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By James L. Withiam, P. C. Kelsall

The manuscript of this paper was not available for publication when the Proceedings went to press. Should the authors elect, they may distribute copies at the time of the Symposium.

Jan 1, 1986

By J. A. Organiscak

The National Institute for Occupational Safety and Health (NIOSH) has investigated various factor effects on cab air filtration system performance. Factors experimentally investigated were intake filter efficiency, intake air leakage, intake filter loading (filter flow resistance), recirculation filter use, and wind penetration. Adding an intake pressurizer fan to the filtration system was also investigated. Results indicate that the intake filter efficiency and recirculation filter were the two most influential factors on cab protection performance. Use of a recirculation filter significantly reduced cab penetration over the intake air filter by itself due to the multiplicable filtration of the cab interior air. Cab penetration was also affected to a lesser extent by intake filter loading and air leakage. Adding an intake pressurizer fan notably increased intake airflow and cab pressure while providing only minor changes to cab penetration.

Jan 1, 2008

This paper was developed as part of an effort by the National Institute for Occupational Safety and Health (NIOSH) to identify risk factors associated with bumps in the prevention of fatalities and accidents in highly stressed, bump-prone ground conditions. Changes of failure mechanism with increasing confinement, from extensional- to shear-dominated failure, are widely observed in the rupture of intact specimens at the laboratory scale and in rock masses. In the previous analysis conducted in 2018, both unconfined and triaxial compressive tests were conducted to investigate the strength characteristics of some specimens of a Utah coal, including the spalling limits, the ratio of apparent unconfined compressive strength (AUCS) to unconfined compressive strength (UCS), the damage characteristics, and the post-yield dilatancy. These mechanical characteristics were found to be strongly anisotropic as a function of the orientation of the cleats relative to the loading direction.

Jan 7, 2020

By F. Woodcock, A. R. Laplante

A test to characterize the amount of gravity-recoverable gold (GRG) in an ore is described. Typical GRG results are given and possible uses are discussed. The overall database, which includes 68complete tests, is presented. The ore samples treated had an average GRG content of 63% of the total gold in the sample, with a standard deviation of 20% and a range of 3% to 97%. Both the F8(, of gold and the GRG content at a grind of 100% finer than 850 pm correlate well with the overall GRG content (at 80%finer than 75 pm). The primary use of the test is to determine whether gravity recovery should be used and how. Results can also be used to predict gravity recovery, as many of the ores tested are from plants employing gravity recovery. Gravity-circuit simulation can be used to refine recovery estimates or for optimization studies.

Jan 1, 2000

By M. Moats, J. Young

Short term laboratory cell electrorefining experiments were performed to examine the impact of electrolyte composition, current density and temperature on deposit structure, roughness, and adhesion to 2B mill finished 316L stainless steel. Copper electrodeposits were produced using synthetic electrolytes with thiourea and the continuous addition of glue. Deposit structures were evaluated using X-ray diffractometry. Surface roughness was measured using profilometry and analyzed using scaling analysis. Finally, an internally developed method was used to measure the force required to remove the electrodeposited copper from stainless steel to determine adhesion strength.

Mar 2, 2022

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 Jerry Dollinger, Levent Ozdemir

An extensive series of laboratory cutting tests using linear and rotary cutting machines were carried out with the objective of investigating the feasibility of achieving very high rates of penetration with TBMs in rocks of low to medium strength. These tests were performed with large diameter disc cuttrs at cutter path spacings and penetrations of up to 12 and 1.75 inches, respectively. A predictor model was also formulated to characterize rock cutting at large spacings and penetrations.

Jan 1, 1987

By Richard Klimpel

The laboratory ball mill grinding of coal/water slurries is described for three coals. Emphasis is placed on the measurement of specific rates of breakage for various operating conditions. Corresponding rheological information is also presented based on data collected using a rotational viscometer. A rheological explanation of the influence of various slurry fluidity conditions on the specific rates of breakage is presented. This rheological approach has proved useful In both the identification of suitable chemicals for increasing breakage rates in coal/mineral slurry grinding and in the plant scale implementation of dense slurry grinding systems.

