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By E. F. Draskovich

In 1984 a high temperature heat recuperation system was installed in the pellet plant of the National Steel Pellet Company located in Keewatin, Minnesota. The system is similar to those of Cleveland Cliffs Empire and U.S. Steel's Minntac operations. It recovers hot process air from the cooler by induced flow, and directs it to an intermediate zone between the drying and preheat zones on the grate machine. This system recently underwent further modifications in April 1985, following initial operation in 1984. The M. A. Hanna Company, which manages the property, developed the design criteria and made the subsequent recommendations for modification through its research facility in Nashwauk, Minnesota.

Jan 1, 1986

By S. Klein, M. McLeod, K. Johnson

The East Bay Municipal Utility District (EBMUD) delivers water to the San Francisco Bay Area through an aqueduct system extending from the Sierra Nevada Mountains to the East Bay. This aqueduct system, the Mokelumne Aqueducts, are comprised of three 82-mile long steel pipelines. The portion of the aqueducts crossing the Sacramento-San Joaquin River Delta is recognized to be vulnerable to seismic and flooding hazards. Previous studies evaluated alternatives for mitigating these hazards and increasing the reliability of the aqueducts for the next 100 years. The preferred solution involves construction of a 16.5-mile tunnel across the Delta and re-routing the existing aqueducts through this tunnel

Dec 1, 2022

By H. T. Mulryan

Talc is used as an essential ingredient in a wide variety of plastics applications ranging from polyester body patch compounds through polypropylene automotive, appliance, and household furniture components to high performance parts made from liquid crystal engineering resins. The paper focuses on polyolefin applications; the three tier market for talc in polypropylene; the effects of various talcs in typical compounds; and trends in each market segment. Emphasis is given to emerging markets, examples of which are polypropylene compounds which mimic higher cost resins, and polyethylene films, customer requirements for talcs for these purposes are discussed.

Jan 1, 1993

By K. E. Yassin, A. Yehia, M. Amar

Phosphate ores are the source of many commodities, such as phosphorus element, P2O5 and fertilizers. Discarding a large percentage of fine phosphate particles produced as slimes during phosphate ore processing represents a severe environmental problem, besides making the beneficiation process uneconomical. The phosphate industry is interested in a process that is efficient, with high grade and high recovery; ensures economical feasibility, with low operating cost; and is environmentally sound, with low toxicity. Numerous investigations have been conducted to try to find better processing techniques and reagents. However, reagent requirements and recovery limitations may be so high that the end does not justify the means. Reagents of biological origin are of special interest because they offer specific interactions with minerals, reduced operating costs, environmental acceptability and flexibility in adaptation. Recently, there has been a growing interest in using microorganisms as flocculants for mineral fines and as flotation collectors. 

By Richard V. Good, John B. Harvey, Lloyd S. Jones

INTRODUCTION The term "Rapid Underground Excavation" is generally associated with high speed tunnel advance with large volumes of excavation, and indeed this is the type of work for which most of the recent innovations in methods and new machinery have been developed. However, the term applies as well to any underground excavation process that results in an earlier project completion than would be expected with conventional methods, and hopefully with a decrease in total unit excavation cost. Often significant progress has been made during the primary stages of an underground construction project and then an inordinate amount of time and effort has been expended on small units of "miscellaneous" excavation which has delayed the overall project completion and escallated overall unit costs. Construction at the Nevada Test Site of the Atomic Energy Commission for underground testing frequently requires significant amounts of so called "miscellaneous mining" such as short access drifts, cross cuts, alcoves, niches and concrete keyways. Many of the keyways must be excavated without disturbing the rock beyond the excavation lines and construction scheduling often dictates that much of the work must be accomplished without disturbing sensitive electronic equipment already installed. In order to cut down on lengthy and costly delays required for the tedious manual excavation of much of this miscellaneous mining, a market search was made for suitable mechanical excavation equip-

Jan 1, 1997

By Gordon A. Gross

Banded siliceous manganese-iron bearing sediments recognized as distinctive facies of Algoma type iron-formation constitute low grade resources of manganese in many countries. Manganiferous facies associated with oxide and carbonate facies of iron-formation have iron to manganese ratios ranging from 0.2 to 2 and commonly about one. Manganiferous facies up to 30 meters thick occurring separately or with other iron-formation facies are associated with cherts, carbonates, shales, turbidites, tuffs and lavas. Primary cherty manganiferous facies and their gondite metamorphic equivalents represent significant manganese resources and are protores for higher grade deposits derived by secondary enrichment processes.

