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By J. T. Kline

This paper will present a review of the underground leaching of remnant copper mineralization left as a result of the block cave mining operation at the Lakeshore Mine in Casa Grande, Arizona.

Jan 1, 1985

By Khosrow Badiozamani

Traditionally the mining industry has been lagging in application of computers in their daily or long range plan activities compared to other industries. The question then remains as to how the technology of higher computing capacity for less cost is going to affect the mining industry and how the lukewarm reception of engineers in acceptance of computerized mine planning in the past is going to change because of the new wave of high techology. These questions and the reasons for the lack of usage of computerized mine planning systems by engineers will be evaluated in this paper. In addition, alternatives available to the mining industry will be analyzed and the direction of the future "user friendly" software will be discussed.

Jan 1, 1984

By Y. Topkaya, R. E. Johnson, D. Buttinelli, B. R. Palmer, A. Geveci, L. Stoppa, C. Lupi, F. Pochetti

Representative samples of a composite mixture of three typical Cu/Zn complex sulphide ores, namely Black-, Yellow- and Altered-ore, from the Cayeli deposit in Turkey, were used for leaching tests in 2.2 M FeCl3, or 1 M CuC12-2 M NaCl solution in the temperature range from 313 K to 363 K (40O to 90O C), with and without the presence of an organic solvent for elemental sulphur, such as CCl4. The leaching rates of copper and zinc were quite high, as expected, in FeCl3 solution and complete recovery of both metals was obtained at the highest temperature when the solvent was present. However in CuC1, solution, extraction yields of the order of 95% only for Cu and Zn were achieved and the positive effect of the solvent was not clearly shown. The kinetics curves of Cu leaching by FeCl3 indicated a model of reaction rate depending on the particle surface, as in a chemically controlled reaction, in tests with the presence of CCl4. Without the solvent, or in CuCl2 media, the model of the diffusion controlled reaction seemed to prevail. Values of apparent activation energy, in both of the leaching processes, were determined and compared with those reported in literature.

Jan 1, 1993

By Lee W. Saperstien

At the heart of the mining process are a number of basic and fundamental tasks whose regular and repeated performance constitute the mining cycle. As will be discussed presently, these tasks are the basic components of the mining system. Section 9, Production Operations, provides the mine designer and engineer with an understanding of these tasks and with sufficient design principles to allow this person to create an efficient mine system. This section is meant to be an introduction and adjunct to subsequent sections that describe specific mining systems. However, sufficient design information is included here for the independent design of mine systems that may not be described elsewhere or for subsequent verification of existing designs. For the purposes of this section, mining subsumes excavation; thus this material applies to any excavation process. Accordingly, this section is written in general enough terms to include both surface and underground mining. It may be used also for civil engineering excavations that often involve the same steps. Obviously, the actual procedures undertaken in any specific mining system will appear to be very different from those taken in any other system. This is certainly true when comparing surface with underground methods. Yet the fundamental principles are often the same. This segment is written to explicate the basics. Wherever appropriate, the section will suggest the differences between the application process to surface or to underground mining.

Jan 1, 2008

By N. Cruickshank

Gas outbursts occur as sudden eruptions of gas and minerals from the face of a mine heading as the heading approaches potentially burst-prone (or anomalous) zones of rock. Such outbursts have resulted in considerable damage to equipment and in some cases lives have been lost. Characterizing these anomalous zones and detecting their presence is therefore vital to safe mining. Certain significant characteristics associated with the outburst-prone zones are: (1) the presence of fluid inclusions, (2) unstable stress conditions, (3) characteristic geologic structures, (4) certain physical properties of the rock, and (5) micro-seismic activity. Geophysical and engineering methods for detecting these characterisitcs are discussed and are considered with respect to their past success and future potential for predicting gas outbursts.

