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By Christopher C. Woomer

Cyprus Shoshone Mine uses the longwall method to extract a deep, thick, pitching coal seam in the Hanna Basin of South Central Wyoming. The immediate, and main roof rock consists of weak, thinly-bedded, silty mudstones with weak, interbedded fine-to medium-grained sandstone. Tailgate ground control has been a critical factor impacting productivity at the mine. A gateroad condition mapping program for the 11 left longwall gateroads indicated potentially severe ground control problems for the tailgate. It was predicted that the existing, secondary support pattern of wood cribs would not provide adequate support capacity. As predicted, severe deterioration of the tailgate occurred in the form of a roof cutter, sloughing ribs, and failing wood cribs. Productivity was affected and additional support was required. Shoshone personnel evaluated several options for providing the additional support needed in the tailgate. The additional support system and placement method had to satisfy several requirements with respect to access, materials handling, placement method, set-up time and support capacity. Approximately 6,000-ft. of deteriorating tailgate had to be supported. The initial wood crib support system left a 6-ft. walkway for access and construction of the additional support. This access was further reduced as the roof loaded the wood cribs. This eliminated the possibility of mechanized material handling to the construction locations. All materials would have to be transported by hand. The additional support system had to be placed quickly to stay ahead of, and keep pace with, the required longwall advance rate. It had to incorporate the existing wood cribs and provide at least 500 tons of extra support capacity. And most critically, the system could not affect longwall ventilation. Longwall coordinators and engineers made the decision to use a low density, pumpable cement known to the industry as TeksealTM, to provide the system required. A 200 psi ultimate strength mix was decided on to provide the required load capacity. The existing cribs were formed with 1-in. by 6-in. boards and brattice cloth to provide the containment. To overcome the access limitations, three boreholes were drilled from the surface to the tailgate on 2,000-ft centers. A mobile pumping station was established on the surface and the TeksealTM was pumped 900-ft. down the boreholes through a 1.5-in. steel pipe, then as much as 1,800- ft. along the tailgate entry through 1.25-in. miner spray hose. The materials required for the TeksealTM supports could all be carried into the construction locations by hand. As a direct result of incorporating relatively new methods of pumping high yield, low density, cementitious grouts, the Shoshone Mine reduced downtime due to tailgate ground control problems by approximately 70% in comparison with previous Longwall panels. The longwall set three monthly production records while mining the 11 left longwall under the deepest cover, steepest pitch, and most extreme ground control conditions ever encountered at the mine.

Jan 1, 1995

By J. V. Atwood

The U.S. Bureau of Mines has developed a novel Double Membrane Electrolytic Cell (DMEC) that exhibits unique features for recycling contaminated metals and metal alloys. The DMEC incorporates two anionic ion exchange membranes, separating anodic and cathodic regions of the cell. The ion exchange membranes prevent significant transport of unwanted cationic impurities to the catholyte from the impure anolyte while the anion/cation balance in cell compartments is maintained through the free movement of anions between compartments. The membrane barrier makes it possible to electro refine highly contaminated materials or to electrowin from solution while utilizing alternate anode reactions. Sinceanolyte and catholyte cross contamination has been eliminated, premium cathode products are produced. The DMEC has been tested at bench, pilot, and commercial scales. Configuration of the DMEC, cell operation, scale, up efforts, and significant design factors are discussed. Two separate recycling investigations utilizing DMEC technology are presented. The first investigation examines recovery of high purity cobalt and nickel from severely contaminated super aIloy scrap. The second involves? upgrading contaminated cobalt in the U.S. Government's National Defense Stockpile. Capital and operating costs for both potential applications are presented.

Jan 1, 1995

By John Heilig, Patrick Andrieux

"Near-field monitoring of blast induced seismic vibrations is a practical and useful way of assessing blast field behaviour for diagnosis and optimization purposes. It is also necessary in order to provide the information from which empirical vibration prediction equations, such as the one proposed by Holmberg (11 for example, can be derived. (Strictly speaking, the “near field” extends from the blasthole itself to about one charge length away from it; however, throughout this article, “near field”will.most often refer to the outer limit of this zone, from roughly 0.75 to 1.50 charge length away.) In order to obtain reliable data, proper field monitoring techniques are of paramount importance. Once the data are properly recorded, analysis can be done either in the time domain (describing vibration amplitude vs. time) or in the frequency domain (usually describing vibration amplitude vs. frequency)."

