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By J. E. Miller

The development of a new means of measuring the relative abrasivity of a slurry came about by necessity in 1967 during a full scale loop test of a 560 H.P. reciprocating pump handling magnetite slurry. In order to evaluate the life of expendable fluid end parts, the question of the amount of attrition in a re-circulated slurry had to be considered. An expected reduction in abrasivity as a result of this attrition would certainly give erroneous data on a parts life test. There- fore, some means of measuring such change in abrasivity became imperative. Several test methods were investigated1 but it was felt that these did not fully represent the wear due to back and forth rubbing action associated with a reciprocating pump. A "rubbing block" device used some years ago to determine the quality of hard facing materials was recalled, along with its shortcomings, in that an attempt was made to suspend a small percentage of abrasive particles in a colloidal viscous "mud". Erratic results were attributed to the fact that it was difficult to maintain a consistent slurry concentration under the metal wear block and the reciprocating speed was not great enough to maintain good agitation.

Jan 1, 1973

By Richard Giffen, Martha Gross, Luca Pellegrini, Pa Ousman Njie

The Hampton Roads Bridge-Tunnel (HRBT) Expansion project in Virginia includes parallel 1.5- mile (2.4 km) tunnels constructed using a tunnel boring machine (TBM). The TBM launching and receiving shafts were excavated within the footprint of two reclaimed islands abutting the navigation channel for the Port of Virginia. The shaft excavations—a circular tri-cell shaft at South Island, and a circular-rectangular twin-cell shaft at North Island—were supported by slurry walls up to 190 feet (58 meters) below the island surfaces. This paper describes specic design considerations for these shafts, as well as construction and uality-oversight aspects of their excavation and construction.

Jun 23, 2024

By A. E. Kurie

The Great Salt Lake occupies about 1000 square miles whereas its predecessor, Lake Bonneville occupied 20,000 square miles and its shoreline reached 1000 feet above the present lake level. The sediments of Lake Bonneville range from peripheral gravel and sand deposits to central basin calcareous clays and silts, gypsum sands, and saline precipitates. The drilling and engineering tests conducted by the Utah State Department of Highways for many highway structure sites and the construction of Federal Interstate freeway provided engineering and hydrologic properties of Lake Bonneville sediments. Ground water and surface brine exploitation have contributed hydrologic and chemical data; the geologic and mineralogical data are scientific research contributions.

Jan 1, 1967

By Matthew Burdick, Andrew Rule, Erica Bailey

The Second Narrows Water Supply Tunnel, Burrard Inlet Crossing project for the Greater Vancouver Water District entails deep shaft construction, subway sized pressurized face tunneling through highly variable ground conditions, installation of three permanent steel water mains and construction of elaborate valve chambers adjacent to either shaft. The paper discusses key elements of the planning and implementation of 6.69 m Ø slurry mixshield tunnel boring machine (TBM) assembly in a small diameter deep shaft including incorporation of a fully pressurized launch lock, preparations for saturation diving, surface support infrastructure and initial mining sequence.

Jun 13, 2021

By J. R. Schafler, J. L. Brinkman

"The US coal mining industry has suffered a recent decline in profits caused by a combination of decline in commodity demand and more restrictive government regulation, forcing coal mining companies to cease production in numerous mines. A 40% decrease in the total number of coal mines occurred from 1994 to 2000. The number of mines remained relatively constant until 2008 when a change of government sparked a series of new environmental regulations which have contributed to another 15% decrease from 2008 to 2016. In contrast, production has only decreased by 3%, increasing from 1994 to 2008, and then decreasing since 2008. However, this value is skewed by large increases in sub-bituminous coal production and decreases in other coal ranks. Several aspects assist in executive decisions on mine longevity and economic worth. Studies of open source mine data collected by mandated government surveys coupled with commodity history can be used to find relationships between mine closures and these elements, which include statistics on production tonnage, seam height, coal rank, etc. This paper looks at coal mining trends since 1994 by comparing mine, market, and regulation factors that may influence mine closure. INTRODUCTION The US coal mining industry is currently experiencing a decline in both demand and commodity price while facing implementation of more stringent air and water pollution regulations. Company profits have decreased significantly, forcing several major companies to declare bankruptcy. The industry was required to adapt to survive. Many of these companies have adjusted by abandoning mines; the last two decades have seen a drastic decrease in the number of mines. To discover the primary causes of this downturn, three major aspects must be studied: properties of abandoned mines, commodity history, and regulatory impact. TRENDS SINCE 1994 Each year, US coal mines are required to submit data on a wide variety of categories to the Mine Safety and Health Administration (MSHA) and the US Energy Information Administration (EIA). This data includes administrative records, production values, and information regarding the attributes of the mined material and the mine itself. Each year since 1996, EIA has released a report summarizing the data from two years prior. Additionally, MSHA maintains a database containing a collection of all the most current data. These resources are the primary sources for the following figures."