Jan 1, 1985

By N. S. Tanious

The need to provide better mine roof support and control in longwall tailgate entries prompted the Bureau of mines to search for a replacement product for wood cribs. Their search isolated steel-fiber-reinforced concrete (SFC) as the most effective replacement. Through successful laboratory and underground mine tests, handmade SFC cribs proved to be a viable and more effective roof support system. However, to ensure wider usage, U. S. Steel Mining Co. initiated a joint development and evaluation program with Burrell Construction Company in order to mass produce SFC blocks of reasonable dimension, weight, and cost. Small specimens and full-size cribs were evaluated during this program to determine their compressive strength and post failure characteristics. After considerable testing and adjusting of various concrete mixtures, a final formulation for the SFC crib blocks was selected. That formulation permitted the construction of SFC cribs possessing a nominal crib strength of 3200 psi (22.1 x 106 Pa) and a nominal modulus of elasticity of 1.0 x 106 psi (6894.76 x 106 Pa). These SFC cribs can support from 3.5 to 14.5 times as much load as a wood crib, depending on the size of the wood crib being replaced. Both laboratory and limited mine tests, conducted by U. S. Steel Mining Co. have shown the SFC crib to be an economical and effective means of roof control.

Jan 1, 1984

By J. D. Vincent

The Mission By-Products Plant at the Mission Concentrator of the American Smelting and Refining Company, some 20 miles south of Tucson, Arizona in the Twin Buttes mining area, has been in operation slightly over a year. The plant produces a molybdenite concentrate a copper concentrate and, at times, a zinc concentrate. An intensive test program of over three years was conducted at Mission to make the recovery of molybdenum economic. Briefly it was found necessary to make a scavenger concentrate in the copper mill before it was possible to recover economic quantities of molybdenite. By so doing there were resulting additional recoveries of copper, silver and zinc. This program resulted in the design and construction of the existing plant. A paper by the authors discussing the test work and the design was presented at the, October 1965 meeting of the American Mining Congress in Las Vegas, Nevada, by Mr. Wayne Bossard.

Jan 1, 1966

By Duane A. Smith

Introduction From the days of the Spanish in the eighteenth century, Colorado's San Juan mining district has attracted miners and public interest. The Spanish left behind names - San Juans, La Plata, Animas, legends of lost mines, and the remains of a few scattered mining operations. They came, but did not stay. Again in 1860-61, as a spinoff of the Pike's Peak gold rush, prospectors climbed the mountains and descended into the canyons searching for gold. They found some, not enough to convince them to remain and confront the isolation, often hostile environment and the Utes, who rightfully felt this to be their home. Not until the 1870s did miners come to stay. In their wake little camps grew in the high valleys and squeezed into narrow canyons. Nowhere else in Colorado were there more rugged mountains, a higher average elevation, nor a climate that one old Swede said was "three months of mighty late fall and nine months of winter." The San Juans proved eventually to be a mineral treasure chest. At the moment, however, the prospectors sought gold. Then they discovered silver deposits and the first rush was on. It got started just in time to be completely overcome by the Leadville excitement. At Leadville, investors almost fell over themselves to buy claims and stock in the hopes of becoming another millionaire like Leadville's own Horace Tabor. The San Juaners could only look from the sidelines and speculate how it might have been had fate been kinder. Fate was seldom kind, as these pioneers quickly discovered. From the mid-1870s on, the San Juaners wrestled with some major problems. And the fate of their district rode in the balance. The problems they faced were similar to those of other Colorado districts, compounded by their geographic isolation. Every mining district needed the best transportation system available, experienced investors combined with sound investment, and mineral reserves to develop. The San Juans offered the last in abundance. It was hoped the first two would appear. Railroads - much needed transportation link Nothing was more desired than railroad connections, the penultimate nineteenth century form of transportation. Colorado's own, the Denver & Rio Grande, resolved the issue with its mountain-hugging narrow gauge. As early as the mid-1870s, the D&RG dreamed of tapping this potentially lucrative market in southwestern Colorado. A national economic depression and then the Leadville silver excitement prevented immediate construction. Not until 1879-80 did survey crews start work.

Jan 2, 1988

By J. Roth

PROLOGUE Nowadays, where production costs and energy costs are increasing and at the same time requirements in fineness and purity of industrial mineral products are getting higher and higher, industry has to look for more efficient grinding systems and developments to produce these products more economically. Therefore lots of new developments in high energy jet mill pulverizing have been made. In the main, however, these developments involved more or less just the new principle of fluidized bed jet pulverizers but not the older spiral jet mill principle. In some cases, especially in the filler industry where laminar minerals are used and higher aspect ratios are required, the spiral jet mill principle has advantages in a better delamination of these minerals. To comminute minerals down to products with a d97 < 3 µm, the specific energy consumption increases up to 2,000 kWh/t – 3,000 kWh/t or even more, depending on the grindability of the mineral. So the production of these fine materials is quite an expensive task. But jet mill grinding is and will be the most favorable method to produce micro-products and in the near future nano-products, despite the high energy consumption.