Jan 1, 1995

By R. Kanniganti

The primary problems of pillar design in seams subject to interaction are due not only to difficulties in predicting loading, but also to the often unsymmetrical nature of the stress fields. The effects of uneven stress fields on failure patterns within a pillar were studied wing a two dimensional finite element method. Lower seams, including ultra- close mining situations were evaluated considering conventional pillars. Pillar case study data for under mining were analyzed to determine if empirical trends in stable pillar sizing could be derived. Recommendations for multi-seam pillar design are made, based on anticipated loading conditions within a pressure bulb. Applications of the research results are demonstrated using case studies

Jan 1, 1995

By P. Tsang

To gain insight into the current status of pillar design practice in the underground coal mines of United States, a survey has been undertaken in the late 1993 and early 1994. A total of 552 room-and-pillar mines and 75 longwall mines have been surveyed to collect general, geological and mine plan information. The collected information are critically analyzed with special emphasis on the pillar design criteria adopted in these mines. A safety factor analysis has also been carried out for the pillars in room-and -pillar mines.

Jan 1, 1995

By Edgar Peek

Lixiviant regeneration is by definition a precondition for any hydrometallurgical process. In chloride hydrometallurgy either HCl or Cl2 has to be regenerated in order to establish an economically viable metallurgical process. One such regeneration process is widely used with steel pickling where HC1 is regenerated through the thermal decomposition of ferrous chloride in either spray roasters or fluid bed pyrohydrolyzers. This standard HC1 regeneration process deserves to be considered as a potential separation process, since thermodynamic calculations show that a fluid bed pyrohydrolyzer can function as a ferrous-nonferrous separator. Several nonferrous,metals such as zinc, lead and cadmium can be volatilized as a chloride under ferrous chloride pyrohydrolysis conditions. If such a nonferrous metal volatilization could be achieved in the case of slurry feeding of "contaminated" iron oxides, then this would increase the Fe/H2O ratio of the (process) feed and thus save on fuel per ton of iron, while yielding a marketable iron oxide product. Previous test work on synthetic materials revealed that the near-complete separation of zinc, lead and cadmium from iron oxide was possible in a pyrohydrolytic atmosphere, even if zinc was present as zinc ferrite (more than 99.5%). This investigation, which was carried out in a tube furnace at 1100 K has now been extended to treat synthetic zinc minerals and also franklinite ore. For the latter, it was found that 85% zinc volatilization could be achieved in 4 hours at 1300 K. It is postulated that complete zinc volatilization could not be attained due to the formation and/or presence of gahnite and hardystonite, which might be stable in HCl/H2O atmospheres at 1100 K. The effect of adding small amounts of calcium chloride to react with gahnite and hardystonite to give zinc chloride and both calcium aluminates and silicates is being discussed. Test work on slurry feeding of this complex ore in a recently constructed 4-inch diameter fluid bed pilot unit has been planned for the near future.

Jan 1, 1995

By S. Ajima

The Naoshima Smelter and Refinery is the most important copper operation of Mitsubishi Materials Corporation. There are a Mitsubishi Continuous smelter and a conventional type of copper tankhouse. The continuous smelter with 240,000 mtpy of anode production was commissioned in May 19914 replacing two existing smelters, i.e an original Mitsubishi Process line and a conventional reverberatory furnace line. In July 1992, the copper tankhouae was expanded for the purpose to close the gap of production capacity between the smelter and the tankhouse. The cathode production capacity was increased from 13,800 to 15,800 mtpm. By these plant modifications, the distribution of minor elements was significantly changed and the impurities load is getting on increase reflecting recent shortage of clean copper concentrates supply. The paper discusses the distribution of minor elements and the impurity control strategy at the smelter end the refinery.

Jan 1, 1995

By C. C. Clark, R. R. Backer, J. D. Vickery

This report presents the results of tests conducted by the U.S. Bureau of Mines to determine the transport characteristics of highly concentrated paste backfill mixes made from dewatered total mine tailings. The slurry concentrations of the mixes were all above 78 pct by weight with slumps ranging from 6.4 to 16.5 cm (2.5 to 6.5in). Laboratory material property tests and full-scale pumping tests were conducted using pipe diameters of 102,128, and 154 mm (4, 5, and 6 in) and a positive-displacement pump. The results indicated that the tested backfill mixes can be successfully transported as a stiff paste and identified the influence of and the interaction among the various mix and system variables.

