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By M. L. Tucker, William H. Langer

Many countries, provinces, territories and states in the European Union, Australia, Canada, the United States and elsewhere have begun implementing sustainability programs. Most of those programs, however, stop short of sustainable management of aggregate resources. Sustainable practices do not always have to be conducted under the title of sustainability. This case study describes how Lafarge implemented the principles of sustainability even though there was an absence of existing local government policies or procedures addressing sustainable resource management. Jefferson County is one of three counties in the six-county Denver, CO, region that has potentially available sources of crushed stone. Crushed stone comprises 30percent of the aggregate produced in the area. And it plays a major role in regional aggregate resource needs. Jefferson County is home to four of the five crushed stone operations in the Denver region. Lafarge operates one of those four quarries.

Jan 1, 2004

By M. A. Weaver

This paper will investigate the historic and present state of the bituminous coal industry within the Commonwealth of Pennsylvania, with special emphasis on surface mining operations. It will address pertinent parameters such as production, markets, quality, number and size of operations, price, and productivity from a statistical viewpoint. In addition, relevant statistical parameters of select areas of the Appalachian Coal Region will also be presented and discussed.

Jan 1, 1989

By John A. Herbst, Per-Olaf Samskog, Jan Bjorkman, Yi Chang Lo

The study described here is concerned with the development of a model for the simulation and optimization of a rod milllpebble mill circuit. A series of laboratory tests was conducted to investigate the effect of critical operating variables. The pebble mill model structure used was a population balance type which accounta for impact breakage and fines production from pebble wear. Model parameterization and verification were performed using data obtained in batch tests and in a plant test campaign. The model developed was found to provide accurate predictions of plant-scale grinding. The prediction errors are less than 21 for the product size and 31 for the mill power required to achieve that product with a mill volume scale-up of 14,000 to 1. These results indicate that accurate extrapolations from laboratory batch data to plant scale performance are poaaible using the population balance model and scale-up prediction procedures for pebble mill circuits as well as ball mills. Preliminary indications are that the new model developed here will provide vital input for pebble mill optimization and process control as well as pebble mill design.

Jan 1, 1990

By Paul J. A. Lever

The mine environment is dynamic and operating conditions change continually and are difficult to predict. New equipment, variable geological conditions, modified layouts, and different equipment operators make monitoring and control system difficult to apply without continual software maintenance. The paper reports on algorithms that were developed, encoded with Knowledge Craft Tools, and tested on underground coal mine data to adapt to the dynamic environment. The system receives data from sensors in near real time and then identifies patterns in the data. Using a set of mode features the data is automatically checked to determine the present operating mode. When the operating mode changes from the previous shifts, the system automatically learns the new mode characteristics and uses that mode context for further data analysis. The concepts presented in this paper are applicable to a wide variety of mining scenarios, not just underground coal mining.

Jan 1, 1992

By Paul C. Schmall, Arthur B. Corwin, Hugh S. Lacy, Derek Maishman

For reasons of hydraulic design and constructability, water supply tunnel systems are often located relatively deep, in competent rock. Where the rock lies below a thick cover of water bearing soils, artificial ground freezing offers a low risk, cost-effective method of constructing access shafts. Several examples, in Kansas City, MO and in Brooklyn and Queens, NY, illustrate the use of freezing to provide structural support and ground water exclusion. In the case histories presented, the shafts range from 6m to 12m (20 to 40 ft) in diameter and soils vary from clays to boulder beds with depths in excess of 73m (240 ft) to competent bedrock. Where tunnels for infrastructure are designed to be driven in rock, vertical access may encounter a considerable thickness of overburden soils with groundwater. In such cases, shaft sinking problems are analogous to those confronted by mining engineers over 100 years ago. At that time, newly developed refrigeration machines were set to freeze the ground water and stabilize running sands. Although modern technology has refined our efforts, the basic features of the ground freezing to be described here are the same as those used in the last century. Vertical holes drilled on a circle surrounding the shaft site are equipped with leak-free steelpipes through which a refrigerated brine is circulated. In this manner, a frozen cylinder, seated in rock, is formed when the earth freezes between adjacent pipes. Shaft excavations take place inside a self-supporting, ground-water excluding structure. For mines, no better method of sinking production shafts through deepwater-bearing ground has yet been established. Indeed, major deposits of coal, potash, and salt would have remained inaccessible to this day were it not for the continued use of artificial ground freezing. If mine shaft freezing became relatively commonplace, early applications to civil engineering were few. Mussche and Waddington (1946) mention only five projects between 1892 and 1935; three of these relate to subway or vehicular tunnels in Paris, Antwerp, and (the most extensive) at five locations of the Moscow Metropolitan Railway development. In the United States, the method was used to spectacular effect in 1936, freezing about 3,000 cubic yards of silt to stop a slide

