Search Documents

By Johannes Jäger

"A composite shell lining typically consists of an outer permanent sprayed concrete shell, a water proofing layer and an inner sprayed or cast concrete shell. Composite shell linings become more and more popular and have been built recently on large scale infrastructure projects. Surprisingly there is very little published literature on the actual structural design of composite linings. As a consequence there is a lack of common understanding on how to design a composite lining structure. Composite action of the outer shell (primary lining) initially carrying short term ground loads and the “unloaded” inner shell (secondary lining) require nonlinear concrete modelling to be able to assess the bearing capacity of the composite lining structure adequately. The composite action of the waterproofing membrane and the inner and outer shells can be considered either by simplified closed form solutions or by numerical models. Strength and stiffness parameters of membrane and concrete govern interaction of inner and outer shell. This paper should contribute to understanding composite lining behaviour with focus on the bearing capacity at limit state by taking into account the actual loading history. Possible ways and concepts on how to deal with these topics are presented, however a broader discussion on limit states of the composite lining materials – also in the long term will be required to come to an agreement on composite lining design methodology. INTRODUCTION Composite Lining Technology Traditionally the construction of shotcrete lined tunnels incorporates primary and secondary linings, separated by a sheet or a sprayable waterproofing membrane. The primary lining shotcrete is considered to be structurally temporary and the secondary lining to be permanent, leading to designs which ignore the bearing capacity of the primary lining in permanent condition. There was general perception that the shotcrete lining installed immediately at the tunnel face, experiencing strains up to 1% and even cracking in the early age, combined with mesh reinforcement additional support measures like lattice girder, spiles and bolts cannot be considered as a permanent structure. But also former shotcrete mixes showed significant weakness with respect to durability suggesting a more temporary nature of primary lining shotcrete. On the other hand it was clear that primary lining shotcrete does not disappear, it may lose probably a certain percentage of its bearing capacity, but discounting any contribution from the primary lining at all was considered inherently conservative. There were different strategies to account for the risk of reduced durability and bearing capacity of the primary lining, either by selecting moderate ground loads for the secondary lining design, by assuming that some residual load will be carried by the primary lining. This approach is very much based on experience. Another more rational possibility is to assume that the primary lining degrades into a rocklike material, which is weaker than the primary lining shotcrete but still imparts some strength to the ground around the secondary lining, but does not need to comply with any concrete design codes any more."

Jan 1, 2016

By Jerry Harrington, Brad Wigglesworth, David C. Beling

Commercial operations at the open pit, heap leach Crofoot Mine commenced in April, 1988. Approximately 13,600 tonnes (15,000 st) of low grade pregnant solution are treated daily using a Merrill-Crowe circuit. Acceptable gold recoveries from these low grade solutions can be obtained by optimizing solution pre-treatment prior to zinc addition.

Jan 1, 1990

By R. M. Bricka, T. J. Olin

Heavy metals contamination is an environmental problem at Army installations engaged in firearms training and munitions production. At these facilities, weathering and corrosion of expended munitions and leaching from wastewater lagoons, landfills and burn pits have resulted in heavy metals contamination of the soil. The principal metals encountered in firing-range soils are lead, copper and zinc. Cadmium and other metals, such as antimony, that are often incorporated in the munitions are sometimes seen in lesser concentrations. Mercury is associated with various propellants and, while present in much smaller concentrations, is of concern because of its acute toxicity. Chromium is primarily associated with plating operations. The transport of metals into groundwater has been confirmed at some locations, which has required treatment of the soil and groundwater at these sites. Certain treatment processes for contaminated soil produce metals-laden extracts, which also require treatment before reuse or disposal. Ion exchange is generally quite effective for removing metals from aqueous streams. However, resins are expensive and must be regenerated, and activated carbon is generally less effective for most metals and also requires regeneration. Therefore, alternative effective and economic sorbents are needed. Twelve sorbents were screened in initial batch testing. These included activated carbon, bark, chitosan, crown ether, corn cob, xanthate, clay (kaolinite and montmorillonite), peat moss, seaweed and reagent-grade zeolite (aluminosilicate, Sigma Product No. Z3125). Of these, zeolite demonstrated the highest capacity for Pb, Cr and Cd. For this reason, zeolite was selected for further testing in batch, kinetic and column studies. Materials and methods Zeolite. The zeolite used in the second-phase batch and column studies was obtained from a natural deposit of clinoptilolite-rich rock located in South Dakota (Rocky Ford SDH) (Desborough, 1996). Large blocks of the material were crushed and sieved into the following three particle size ranges: 0.5 to 1.0, 1.0 to 4.0 and 2.0 to 4.7 mm. This material demonstrates high structural stability in acidic solutions (pH 2.5) (Desborough 1996) and has a measured surface area of 30 m2/g. The measured total cation-exchange capacity (TCEC) was approximately 10 meq/100 g. This is well below what has been indicated for commercially available zeolite, which has been reported to be about 180 to 220 meq/ 100 g. The TCEC test was repeated (Method 9081, SW 846) using sodium acetate. The test resulted in a TCEC of 54.5 meq/100 g. The difference between values obtained for this material and published values for zeolites may be attributable to the greater heterogeneity in the material used in this study, compared to commercially available materials, or to the effect of the relatively large particle sizes utilized. Batch studies. Seven batch studies were conducted using synthetic metal solutions and soil extracts (Table 1). Extract composition: The P-extract was prepared by sequential surfactant extraction of organics from a burnpit soil followed by acid extraction of metals. The pH of this solution is approximately 1.1. A number of metals and organic compounds were present in the soil. Analysis of the extract was restricted to Pb, Zn and Cu concentrations for this study. The FBH extract was produced from a firing-range soil that was oxidized with a 0.01 M CaO solution and then extracted with 0.1 M acetic acid. This was filtered through 0.5-µm Whatman No. 5 filter paper and stored at room temperature. The pH of the FBH extract was approximately 4.5. pH Control: Calcium carbonate (CaCO3) may be present in the zeolite horizon or bed. Calcium ion (Ca") is released from the exchange sites when in contact with solutions containing ions for which it is more selective, such as lead. This results in a rise in solution pH over time. Acid washing removes most of the carbonates, eliminating the need for a buffer. Batch studies were conducted using both acid-washed zeolite (AW) and unwashed zeolite (UW) for performance comparison. The UW zeolite was rinsed with distilled deionized (DDI) water to remove fine soil particles. Both materials were dried at 105°C (220°F) overnight, so that the dry mass could be determined. Column studies. Ten column studies were conducted. Because it was expected to have the best hydraulic properties, the largest particle