Jan 1, 1995

By Lyman G. J

The volumetric distribution of valuable mineral, or phase, within a set of particles is called the liberation distribution. To optimise a mineral processing plant it is necessary to know the liberation distribution in most of the streams, especially those adjacent to separation devices. Possibly the most common method of analysing ore particles is to section sets of similarly-sized particles. However, the observed sections can appear liberated even if the particle is composite. This means that the 'apparent' liberation distribution can be very different to the 'actual' liberation distribution. This discrepancy is called stereological error. One must then somehow estimate the actual liberation distribution using the apparent liberation distribution. This problem is called the liberation distribution problem and its solution is the subject of this paper. The solution is based on a sorting algorithm which uses geometric probability equations. These equations are based on the assumption that sectioning is isotropic and uniform. Apart from these assumptions the equations are completely independent of particle shape or texture. The algorithm is verified by numerical simulation and experimental methods. For the numerical simulations the correspondence between the actual and estimated liberation distributions is excellent. For the experimental methods, the agreement is not as good and appears to be due to experimental errors.

Jan 1, 1995

By Robert F. Holub

The U.S. Bureau of Mines (USBM) has tested a personal dosimeter for measuring radon decay products that is manufactured by Tom Scurry Associates. The tests were made to determine the accuracy of the dosimeter system for record keeping of radiation exposures to radon decay products encountered in mining. The radioactivity-detecting head is based on a design developed by the USBM, and the associated air pump was developed by the manufacturer. The dosimeter system was tested in the USBM radon chamber. The detecting head uses CaF:Dy thermoluminescent phosphors and is mounted on a self-regulating air pump. Batteries supply power sufficient for an 8-h shift. The dosimeter system is worn on the miner's belt. Dosimeter calibration tests were performed by the USBM. In addition, the pumps were tested and evaluated under continuous flow conditions. The results of these tests indicate that the Tom Scurry Associates Model DOSI600 dosimeter is suitable for general use in mines where record keeping for natural radiation exposure is required.

Jan 1, 1995

By Ghassan Skybey

Australian coal mines uses state of the art technology in coal rib reinforcement. This paper highlights the development over the past 15 years in coal rib support technology, along with the advantages and disadvantages of each system. It also outlines the current trend in using coal rib reinforcement in speeding up the dowels installation to improve the current low drivage rate. An innovative cuttable dowel is discussed which improves the drivage rate. This new dowel is self anchoring it uses no resin anchor it has a 5 tonnes (5.51 tons) anchor capacity and can be fully installed in approximately 10 seconds.

Jan 1, 1995

By Christie A. B, Swain A, Brathwaite R. L

This study provides quantitative data on vein distributions within seven selected epithermal systems, four deposits hosted predominantly in rhyolitic rocks: Ohui, Wharekirauponga, Neavesville and Komata, and three major deposits mainly hosted in andesite: Martha Hill, Golden Cross and Karangahake. The technique of fractal analysis was used to help quantify vein distribution patterns. The fractal dimensions (D) obtained are related to the number of veins per metre, the degree of vein clustering, and vein thickness. An increase in any of these tends to increase the fractal dimension. It is the relative relationship of these parameters that is important for the characterisation of vein distributions, and the comparison of different deposits. Within the same systems, the rhyolites are characterised by lower vein thickness and vein density, but have a higher degree of vein clustering compared to the andesites. Sections that are deeper and more centrally located within the epithermal system and/or close to major structures, tend to have a greater degree of vein clustering, higher average vein thickness and density, and higher thickness to density ratios. This depth control is most pronounced in epithermal gold-silver systems because they have formed at shallow crustal levels where physico-chemical conditions change drastically both vertically and laterally. In addition to lithological and structural control at vein scale, deposit scale structure is of great importance in the deposition of economic mineralisation. Large open vein structures capable of sustaining high fluxes of hydrothermal fluid, favourable for the formation of large, high-grade gold deposits, are best developed in andesite sequences.