Jan 1, 1982

By R. L. Pozzo

A previous investigation showed that corrosion currents estimated from polarization curves for the pyrrhotite-grinding media system under abrasion correlated well with corrosion currents estimated from marked ball wear test data by applying the Faraday's Law. Freshly abraded metal debris were magnetically attracted to pyrrhotite and lowered the rest potentials of the mineral particles, thereby affecting the corrosive wear. The investigation was extended to explore the interactions between a nonmagnetic sulfide mineral, pyrite, and abraded metal debris and their effects on the corrosive wear mechanism. The electrochemical behavior of a three-electrode system involving pyrrhotite, pyrite and grinding media was also investigated as a first step towards elucidating the nature of interactions that occur in the grinding of complex sulfide ores.

Jan 1, 1987

By Robert Cook, Valeria Zarate, Jason Hallowell

The long hole open stoping (LHOS) method is widely used in underground mining. While methods to predict stable stope geometries are well established, the ability to maintain a stable back often assumes effective ground support across the full stope span. The efficacy of the support strategy is dependent on rock jointing, quality, density, top cut width and height, and the type, amount, and orientations of bolts installed. However, it is becoming increasingly common for operators to assume narrow top cuts in service of wider stope spans with minimal bolting coverage. Failure to account for the required top cut drift size and support requirements can ultimately lead to raveling type instabilities along stope shoulders that result in back collapse. A new method has been developed to evaluate the minimum top cut dimension necessary to accommodate wider stope spans with various rock bolting configurations. Due to the economic impacts of top cut development and support, this is a critical consideration in the accurate costing and scheduling of a LHOS operation. Tables 1 lists the acronyms are used throughout this paper.

Feb 1, 2025

By D. Lee Petersen, Charles R. Nelson, Marvin Marshak

INTRODUCTION Construction is underway on a laboratory cavern 713 m below surface at the Soudan Mine, Tower-Soudan State Park, in northeastern Minnesota. The 13.9 in wide by 11.6 m high by 71.8 in long cavern will provide a laboratory space for basic research in physics, in which experiments can be conducted with greatly reduced interference from cosmic radiation. A first generation experiment, called the Soudan 1 detector, is currently operating in a converted drift 591 in below surface at the mine. The initial phase of the Soudan 2 detector will be an 1100-metric ton unit, which will occupy approximately a 19 m length of the cavern. Control and monitoring equipment will be in a prefabricated shop office enclosure erected in the cavern. The location and planned usage for the laboratory cavern present special excavation, lining, and outfitting requirements. Temperature and humidity control, a relatively clean dust-free environment, and a long service life are required. Low cost and risk to the owner were basic requirements due to the nature of the funding. The most common type of site selected to meet these two constraints is either an operational mine or a civil works facility such as a road tunnel. There are often serious problems for such laboratories because of ongoing operations such as blasting, hauling, etc. Most of these problems do not exist for the Soudan 2 laboratory because the mine is used as a historical site with regular tours only in the summer season. The laboratory owner, the University of Minnesota, and the park owner, Minnesota Department of Natural Resources, are both public agencies of the

Jan 1, 1985

By G. B. McClurg

China was nota factor in the supply of fluorspar to the United States until the early 1980's when it shipped in its first package of Metallurgical lump, that not only was higher grade than the Mexican Metallurgical spar but was also about $30.00 a ton cheaper landed at Burnside. Representatives of the Mexican Fluorspar Institute and several producers made trips to see the Chinese operations supplying their once reserved market place. China, an enigma to most Westerners suddenly became the new contender, with prices that were disgustingly low or so thought the other exporters. Of course China has been mining, producing, consuming and exporting from 400,000 to 500,000 tons per year of various grades of fluorspar but until the first partloads came to the U.S., very little attention was paid to their exports by American-continent producers or consumers.

Jan 1, 1986

By G. A. Kordosky

Solution mining followed by solvent extraction-electrowinning (SX-EW) is one possible way to economically extract copper from ore bodies which cannot otherwise be profitably exploited. Published costs for the unit processes of SX and EW are out of date especially in view of the newer reagents now available and the newer circuit configurations, This paper updates the costs for SX-EW in 1985 dollars and also discusses some of the trade-offs which must be made when designing an SX-W plant.