Jan 1, 1999

By Kerry M. Masson

Perhaps the hottest item on the agendas of most state legislators this year is the state budget. The main question: Where will all the dollars come from to finance health care programs, state jobs, unemployment compensation programs, and on and on? This is especially so since people are out of work, business bankruptcies are up, sales are down, and incoming revenues from some sources have decreased or dried up. A sure bet is that state taxes will be increased in some form or another. The mining industry could face increased income taxes, property taxes, severance taxes, or even a host of new taxes (if the state does not already have them) like a gross receipts tax, investment tax, or tax on revenues made outside state borders. That's bad news for an already depressed industry, even though increased taxes may be the least of the industry's worries in the current economic climate. While reopening existing mines and developing most new mineral projects depends primarily on higher commodity prices, new taxes still could pose long term concerns for mine project development. Just how mineral tax law impacts a project is not easy to figure. It involves a complex set of calculations based on interpretations of numerous federal, state, and local tax laws that change almost annually. At best, projections of tax effects for the life of a mine are educated guesses. At the same time, projections are necessary to evaluate the economic feasibility of a mineral project. At a recent Technology Transfer Seminar, the US Bureau of Mines introduced a computer software program designed to evaluate the feasibility of a mineral project and to determine the tax effects on the project's discounted cash flow rate of return (DCFROR). The program, called MINSIM, began in 1967 as a 200-statement FORTRAN II program for evaluating a hypothetical large-scale open-pit gold mine. This single-commodity oriented program employed discrete simulation techniques and a continuous DCFROR was used to measure the effect of changes in revenues and costs. Over the past 15 years, MINSIM has developed into a program 70 to 100 times larger than the original. Basically, it will analyze costs and parameters specific to an identified deposit, then determine the DCFROR. Or by using a specified DCFROR, it will determine the primary commodity price required to attain that specified rate of return. MINSIM, which is explained in detail in this article, is available from the Division of Minerals Availability, USBM free of charge. Written in FORTRAN IV, it comes on punch cards or magnetic tape and is compatible with most major computer systems. The MINSIM Program The main objective of any freeenterprise mining venture is to make a profit. To determine profitability of a given project, alternate methods of operating and financing must be evaluated. That is the purpose of MINSIM. While there are a number of methods of evaluating the economic profitability of a mining project, MINSIM uses the Discounted Cash Flow Rate of Return (DCFROR) method as its major criterion because DCFROR considers the time value of money and gives the truest measure of profitability. One disadvantage is that the calculations are deposit oriented. In other words, MINSIM analyzes only those costs and parameters specific to the deposit. It cannot be used to evaluate the overall corporate picture. The program is designed to simultaneously handle five different commodities and a leach operation for any type of mining project. For example, analysis of a coal project would include only one commodity-coal at the mine mouth. Analysis of a copper operation might include numerous commodities-from the raw material to the refined product. Input MINSIM considers capital investment-recoverable exploration, acquisition, and development costs; depreciable capital investments such as mine plant and equipment, mill plant and equipment, and infrastructure costs; all general and commodity specific operating costs; and the cost of alternate financing methods. The program has the capacity to incorporate different types of depletion allowances, numerous commodity-dependent severance taxes, variations of property taxes, and many methods for calculating state or provincial taxes. There are even many different ways to calculate federal and national taxes. The capacity to handle tax variations is generated from an internal subroutine in the program called the "open file." The user can reconstruct, customize, or evaluate any kind of tax desired. Outputs Given this kind of capacity for numerous input parameters, MINSIM is capable of the follow¬ing major outputs:

