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Underground instrumentation and observations at longwall panels have demonstrated that the growth of main roof causes an extremely high roof weighting on the shields. It can sometimes result in catastrophic effects on the support when the roof weighting intensity far exceeds the support capacity. In this paper, a comprehensive study was conducted on characteristics of main roof breakage and its effects on shields at different locations, based on the monitored shield data, theoretical analysis, and finite element analysis. With the help of theoretical analysis and numerical modeling, stress distribution and redistribution in the main roof were analyzed in detail to define main roof failure modes and understand the maximum roof weighting intensity imposed on the shields. From this study, it was found that the effects of main roof breakage on shields are chiefly related to the shield initial setting condition and the final failure mode of the main roof.

Jan 1, 1994

By Ali Soltani, Scott Santti

The Gold Quarry Mine is a large scale open pit mine located 11.3 km (7 miles) north of Carlin, Nevada. The operation consists of an open pit mine, two milling facilities, a leach crushing plant, and three dump leach pads. Gold Quarry is operated by Newmont Gold Company, which is 90.1% owned by Newmont Mining Corporation, a Denver based company. The property is the largest of the three gold producing properties operated by Newmont Gold Company on the famous Carlin Trend. This paper will give a general overview of the Gold Quarry mining facilities and detail mine operating practices. Specifics on cost saving ideas being implemented and those under investigation will be discussed.

Jan 1, 1989

By R. M. Damodaran

The flotation performance of Florida phosphate rock was evaluated in terms of the mixing behavior of reagents and particulates during anionic conditioning of phosphate slurries. The various conditioning variables that influence mixing, namely, solids loading, agitation speed and conditioning time, were investigated to determine their effect on reagent coating of the particles. The phosphate recovery was used to monitor the conditioning efficiency. The mixing characteristics of the phosphate feed were evaluated in terms of the ratio of the mixing power (P) to the minimum power (Pm) required to keep the slurry in suspension. It was found that mixing conditions govern the conditioning time required to obtain a high recovery. Reagentization was slower at lower P/Pm ratios. At higher P/Pm ratios, the flotation recovery was optimized, and the agitation speed was found to have no significant effect. Optimum mixing conditions were obtained for a74 wt% slurry at an agitation speed of 450 rpm (47 radians/sec). Under these optimum mixing conditions, the collector dosage required for an improved recovery was lower and the conditioning time was shorter.

Jan 1, 1997

By Stephen P. Winkelmann

The expansion of gold production in Nevada's Carlin Trend over the last few years has been staggering. To increase gold production while minimizing capital requirements and providing for the safe and efficient mining and processing of ores has required a tremendous effort by the mine engineering group at Newmont Gold. Organizational changes were implemented by the company to effectively deal with a full range of engineering problems. Specially developed computer software and its applications will be explained in this article as well as improvements in the techniques used in converting geologic resources into reserves. Scheduling procedures for the mining of multiple pits to feed multiple processing facilities will likewise be presented. Ore control procedures and current mine engineering practices are discussed. Growth at Newmont Gold Expansion of production levels at Newmont Gold Co. was brought about primarily by the economic incentive to exploit increased reserves. From 1987 to 1989, mined production increased by 260%, gold production by 238%, and manpower by 166% (Table 1). These increases came quickly and demanded

Jan 1, 1990

By S. Guo

In this paper, a model for the resin anchor bolt system is developed in which the smooth bar is modeled by using one-dimensional truss elements and the resin annulus is modeled by using axisymmetric elements. These two submodels are combined together and then incorporated into the' existing computer code ROOFBOLT. After this development, all of the components in the resin anchor bolt system including smooth bar, bearing plate and resin annulus can be correctly modeled.