Jan 1, 2017

By Ryan Ward

The Missouri River Intake Screen Structure and Tunnel (MRISST) is one phase of the Red River Valley Water Supply Project (RRVWSP), a vital piece of infrastructure in the state of North Dakota to transport water to drought-laden communities in the eastern half of the state. The scope of work consists of constructing a cofferdam in the Missouri River, mining a 1,600-foot by 74-inch tunnel from a secant pile shaft near the riverbank into a cofferdam, and erecting a 40-foot Y-shaped vertical pipe structure in the cofferdam to support the intake screens. Construction personnel worked in the river through the North Dakota winter to construct the cofferdam and contended with high hydrostatic pressures and raveling sands, gravels, cobbles and boulders while mining the tunnel. Diligent planning and meticulous execution were essential to overcoming the challenges encountered below the Missouri River.

Jun 13, 2023

By Paul K. Sims

The Central City district is one of several adjacent mining areas in the Front Range, Colorado, that contain precious metal-bearing sulfide veins of Laramide (Late Cretaceous and early Tertiary) age. The districts are in the Front Range segment of the Colorado mineral belt, and are characterized by porphyritic igneous rocks of intermediate composition that have intruded Precambrian crystalline rocks in the core of the Front Range. The veins and minor stockworks that constitute the ore deposits in the district were formed largely as fracture fillings. The veins range from simple fissures to complex, branching lodes, and commonly range from less than 0.5 to about 1 m in width. The principal values are in gold and silver. The common metallic minerals are pyrite, sphalerite, chalcopyrite, tennantite, and galena; minor minerals are enargite, pitchblende, and gold tellurides. Quartz, cryptocrystalline silica, carbonates, fluorite, and barite compose the gangue. The ore deposits have a well-defined concentric zonal arrangement. A core of pyrite veins (central zone) is surrounded by a peripheral zone of galena-sphalerite vein with gold and silver. An intermediate zone contains transitional veins that have minerals characteristic of both the central and peripheral zones. The minerals were deposited in three stages during a single period of mineralization: uranium; pyrite; base metals, gold and silver. The wall rocks were altered primarily during pyrite-stage mineralization. Sericite envelopes developed adjacent to fractures, and were succeeded outward by zones of argillized rock. The valuable ore minerals were deposited in ore shoots localized by several types of structural controls, principally vein intersections, the physical nature and structure of the wall rocks, and irregularities along the fractures themselves. During supergene alteration, gold was concentrated in the upper, oxidized parts of the veins, commonly to depths of 50 m. The precious metal-bearing sulfide ore deposits are closely associated in space and time with the Laramide porphyritic igneous rocks and are believed to have been derived from hydrothermal fluids related to the magmatic activity. The ore deposits have mesothermal aspects and apparently formed in the temperature range 200°-320°C.

Jan 1, 2013

By C. L. Karr

Researchers at the University of Alabama are investigating artificial intelligence based computer models of mineral processing systems. Two approaches have been found to be particularly effective in developing data-driven computer models. The first approach employs neural networks which are computational paradigms based on the mechanics of the human brain. They are able to extract the basic relationships between input and output variables from large data sets. The second approach combines fuzzy mathematics with genetic algorithms to produce an adaptive modeling system. Fuzzy mathematics provide computers with the capability of manipulating abstract concepts like those which humans use so effectively in decision making. Genetic algorithms are search algorithms that mimic evolutionary processes apparent in nature. Together, these two techniques can be used to produce an effective modeling system. In this paper, the two approaches to modeling are compared and contrasted with respect to accuracy and computational time while used to model three mineral processing systems: (1) a grinding circuit, (2) a hydrocyclone separator, and (3) a flotation circuit.

Jan 1, 1997

By Bruce E. Kester

The concurrent observation of the phenomena of alkali-aggregate reaction and development of efficient dust collection systems on rotary kilns made mandatory the process modifications to produce low alkali cements. Such low alkali cements as were available prior to these recent changes were either the rare result of low alkali raw materials, the loss of alkalies with dust loss from the kiln stack, or in some instances by the use of CaC12 in the kiln feed to increase volitalization of the alkalies and their subsequent loss or discard with the normal dust emission from the kiln. The relative slowly soluble nature of natural occurring alkali minerals in cement raw materials as compared to the very soluble nature of the alkali salts as present in cement kiln reaction products, either in clinker or in dust emission led to the development of the water leaching system. Two distinctly different problems of leaching are created by the two major systems of portland cement production, the wet and dry processes. The wet process is characterized by moderate dust loads and concentration of soluble forms of alkali in the dust. Further the return of the leached dust slurry does not materially change the characteristics of kiln feed on reintroduction and subsequently does not materially influence kiln operation. The dry process differs in high levels of dust emission and the presence in the collected dust of large amounts of unreacted kiln feed with its sparingly soluble alkali minerals. In the dry process reintroduction of leached dust slurry changes the dry process to what may be classed as a damp process. This change results in some decrease in kiln capacity and creates conditions of operation which are uncommon to either the wet or dry process.