Jan 1, 1986

By Georges Verly

The estimation of local recoveries is an important issue in a selective mining operation. Two techniques, probability kriging and multigaussian kriging, are applied to estimate local recoveries at Jerritt Canyon. The pros and cons of each method are discussed in light of the results. Both methods provide simple and satisfactory solutions to the problem of estimating local recoveries. Consequently, they can be useful tools to work with in a selective mining operation.

Jan 1, 1984

By D. G. Hartley

The major copper loss at Mount Lyell is in the coarsest particles presented to flotation. An analysis of data collected from the five primary and six secondary ball mill circuits showed that grinding was limited by low breakage rates in secondary mills, possibly due to oversize balls. For 5 months, the make-up ball size for one secondary mill was reduced from 50 to 30 mm. Frequent steady-state tests indicated that overall average breakage rates could be increased by about 70% using smaller balls. A mathematical simulation of the whole circuit with increased breakage rates showed that the resultant finer grind was likely to improve copper recoveries by about 22.

Jan 1, 1981

By Gabriele Eccher, Michele Caponero, Paolo Cucino, Roberto D’Angelis

"This paper describes the optic fiber structural monitoring system implemented for Pavoncelli Bis tunnel. The paper highlights the optic fiber sensors customization capabilities, how they smoothly fit precast concrete lining processes and TBM operations, and how a lifelong service monitoring can be achieved. An overview of readings’ evolution during excavation concludes the paper.INTRODUCTIONPavoncelli Bis is a 10 km hydraulic tunnel designed to by-pass the existing Pavoncelli tunnel which experienced severe damages during the 1980 Irpino-Lucano earthquake, in south of Italy (Barla 2009). Pavoncelli Bis excavation work commenced in 1988-90, however, when excavation approached pk. 0+583 in 1992, water percolations became more and more consistent and resulted in work suspension. The tunnel was eventually sealed at pk. 0+383, leaving a flooded section between pk. 0.383 and pk. 0+583. Work resumed in 2012 where EPB-TBM excavation was adopted to cross the flooded section and to overcome complex hydro-geological conditions in various lito-types and, in particular, in the Varicolori Clay-shales area (Figure 1).Consequently, stress evolution monitoring is extremely important during construction and during the service life of tunnel lining in clay-shales and in faults areas. In particular, the paper focuses on the monitoring system proposed for the newly EPB-TBM excavated portion from pk 0+583 onwards where optic fiber sensing technology was chosen for its reading stability and reliability in presence of water and its ability to be connected in series and remotely interrogated at kilometers of distance. FBGS OPTICAL FIBER SENSOR TECHNOLOGYFiber Bragg Grating Sensors (FBGS) are gaining increasing attention in the field of experimental stress analysis. Basically, Fiber Optic Bragg Sensors are strain-measuring devices and therefore provide many of the advantages of the well-known metal foil strain gages (Kreuzer 2007).Bragg gratings are written into so called single-mode fibers. These fibers consist of a very small inner core of 4 to 9 µm diameter and an outer part (cladding) of pure glass (SiO2) of 125 µm diameter. The difference of refraction indexes between inner core and cladding causes the light to propagate only inside the small core."

Jan 1, 2016

By L. Martin, M. Raffaldi, M. Stepan, D. Benton

The Office of Mine Safety and Health Research, Spokane Mining Research Division, is continuing its high-energy, high-displacement testing of field-scale shotcrete panels. A test program was developed to determine the relationship between applied force, displacement and energy for both unreinforced and reinforced shotcrete panels. Reinforcement options consisted of synthetic macro-fibers, sprayed polyurea liners, chain-link mesh, welded-wire mesh and combinations of them. During testing, photogrammetry was used to measure the geometric changes of the panels, including volume changes and panel cracking. These measurements were correlated with the load and displacement data, allowing visual observation to be related to the applied force and displacement. The test results provide a comparison of the mechanical performance of the various panel types and can assist in interpreting the condition of installed surface support. Visual assessment of the loading cycle and strength capacity of shotcrete in underground excavations will improve mine safety by providing a means to better quantify the stability of installed shotcrete support.