Jan 1, 1995

By W. G. Pariseau

Introduction Caverns of 50 m in linear dimension at depths below 2300 m with a life of more than 25 years are proposed for the next generation of water-filled neutrino detectors. Little precedent exists for excavations in such an extreme environment, although some guidance is available from mining experience at great depths, for example, in South Africa, in Canada and at the former Homestake Mine in the U.S.A. Unlike mining for ore, there are choices available in the construction of such caverns that may mean the difference between success and failure. These choices should be informed by rock engineering principles. Recently proposed guidelines for orientation of brick-shaped caverns where the long dimension is a small multiple of the short dimension indicate that the most favorable orientation is with the long and short dimensions parallel to major and minor preexcavation principal stresses (Pariseau, 2005). Numerical analyses at reduced strength indicate some yielding at cavern walls should be expected but that an equilibrium state is quite possible and is aided by arching the back into a spherical dome when the cavern is an empty cylinder (Tesarik and others, 2002). The same indications of stability occur with brick-shaped caverns. However, the most dangerous situation occurs during the excavation sequence to final cavern dimensions. There are any number of excavation sequences that lead to the same final cavern shape, so there is an opportunity to partially optimize the sequence with construction guidelines that minimize peak stress concentrations during construction. This contribution discusses three practical excavation sequences that lead to the same brick-shaped cavern in the strong, massive Yates formation at the Homestake Mine where considerable rock mechanics data has accumulated through the years(e.g., Pariseau, 1985, Pariseau and others, 1995) and where actual mining on the 8000 Level indicates a strong possibility of successful investment in the next generation of large, deep neutrino detectors. The main results are: (1) a favorable brick-shape is one with dimensions in the same proportion as the preexcavation principal stresses (compressionpositive), and (2) favorable orientation of the most extreme but temporary shape of excavation is also best for the construction sequence. Analysis results from a mix of Homestake Mine data and possible excavation geometry illustrate the advantages of these guidelines.

Jan 1, 2006

By V. B. Menon, L. D. Michaels, M. E. Mullins

Introduction The cleaning of coal to remove sulfur and inorganic impurities has, in recent years, become an essential operation in any coal utilization process. US coals, on average, contain about 3% total sulfur, of which more than 60% is generally inorganic or pyritic sulfur. Existing technologies such as heavy media cycloning, selective agglomeration, and electrostatic separation have the potential for removing about 80% of the pyrite from coal (Khoury, 1981). In view of the large volumes of coal being used today, there exists a need for the development of new processes to further improve the separation of pyrite from coal. Colloidal particles in suspension possess surface charges that are related to the chemical composition of the particles. In aqueous suspensions, the surface charge is a function of pH. For coal-pyrite mixtures, it is possible, by an adjustment of the pH (also a function of polar molecules), to reach a state where the charge on coal is very close to zero, but the charge on pyrite is still substantial. The introduction of collector particles with a charge opposite that of the pyrite should then result in the selective flocculation of pyrite and collec¬tor. These flocculates should settle out much faster than coal and could be removed from the bottom of the settling column. This note discusses our preliminary observations of the effect of clay-based collector particles, especially bentonite, on the settling behavior of coal and pyrite. These experiments were conducted with a view to developing a new electrokinetic flocculation process for separation of coal-pyrite mixtures. Experimental The objective of the experiments was to determine the effects of clay-based additives on the settling rates of clean coal, pyrite, and coal-pyrite mixtures. Illinois Colchester (No. 2) coal was obtained after processing in an existing coal cleaning facility. This coal was reported to contain less than 0.3% pyritic sulfur, which was in the form of a fine powder with an average particle size of 5µm. Pyrite (of average particle size 5 µm) was also obtained from the same facility and reportedly contained less than 0.1% coal. The zeta potentials of coal and pyrite in water were measured as a function of pH using a zetameter. The pH was adjusted by adding sodium hydroxide or hydrochloric acid to the suspensions. Sedimentation experiments were conducted in 50-mL glass cylinders, and settling rates were measured by noting the height of clear liquid above the settling front as a function of time. Settling behavior was also charted by periodically taking photographs of the system. The following systems were investigated: •a slurry consisting of 2.5 g of clean Illinois Colchester coal in 50 mL of water of pH 6.0, with and without the addition of 0.5 g of bentonite (Fisher, purified grade) ; • a slurry consisting of 2.5 g of pyrite in 50 mL water of pH 6.0, with and without the addition of 0.5 g of bentonite ; and • a slurry consisting of a mixture of 1.25 g clean coal and 1.25 g pyrite in 50 mL water of pH 6.0, with and without the addition of 0.5 g of bentonite. In addition, experiments were conducted with kaolinite (Bath, South Carolina) and alumina (Fisher, purified grade) as collector materials to verify the observed effects. Results and discussion Figure 1 shows the zeta potential values for the Illinois coal and pyrite as a function of pH. The zeta potentials of coal and pyrite decrease with increasing pH, changing from an initially positive value at low pH to a negative value at high pH. The point of zero charge (PZC) for the coal is at a pH of 6.2, while the PZC for pyrite occurs at a pH of 10.3.