Jan 1, 1995

By Michael K. Rhodes

A 120 tonne per day BacTech bacterial oxidation plant treating refractory gold concentrates for Gold Mines of Australia's Youanmi project in Western Australia commenced operation September 1994. This was the first commercial application of the BacTech process. A pilot plant trial on concentrates produced from Youanmi ore was carried out at BacTech's laboratory in Perth. Results and measurements from this trial were used by Signet Engineering Pty Ltd to design the commercial plant. This paper cover the results obtained from the piloting, their implementation in the plant design and the initial commissioning of the full scale plant.

Jan 1, 1995

This paper describes several sources of external dilution affecting the stope walls during underground sub-level and bench stoping. Factors which control ground behaviour such as the geometry of the openings, the influence of geological discontinuities, stress re-distribution and blasting practices are discussed. Crown stope instability due to stress concentrations induced by changes in the excavation geometry, is discussed and the most efficient ways to sequence blasting within a stope are analysed. Effects of undercutting by blasting, blast damage in the near field and cut-off slot blast designs are analysed. The influence of dynamic loading on the exposed walls as well as the practice of blasting fill passes within stope crowns are discussed.

Jan 1, 1995

By N. V. Gorelikova

A new type of zirconium mineralization has been recognized in the Devonian volcanic rocks from an orogenic depression in the Central Kazakhstan. The most characteristic features of this deposit are the fine-grained nature of the zirconium mineralization, an unusual texture of the zirconium ores, and a close association of zirconium with phosphorus in the ores. Zircon grains form fine globular aggregates with the features of hexagonal crystal habit. In addition to crystalline zircon, the ores contain metacolloidal zircon, similar to hydrozircon. The morphological and textural features of the zirconium ores suggest that the deposition of ore deposits took place at a low temperature from colloidal solutions. It is believed that this deposit should be considered to be a new type of zirconium mineralization that is related to low-temperature hydrothermal processes.

Jan 1, 1995

By A. K. Bakshi

Mineral suspensions show Newtonian flow properties at lower solid concentration, but change into non-Newtonian regime as the solids content is increased. For Newtonian fluids viscosity is independent of shear rate, but for non-Newtonian fluids it varies with rate of shear. Therefore, measurement of viscosity at a shear rate, different from the process will be futile unless the slurry is Newtonian. This is especially true for hydrocyclone operation, where the rate of shear is different at different points within the hydrocyclone. In this case, it is very important to determine the flow type of the suspension before attempting to establish any correlation between viscosity and process efficiency. A new technique to distinguish such changes in flow type has been developed. This involved a co-axial cylinder type viscometer which measured apparent viscosity at a low shear rate, and a vibrating sphere type viscometer which measured the apparent viscosity at a high shear rate. Special precautions were taken to allow measurements of viscosity of rapidly settling mineral suspensions. Because the vibrating sphere viscometer operated at a much higher shear rate than the rotating viscometer, the two instruments together could determine the shear-rate dependency of the viscosity. Ground silica of 80% passing 65~m size in water was used to prepare slurries at concentrations ranging from 1O-70wt% solids. Viscosity of each slurry sample was measured simultaneously by both the viscometers and the results were compared with each other. With this technique, it was found that all the silica slurry samples were in the Newtonian flow regime.

Jan 1, 1995

By M. C. Williams

The solution of the dynamic population balance model (PBM) of a closed grinding network consisting of a mill, sump, and cyclone is problematic. The fact that the dynamic PBM model equation solution to the Inverse Problem for grinding systems is degenerate or underspecified is demonstrated. Two numerical solution approaches to the Inverse Problem are used. These are: 1) providing additional constraints on breakage selection functions or 2) performing the Arbiter-Bhrany (or other) normalization of the selection functions. Actual experimental anthracite batch grinding data is used to demonstrate the non-unique functionality of the batch dynamic mill selection and breakage functions for a real physical system. The Levenberg-Marquardt algorithm for systems of constrained non-linear equations is used to solve the batch dynamic PBM grinding equations to obtain the grinding selection and breakage rate functions. Different solutions to the same PBM transport equations are provided. The mill, sump and hydrocyclone were modeled as a CSTR operating at various retention times. Batch dynamic PBM data was used to provide the mill kinetic and breakage selection function data. Two different solutions were obtained depending on the numerical solution approach. The severity of the non-uniqueness problem for dynamic grinding is demonstrated. Each solution approach to a dynamic PBM with transport, while giving the same prediction for a single batch grinding time, gives different solutions or predictions for mill composition for other grinding times. This fact makes dynamic nodal analysis and control problematic. The fact that the constraint solution approach gives a solution may suggest that normalization for closed networks is not necessary. Differences in solutions to the PBM cannot be excused away by inaccuracies in the data used to model the grinding phenomenon.