Jan 1, 1999

By Syd S. Peng

According to accident statistics (l, 2), roof fall accidents occur quite frequently at the intersections of underground? openings and account for up to 30% of the roof fall fatalities. But this figure will certainly go up considerably if roof falls not associated with any fatal accident are included in the analysis. Unfortunately, nonfatal roof falls are seldom documented. In the underground coal mines, there are two types of entry intersections. One is the three-way (V type) and the other is the four-way (T type) intersections. A three-way intersection occurs whenever the mainline track haulageway turns at an angle into a section haulageway. The four-way intersections by far the most common type in the U.S. under-ground coal mines are formed by the intersections of two entries which are oriented perpendicular to each other or by the intersections of entries and crosscuts. However, crosscuts are frequently driven at an angle to the entry to facilitate machine movements. The four-way intersections formed by this method of crosscut development are angled. At the intersection of two underground openings, the diagonal roof span is wider than the width of each individual opening. This is one of the major reasons why roof falls occur more likely at the intersections than in the entry between pillars. Consequently, special intersection support plans are usually employed (Figs. 1 and 2) for intersections. The most popular practices are to decrease roof bolt spacing 1 ft. less than or to increase roof bolt length 1 to 2 ft. longer than those employed in the entry between pillars (3). The increase in bolt length or decrease in bolt spacing can be applied to all of the bolts in the intersection or employed only for the strategically located bolts depending on the individual mine practices. These rather generalized practices seems to be adequate for some areas but in many cases inadequate for others. Occasionally, the neighboring two lines of chain pillars are staggered such that the crosscuts in one row of chain pillars face the centers of the chain pillars in the neigh-boring rows. This layout forms T-type three-way intersections which are also inadequate for most weak roofs (3, 4). A study was therefore initiated to develop special techniques for intersection supports. The first phase of the study was the analysis of the stress fields for the underground entry intersections. A three-dimensional stress analysis was necessary for this purpose. Unfortunately, the three-dimensional problems of complicated boundary conditions are beyond the existing analytical methods. The three-dimensional finite element method (FEM) was therefore employed in this study. In the analysis, square pillars of 40 feet wide and an entry height of 8 feet were assumed while entry widths varied at 14, 20 and 26 feet. This model was selected to simulate the mine where roof falls data were collected. The second phase of the study was the collection of field data. The sizes of the roof falls including heights, lengths and widths were collected and analyzed. In the third phase study, the results of the first and second phases were compared and discussed. The analysis of field data revealed an arching zone within which roof falls occurred. The arching zone above an entry obtained empirically was compared with the calculated stress contours. Assuming that the bolts must be anchored in the rock strata outside the arching zone, the preferable systems of bolting were proposed. Also the amount of pretension required to inhibit sliding between layers was discussed.

Jan 1, 1978

By R. C. Ford, W. L. Niccoli, J. B. Finley

All mining operations are superimposed on natural hydrologic systems. As a result, mining operations are influenced by natural hydrologic processes and require water management systems to successfully conduct mining activities. Managing water and mining-related solutions is a critical task at all stages of the mine life because of the time-dependent nature of natural and mining-related flows. Effective operation of the mining water management system requires a “systems” approach that integrates the time-dependent effects of all water and mine solution handling components. This paper discusses the concept and application of dynamic systems modeling to address the time dependent nature of mining water management systems.