Jan 1, 1988

By D. B. Buddecke

Powell Bend Mine, located in Bastrop County, Texas, is owned by the Lower Colorado River Authority (LCRA). The mine is operated under contract by the Powell Bend Mining Company (PBHC), an affiliate of Pittsburg and Midway Coal Mining Co., and produces 210,000 tons of 6500 BTU/LB lignite per year for LCRA's Fayette Power Project near La Grange, Texas. PBHC operates the surface strip mine one shift per day, five days per week with a total of nine employees; six operations/maintenance and three office/supervision. The mine's productivity in 1988 averaged 100.3 tons per manshift using an l8-cubic yard dragline to uncover the lignite. Delivered cost to LCRA, F.O.B. mine, is $6.11 per ton, which includes water control and final reclamation.

Jan 1, 1990

By R. W. Utley, J. Carr

The tremendous growth in grinding mill size and horsepower during the 70s demanded advancements in gear cutting technology and equipment for the 80s. A new standard in gear cutting machines is now used to generate-cut large open gear sets to over 12.2 m (40 ft) in diameter at an AGMA quality level much higher than the accepted levels a short five years ago. The precision of the resulting gear set assures maximum tooth contact with the resultant longer gear set life.

Jan 1, 1987

By R. T. Webber, D. Moffett, D. W. Averill, G. H. Kassakhian

INTRODUCTION In Canada, radium-226 is removed from uranium mining and milling effluents by the addition of barium chloride to precipitate barium-radium sulphate. Large settling ponds are provided to effect solid-liquid separation. However, the barium-radium sulphate precipitate [(Ba,Ra)S04] is a fine, slow-settling crystalline solid which is not easily removed by simple sedimentation systems. Consequently, settling pond effluents may contain appreciable quantities of particulate or suspended radium-226, depending upon the specific pond system and/or the time of year considered. Also, current technology is expected to be incompatible with ultimate disposal goals since safe recovery of the barium-radium sulphate sludge from the settling ponds may be difficult to achieve (IAEA, 1976). Under the auspices of Environment Canada, a Government-Industry Mining Task Force established a Radioactivity Sub-Group in 1974 to assist in the development of effluent regulations and guidelines for the uranium mining industry. Among the recommendations of the Sub-Group was the need to seek more effective methods of radium removal, including development of physical--chemical treatment systems as an alternative to settling ponds. In response to the Sub-Group recommendations, a bench scale feasibility study began in March 1976 at the Wastewater Technology Centre (WTC) of Environment Canada. The bench scale work was expanded and accelerated in 1977 with financial assistance provided by the Atomic Energy Control Board. The results of this study indicated that coagulation and flocculation of the (Ba,Ra)S04 precipitate greatly increased settling rates (Wilkinson and Cohen, 1977). Subsequently, a research program with a larger scope was initiated in January 1978; this program is jointly managed and funded by government and industry as indicated in Table 1. The principal goal of the Joint Government-Industry Program is the development of a physical-chemical process to reduce the radium-226 content of uranium mining and milling effluents. The following effluent radium-226 activities were established as targets for the program: 0.37 Bq/L (10 pCi/L) as total radium-226; 0.11 Bq/L (3 pCi/L) as dissolved radium-226. Process development work was undertaken at bench scale at the WTC and at