Jan 1, 1982

By L. Xu, N. I. Jayaraman, R. Bhaskar

The objective of this study is to develop a better understanding of the collection characteristics of dust measurement instruments used in mine dust control research with respect to properties of quartz and coal dust. Coal and quartz dust of narrow sues, with aerodynamic median diameters being approximately 2 µm, 4 µm and 10 µm, with quartz contents of l0%, 20%, 30%, 40% and 50%, were released in an aerosol characterization chamber using a fluidized bed aerosol generator. Dust was collected in MSA personal gravimetric samplers with l0-mm nylon cyclones, total dust samplers and Sierra 298 inertial cascade impactors. The samples were analyzed for mass and quartz content. A total of 21 experiments were performed for this study. The mass and quartz collection efficiencies of the total and respirable dust samplers and the impactor were determined. The data show that the amount of dust collected by the respirable dust sampler (respirable + oversize dust trapped in the cyclone pre-classifier) was, in general, less than the amount collected by the total dust sampler. The amount of dust collected by the impactor was higher than that collected by the total dust sampler. Quartz analyses of the airborne dust samples showed that the total dust and respirable dust samplers (including oversize dust) collect less quartz dust than at inertial impactor. The larger the median particle sire of the quartz and coal mixture, the lower the quart content of the dust collected in the samplers. For all three sires, the impactor was a better collector of quartz than the other instruments.

Jan 1, 1994

By S. L. de Moraes

This study aimed to identify a way to reduce the use of bentonite in the pelletization of magnetite. With this goal, different combinations of binders were compared to bentonite by examining the quality of pellets obtained by balling drum agglomeration. Pellets were subjected to routine tests that included simple compression of the wet and dry 105°C pellets, dropping wet pellets to determine their ability to survive handling and submitting pellets to thermal shock to determine how they tolerate drying and preheating. The best results use sodium silicate (1.5%) as a binder and show that it is possible to pelletize iron ore without using bentonite.

Jan 1, 2010

By Jamal Rostami, Wei Hu

Efficient performance of EPB TBMs in clayey ground is primarily dominated by the flow capability of the excavated muck in the cutterhead and screw conveyor. Currently, Consistency Index approach is used to evaluate clay clogging potential, but it does not include the effects of surcharge pressure on clay behavior. In this paper, a macro-scale soil rheometer is introduced to assess the clogging potential under various water content and surcharge loading conditions. The results show that, in addition to water content, surcharge pressure has clear impact on clay clogging too. In practice, Consistency Index chart can be refined to incorporate the impact of face pressure to better simulate the EPB tunneling conditions.

Jun 13, 2021

By R. D. Doepker, P. L. Drake

The dissolution of metals from various metal- mine tailings has been studied through a series of submerged tailings batch tests at US Bureau of Mines laboratories. Tailings selected for this study included both reactive (as determined by column leaching studies) and benign tailings. Metal mobilization in aerated (97% saturated with oxygen) samples appeared to be consistently greater than metal dissolution from stagnant (79% or 70% saturated with oxygen) waters. In the early weeks of the study, sulfate concentrations increased with solid-liquid contact time, while calcium dissolution remained early constant. Metal concentrations varied in relation to solid-liquid contact time and aeration. Leachate pH appeared to be nearly independent of solid-liquid contact time for basic tailings. Reactive tailings having both a submerged and a surface component demonstrated increased metal mobility.

Jan 1, 1991

By R. D. Doepker

The dissolution of metals from various metal-mine tailings has been studied through a series of submerged tailings batch tests at U.S. Bureau of Mines laboratories. Tailings selected for this study included both reactive (as determined by column leaching studies) and benign tailings. Metal mobilization in aerated (97 pct saturated with oxygen) samples appeared to be consistently greater than metal dissolution from stagnant (79 pct or 70 pct saturated with oxygen) waters. In the early weeks of the study, sulfate concentrations increased with solid-liquid contact time, while calcium dissolution remained nearly constant. Metal concentrations varied in relation to solid-liquid contact time and aeration. Leachate pH appeared to be nearly independent of solid-liquid contact time for basic tailings. Reactive tailings having both a submerged and a surface component demonstrated increased metal mobility.