Jan 3, 1983

By Ian M. Loomis, Keith G. Wallace

The Waste Isolation Pilot Plant (WIPP) is a U.S. Department of Energy research and development facility designed to demonstrate the permanent, safe disposal of U.S. defense-generated transuranic waste. The waste storage horizon is 655 m (2150 ft) below surface in bedded salt. To date the WIPP project has not emplaced any waste. There are three intake shafts used to supply air to the underground. All air is exhausted though a single return shaft. The total design airflow during normal operations is 200 m3/s (424,000 cfm). The ventilation system is designed to provide separate air splits to construction, experimental, and storage activities. Separation is achieved by isolating the storage circuit from the construction or experimental circuits with bulkheads. Any air leakage must be towards the storage area of the facility. Field studies have shown that the pressure differential necessary to maintain the correct leakage direction is susceptible to the effects of natural ventilation; therefore, extensive studies and analyses have been conducted to quantity the natural ventilation effects on the WIPP underground airflow system. A component of this work is a monitoring system designed to measure the air properties necessary for calculation of the natural ventilation pressure (NVP). This monitoring system consists of measuring dry bulb temperature, relative humidity, and barometric pressure at strategic locations on surface and underground. The psychrometric parameters of the air are measured every fifteen minutes. From these data, trends can be determined showing the impact of NVP on the ventilation system during diurnal variations in surface climate. Both summer and winter conditions have been studied. To the author's knowledge this is the first reported instance of automatic and continuous production of time and temperature variant NVPs. This paper describes the results of the initial monitoring study. INTRODUCTION The ventilation system at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico, is designed to perform two distinct functions. First, it supports normal mine ventilation requirements complying with all state and federal mine regulations. Second, the system is designed to prevent an uncontrolled release of radioactive contaminants from the storage and transportation areas of the facility. Although a nuclear radiation release in the facility is considered unlikely, many special features are implemented in the ventilation system to prevent the possible spread of contamination. The facility is constructed with the waste transportation and storage areas separated from the mining and non-radioactive experimental areas. The ventilation system is designed such that air leakage is from the mining and experimental areas to the storage areas. Furthermore, radiation detectors are located throughout the storage and waste transportation areas underground and an exhaust filtration building is installed on surface to prevent the possible release of radiation to the environment. For over two years the underground ventilation system has been rigorously tested and balanced. It was during this period that the adverse effects of NVP were noticed and subsequently quantified. From extensive field studies and computer models, several mitigating features were designed and constructed and special operational procedures were implemented to control the impacts of NVP. To quantify more accurately the NVP at the WIPP, a continuous monitoring system was installed. This monitoring system consists of measuring dry bulb temperature, relative humidity, and barometric pressure every fifteen minutes at strategic locations on surface and underground. From this psychrometric data, the NVP is calculated. Fan operating pressures and flows and strategic differential pressures are recorded from the site Continuous Monitoring System (CMS). The monitoring system provides a means of evaluating how the ventilation system behaves in regard to climatic conditions and to judge the efficacy of the mitigating features and operational procedures. To the author's knowledge, continuous calculation of NVP as a function of time and surface temperature has not been previously reported. Overview of the Waste Isolation Pilot Plant The U.S. Department of Energy determined that the plastic nature of bedded salt may provide the best solution to isolate transuranic (TRU) waste from the biosphere. Initial evaluations at the WIPP site began in 1974. In 1979, the United States Congress enacted Public Law 96-164 for the construction and development of the WIPP project. The mission of the WIPP is to demonstrate the safe, long-term disposal of TRU waste generated by the national defense programs of the United States. TRU waste is classified as a low to medium level waste. The waste is stored in drums and does not produce significant heat (not greater than 1 W per drum). The WIPP site is located approximately 47 km (29 miles) east of Carlsbad, New Mexico in the Chihuahuan Desert. The repository is located in the 630 m (2000 ft) thick Salado Formation. This Permian Basin salt deposit is about 225 million years old and appears to have been minimally disturbed by earthquake, faulting, and ground water activity since it was deposited. The underground facility is 660 m