Jan 1, 2000

By Tim Neil, O&apos

Large is the applicable adjective here. The largest hydraulic shovel in the world, the largest copper mine in the world, the largest copper producing company in the world. The O&K RH 300 hydraulic excavator has been put into service to move overburden and mine ore at the Chuquicamata open pit mine of the Chilean state copper mining company, Corporation Nacional de Corbre de Chile (Codelco). A large shovel: Equipped with a 26-m3 (34-yd&apos;) rock shovel, the RH 300 is able to fill a 170-t (187-st) truck in three passes with cycle times of 30 seconds. A large mine: At present, the Chuquicamata pit is 4 km (2.5 miles) long, 2 km (1.2 miles) wide, and 520 m (1700 ft) deep from rim to bottom bench. The current 450 kt/d (496,000 stpd) of material mined will increase to 600 kt/d (661,000 stpd) when the expanded production rate is reached in 1989. (Chuqui Expansion details, p. 20). A large mining company: Codelco&apos;s total output from its two open pit and three underground copper mines is more than 1.1 Mt/a (1.2 million stpy) of copper. This makes Codelco by far the largest copper producer in the world. It accounts for about 15% of the Western World&apos;s copper requirements. Chuquicamata is located in the hot and arid Atacama desert of northern Chile. The mine is located 240 km (150 miles) northeast of the port city of Antofagasta. Mine elevation is 2700 m (8850 ft). Chuquicamata&apos;s known reserves of oxide and sulfide ores amount to more than 450 Mt (496 million st) of contained copper. There are also reserves of more then 1.4 Mt (1.5 million st) of contained molybdenum. Originally, Chuquicamata was a rail pit. The shovels loaded rail cars hauled by locis on tracks along the benches. During the 1970s, the rail transport was replaced by truck haulage. Crushing and conveying rock waste in the pit is the latest step in the continuing evolution of more productive and economical methods of materials movement. In 1990, the in-pit crushing plant will be in operation. The waste will be mainly transported out of the pit on belt conveyors rather than trucks. The system will incorporate a 9.6-kt/h (10,600-stph) semi-portable crushing station, a 14-km (8.7-mile) conveyor using 1.8 m (6 ft) wide heavy duty belts, and a tripper-spreader to stack the waste dumps. Since Chuqui went into production in 1915, more than 2.5 Gt (2.8 billion st) of material has been excavated. This includes nearly 1.7 Gt (1.9 billion st) of ore from which some 16.4 Mt (18 million st) of copper has been recovered. The Chuquicamata porphyry type ore body is an altered and fractured intrusive granodiorite or quartz-monzonite porphyry that carries the mineralization. The action of ground water on primary sulfide minerals in geo¬logic time has created oxide ores and a zone of secondary enrich¬ment. The oxides occur above the sulfide zone and are also mixed with the upper parts of the latter. At Chuquicamata, the current grade of 1.5% copper is expected to decline to about 1% by 1995. To maintain metal production at cur¬rent levels, it will be necessary to increase ore production rates by about 50%, as mentioned, to 153

Jan 1, 1988

By R. M. Jacobs

Can your company afford to issue a check today for $100,000, $500,000, $2,000,000, or $22,000,000? This is what it might cost your company if it is on the losing end of a product liability suit. During the past 10 to 15 years, the number of product liability actions has grown from a handful per year level to a hundreds of thousands per year level. Settlements and awards in the tens and hundreds of thousands of dollars are not unusual in these days. The largest award that the authors haw heard about is a case involving a private airplane and the death of four men, which was awarded over $22,000,000. In the materials handling field, a fork lift truck, ordered with an overhead guard, was delivered without a guard because one was not available at the time. An accident with serious personal injury followed. Wouldn&apos;t it have been better to have waited until the guard was available before delivering the unit? Answer: a quarter of a million dollars better -- the cost of the settlement. Hoisting devices are also not without their liability precedents. In a 1960 case, an employee was injured when a load abruptly fell from a hoist. It was determined that the operator could not possibly have caused such a fall had the hoist been functioning properly. The case was compounded when the manufacturer of the hoist contended that the load had been improperly connected to the device, since the same hoist was used to remove the weight from the injured man without another malfunction.