Jan 1, 1963

By C. Abbruzzese, L. Piga, P. Fornari, S. Ubaldini, R. Massidda

The effects of certain variables on the extraction of gold by thioureation have been investigated on a quartzose gold-bearing ore using a statistical multifactorial strategy. The factors taken into consideration were milling time (which corresponds to a given grain size), oxidant concentration, thiourea concentration and liquid/solid ratio. The influence of these four variables was ascertained first by a full factorial design at two levels for each variable (16 runs). This permitted the estimation of first-order effects of the factors affecting the process. Then 9 runs were added whose levels were both in the centre of and outside the axes of the previous plan thus originating a central composite design. This permitted estimation both of second-order effects of the factors involved and of parameters of a second-order polynomial model. The results show that extraction of gold depends only on milling time and oxidant concentration, at least in the experimental range considered. The equation fitting experimental data, as calculated by the least squares method, allows a response surface to be drawn. Due to the low gold grade of the ore (6 ppm) statistical analysis could lead to contradictory results, hence strict observance of Gy's rules for sampling and very accurate and precise chemical analyses were required.

Jan 1, 1995

By Leonard B. Rothfeld

For many years, pulverized coal (PC) boilers in utility power plants have been the dominant market for domestic coal. Today, two new coal utilization technologies challenge the PC boiler's dominance. Atmospheric fluidized bed combustion (AFBC) and "coal gasification/combined cycle" (GCC) stand on the verge of commercial demonstration in the utility environment at a scale of 100 MW. Developed over the past decade, these technologies respond to the demands for cleaner ways to burn coal and for more flexibility in fuel supply. In the near term, these are the "clean coal" technologies most likely to have a significant impact, because they are ready for commercial application. As for environmental acceptability, consider that just a few years ago one of the environmental slogans was "no coal in California." Indeed, the only large quantities of coal above ground in California at that time were in transit on the way to Asia. Today, thanks to new technology, we can point to two operational coal-burning plants in California and one in the works: * Cool Water GCC demonstration plant (100 MW) * California Portland Cement AFBC commercial cogeneration, near Riverside (190 000 lb/hr steam) * Energy Factors AFBC commercial cogeneration at Stockton, to be operational 1988 (44 MW)

Jan 1, 1987

By Ehsan Alavi, Eren Kusdogan

The City of Toronto’s Coxwell Bypass Tunnel is currently being constructed by North Tunnel Constructors ULC, a joint venture of Jay Dee Canada, C&M McNally Tunnel Constructors and Michels Canada. This project includes construction of approximately 10.5 km of 6.3 meter finished diameter rock tunnel, five 20 meter diameter storage shafts and eleven tunnel connection drop shafts, along with associated deaeration and adit tunnels. This paper describes progress on the project to date and reviews the risk mitigation measures utilized on the project to move the project forward through tough geological conditions during shaft excavation and tunneling phase of the project.

Jun 13, 2023

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 A. Hammons

Automated temporary roof support (ATRS) systems have been incorporated into roof bolters since the 1970's. During roof bolting, many injuries have occurred from large pieces of draw rock falling inby the ATRS beam and tipping back into the operator's area. Other injuries have occurred due to smaller, sharp rocks falling onto the operator's hand and arm during initiation of roof bolt drilling. These injuries are attributed to weak immediate roof, sometimes called roof skin failure. Even though ATRS systems support the roof and provide a measure of protection against roof skin failure, additional hazards sometimes do exist immediately inby and outby the supported roof. Design innovations such as the ATRS mounted rocker pad deflector systems have been designed to improve the roof bolter operator safety. This paper will inform the reader of the hazards, machine evolution through different design solutions, and the current state of the art in preventing roof skin failure injuries when roof bolting.