Jan 1, 1993

By Duane A. Smith

Horace Tabor. No 19th century Colorado mining man is better known but, unfortunately, probably less understood. He is little appreciated for his significant contributions to the industry and the state. A century ago, Tabor was headline news. The legend today, however, has become so all pervasive and so interwoven with fact that the two are hard to separate. For example, he never told Baby Doe on his death bed to hang on to the Matchless mine. Yet this has emerged as staple Tabor fare. So much attention has been focused on his matrimonial triangle that it overshadows the man. Symbol of mining's reward Tabor traveled west in the 1859 Pike's Peak gold rush. In the next generation, he came to symbolize the rewards mining might lavish on an individual. The Leadville Daily Herald (Sept. 10, 1882) could write, without exaggeration, that "the extent which the mining industry of Colorado is under obligation to Tabor cannot be easily estimated - what he has done for Leadville and Denver is patent to all." It had not come easily, nor had Tabor started out a success. His early placer mining at Payne's Bar, near present-day Idaho Springs, CO, had turned no fortune. So in 1860, he, his wife Augusta, and son went south to Colorado City, then over Ute Pass and up the Arkansas Valley to Oro City. Arriving soon after the initial discovery, Tabor staked a good claim. With a sharp eye, he and Augusta broadened their base by establishing a store. Both mining and business would pay dividends in the following years. By the season's end, though, Oro City was already declining. Always on the lookout for a richer district, Tabor and his family moved the next year across the mountains to promising Buckskin Joe. The familiar pattern followed, with the store and post office being the center of their attention. Mining investment and management now replaced the earlier physical panning and sluice operating. Seven years later, the Tabors abandoned Buckskin Joe and returned to Oro City. It had moved up California Gulch to be near the district's best mine, the Printer Boy. Middle class was not enough Middle class respectability, plus a steady income, was the Tabor's by the 1870s; fine as far as it went. But it proved far from the fortune Horace had always been seeking. Oro City languished in the backwash of Colorado mining and Tabor seemed like many men who had drifted around the Territory following the ebb and flow of mining. His faithful wife Augusta had been a steady factor in the success the family achieved. She helped year after year to operate the store and post office. Not simply the happy-go-lucky individual he has often been portrayed, Tabor was a hard working businessman/mine owner. An R. G. Dun and Company agent evaluated him in 1876 "Net worth $23,200. Is a very shrewd businessman and not liable to lose money, has a good chance to make money as he had no competition." Leadville: Tabor's silverlined-fortune After all those years on the Colorado mining frontier, in 1877, Lake County's wealthiest and most respected merchant made another move. It was short in distance, only 4 km (2.5 miles) down California Gulch, then a little north to a new mining camp. This new camp, soon named Leadville, gave birth to the Tabor fortune and legend. Middle-aged (Horace was 47), the Tabors once more set up their general store and found themselves in the midst of the open¬ing of a new district. This time silver beckoned and not the gold that had brought them West 18 years before.

Jan 1, 1989

By J. D. Patsey, G. T. Lineberry

Introduction A computer program was developed for analyzing drum-type hoists before modifying an existing system or designing a new one. Its use permits the preliminary evaluation of a system before seeking technical assistance from mine hoist designers and manufacturers. The user-friendly program accepts a variety of data and analyzes hoisting systems for any balance state. The program can be used to calculate skip capacity to yield a desired production rate, solve for drum face width, select a permissible wire rope, estimate total horsepower of the hoist plant, and estimate annual power cost. Whether required for a large mining complex or for a relatively small operation, a hoisting system must be carefully designed to ensure the efficient, reliable, and safe flow of material. Because shaft sinking and hoist installation can total between 2.5% and 3% of the cost of opening a deep mine, proper hoist selection is critical. Today's mining engineer has at his disposal the most powerful design and analytical aid ever, the microcomputer. There is, unfortunately, limited software for the study of hoisting systems, unlike that for other materials handling equipment (Manula and Albert, 1980; Prelaz et al., 1964; Bucklen, 1969; Thompson, 1985). HOIST reduces a time-consuming set of calculations to a concise package of interrelated subprograms. A literature review revealed no common-user programs to analyze hoisting systems, although at least four major hoist designers/manufacturers/installers have their own in-house programs. To provide a tool with which the mining engineer could preliminarily analyze a materials hoisting system or could check the calculations of a hoist contractor, a computer program was developed. HOIST was written in BASIC for the IBM-PC for ease of program adaptation and to encourage field use on compatible systems. Details of program development are omitted, since the basic principles of hoisting analyses are relatively straightforward, simple, and readily accepted (Harmon, 1973; Nordberg, n.d.; Adler, 1957). Program features, intended usage, and benefits of the computerized solution are emphasized over theory development and mathematical rigor. Background The mine hoist system that is selected and installed at a mine is the "lifeline" of that mine, with installations lasting 20 years or more. Thorough study is warranted to ensure that productivity demands are met at a minimum cost per ton. The increased cost of a large, powerful, high-speed hoist must be offset by increased production to justify its selection. To optimize this tradeoff, an extensive hoisting analysis should be performed. The analyses to properly size the skip (or cage), the drum, and the hoist drive are conducive to computerization, permitting rapid evaluation of changeable operating and design parameters, such as velocity, acceleration, state of balance, and productivity demand. The program is particularly useful in conducting sensitivity trials, such as investigation into the effect of change of productivity on skip capacity and on horsepower of the hoist drive. HOIST is currently limited to the study of drum-type hoists with cylindrical drum(s). However, only minor changes to the program would permit analysis of friction hoists and conical drum configurations. Model development and testing The program is based on accepted equations and physical relationships. Examples of manual calculations formed the basis for decision points and program branching. Data is input in the order that it would be needed if the problems were solved manually. The choices are arranged likewise. HOIST was developed in sections, with manual solutions performed to check program logic. The testing became more rigorous as sections were completed. Output from one section becomes input for following sections, as appropriate. The simplified flow diagram of HOIST is given in Fig. 1.