Jan 1, 1995

By Mohsen Sanai, Paul Gefken

"SRI International has developed and patented* a castable dilute explosive tile @ET) that offersunique advantages over conventional high explosive. The primary advantages of DET are that itsdetonation pressure can be adjusted over a wick range and its impulse can be controlled independently by adjusting its thickness and configuration. Because DET has a much lower detonation velocity than conventional explosives, the pulse duration produced by DET is as much as 10 times longer than the pulse duration produced by conventional explosives for equal explosive weights. These features of DET present several advantages to the mining industry. For example, DET can be tailored so as to control fragment size and distribution to enhance extraction of desired elements from ore or breakup of specific regions."

Jan 1, 1995

By Somerville M, Muray A, Bocking M

Australia has an extremely large total hot dry rock (HDR) resource above a depth of 5 km, equivalent to 7500 times its present annual energy consumption, of which 80 per cent underlies the Great Artesian Basin. The resources most likely to be exploited first are those residing in homogeneous granitic bodies beneath sedimentary basins containing insulating rocks such as shales and coal measures. In the Sydney Basin south of Muswellbrook, an area of high geothermal gradient corresponds to a gravity low thought to be a buried granite body at a temperature of possibly 250¦C. This locality is suspected to have the ideal geological characteristics for Australia's first hot rock test facility. Australia's high HDR potential is possibly unique in the world, in that the potential sites satisfy four independent, geological conditions, each considered as favourable for the creation of a resource, and for the ease of extracting that resource. They are: ò Higher crustal heat generating capacity than that of normal continental crust. ò Much of the Australian continent is covered by sedimentary basins which contain a high proportion of shales and coal measures that have low thermal conductivities, thus providing an insulating blanket for the heat being generated beneath. ò The sedimentary basins are in many places underlain by large untectonised granitic bodies that are not only a major contributor to heat generation, but also ideally suited to the establishment of HDR reservoirs. ò The crustal shortening stress field that is found in the majority of the Australian continental crust results in a vertical minimum principal stress orientation which should result in the development of favourably oriented horizontal stimulation cells necessary for maximising an HDR resource.

Jan 1, 1995

By Bearman R. A

The majority of published material regarding the operation of crushing machinery is concerned with simulation of performance rather than design of equipment. The reason underlying the bias in published material relates to why research is carried out and who undertakes the research. Two distinct types of research can be identified: 1. Internal research by crusher manufacturers - generally related to mechanical design, value engineering and to the commercial realities attached to sales demands. Any work on basic crusher geometry or rock/machine interaction is of a sensitive nature and rarely enters the public domain. 2. Academic research - mostly confined to modelling of crusher performance and simulation. This is not because of any bias, but crusher design requires access to manufacturers data or at least an in-depth understanding of crusher design, which is rarely available. The crushing of rock is a complicated problem. It involves three aspects; the machine geometry, the material composition (type of rock/feed size distribution) and the machine/rock interaction. The machine geometry is often ignored in empirical mineral processing simulations, while the response of different feed materials is only nominally addressed in machine specifications provided by manufacturers. The manner by which the machine produces a stress field and causes different types of breakage for different rocks (or the machine/rock interaction) is sadly neglected by both groups. All three aspects must be considered collectively to successfully understand and model the entire crushing process. 1. Centre for Mining Technology and Equipment, Julius Kruttschnitt Mineral Research Centre, University of Queensland, Isles Road, Indooroopilly 4068 Qld. The importance of crushing is often underestimated. In mining and mineral processing the invisibility of the crushing process is understandable as it merely provides a coarse reduction stage prior to the intricacies of mineral extraction. However in the quarrying industry crushing and screening basically provide the finished product. A brief overview of the quarrying industry shows the importance of crushing. Figure 1 gives production figures for most of the western European countries, Australia and the USA.

Jan 1, 1995