Jan 1, 2009

By William A. Wallace

Common mineral resources (sand, gravel, crushed stone, etc.), which are so necessary for the construction of metropolitan areas, are rapidly being depleted or otherwise rendered unavailable in the very areas that need them most. However, the problem of planning for these resources involves a number of independent and dependent variables that must first be defined and related. Finally, a dollar value must be assigned where possible. Complex interrelationships between the variables and their dependence on outside factors has made mathematical "solution" of the problem of planning for non-renewable mineral resources difficult at the present time. Therefore, the use of computer simulation is suggested as a means by which this complex problem can be investigated. The purpose of this paper is to report on a continuing research program whose objectives are: (1) to delineate the factors involved in planning for the utilization of common mineral resources in urban-suburban environs; (2) to construct a planning model for these materials amenable to computer analysis, (3) evaluate the model by using test cases, and (4) perform a sensitivity analysis to determine the initial parameters in future planning for these materials.

Jan 1, 1968

By Edward C. Mabbs

U.S. industry must increase its productivity or lose its competitive position in the rapidly expanding and inter-dependent world markets. Recent improvements in material handling techniques and equipment, coordinated with production processes, provide one of the greatest opportunities to increase productivity. Successful managers must learn how to take advantage of these material handling opportunities to gain competitive position.

Jan 1, 1973

By Taeyong Lee, Cole Bales, Matt Fowler, John Horne

Mitchell Point Tunnel near Hood River, Oregon is one of the more unique segments of the Historic Columbia River Highway and State Trail being constructed through the Columbia River Gorge. This 650-foot bike/pedestrian tunnel set to open in 2024 is being delivered by FHWA in partnership with Oregon DOT, Oregon State Parks, and the U.S. Forest Service. Primarily driven using drill & blast excavation methods through basalt, the shotcrete and dowel-supported tunnel features masonry portals and ve window adits that provide illumination and views of the river similar to the original highway tunnel of many vistas built in 1915 that was removed in 1966 to make way for Interstate 84. This paper summarizes the planning, design, and construction.

Jun 23, 2024

By Daniel McNamee, Wern-ping N. Chen

The Amtrak East River Tunnels include four tunnels, Line 1 to Line 4, which extend from New York Penn Station in Manhattan, under the East River to Sunnyside Yard in Long Island City. Since fall 2015, Amtrak has initiated a program to repair and reconstruct the century-old tunnels, including structural repairs of all the tunnels and reconstruction of the Line 1 and Line 2 tunnels. The reconstruction includes bench wall demolition and replacing and installing the following elements in the tunnels: direct fixation track, traction power, signal, communication, and tunnel fire/life/safety components. This paper provides design and site investigation challenges and knowledge gained from this program.

Dec 1, 2022

By I. Ward, E. Milosavljevic, M. Botz

"The silver nitrate titration method is a rapid and acceptably accurate means of analyzing for cyanide in leach solutions that contain primarily free cyanide. However, in leach solutions containing elevated levels of copper, the titrimetric method overestimates the concentration of free cyanide and underestimates the concentration of weak and dissociable (WAD) cyanide. The authors have developed a modified potentiometric (MP) titration method for determining WAD cyanide that overcomes issues associated with high copper levels in solution. The new MP-WAD method involves addition of a chemical ligand to the sample prior to silver nitrate titration to release cyanide bound to copper. Once released from copper, cyanide in solution is no longer affected by the presence of copper, and titration results are quantitative rather than empirical. In multiple laboratory trials with synthetic solutions and complex actual leach solutions, analytical results obtained with the new MP-WAD method were found to be within about ±5% of analyses obtained with the USEPA OIA-1677 WAD cyanide analytical method.IntroductionThe silver nitrate titration method is widely used to estimate the concentration of cyanide in leach solution for purposes of cyanidation process control. Cyanide determined by silver nitrate titration is commonly referred to as “free” cyanide, but frequently should be referred to as “titratable” cyanide. By definition, free cyanide is the sum of the concentrations of aqueous hydrogen cyanide HCN(aq) and the cyanide anion CN- (ASTM, 2010). Titration will only yield a reasonably accurate measurement of free cyanide when metal-cyanide complex concentrations (e.g., cadmium, copper, mercury, nickel, silver and zinc) in solution are low. In other words, titration will only yield a reasonably accurate measurement of free cyanide if the solution primarily contains free cyanide."

Jan 1, 2015

By M. Y. Fisekci

Subsidence measurement methods, applied over the thick and steep seam mining in the Rocky Mountains Region of Western Canada are described. The studies to date indicate that two new subsidence monitoring techniques appear to be the most suited methods for our conditions. The computerized telemetry and aerial photogrammetry systems are being tested for the reliability of the systems during the winter months within the network of laser surveying over the workings of the new hydraulic mine. The site particulars and the mining method of the concerned area have been described briefly. The observation over the old hydraulic mine indicate that panels adjacent to each other do not obey identical subsidence phenomenon.

Jan 1, 1982