Jan 2, 1987

By Ted H. Eyde

Nearly 17 years ago a major producer of synthetic zeolites started an extensive exploration program for natural zeolite deposits which resulted in the discovery of over 170 occurrences in the western United States. A few years later several of the other producers and consumers of synthetic zeolites also started similar exploration programs. Since then, small quantities of natural zeolite minerals have been produced from at least 12 deposits in the United States. Of these the Bowie deposit, about 13 miles north of Bowie, Arizona, is the most important,having produced over 5,000 tons of vitric tuff zeolitically altered to the mineral chabazite and minor amounts of the minerals erionite and clinoptilolite. Mining Districts and Mineral Deposits of Arizona compiled by Charles A. Mardirosian, Consulting Geologist, estimates the value of the total production from the Bowie deposit at a very conservative $2,000,000. Unfortunately, none of the companies responsible for the discovery and the initial production of natural zeolites made any effort to develop the high volume, low cost applications of this unique mineral raw material. Instead, they developed only the high unit value uses to supplement their existing synthetic molecular sieve product lines. With the producers of synthetic zeolites thinking in pounds and not in tons, further development of natural zeolite deposits stagnated for over a decade.

Jan 1, 1974

By A. J. Kroha, N. Wesis

Most copper mines produce both ore and low-grade "leach" rock or acid waters that contain recoverable copper. The sulfide ores pre¬dominate, and a portion that is too low grade for milling to produce concentrates for smelting, but has to be mined and trucked away anyhow, may be leached successfully with acid in dumps. Most of this leach material consists of sulfides and silicates or carbonates, and if the gangue is such that it consumes a high quantity of acid, this factor may rule out a leach operation. There are also valuable deposits that contain mostly acid-soluble copper, or occasional sulfide ores from which a sulfide concentrate can be roasted and acid-leached to produce a copper-bearing solution. Finally, there are milling ores in which the lesser part of the copper is acid-soluble and can be precipitated with iron or synthetic inorganic precipitants that produce metallic copper or copper sulfides that will float with the sulfides. Ordinarily, ores that contain copper associated with the sulfur ion, such as in the minerals chalcopyrite, chalcocite, bornite (and others), are milled to produce a 25-30% Cu concentrate for smelting, while a lesser amount of acid-soluble copper may be converted from solution to cement copper on iron scrap. A fast-growing percentage of such copper, however, is removed from solution with exchange resins or organic compounds in organic carriers such as kerosene (solvent extraction), then eluted with strong acid and subjected to electrolytic precipitation either in marketable form or as anodes that can be refined further. From the point of view of conventional copper smelting, copper flotation concentrates and cement copper are of chief interest in this chapter. Table I is a condensed open schedule for concentrates that generally run between 25 and 35% copper, and much less frequently as low as 12-15% or as high as 65-75% copper, the former being due to intimate relationship with pyrite (like the former United Verde Extension), and the latter representing such ores as the Bolivian Coro¬coro ore in which the copper is in the form of chalcocite in sandstone. These extremes are no longer common. When they occur, a special purchase schedule has to be negotiated. Included in Table 1, copper precipitates (cement copper) generally run from 70-85%a copper, and the same basic purchase schedule is used as with flotation concentrates. Sulfide Flotation Concentrates The sulfide copper concentrate produced in the mill as a flotation froth, with water then added for transportation of the heavy mineral particles from the flotation cells to thickeners, may run 60-80% water by weight, and the removal of water down to 25-50% by weight by means of thickeners, followed by further dewatering by continuous vacuum filters to 7-18% moisture by weight (depending on size of solids by screen analysis and also by content of clay) is a critical operation. Mill operators would like to produce a filter cake with 7-9% moisture content, but even with the help of steam on the filter this desirable condition is seldom realized when the concentrate is as fine as 80% -325 mesh. More commonly, the final concentrate is reground in pro- to produce best copper recovery and grade of concentrate (or molybdenite separation). In those cases, increasingly frequent, the filter product may not be a cake at all, but a mud that is hard to handle-even requiring a thermal dryer. Greater difficulty of form¬ing a manageable cake often comes from the copper-molybdenum separation by flotation, because the alkaline sulfides and hydrosulfides, or cyanide, or other similar reagents used for the separation, may leave the now relatively molybdenite-free copper concentrate even more difficult to filter. Handling a wet filter cake is difficult enough when its destination is only a short distance away-a matter of yards rather than miles. In those cases the filter cake may be thermally dried near the point of production, using rotary or multiple hearth, or fluidized-bed dryers. Alternatively, the concentrate may be pumped or carried in slurry form to the smelter and filtered there, or it may be spray-dried and compacted. For transportation to a smelter just a few miles to a few thousand miles away by ship or railroad other factors may be important, such as: in shipping by sea, avoidance of spontaneous combustion; in shipping by rail, losses by leakage if too wet or by wind and sun if too dry. It is the responsibility of the millman-usually the mill superinten¬dent-to make sure that his concentrates are in satisfactory condition when they leave the mill so that they meet these requirements: 1) They must have been accurately sampled and dry-weighed, the latter meaning that a moisture determination and gross weight must have been taken. 2) They must be dried sufficiently when necessary to prepare them for safe transportation. 3) They must arrive at the smelter with reasonable likelihood that they can be check-weighed and sampled fairly and equitably,

