New York City system. The Croton aqueduct runs nearby as shown on Figure 2, but does not connect into the two reservoirs. From Hillview Reservoir the water is supplied to the city via three main distribution tunnels, known as City Tunnels 1, 2, and 3. City Tunnel No.1 was developed in the 1920s as part of the Catskill system. City Tunnel No. 2 followed in the 1960s as part of the Delaware system. City Tunnel No. 3 (CT3) is partly under construction and partly in operation, and is being implemented to permit the other distribution tunnels to be taken out of operation for the first time for inspection and maintenance. Presently CT3 is supplied with water from Hillview Reservoir via a large underground valve chamber, the Van

Jan 1, 2007

If it had not been for the almost unbelievable adventures that came before and after, the last ten months of 19 15 would have been exciting enough for anyone. As it was they were a cheerful interlude. I spent most of the time on our Warren operations catching up on a lot of underground work and visiting Ajo every few weeks to see if my Chuquicamata visit might help solve the New Cornelia problem. While the difficulties were finally solved, at times they seemed almost hopeless. About all I could do to help was to make sure that the ore sent to the pilot plants represented the average ore that must be treated in the final 5000 tpd mill. Dr. Ricketts and John Greenway worked tirelessly with the best consulting advice they could obtain. Credit for the final success was due chiefly to their efforts. Since our old group had given up its "Merry Widow" home in Warren, a few of us got rooms in the company-built Cole Building over the Warren grocery store. This included Jim Lewis, Roy Mitchell, Steve Landon, Paul Stevens, and Hubert d'Autremont who came from Duluth to join our legal staff. Later we rented a small house two blocks from the Calumet and Arizona office. With the now flourishing country club only a 10-min walk away, and an electric car running to it every half hour or so, we were able to give parties in return for the hospitality of our friends. One of the most pleasant episodes came by luck a few days after I got back from Chile. Chester Congdon, a leading director in Calumet and Arizona, with his wife and their daughters, Elizabeth and Helen, spent a couple of days at the Greenway house before making an auto- mobile trip across the desert from Tucson to Ajo. At the same time I arranged to examine the small but rich Bush and Baxter copper mine a few miles from Tucson. At a party in Warren we found we would all be staying at the Santa Rita Hotel in Tucson, and I took my South

Jan 1, 1976

By Robert J. F. Goodfellow, William A. T. Meakin, Kevin Clarke, Eric Cole

INTRODUCTION New York City Water Supply—Background and History Since the 1840s New York City has been developing the largest, and perhaps, the best urban water supply and distribution system in the world in terms of quality and reliability. One of the engineering marvels of the modern world, the New York City water supply and distribution system serves a population of almost nine million, including residents in nearby Westchester, Putnam, Ulster, and Orange Counties of New York State. The average daily supplies presently are running at almost 60 m3/sec(about 1,350 million gallons per day). The watershed for the New York City water supply system, under the jurisdiction of the New York City Department of Environmental Protection (NYCDEP), consists of19 reservoirs and three controlled lakes, and covers an area of approximately5,000 square kilometers (about 2,000 square miles) north of New York City. The watershed total available storage capacity is about two billion cubic meters (560 billion gallons) and is divided into three reservoir systems: the Catskill and Delaware watersheds located West of the Hudson River; and the Croton watershed, located east of the Hudson River, see Figure 1. The first element of the system, the Croton Aqueduct, started operations in 1842.Through several updates and expansions, the present-day Croton system was in place by 1911, providing a potential maximum supply of about 15 m3/s (about 340 mgd). The system includes ten reservoirs and three controlled lakes. In the late 1800s, with the tremendous growth of the City, New York City water engineers began to look for additional sources. Between 1907 and 1929, the City acquired water rights and constructed a new 148 km (92 miles) Catskill aqueduct to convey water from the Ashokan Reservoir to the City. The Catskill system also included the construction of the Kensico and Hillview Reservoirs just north of the City,