Jan 1, 1973

By M. H. Pettibone

During the past decade, the size of grin- ding mills has steadily increased. Mills 11 m in diameter with 9 mW motors have been installed with even larger units on the drawing board. The rising costs of energy and labor have spurred interest in improving efficiency while reducing capital investment and operating labor. Autogenous and semiautogenous grinding have experienced renewed interest as efforts to reduce operating and capital costs have increased.

Jan 1, 1981

By Aydin Shaterpour Mamaghani, Bilgin. Nuh, Engin Dogan, Tayfun Erdogan

"Improved safety and more environmentally friendly operation are basic advantages of mechanical excavation over the drill and blast method. Raise Boring Machines (RBMs) are one of the types of these machines which have recently been increased use in Turkey. The excavated hole with RBM is more stable than other methods and has better air flow, making it ideal for ventilation shafts. This paper is a summary of the performance of a RBM in the Balya PB-Zn Mine in Turkey. Length and diameter of the ventilation shaft are 200 m and 2.4 m, respectively. The geological and geotechnical characteristics of the strata excavated in the mine are first given and later the validity of a model developed to predict the machine performance is discussed. It is believed that the results of this study and the model given to estimate the performance of the RBM will be useful guide for future applications. INTRODUCTION Raise boring technology was developed to meet the demands of the mining industry, but has also found numerous applications in tunneling or infrastructure projects for ventilation purposes. Raise boring machine uses a small diameter drill rod, around 230-350 mm to drill a pilot hole down to the required depth up to around 2000 m. Once the pilot hole has been drilled to the desired depth, a reamer of up to 9 m diameter is attached to the drill rod. The reamer is then pulled back up to the upper level, creating a round shape. Continues operation provides a faster advance rate than other methods. RBMs are suitable both in hard and soft rock. The flexibility in different angles and diameters is a great advantage compared to drill and blast excavation method. RBM creates a shaft with smooth walls which usually does not require lining. The hole is more stable than a drilled and blasted method and has better air flow, making it ideal for ventilation shafts. Raise boring is convenient method in competent rock; however several problems are faced in geological formations where geological discontinuities are dominant. Moreover, assembly and disassembly time may be long in some cases. The performance and operational parameters of the excavating machine should be predicted prior to starting the excavation operations in order to fulfill the economic requirements of the project. In the light of this fact, the main objective of this investigation is to summarize a case study on raise boring machine performance and suggest a new model based on laboratory test results. First, general description of the mine and project are provided. Then, the physical and mechanical characteristics of the samples taken from project area are discussed. In the third section, performance and operational parameters of RBM are investigated to understand the machine behavior in different rock characteristics and also to collect a useful database for further investigation. In the fourth section, a new model for performance estimation of RBM are recommended."