Jan 1, 2002

By Robert M. Valentine, Randall L. Lentell

Interpretive geotechnical investigations were performed for the construction of approximately 15,250 m (50,000 ft) of wastewater interceptor tunnels in Austin, Texas. Subsurface materials consist of claystone (or clay shale), siltstone, altered volcanic tuffs, chalk and limestone. Special conditions include multiple crossings of Onion Creek with cover ranging from about 1/2 to 3 m (2 to 10 ft.), and the potential for mixed-face conditions consisting of water-bearing gravels overlying clay shale or siltstone. The methods and results of the geotechnical investigations are discussed and the inferred construction conditions are compared to those encountered during tunneling. A suggested format is presented for interpretive geotechnical reports for underground construction projects.

Jan 1, 1985

By Levent Ozdemir, Gerald Dollinger

An extensive series of linear and rotary cutting tests were run in soft and medium strength rocks at the Earth Mechanics Institute of the Colorado School of Mines to investigate the possibility of very high speed mechanical excavation for tunnel, raise, and shaft boring. The results of these tests demonstrate that cutter penetrations of 38.1 mm (1.5 inch) and cut spacings up to 228.6 mm (9 inch) are possible in such rock without exceeding the bearing capabilities of the cutters. It was also demonstrated in vertical boring tests that continuous excavation rates up to 38.1 m/hr (125 ft/hr) can be achieved with state-of-the-art technology provided sufficient thrust and torque is available. A predictor model for soft rocks was also developed using the test data. Analysis of this model shows that the errors between the predicted and observed cutter normal loads appear to be independent of cutter diameter, tip width, cut spacing, and depth of penetration. This suggests that the structure of the model is correct with respect to these variables. An analysis of the coefficients in the model was also made and a correlation found between the principal coefficient and Unconfined Compressive Strength. The second coefficient in the model was found to be similar in magnitude to rock properties such as Brazilian Tensile Strength, Shear Strength and Point Load Index.

Jan 1, 1989

By Chris Joyce, Peter Ryan

Investigation of the occurrence and significance of acid drainage from mine sites in Australia has received a degree of attention in recent years. For contemporary and future projects, particularly those in hi1;1her rainfall areas, the focus on prediction and resolution of acid drainage issues is. likely to increase. This paper describes the preventative and remedial measures adopted at three metalliferous mines in northern Australia at which acid drainage was identified as a key issue with respect to project environmental management and rehabilitation. The thre case studies respectively comprise an active, ·1 recently decommissioned and an abandoned operatiou which was rehabilitated in the mid '80s.

Jan 1, 1991

By G. B. Misra

Attempts have been made during the last three decades to establish a correlation between respirable dust dosage and the degree of progression of pneumoconiosis or silicosis amongst mine workers. Fair correlation has been possible only after the Johannesburg Pneumoconiosis Conference established mass concentration of dust in the respirable size range as the true measure of the incidence of pneumoconiosis. The author had established a good correlation between cumulative total respirable dust dosage as well as cumulative silica dosage and the category of pneumoconiosis according to ILO classification at Mufulira Copper Mine. Studies at Hutti also show a linear relationship between the average cumulative dust and silica dosage md the category of pneumoconiosis. However the maximum tolerable cumulative dust dosage for - prolonged exposure is 182 mg month/m3 - at Hutti as compared to 275 mg month/m3 at Mufulira. Similarly the maximum tolerable silica dosage for - prolonged exposure is Only 35 mg month/m3 at Hutti as compared to 55 mg month/m3 at Mufulira. The TLV for dust concentration at Hutti works out at 0.6 mg/m3 compared to 1.1 mg/m3 at Mufulira and the TLV of silica concentration at Hutti is 0.117 mg/m3 compared to 0.25 mg/m3 at Mufulira. The Hutti figure is however, closer to the TLV of 0.1 mg/m 3 recommended by ACGIH.