Jan 1, 1980

By Luis R. Bittencourt

Research efforts have been made to characterize a refractory Brazilian bauxite ore composed basically of gibbsite, kaolinite and quartz. Detailed polished-section microprobe analysis of the unbroken ore has been used to describe the liberation characteristics and the association between mineral phases. The linear grade distributions for selected particle size fractions were determined by means? of a particular implementation of King's Random Fracture Model that uses the exponential model for the distribution of linear intercepts through both dispersed (kaolinite) and continuous (gibbsite) phases. The corresponding volumetric grade distributions were then determined by means of a constrained optimization technique for the solution of the transformation equation. Batch flotation experiments were carried out to determine the kinetics for particles of different sizes and the results correlated with the liberation spectrum for each size class.

Jan 1, 1991

The trend in the U.S. coal industry in recent years has been a continuous increase in the percentage of coal produced by surface mining methods. Though the predicted energy demands promise a good market for coal, growing legal and environmental issues make the exploitation of a coal deposit by surface methods a difficult and challenging task. Major emphasis has to be placed on the development of integrated mining and reclamation schemes which enhance the possibilities of post mining land uses. Since no major breakthroughs are foreseen in the near future in surface mining equipment, innovative applications of current equipment must be developed. Draglines have been and are expected to continue as the primary earthmovers in surface mining of coal. A dragline simulation model has been developed which has the capability to analyze various deployment schemes such as conventional side casting, advance benching, and extended benching. The mathematical aspects of the model, the input data, and the output results are discussed with reference to an application in an operating mine. The model can be used to select a suitable dragline for given geological and mining conditions and to study the effect of alternative mining layouts and spoiling plans on machine production.

Jan 1, 1979

Your assessment of the minerals business. I would first like to express our profound sadness and sincere condolences to the families of the miners who lost their lives in recent mine mishaps particularly in West Virginia, and other locations. Any loss is unacceptable. It is time to review and, if required, re-establish a rigorous health and safety agenda in the mines. It must involve a review of health and safety regulations. And innovative training methods for sensing, awareness and mitigation of health and safety hazards must be developed. As far as the minerals business is concerned, I am excited about the outlook for mining. Over the last 20 years, global demand for minerals has closely mirrored the growth of the gross domestic product. Minerals re-main a major part of the world’s economic foundation. And that will continue to be the case. It is no surprise that the fortunes of the mining industry rise and fall with general economic trends. Globally, mining has been strong — thanks to the explosive economic growth in Asia. The U.S. mining industry has performed reasonably well, with notable strength in the metals, coal and construction and aggregate areas and with some softness in the industrial minerals sector.

Jan 1, 2006

By K. A. Natarajan, K. S. N. Murthy

Growth of Thiobacillus ferrooxidans on pyrite mineral surfaces and in 9K leach media was studied through estimation of bacterial protein in the different phases. Bacterial attachment was found to be governed by particle size of the mineral, period of incubation and by stationary or agitation conditions used during incubation. Increased bacterial growth in the liquid as well as on the solid phase was observed with decreasing particle size and increasing incubation periods. Increased bacterial attachment to pyrite mineral surfaces was observed to promote iron dissolution.

Jan 1, 1993

By B. S. Hulvey

Thin support liners are becoming more accepted and being developed with improved properties because the mining industry as a whole has been offering underground safe test trial sites. This is because of the huge potential for such products. Recent developments tend to indicate that the technology is “coming of age” and these are discussed in this paper.