Jan 1, 2005

By Joachim Klein, Frank Reimann

Nodular-graphite cast iron (GGG) is a material similar to steel, and one which exhibits excellent properties, in particular for components exposed to pressure. GGG cast iron has been used in many cases when sinking mine shafts with conventional tubbing. With linings made of cast iron tubbings (the backfill concrete is not integrated into the calculations, and merely serves as bedding) the properties of the cast iron can be made full use of, provided the tubbing is made to the appropriate cross-section. Calculations have shown that better static values can be arrived at when using cross-sections other than those of tubbings made to conventional German standard. The cross-sectional design of the new types of shaft lining made from GGG is to be developed on these lines irrespective of the cast iron structure being only stressed component or its restistance function being combined with the one of concrete. GGG 50 is used for the first time to make the reinforcing inner liner of a main shaft currently sunk in Germany. The physical properties of nodular-graphite cast iron, strength and deformability, suggest that, in the future, its application will not be restricted to shaft support but also in tunneling. New moulding techniques with better three-dimensional modelling resulted in new tubbing designs as installed e.g. for the Hannover underground at present. Shield-driven tunnels have to withstand earth and water pressure, apart from axial machine loads. In this field time is money as well. Therefore easy handling and quick installation are necessary for successful, use. Last but not least, safety is of first-order importance for work in shaft sinking and tunneling. Cast iron lining systems, accordingly, are adequate systems, in particular for excavations underneath water for transport systems and for goods and passengers.

Jan 1, 1987

By B. C. Lewis

Have technological advancements in underground coal mining driven people's skills to new highs or have the expanded skills of mining people driven the industry's technological advancements. Who knows? What we do know is that both our technology and our people have made meaningful and significant advancements. Overall, longwall systems continue to increase productivity and retreat faster. Globally, gate road development is the primary bottleneck in a longwall mine. The primary bottleneck in gate road development is roofbolting. Generally, roofbolting is the bottleneck in room and pillar operations as well. This paper will present an integrated manufacturer's (Joy Mining Machinery) vision of the future in comparison to current equipment performance. Particular emphasis will be placed on roofbolter technologies.

Jan 1, 1999

By John S. Hutchins, David L. Wassum

Mining engineers are ready to take a big step into a new field-oil mining. To understand the subject, one must look at the world's oil supply and demand as well as petroleum technology successes and failures. The US has an abundance of solid hydrocarbon and uranium energy resources, but 75% of its energy for industry, transportation, manufacturing, and space heating comes from liquid petroleum and natural gas. So there are increasing efforts to discover new oil reserves; today the number of drilling rigs operating in the US is at an all-time high. But with 80% of the world's wells already located in the US and Canada, good new exploration prospects are difficult to find. The cost of drilling deep new wells has also greatly increased. The US faced a similar situation in the early 1950s, when primary oil production declines began. During that time, the petroleum researcher introduced secondary recovery techniques such as water flooding and gas injection. This increased the average amount of extractable oil from discovered US reservoirs from 17% to 33%. Production soared and the world petroleum price remained stable until the end of the 1960s. Secondary recovery techniques were then supplemented by tertiary oil recovery technologies-increasing sweep efficiency with such things as CO2 injection-that are, so far, only partially successful in most petroleum fields. Even so, these technologies could raise cumulative recovery expectations to 35-38%. The "lost" oil in depleted US reservoirs equals 48 km3 (300 billion bbl) of conventional oil, or 12 times the current recoverable reserve base. At the present rate of US consumption-1 km3/a or 6 billion bbl/a-this is enough to run the US for 50 years without importing any oil. Moreover, there are 16-24 km3 (100-150 billion bbl) of as-yet unrecoverable heavy oil and tar sands in the US.