Jan 1, 1985

By Sahendra Ram, Ashok Kumar, Rakesh Kumar, AMIT KUMAR SINGH, Dheeraj Kumar, Arun Kumar Singh, Rajendra Singh

This article offers an examination of a retreat mining method conducted at the Pinoura Mine in India from 2010 to 2017. The method is atypical for coal mines of India’s coalfields. The method executes depillaring in a single pass and does not require the formation of galleries and support installation in splits, thus, reducing the cycle time. A variety of observations are discussed throughout this work and emphasis is placed on field measurements and depillaring under weak roof (RMR = 40–45). This paper discusses design techniques, specifically the estimation of the snook (remnant pillar) size, and important practical observations after the fact. The execution of this method was eventually conducted in eleven panels.

Aug 4, 2020

By T. L. Heidrick

Late Cretaceous-early Tertiary Cordilleran porphyry Cu-Mo districts and their consanguineous Zn-Pb-Ag-Au-W vein and replacement deposits of the Rocky Mountain region comprise one of the largest, best studied, diverse, complex, puzzling, and richest compound metallogenic provinces on earth. A concise space-time definition of intermineral plate, regional and local structure-tectonic frameworks is crucial to deciphering their diachronous metallogeny and enhancing the explorationist's odds of future discovery.

Jan 1, 2013

By R. J. Sandberg

The Copper Creek area, part of the Bunker Hill District, Pinal County, Arizona, lies within the southwest porphyry copper province of North America at the intersection of a northwest trend and an east-northeast trend of Laramide porphyry copper deposits. The Copper Creek area has been mined and explored for copper and molybdenum since the early 1900?s. The majority of this work focused on the more than 400 surface exposed breccia bodies. In the 1960 to 1970?s deeper drilling discovered a deep porphyry copper-like setting. Redhawk Copper currently has NI 43-101 compliant resources of about 0.652 billion pounds of measured and indicated and 2.745 billion pounds of inferred copper equivalent in breccia hosted and porphyry style deposits. See Figure 1.

Jan 1, 2010

The Newmont Boddington Orebody (NBO) is a large, diffuse Au/Cu orebody in Western Australias South-West corner with approximately 20Moz Au in current Reserves. The current sulphide Resource is reported after calculation with the non-linear estimation technique Uniform Conditioning to account for the mining selectivity being smaller than the average drillhole spacing. Simulation of Au grade is also run over the entire orebody reviewing risk and uncertainty. There are differences in results from the two methods. These have been investigated and the lessons learned of the influencing parameters and effect of technique alone, are helpful for applications to other orebodies.

Jan 1, 2010

By Cleland N. Conwell

Intermittent coal mining has been conducted in Alaska for over a century. The first report of coal in Alaska was by the Veechy expedition of 1826 and 1827. Whaling ships used coal from Corwin Bluff near Cape Beaufort during the early and latter parts of the 19th century. The first coal mine in Alaska -- and probably the oldest in the Pacific coast of North America -- was opened by the Russians at Port Graham on the southwest tip of the Kenai Peninsula. The mine was operated from 1855 until 1867 when the United States took possession of Alaska. From 1880 to 1915 coal mining was carried on intermittently at several localities including Unga Island, Herendeen Bay, Chignik Bay, Kachemak Bay, and several points along the Yukon River. Small coal mines along the Yukon River provided fuel for the river steamers traveling from St. Michaels to Whitehorse. The area of sustained coal production began with the completion of the Alaskan Railroad from Anchorage to the Matanuska coal field in 1916 and to the Nenana field in 1918. Coal production continued to increase until 1953, at which time the oil and gas fields in Cook Inlet were developed. Oil and gas eventually replaced- the Matanuska coal as a means of providing heat and power. The military in the Anchorage area shifted from coal to oil in 1967 causing a decrease in production. The increased demand for electric power in the Fairbanks area offset the decline and coal production started to increase. In 1969-1970 the Golden Valley Electric Association constructed a mine-mouth power plant 70 miles southwest of Fairbanks near Healy and a power line to Fairbanks. LOCATION OF COALS IN ALASKA Coals are found in all geographical subdivisions of Alaska. Coal in Alaska ranges in age from Carboniferous to Tertiary, and grade from lignite through anthracite. Figure 1 shows the locations of Alaskan coal fields. The only fields that have been developed extensively are the Matanuska and Nenana. Figure 2

Jan 1, 1972

By Richard Emberley, Timothy Shaw, José L. Torero, Jurij Karlovsek, Timothy Gibson