Jan 1, 1990

By Nobuharu Isago, Atsushi Kusaka, Kosuke Kawata

"Strong earthquakes occur frequently in Japan, and some rock tunnels have sustained severe damages on their permanent lining. Many road tunnels, which were constructed by conventional steel arch support and timber lagging method, exist in Japan and they need risk mitigation measures against earthquakes as per our empirical knowledge. Many reinforcing measures for deformed tunnels that may be effective against earthquakes are developed; however, behaviors during earthquakes are not fully understood.In this study, static loading tests and numerical analysis, which simulate a loading condition during earthquakes, were carried out to clarify the effect of the countermeasures. The Load-bearing capacity is estimated for the tunnel structures facilitated by the installment of an inverted arch; however, a joint between inverted arch and sidewall become structural weakness. Rock bolts and carbon fiber sheets have a potential able to mitigate the risks of collapse of the lining by the forces from an earthquake.INTRODUCTIONA number of rock tunnels with no apparent unfavorable ground conditions suffered severe damage, including the collapse of their permanent lining, in large seismic events such as the Chuetsu Earthquake in 2004 (e.g., Mashimo 2005). Since these tunnels were considered to exhibit the required structural strength to survive earthquakes, studies are being carried out to clarify the mechanical behavior of tunnels during earthquakes and their damage mechanism (e.g., Kusaka et al. 2009); however, the aseismic design methodology for mountain tunnels has not yet been established.In many cases of earthquake-damaged tunnels, some defects already existed, such as improper construction and deterioration of lining concrete. Although countermeasures are usually implemented against such problems, their earthquake-resistant effect was not fully understood.In this study, static loading tests and numerical analyses to reproduce these tests were carried out assuming that a rock tunnel was affected by the earthquake to clarify the mechanism of the lining damage and the effect of the countermeasures."

Jan 1, 2016

By Joseph M. Keane

Introduction The English word "sedimentation" is derived from the Latin verb "sedere" meaning to sink down. As a mineral processing unit operation, sedimenta¬tion has been defined as the separation of a suspension into a supernatant clear fluid and rather dense slurry containing a higher concentration of solid (Brown, G.G. 1960). Sedimen¬tation has been historically subdivided into thickening, which has the primary purpose of increasing the solids content of one of the thickener prod¬ucts relative to the feed stream, and clarification, which has the primary purpose of removing solids from the feed stream to produce a product essentially free from particu¬late matter. There is no absolutely precise distinction between these subdivisions and in certain applica¬tions, both objectives can be accom¬plished. Major Design Factors The capacity of conventional metal¬lurgical sedimentation devices is a function of slurry throughput and its attendant settling rate. Important factors, recognized by early investigators (Taggart, 1972), which influence the settling rate of a given metallur¬gical slurry include: Feed dilution or solids-liquid weight ratio Size and shape of the particulate solids Specific gravity differential between the solids and liquid phases Presence of electrolytes and/or flocculants Pulp viscosity Slurry temperature In addition to the foregoing histor¬ical factors, recent investigators have noted (Pearse, M.J., 1977) that other parameters which may have an influence upon settling rate and, thereby, thickener performance include: Method of flocculant application Particle size distribution Particulate wetting characteristics Feeding arrangements Rake speed and type Existence of convection currents Wind disturbance Evaporation All of the above factors should be examined and the effect upon thick¬ener performance brought about by manipulating the factor over the expected operating range should be determined if performance optimization is desired.

Jan 1, 1986

By J. E. Lawver, F. S. Knoll

Introduction Electrostatic separation is the selective sorting of solid species by means of utilizing forces acting on charged or polarized bodies under the influence of an electric field. Electrostatic separation is effected by adjusting those forces acting on particles due to the electric field as well as co-acting forces such as gravity or centrifugal forces so that the different species will have different trajectories at some predetermined time. Electrostatic separations can be broadly defined as being either electrophoretic or dielectrophoretic. Electrophoresis is the separation of charged particles in an electric field, whereas dielectrophoresis is the separation of neutral particles in an electric field1. Examples of an electrophoretic separation can be found with sepa¬rations that use corona charging (ion bombardment), contact charging (triboelectric) and conductive induction. Dielectrophoresis motions are due to the stress and repositioning of charges, i.e. polarization of a neutral particle when exposed to a non-uniform electric field. Separations made using corona discharge devices are often called high-tension, electrodynamic or ion bombardment separations. These are the most prevalent in use today in mineral processing. Dielectrophoretic separation of most minerals is based on differences in dielectric constants of the solid species and usually requires the use of expensive intermediate dielectric fluids. Dielectrophoresis has not been employed for industrial mineral separations, though its effects pose interesting possibilities1, and pilot-plant units developed by the U.S.B.M. are available for testing2. Our discussion will be limited to the three forms of electrophoresis found in commercial practice. Typical Industrial Separations Typical industrial applications of electrostatic separation are: 1. Dry concentration of heavy minerals: ilmenite, rutile, zircon, monazite, xenotime, columbite-tantalite, cassiterite, hematite, scheelite and others. 2. Separation of salts: halite-sylvite, etc. 3. Purifications of foodstuffs such as the removal of impurities and