Jan 1, 2016

By Michelle Mangione, John Kuyt, Zili Li, Michael Mooney

"Twin bored tunnels are commonly used for a variety of road and tunnel projects throughout the world.A major component of these twin tunnel projects is the construction of connecting cross passages that provide emergency access between tunnels and space for tunnel service equipment. Cross passages can present significant geotechnical risk and technical challenges to a project – support systems must be considered for redistributing loads around the mainline tunnel openings and supporting new loading resulting from excavation activities. Additionally, cross passages pose risks to construction schedule and cost because of their sequencing at the end of construction, so mitigation of schedule overruns can be critical. By observing field instrumentation data records from completed projects, a better understanding of the force development in each temporary structure can be achieved with indication of which structures are the most critical to support ground loads.This article discusses the data obtained during the Brisbane Airport Link construction project, a road tunnel located in Brisbane, Australia. Strain gauge instrumentation data from the precast segmental lining and propped opening steel sets is presented with relation to the construction sequence and local geology. Interpretations and conclusions based on the observed trends are proposed, with several key mechanisms affecting the loading and unloading identified.Brisbane Airport Link project overview. The Brisbane Airport Link project in Brisbane, Australia, connects central Brisbane to the airport located northeast of the downtown with more than 7 km (4 miles) of twin-bore road tunnels, two lanes each, with several caverns, interchanges and access ramps constructed along the alignment to connect to other key routes in the city. The project was executed under a public-private partnership (P3) scheme, funded and operated by the consortium BrisConnections. The main contractors were a joint venture of John Holland and Theiss, while the design was carried out by Arup and Parsons Brinckerhoff.Construction of the tunnels was conducted using a combination of 17 roadheaders and two 12.5-m (41-ft) double-shield Herrenknecht tunnel boring machines (TBM) (Harding & Francis, 2013). The TBMs were used in earth pressure balance- (EPB) type closed mode for the initial portion of their drive, starting at the northeast end of the alignment. Tunneling started in soft ground, weathered rock, and mixed face conditions initially, progressing to competent sedimentary rocks as the drive continued. Support was accomplished using a 12.1-m (39.8-ft) diameter steel fiber reinforced concrete (SFRC) segmental lining installed behind the TBMs in nine segments + one key arrangement. The innovative design of these segments is detailed in the paper by Harding and Francis (Harding & Francis, 2013). Ancillary roads and underground interchange caverns were constructed by sequential excavation techniques using roadheaders, accounting for nearly half of the total underground excavations."

Mar 1, 2017

By Emily Sarver, Cigdem Keles, Jonathan Gonzalez

The study re-examines respirable coal mine dust samples using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). It finds that SEM tends to overpredict the abundance of dust from rock strata and underpredict coal content, possibly due to coal-mineral microagglomerates (MAGs). The findings suggest that MAGs could be valuable in improving dust controls in mines.

Feb 10, 2022

By Charles G. Zink

Early anthracite "deep mining" methods, production, manpower. underground transportation, labor, safety and reserves are reviewed and compared to the present and to future requirements which must be met in order to economically win the fourteen million tons of untapped reserves and to keep the product competitive in the market place.

Jan 1, 1971

By Robert A. Bauer

Investigations of bedrock within subsided areas over abandoned coal mines reveal) very little disturbance of the bedrock. In areas that have surface subsidence of .3 to 1 m (1.0 to 3.25 ft), examination of cores from exploration drilling and investigations of the boreholes by means of closed circuit television have shown that fractures are spaced at least .9 to 3.6 m (3 to 12 ft) apart and are located within a zone 6 to 15 m (20 to 50 ft) above the collapsed area in coal mines 42.6 to 112.7 m (140 to 370 ft) deep. The dip of the fractures ranges from 25 to 60 degrees, cutting across nearly horizontal sedimentary bedding planes. Typical core recovery is 80 to 95 percent within the subsided areas and 100 percent outside the subsided areas.

Jan 1, 1984

By Henrique Garcia Pereira

In a large scale mining project, the global feasibility study must take into account the interdependence of three sub systems: the geological subsystem, represented by the orebody model; the technological subsystem, consisting .of mining and ore dressing models; and the economic subsystem, including the selling price of final product, production costs and investments. In cases where the ore is heterogeneous, the interdependence between geological and technological subsystems may be assessed by a Data Analysis technique such as Correspondence Analysis (CA). This technique was applied by David and Dagbert (1975) on examples of data from geochemistry and geology. In the approach used in this paper, CA is used to create the basic framework for defining different types of ore. The final definitions of ore types take into account the mi¬ning method and the results of applying beneficiation processes to the ore.

Jan 1, 1982