"Tunnel closures are highly undesirable and the lengthiest are generally attributed to structural failures (e.g. Mont Blanc). Although historical data shows structural failures are closely linked to fire, design parameters for tunnel safety are not well defined. Current research has focused on defining the fire heat release rate and temperature, but these parameters cannot be easily used to determined structural performance. The energy transferred to the structure, the heat flux, is required but current literature lacks these values. Full scale experiments were undertaken on passenger vehicles resulting in heat fluxes between 20-70kW/m2. Analysis shows a vehicle fire’s duration is closely linked to its mass. Further analysis shows small vehicle fires can be scaled as a function of the tunnel diameter and the characteristic height of the desired vehicle. The present work provides engineers an appropriate design methodology to undertake informed thermal-structural analysis to minimize the risk of tunnel structural failure.INTRODUCTION Quantifying the effects of a tunnel fire depends on many factors such as the type of occupants, their vehicles and spacing, ventilation conditions and the geometric shape of the tunnel (Ingason and Lonnermark 2011). For design engineers investigating the thermal-structural performance of a tunnel, these factors are typically converted into spatial and temporal temperature distributions (Usmani et al. 2001) using various design curves such as those of ISO834-1, Hydrocarbon, Rijkswaterstaat (RWS) or RABT-ZTV (Promat 2013). However, to define a temperature profile through a structural element these curves require a heat transfer model that incorporates an appropriate boundary condition. The appropriate boundary condition is the net heat flux which is the result of a complex energy balance. For use in heat transfer calculations the net heat flux must account for the tunnel geometry as well as thermal properties of a given structural element and all other surfaces and mediums affecting the transfer of heat (Torero 2014)."

Jan 1, 2016

By Robert F. Reeves, Stephens A. Avary

Introduction People, systems, methods, and organization make up maintenance productivity. Methods promote efficiency in operations, systems ensure consistency and continuity, and organization maintains direction and control. The common denominator in these techniques, though, is people. Management systems can be technically correct, but fail to work because management systems do not work by themselves - people make them work. Therefore, the foundation for mine maintenance productivity must begin with the people involved. Traditionally, the emphasis placed on mine maintenance, as opposed to production, is not proportional to the impact that maintenance has on a mining operation. The performance and productivity of mine maintenance substantially affects the operating costs, revenues, and profits of the mine. The mining industry has recently experienced a period of economic depression. While it has created financial problems in all segments of the industry, it has caused the industry to focus on the need for improved productivity. Mining companies that have made investments in productivity during this period will have a competitive edge during the recovery, and mine maintenance may be the best place to put that investment. Future lost production and maintenance cost problems can be avoided if mine management has the foresight to seize the opportunities that now exist. Background Technological improvements over the last 30 years have been dramatic in the industry. Before these changes, mining equipment was not very sophisticated. So maintenance needs were not very sophisticated. Maintenance people were not required to have any formal training in mechanical or electrical skills. At many mines there was no formal maintenance organization. The mechanic was a part of the section crew and received direction from the face boss. Mine maintenance was not a function, it was a task. Technological change in mining came about in response to an expanding economy and greater demand for mined products. The past 20 years brought about a change in the kind of individual needed to mine ore and coal, and an even greater change in the person needed to maintain equipment. Equipment went from mechanical and pneumatic to complicated electrical and hydraulic. Maintenance progressed from being a task to being a function. Types of Mechanics Mine maintenance workers can be grouped into three categories based on experience: mechanics with more than 20 years, five- to 10-years, and less then five years. These groupings have influenced mine maintenance productivity. The 20-plus mechanic has been the foundation of the maintenance force. He had no formal training and his skills were acquired on the job. As new equipment was introduced, he learned to repair it by trial and error. Not all of what he learned was correct. Personal initiative and conscientiousness are characteristics of this group. They have experienced the bad times and the good, and appreciate the opportunity to work. The five- to 10-year group worked with the older, more experienced mechanics to acquire maintenance skills. These mechanics came in during industry boom times, and many progressed quickly by being in the right place at the right time. Many in this group have difficulty with diagnostic trouble-shooting, and depend on changing out parts to identify problems. This group is generally more mobile and less apt to have a strong work ethic. Mechanics with about five years experience have vocational training, some formal education or basic skills training. Like the five- to 10-year group, these miners are mobile and tend to move readily to satisfy their changing needs. These two younger groups are less apt to feel any loyalty to the employer or obligation to be productive. Their attitudes and abilities reflect the influence of their general age groups, and has a definite impact on mining productivity. Past Requirements In the 1960s, the basic requirements for a maintenance supervisor was that he be a top mechanic, get along well with the men, and be a hustler and improviser. He learned the details of new equipment as repairs were needed. Oftentimes, this individual would be the only person on the property with the ability to read prints, use diagnostic testing equipment, and troubleshoot using an analytical approach. This approach to maintenance is sufficient when the equipment design is reasonably uncomplicated. Management Changes As technology progressed, organized labor gained strength, government regulation increased, and the job of supervising and managing people had to change. The environment has changed and

Jan 11, 1983

By K. Y. Haramy, K. Hanna

Early identification of adverse geologic conditions and high stress concentrations during the high-speed extraction of coal using modern mechanized longwall systems is a major challenge facing the mining industry. Often, unexpected geologic anomalies that affect rock mass quality are encountered more rapidly, leaving the mine operator with insufficient time or information to deal with the changing ground conditions. The RockVision3D™ seismic tomographic system, developed by NSA Engineering, Inc., offers substantial benefits over conventional geologic/stress-detection methods and has been used successfully in coal mines worldwide. Tomographic images, produced economically and in near-real time, are easy to interpret, allowing mine operators to deal with potential hazards on a day-to-day basis.