Jan 1, 1987

By B. Anameric, S. K. Kawatra, K. B. Rundman

The iron nugget process is an economical, environmentally friendly, cokeless, single-step pig iron making process. Residence time dependent process requirements for production of pig iron nuggets at a fixed furnace temperature (1425 C) were investigated. Three chemically and physically different products were produced after complete reduction to iron, depending on the residence time in the furnace. These products were direct reduced iron (DRI), transition direct reduced iron (TDRI), and pig iron nuggets (PIN). The increase in the carbon content of the system as a function of residence time was detected by optical microscopy and Microhardness measurements. Sufficient carbon dissolution for the production of pig iron nuggets was obtained after 40 minutes residence time. The pig iron nuggets produced had chemical and physical properties similar to blast furnace pig iron. They were liquid state products and slag was completely separated from the metal.

Jan 1, 2005

By U. S. Sawant

During the last few years, Process Machinery Division, Rexnord, has conducted extensive research on the effects of cone crusher variables such as speed, throw and cavity design on the productivity of the crushers. Simultaneously, Rexnord's engineers have developed advanced design and testing techniques and criteria that assure efficient and reliable crusher designs. The combination of these two has resulted in a design of the 2390 Omnicone (1000 hp) crusher which fits on an existing 7 ft. Symons foundation and yet is capable of producing twice the tonnage compared to our 7 ft. super heavy duty (500 hp) crusher. Both speed and throw can be varied to give a wide application flexibility from making twice the tonnage to the finest product. The 2390 Omnicone also incorporates innovative features such as full balance, cavity clearing, adjusting under load with automation capability, maintenance-free seals, one head for all cavities, ease of maintenance and servicing, etc.

Jan 1, 1987

By T. A. Jones

The Kelsey Centrifugal Jig is an enhanced gravity concentrator capable of separating fine minerals and/or minerals with relatively small differences in specific gravity. Since the first commercial installation at the Renison Bell tin mine in Australia, development and improvement in hardware has continued, including the introduction of the high-capacity J1800model Kelsey Jig. The Kelsey Centrifugal Jig is widely applicable to fine mineral recovery duties, with key application areas including mineral sands, tin, gold and nickel. Other areas of application include: iron ore, base metals, chromite, PGMs, soil remediation and scheelite. The latest developments on the Kelsey Jig are discussed together with a review of recent installations involving: • Fine gold / sulphide recovery from leach tailings • Magnesium mineral removal from nickel sulphide concentrates • High-grade zircon recovery from plant tailings

Jan 1, 2004

By Thomas Fliess, Klaus-Christof Ritter, John R. Sturgul

The optimum flow of materials through a smelter is an extremely important phase of the mining cycle. A typical copper smelter will have up to $US 1,000,000 per day of copper being processed. The motion of the overhead cranes in moving the ladles filled with copper matte and slag from furnace to furnace is prescribed but there can be numerous variables to consider. Some of these variables to the system can be: the speed of the overhead cranes, the number of cranes, the size of the ladles, the size of the furnaces, the number of furnaces and the sequence in loading the furnaces. A simulation model was constructed of a working smelter in the SW of the United States. The model has been used to study the effect of varying parameters of the system. The program runs as follows: an input menu appears on the PC screen and the user can navigate through it and change any of the data; the simulation takes place and the results of the simulation sent to a data file. Animation of the system then is shown on the screen in "cartoon" fashion. The software chosen for the simulation was GPSSI H (') and PROOF Professional (') for the animation. The model presented here is believed to be the first reported simulation and animation model for a complete, working smelter.

Jan 1, 1996

By Walter Meintrup

On Nov. 4, 1981 the newly installed 1000tph wet-process iron-ore ball mill of A/S Sydvaranger completed its first four months of uninterrupted, successful full-load operation in Kirkenes/Norway. This 6.5m diameter mill is driven by a gearless ring or wrap-around motor of 8100kW at 13.1RPM - a first of a kind in this segment of industry. (Fig. 1) This paper analyses the reasons that have led to the selection of this type of drive over more conventional schemes, lists specific advantages of such large mills, and describes in some detail the installation in Norway. General aspects of possible design variations, and application information for designers and users of such mills conclude the presentation.