Jan 1, 2016

By J. Kretschmann

According to the model of product life cycles, the global coal mining industry is in the stagnation phase. The coal demand of the main consumer, China, has peaked in 2013 and is slowly declining. The Norwegian sovereign wealth fund, the world´s largest, has excluded coal-related companies for ethical reasons. Important players like the UN or the EU have already begun to describe pathways towards de-carbonization. Increasing competition between coal mining companies and the mining regions can be expected worldwide if companies want to keep their positions on the global and national coal markets. Companies will focus on the best deposits. European countries like France, Spain or Germany are only forerunners of this development - their centuries of coal production have been finished. The concept of Sustainable Development (SD) is fundamentally based on a model of progress where ecological, economic and social dimensions should be developed equally and positively. But without the idea of competition, the concept of SD is incomplete. Questions arise, such as: How can SD be realized on stagnating or declining markets without guarantees for companies “to live forever”? How can SD be a corporate goal in a phase of decline? How can declining mining regions sustainably progress into a better future? The German hard coal mining industry´s lifecycle has ended in 2018 after 60 years of stagnation and decline. As of 2019, all hard coal consumed in Germany will be imported, especially from Colombia, Russia and South Africa. What has been done in Germany to handle the coal decline in a sustainable way and the lessons learned from this process is described in this paper. It may be useful for mining regions who will face a similar future sooner or later. INTRODUCTION Principally, mining natural resources is a finite business that reaches its limits once the deposits mined are depleted, the resources can no longer be mined in an economically profitable way, or substitutes are pushing the mined products out of the market. An example for the latter is the increasing replacement of coal with natural gas and renewables in power generation in the USA. (Kok 2017) According to the model of the product lifecycle, the global mining hard coal mining industry has reached the stagnation phase. (Kretschmann 2000) Although the coal mining business is more a multi-regional than a global business the trend is obvious. The peak of coal use is behind us, especially because the coal demand of China is slowly decreasing since 2013. (Shell 2018) China´s government has announced investing $360 billion in renewable energy by 2020 and scrap plans to build 85 coal-fired power plants. In March 2018, Chinese authorities reported that the country was already exceeding official targets for energy efficiency, carbon intensity, and the share of clean energy sources. China’s energy regulator, the National Energy Administration, rolled out new measures to reduce the country’s dependence on coal. (Kejun and Woetzel 2017) Coal consumption in the US is facing a 16 % decline in five years from 800 to 670 million short tons between 2015 and 2019 and - according to the EIA – will not rise again. (EIA 2018) The decline is attributed to complex market dynamics from low gas prices because of the “shale gas revolution” (Kok 2017, p. 3) to federal environmental regulation like the Clean Power Plan. The United Nations´ UNEP Finance Initiative is cooperating with the Portfolio Decarbonization Coalition of institutional investors to implement decarbonization strategies across their portfolio. Amongst these investors is the New York State Common Retirement Fund, the third largest public pension plan in the USA. (UNEP 2017) The European Union has already begun to de-scribe pathways to decarbonization. (European Union 2018) The Norwegian sovereign wealth fund, the world´s largest, excluded coal-related companies for ethical reasons. The oil giants Total S.A. and Royal Dutch Shell, tradi

Jan 1, 2019

By Martin C. Jones

INTRODUCTION This paper outlines the methods used to drill and pregrout prior to the excavation of five Mine Shafts in the Coal Measures of the Eastern United States. One example is the use of cement pregrouting of four 240 meter deep shafts and the second is the use of chemical pregrouting of a 360 meter deep shaft. These two examples will be compared and contrasted, both at the investigation stage of each project, and during the drilling and pregrouting itself, to illustrate the different approaches taken and how these affected the outcome, both technically and economically. INVESTIGATION FOR 240 METER SHAFTS In the case of the four 240 meter shafts, site investigation was carried out prior to bid, and information was made available by the Client in the form of a report. This report was based on pressure testing of NQ cored boreholes at each shaft site. Pressure testing was repeated two or more times, at each test setting, using 345 or 690 kPa of water pressure in accordance with the procedure outlined by the U. S. Bureau of Reclamation. Flow readings were taken every minute over a period of ten minutes. Maximum computed permeabilities, for the strata which accepted water under test for the shafts, carried between 1.0 x 10-6 m/s and 3.0 x 10-6 m/s, and total calculated seepages varied between 170&apos; litres/minute to 3891 litres/minute. Although these figures did not indicate an excessive amount of seepage, the Client decided that pregrouting should be carried out, and chemical grouting was not discussed, even though the test permeabilities indicated the use of cement grout would be limited in this case.