Jan 1, 1999

By James L. Kelley

The Twin Buttes Mine, one of the more recently developed large copper mines in the United States, is in the Pima Mining District about 25 miles south of Tucson (Figure 1). Other copper producing mines in the district are the Esperanza-Sierrita mining operations, five miles to the southwest and the Pima and Mission Mines, seven miles to the north. Copper metal production from the Pima District in 1974 totaled 276,728 tons and the Twin Buttes Mine's share was 46,473 tons or about 17%.' The district's copper production was 31% of Arizona State's production and nearly 17% of the production from the United states in 1974. The Pima District thus ranks as one of the major copper producing areas in this country.

Jan 1, 1976

By Thomas V. Falkie, Howard L. Hartman, Bruce R. Palmer, Donald W. Gentry, John E. Frost, Peter T. Luckie, Michael K. McCarter, Lee W. Saperstein

Education in the mineral engineering professions is in the same flux and turmoil as is the entire minerals industry. Overcapacity in some areas, undercapacity in others, and the constant fear of substitution plague education as well as industry. The exercise in long-range planning that The Society of Mining Engineers has undertaken gives an excellent opportunity to examine the problems and the opportunities in minerals engineering education. Charge to the Committee The Educational Activities Committee was asked by the Long-Range Planning Commission (LRPC) to examine SME's future role with respect to "education policy, role and organization, education department, education board, continuing education, short courses, and extension courses." This examination is timely. It follows a reorganization of SME's Education Board designed to make the Board more efficient in its operation, more responsive to the needs of education, and more active in the setting of Society policy on education. In addition, the roller-coaster cycle of boom and bust experienced by the mineral industry in the last decade has been shared by the minerals schools and has created enrollment problems that need to be addressed promptly. Within SME there is much experience on educational issues to draw from and many problems to solve. Major Premise The committee is emphatic in espousing the philosophy that SME should support, in word and in deed, the highest possible standards that can be maintained by the minerals schools. As guardians of the various mineral engineering and scientific professions (geological engineering, geophysical engineering, mineral engineering, mineral processing engineering, and mining engineering), it is appropriate for the Society to be a watchdog for academic standards. One member of the committee put it succinctly, "We need to educate engineers and technologists, not muckers." A vital and profitable minerals industry needs professionals educated by good teachers, equipped with the most modern available methods, techniques, and knowledge, and challenged by their education to be innovative contributors to their chosen profession. Such education occurs only if it takes place in an institution that is vital and challenging. SME can enhance the quality of its membership if it works to maintain the standards of the schools that graduate new members. Education does not end with the award of a degree. It is appropriate for SME to strive for continued technical quality of its membership. To this goal, SME should maintain its attention to the process of licensing professional engineers, and it must continue and expand its efforts in continuing education for the membership. Recommendations for Action The following recommendations were submitted by the committee and then amended slightly by the full commission. The recommendations have support from the SME Board. • SME Education Coordinator and Staff Department of Education - Staff support for education should be provided by someone with experience in engineering education who would be appointed as SME Education Coordinator for all educational activities: accreditation, continuing education, student affairs, and liaison with mineral schools. The Board has approved an Education Coordinator and the position has been filled. • Advisory Committee on Education - SME should recognize, by amending its committee structure, that functions important to education are filled by SME-appointed representatives to the Accreditation Board for Engineering and Technology (ABET), its Engineering Accreditation Commission (EAC), and Technology Accreditation Commission (TAC). It is suggested that these persons, plus the chairman of the Education Council, plus two other persons appointed by the SME Board, form an advisory committee on education. The Board has approved this. • Education Council - The recently organized Education Board, having full agendas for its committee meetings and having

Jan 6, 1984

By A. Noble

The design of separation circuits can be a complex, labor-intensive and costly process. While the engineer?s experience along with extensive data sets and simulation are crucial tools for determining the final solution, a more fundamental approach is suitable to compare preliminary options and reduce the number of potential alternatives. In light of this need, the authors have developed the Circuit Analysis Reduction Tool (CART?). This software package relies on the fundamental principles of linear circuit analysis; however, the solution methodology has been streamlined to automatically incorporate stream splitting and unique separation performance for each unit. The resulting tool allows preliminary analysis of circuit designs without the need of detailed feed characterization. In addition to the basic analytical approach, this paper supports the veracity of the methodology with several simulated examples for various separation models.

Feb 27, 2013