Jan 1, 1982

By S. K. Kawatra, S. T. Bagley, T. C. Eisele

The use of the bacteria Thiobacillus ferroxidans to catalyze pyrite dissolution in coal is well known, and recent investigations have shown that T. ferrooxidans are also capable of rapidly altering the pyrite surface to facilitate its removal from coal by froth flotation and oil agglomeration. However, the effect of reactor design on the bacterial leaching rate is poorly documented, and the ability of bacteria other than T. ferrooxidans to affect pyrite flotation has been unknown. In this study, the effect of a number of different microorganisms on the flotation of unoxidized pure mineral pyrite has been investigated, and it was shown that organisms other than T. ferrooxidans are also capable of depressing pyrite flotation. In addition, comparative studies of leaching in shake-flasks and pachuca tanks have shown that the pachuca tanks allow leaching to proceed to a greater degree and at a significantly accelerated rate.

Jan 1, 1989

By Paul W. Patton, Christopher Scott Smith

The use of ceramic-in-rubber pulley lagging on bulk material belt conveyors is increasing. Many of the applications have been on pulleys originally installed with rubber lagging. There is a consensus that the fiction characteristics of the ceramic material are significantly better but the factors quoted vary, possibly because the more complex traction mechanism of the dimpled ceramic elements on the belt is not well understood. In this paper we will report and evaluate field data from a number of field installations to provide a study of actual friction characteristics in successful applications for those who desire reliable data for using ceramic-in-rubber lagging in new conveyor designs.

Jan 1, 2004

By N. P. Titkov

This paper presents the results of laboratory and pilot plant investigations for the development of efficient methods of beneficiating hematite ores from the Krivoi Rog, Kursk Magnetic Anomoly, Olenogorsk, and other localities. The tests included gravity, magnetic (in a high intensity field), flota¬tion, and magnetizing roasting methods. It was possible to develop efficient beneficiation methods depending on the mineral composition of the ore and degree of dissemination of ore and gangue minerals. The paper shows the relationship between the iron silicate and quartz content of the ore and the technologic indices of the various beneficiation methods. Some of the conclusions based on these investigations and the technical and economic computations related to the cost of one ton of pig iron produced from concentrates obtained by the various beneficiation methods are: 1. If the hematite ore is not disseminated uniformly, it is expedient to use a combined gravity and flotation process. Ore particles up to 50 am. in size are beneficiated by gravity (heavy suspension, jigging, and others) and yield a lump concentrate. The middlings from this process are recrushed and floated; 2. Finely disseminated hematite ores, containing small quantities (less than 5 percent) of iron silicates, are most effectively beneficiated by flotation. Anionic (sulphate soap, tall oil emulsion with various foam depressors) as well as cationic collectors may be used. Depending on the mineral and chemical composition of the ore, it is possible to obtain concentrates containing up to 65 percent iron with an extraction up to 94 percent; 3. Finely disseminated, mixed hematite-magnetite ores may be beneficiated by flotation or a magnetic separation-flotation process; 4. Finely disseminated hematite ores, containing large quantities of iron silicates and earthy hematite ores are most efficiently beneficiated by the magnetizing roasting method. This method will yield concentrates containing up to 68 percent iron with extractions up to 90 percent. Although beneficiation by the magnetizing roasting process is costly, it will nonetheless, when employed on this type of ore, yield the least expensive pig iron.

Jan 1, 1960

By I. Shah, L. G. Austin

A method for quantitative investigation of the phenomena involved in fine grinding of materials that follows the changes in the breakage rates of fine particles has been presented. For relatively hard, brittle, non-coating material like quartz, the slowing down effect of breakage rates starts to be significant at relatively coarse sizes, which goes often undetected in closed circuit grinding systems, producing relatively coarse product, say P80=75µm However, for fine grinding systems, as the -10µm fractions begin to build-up, and classification becomes more difficult, the build-up of fine sizes causes a slowing down effect Compounding this problem is the difficulty of obtaining accurate cumulative weight size distributions in the fine size region.

Jan 1, 1983