Jan 1, 1979

By D. Parks, A. Miller, M. McNinch, R. Jacksha, H. Nickerson

Each year hundreds of mine workers are involved in machinery-related accidents. Many of these accidents involve inadequate or improper use of lockout/tagout (LOTO) procedures. To mitigate the occurrence of these accidents, new safety methods are needed to monitor access to hazardous areas around operating machinery, improve documentation/monitoring of maintenance that requires shutdown of the machinery, and prevent unexpected startup or movement during machine maintenance activities. The National Institute for Occupational Safety and Health (NIOSH) is currently researching the application of Internet of Things (IoT) technologies to provide intelligent machine monitoring as part of a comprehensive LOTO program. This paper introduces NIOSH’s implementation of an IoT-based intelligent machine monitoring system to improve safety during operation and maintenance at a concrete batch plant. INTRODUCTION Of the hundreds of machinery-related accidents occurring every year in the mining industry, incidents involving stationary machinery at surface mines continue to be amongst the most frequent [1]. A National Institute for Occupational Safety and Health (NIOSH) study showed that the majority of fatal accidents involving stationary machinery at surface mines occurred at sand and gravel (38%) and stone (26%) operations. Of these accidents, entanglement in conveyor components were the most common cause of fatal accidents (48%) [2]. The same study stated that one-third of these accidents involved improper lockout/tagout (LOTO) procedures as a contributing factor. The U.S. Mine Safety and Health Administration (MSHA) acknowledged this problem, stating in a recent request for information (RFI) [3]: “Since 2007, there have been 17 fatalities related to working near or around belt conveyors, of which 76 percent were related to miners becoming entangled in belt drives, belt rollers, and discharge points. Factors that contribute to entanglement hazards include inadequate or missing guards, inadequate or an insufficient number of crossovers in strategic locations, and/or inappropriate lock out/tag out procedures. Systems that can sense a miner's presence in hazardous locations; ensure that machine guards are properly secured in place; and/or ensure machines are properly locked out and tagged out during maintenance would reduce fatalities [3].” In response to this problem, NIOSH’s Spokane Mining Research Division (SMRD) is exploring the potential application of Internet of Things (IoT) technologies to provide cost-effective intelligent machine monitoring systems for improved worker safety [4, 5]. SMRD partnered with Central Pre-mix CRH Company (Central Pre-mix) to develop and install a proof-of-concept wireless IoT solution to monitor machinery and conveyors during operation and maintenance. The primary goals of the system were to provide real-time monitoring of access points and facilitate the planning and execution of LOTO procedures

Jan 1, 2019

By William A. Rhoades

INTRODUCTION Ever since miners were faced with the task of moving ore, some form of scraper has been in use. At first, men and beasts of burden supplied the power to move the scraper, and later, machines were developed for this purpose. In the early 1900s, a few mining properties used small pneumatic single-drum winches to pull loaded scrapers to a raise or ore pocket, and the empty scraper then was dragged back to the muck pile by a miner, as shown in Fig. 1. Just prior to 1920, an improvement was introduced, using two single-drum hoists. As illustrated by Fig. 2, the second hoist was used to return the empty scraper to the muck pile. However, this arrangement still re¬quired two men, one operating each hoist. The next developmental step was to eliminate the second man by locating the hoists side-by-side and using one man to control both hoists. As illustrated by Fig. 3, this involved the use of a tail rope over a sheave to pull the scraper back. The greatest progress in development and the great¬est increase in the use of slusher haulers occurred between 1920 and 1930. In 1921, the Sullivan Machinery Co. designed and built the first two-drum scraper oper¬ating on the principle illustrated by Fig. 4. It was powered by a 4.5-kW (6-hp) Turbinair(r) motor and would pull a 450-kg (1000-1b) load at 0.61 m/s (120 fpm). In 1922, this unit was shipped to the Verona Mining Co. of Caspian, MI, and it experienced immediate success in the Lake Superior iron ore district. Since the two-drum slusher was much less expensive and more efficient than hand mucking, the Lake Superior mines were saved from financial disaster when iron-ore prices fell 25% between 1923 and 1925. Immediately there¬after, a demand developed for slushers that would oper¬ate with electric power, which was considerably cheaper than compressed-air power. In 1923, the Sullivan Machinery Co. responded with the first electric-powered double-drum hoist. During subsequent years, design improvements in¬cluded separate tail-drum gearing to increase the tail¬drum speed, as welt as a number of safety features such as rope guides. One result of these improvements and their utilization by the Michigan iron mines was an in¬crease of 100% in the tons of ore per miner per day in those mines between 1924 and 1929. Since the two-drum slusher was capable only of straight-line mucking, it was not a practical machine for use in open stopes. In 1929, the Sullivan Machinery Co. introduced the first three-drum slusher. As illustrated by Fig. 5, two tail drums and one hauling drum were provided. A tail sheave could be placed at each side of the stope, and the ore then could be loaded and hauled to a central point from the entire width of the stope. During the 1930s, progressively larger slushers were demanded. By 1940, two- and three-drum units were available with motor power as high as 45 kW (60 hp), and slusher power continued to increase after 1940. Be¬tween 1951 and 1952, Joy Manufacturing Co. designed a 112-kW (150-hp) two-drum Blusher for the Climax Molydenum Co. Although there has been no demand for a slusher more powerful than this, 150- to 225-kW (200- to 300-hp) slushers are quite feasible at the pres¬ent time. During the last 30 years, many slusher improvements have been made to the operating life, operational safety, and ease of operation and maintenance. Increased tail-drum speeds have decreased overall scraping times. Rope guards, totally enclosed drums, and operator shields have reduced the hazards of injury due to wire¬rope breakage. Improvements in lubrication have made the slushers relatively maintenance-free, with long operating lives. The introduction of spring-actuated drag brakes prevented uncontrolled unreeling of dis¬engaged drums, allowing the development of practical remote-control slusher operation. Remote control now is available in a choice of all-air, all-electric, or air¬electric slushers. APPLICATIONS Quite simply, slushers are used to load and transport material (ore), generally over a short distance of from