Jan 12, 1981

By Christopher J. Bise

INTRODUCTION Traditionally, the purpose of mine ventilation has been defined as diluting, rendering harmless, and sweeping away hazardous gases which may accumulate in the mine workings. In addition, the ventilation sys- tem must keep the mine air as close as possible to the composition of the outside air in order to provide a healthy environment for mineworkers and to prolong the useful life of mine equipment. When plans are being developed for opening a new mine, sound engineering dictates that a calculated estimate be made of both the maximum air quantity requirement and the accept- able mine pressure (head) loss related to the under- ground layout and projections. For efficient mine ventilation, the two problem areas that demand constant attention are (1) the control of fugitive air (through short circuiting or leakage) and (2) the provision of ample airway capacity. Fugitive air is that quantity of air which enters the mine but short-circuits the mine ventilation system through improperly constructed stoppings, doors, overcasts, etc.; it represents an investment in power consumption (to move the air by the fan) while providing little, if any, return on the investment. Typically, efficient mines are those that can deliver 50% of the air handled by their fans to the working faces. Paying close attention to a new mine's ventilation system at the outset can provide numerous benefits during the later stages of mine development. It has often been noted that the main cause of trouble in many mine ventilation systems can be found within a radius of 2500 ft from the fan installation. Ample airway capacity is essential to maintain the mine's head loss within manageable limits. Similar to an industrial ventilation setting, the mine's headings are the ductwork for the handling of air. The difference between normal industrial ventilation and mine ventilation is apparent when more capacity is needed; a plant can install new or larger ductwork, but it is difficult for a mine to install new entries or enlarge existing entries. Air velocities are usually maintained under 800 fpm to limit the stirring up of dust in the intakes. With this in mind, it is usually simple to estimate the number of entries required in the ventilation system. The problem that often arises, though, is when the system's capacity is overestimated and the required head loss to achieve the desired quantity is excessive. Experience has shown that problems are often encountered when the mine's condition requires much more than three inches of water gage to ventilate the mine on a day-to-day basis. Thus, if proper attention is not paid to these parameters in the preplanning and initial development of a new mine, it may take an extremely high water gage to achieve the ultimate quantity. This chapter will not delve deeply into the theory of mine ventilation; many other books have been writ- ten on that subject. Instead, the following sections will point out the important considerations that should take place before the development of a mine ventilation system, as they relate to normal industry practice. FUNDAMENTALS OF AIRFLOW Volume Versus Water Gage The common method of measuring ventilation pressure is in terms of inches of water gage (wg); one inch of water corresponds to a pressure of 5.2 psf (pounds per square foot). Further, airflow follows a square-law relationship between volumes and pressures where, as shown in the previous section, a doubling of quantity requires a quadrupling of pressure. Table 1 shows how heads and quantities are related. Using Table 1, it is readily apparent that, for the same mining conditions, an increase in pressure from one inch wg to three inches wg results in only 34,640 cfm when the initial quantity is 20,000 cfm. Pressure Losses Pressure losses in mine ventilation systems are caused by friction between the heading walls and the air stream and by shock losses due to abrupt changes of the air stream caused by obstructions. The common pressure-loss formula for mine ventilation is: [ ] where H is the pressure loss in inches of water gage, K is the coefficient of friction, L is the length of the airway in feet, 0 is the airway perimeter in feet, V is the air velocity in feet per minute, and A is the cross-sectional area of the airway in square feet. Table 2 lists the US Bureau of Mines schedule of friction factors (K) for mine airways. Recent research indicates that the values of K are slightly less for coal mines than those presented in the USBM Schedule, and Table 3 should be consulted in this instance. It should be

Jan 1, 1986

By Tom Gonzales

At San Manuel, AZ, Magma Metals Co. operates an Outokumpu flash furnace, four Peirce-Smith converters and two anode casting wheels that are supported by six anode vessels. Process gasses from the flash furnace and converters are treated in a two-train/ double-contact sulfuric acid plant. The plant captures 98% of the sulfur. A new flash furnace was commissioned in July 1988. It has since processed more than 2.7 Mt (3 million st) of sulfide concentrate without a major rebuild. The company has gained unique experience in the operation of the flash furnace at high oxygen enrichments with low off-gas dust loadings. New procedures have been developed to maintain secondary material generation at equilibrium and for maintaining metallurgical control of operating parameters. Process flow description At Magma's San Manuel plant, concentrates and other copper-bearing material are blended and conveyed from two separate areas of the plant to three 420 t (465 st) capacity wet charge bins located above the rotary dryer. Flash furnace silica flux is conveyed to a 227-t (250-st) capacity fine flux bin located adjacent to the wet charge bins. The concentrate and flux are blended in controlled amounts and fed into a 168-t/ h (185-stph) gas-fired rotary dryer. The wet charge enters the dryer at 8% moisture and is dried to 0.2% moisture. The dried charge is pneumatically conveyed to a 580-t/h (640-stph) dry charge bin located above the flash furnace. Flash furnace charge is drawn from the bin by two drag conveyors at a concentrate feed rate of 145 t/h (160 stph). The charge is mixed with enriched combustion air and injected into the furnace reaction shaft. In the reaction shaft, the charge is oxidized to form matte, slag and a rich SO, off-gas.

Jan 1, 1992