Jan 1, 2003

By G. E. S. Valadao, J. D. Miller, C. L. Lin

Filtration is an important solid liquid separation technology employed widely in the mineral processing industries. The effectiveness of the filtration operation can be influenced by numerous variables, related to the particulate phase, the slurry rheology and the equipment. The classical approach for analysis is based on Darcy's law. Knowledge of the cake poremicro structure and its correlation to macroscopic cake properties is required to model the filtration operation from a fundamental point of view. Since cake formation seems to occur randomly, a 3D Monte Carlo method was used to simulate cake formation. The configuration for simulation was a space with width of 500 m, length of 500 m and height of 4000 m. Size distributions of five different industrial products whose particle size distributions follow the Rosin Rammler distribution function were used. The particle shape was assumed to be spherical. The simulated cake structures were described in terms of volume porosity (volume of pore space per unit volume of cake) and surface porosity (area of pore space per unit area of a cross section). The results indicate: 1) it is possible to simulate 3D packing, which mimics cake structure, using the Monte Carlo method,2) segregation phenomena occurs during simulated cake formation, 3) the values of calculated porosity for simulated samples B, C, D, and E were lower than those determined for corresponding industrial products Br, Cr, Dr, and Er, and 4)some structures of simulated samples seem to correlate with laboratory leaf test data obtained for different products from plant operations.

Jan 1, 1999

By Changhong Huang, Y. J. Wang

Proceedings of the 6th US Mine Ventilation Symposium SME, Littleton, CO, 1993, pp. 153-161.

Jan 1, 1995

The long-term goal of the Collaborative Research Centre 525 is the identification of options for the resource-sensitive supply and utilization of metallic raw materials. In order to address these issues, an integrated resource management system for metallic raw materials was developed and tested. Simulations were carried out, using the tools and methodical approaches developed in this system, in order to compare alternative operating scenarios for aluminium and copper. However, before these alternative operating scenarios could be formulated and assessed, it was necessary to develop a consistent set of indicators to monitor progress towards sustainable development in the processing and utilization of metallic raw materials. The primary objective of the centre is to develop a set of indicators, which adopt a holistic approach to resource management, thereby enabling the assessment of different operating scenarios within the broadest possible context. The target audience for this research consists of decision-makers in the realms of politics, business and industry, as well as NGO?s.

Jan 1, 2003

By S. A. Bortz

IIT Research Institute has initiated several multi-sponsored research programs. In this paper the methods for developing four of these programs are discussed. In general, a broad area of investigation must be proposed to interest a spectrum of different industries. The work must not touch upon proprietary data and will probably involve a number of scientific disciplines. Thus, the problem to be solved will attract sponsors who need to know more about the area under study but do not wish, as a single company, to commit the resources required to obtain the necessary know-how for their needs. The paper draws on the background of four IITRI multi-sponsored projects: Size Reduction, a study of grinding of material to reduce their particle size; Melt-Formed Ceramics Research, a method of producing dense, polycrystalline ceramics using glass forming methods; Binders in Ceramic Processing, which addresses the problems associated with the use of organic aids for ceramic processing; and a Study in Air Pollution Technology, a program to review and assess pollution control equipment for current and future applications.

Jan 1, 1984

By Jinrong (Patrick) Zhang

Improvement of conventional flotation efficiency, separation of carbonates from apatite, recovery of phosphate values from phosphatic clay and other ways of utilizing the clay, disposal of clay slurries and subsequent reclamation of the settling areas, and conservation of resources and energy remain major challenges in the beneficiation area for the phosphate industry. These problems have been actively investigated by the industry, government agencies, and research organizations for decades with modest success. However, some recent research activities have generated promising results and possible new technologies. The dominant position of the Crago process in phosphate beneficiation is being challenged by some of the single stage processing schemes. Heavy media separation enables one producer to process a portion of high carbonate ores. Separation of dolomite from apatite by reverse flotation of carbonates with phosphate depressants showed potential for industrial application. Consolidation of phosphatic clays in mine cuts using a modified "sandwich" process is being tested. Beneficiation in the acidulation plant or grinding at the mines may be considered in the future.

Jan 1, 1993