Jan 1, 1982

By V. R. Bovino

In the early 80&apos;s, the cover of a major weekly magazine proclaimed the "Death of Mining." A few years ago, mining conventions, similar to this, around the country sported the theme, "The Survival of Mining." Today, the SME announces that "Mining is Alive." Being part of an industry that is simply alive is not very exciting. We can do better! Our challenge must be to flourish, blossom, maximize our potential and expand our horizons. The pace of rejuvenating this industry is still woefully inadequate. The new generation of mining industry leaders recognizes the urgent need for bold operational changes?changes in the way we deal with our employees? changes in the way we achieve productivity? and changes in the way we reward our employees for productivity.

Jan 1, 1991

By Vinton A. Garbesi

The construction involved in the Washington Metropolitan Area Transit Authority (WMATA), Contract No. lK0011 (K-1), encompassed some 2,621 meters of single track parallel tube rapid transit tunnels, 335 meters of cut-cover subway station and appurtenant ventilation structures at each end, and a fan shaft at approximately the mid point of the tunnels. The construction contract was awarded June 7, 1974 to a Joint Venture consisting of Intercounty Construction Corporation, Hyattsville, Maryland, and S $ M Constructors, Inc., Solon, Ohio. The former being responsible for performing the cut and cover construction, and the latter being charged with constructing the running tunnels and fan shaft at their mid point. (See Fig. 1) The problems of mining and supporting, the 183 meters of twin tunnels just east of Court House Square Station, by unique mixed face and soft ground mining methods is the main subject of this report, although a general review of the tunnels in their entirety, as well as the geology encountered in the excavations, is presented to give a better overall setting for the problems encountered. GEOLOGIC SETTING The tunnels for the K-1 contract are located in three general types of material; the first being fractured and metamorphosed ignious rock (quartz-hornblende-biotite gneiss), the transition zone between weathered and competent rock, and in ground consisting of the weathered

Jan 1, 1979

By C. L. Peng, F. F. Min, S. X. Song

"Using a parameter representing the degree of hydration of particles in a liquid called hydration index I, which we derived based on Einstein’s viscosity equation, we evaluated the degree of hydration of fine montmorillonite particles in different aqueous solutions by measuring the viscosities of the montmorillonite dispersions and plotting relative viscosity against volume fraction of dry montmorillonite particles in the dispersions. We investigated the effects on the hydration of montmorillonite in aqueous solutions of (1) the type and (2) the concentration of electrolytes in the solutions and (3) pH. For the same concentration of electrolytes, the hydration index I of montmorillonite was found to increase in the order of Na+ > K+ for monovalent cations and Mg2+ > Ca2+ for divalent cations, and to decrease with increasing valence of cations in the order of Na+ > Ca2+ > Al3+. For both Na+ and Ca2+, the hydration index I first increased with increasing concentration of electrolytes and then decreased after a certain concentration. The hydration index I increased with increasing pH. IntroductionClay minerals have the distinctive ability to adsorb water molecules and hydrated cations in aqueous solutions, resulting in hydration on their outer surfaces and in their interlayer spaces. Many investigators (Jurinak, 1963; Anderson and Tice, 1971; Costanzo et al., 1982; Israelachvili, 1992) had found evidence of ice-like structures of water on clay minerals.This phenomenon of hydration plays an important role in the dispersion and sedimentation of clay minerals in aqueous solutions. To understand clay hydration, numerous experimental and simulation studies have been carried out since 1933, including the recent ones of Hawkins and Egelstaff (1980), Skipper et al. (1995), Karaborni et al. (1996), Salles et al. (2013) and Morrow et al. (2013). Among the factors that can influence a clay mineral’s hydration characteristics are chemical composition, type and degree of isomorphous replacement in its structure, and number and nature of associated exchangeable cations."

Jan 1, 2015