Jan 1, 1986

By Barbery G., A. Maachar, M. Bourassa

Laboratory testing for flotation circuit design is carried out on a routine basis in a large number of lab- oratories throughout the world. Usually a sample of ore, assumed to be characteristic of the material to be processed in a future plant, having a mass of the order of a few kilograms, is ground in a batch ball or rod mill, in the presence of water and some re- agents (for pH control, etc. .. ); after dilution to the adequate solid concentration, the resulting slurry is transferred into a laboratory batch flotation machine, having a volume which can vary from 0.5 to 8 10 -3m3. Various types of machines are in common use, manufactured by the same companies that market industrial size flotation machines. The operation of flotation in the laboratory is carried out by an experienced technician, who uses parameters such as impeller rotation speed, air flowrate addition, froth height, froth removal rate, in conjonction with reagent addition sequence, to "test" the ore. After flotation, the froth products ("concentrates"), and the solids remaining in the cell are filtered, dried, and analyzed for the various elements of interest. For flotation circuit design, a kinetic test is usually carried out, in which the froth products obtained at various times are collected to assess the time response of the ore in the laboratory machine with the combination of reagents used. Although this description is rather sketchy, it enables to outline some of the major difficulties in using laboratory data for flotation circuit design: 1. ore sample representatively 2. feed preparation procedure (laboratory compared to industrial scale) 3. laboratory procedures (type of ma- chine, type of operation, experimental errors. . . ) 4. flotation machine scale-up 5. flotation kinetic scale-up 6. flotation circuit design using laboratory data These various points will be discussed in the present paper, in order to stress the problem areas as well as possible solutions. ORE SAMPLE REPRESENTATIVITY It has been stated many times that one of the major problem in designing a flotation circuit is the representatively of the sample to be taken. Sampling of an ore body during prospection and evaluation is a specialized field, which has been progress in with the introduction of geostatistics. The application

Jan 1, 1986

By W. M. Jr. Aubrey, R. L. Stone

INTRODUCTION Most metallic minerals and some industrial minerals have a relatively high specific gravity and most have at one time or another been concentrated by gravity methods. The principles of gravity concentration are straightforward, well documented and easy to understand, but in practice there are many pitfalls that await the engineer in the development of an integrated flowsheet. Gravity concentration equipment has a long history of use and there is a great diversity available. The equipment is capable of treating material over a broad size range, only falling off in efficiency in the very fine sizes. Gravity concentration is also inexpensive, generally free of environmental problems, and commercial equipment can process large tonnages of ore with a minimum of capital cost. As might be expected of an efficient and low cost process, the bulk of the tonnage quickly and inexpensively. Another obvious application is treating mineral deposits such as hematite and manganese ores that are sufficiently liberated after a minimum of crushing to allow production of a coarse concentrate that will meet market specifications. Except for hand picking and mechanical sorting, there is no competing process on coarse size material. Conversely, it is sometimes obvious that gravity concentration does not warrant consideration. Examples are ores that require very fine grinding to attain liberation, for ores where the minerals of interest have a gravity similar to the gangue, and ores that are strongly magnetic. Actually a mineral processing engineer may not know if gravity is the best way to concentrate an ore, but he should have little difficulty recognizing when gravity concentration deserves consideration based upon specific gravity differences and liberation gravity concentration has wide use. size. His challenge then is to At times its selection as the identify and test the applicable primary concentration process is processes, to develop a obvious. Low grade placer deposits metallurgical balance and flowsheet of tin, gold and beach sands usually for the best process, to estimate are only profitable because gravity production rate over the life of concentration is able to throw away the deposit and to make equipment

Jan 1, 1986

By M. J. Ross, D. A. Norrgran, J. A. Wernham, J. N. Orlich

INTRODUCTION Laboratory testing for magnetic concentration circuit design is a requirement, just as it is for most other types of concentration. Natural variations in raw materials allow on1 y the broadest of generalities to be made regarding magnetic separation. Further, magnetic fields are geometry dependent, leaving fundamental models of a separator overly dependent upon the exact conditions for which the models were derived. Despite this, an understanding of the basics of magnetic separation and of the problem to be attacked can result in rapid progress towards the final circuit design with a relatively simple testing program. Magnetic Separation Basic Principles A magnetic field can readily be understood in terms of lines of flux. A familiar demonstration of these lines of flux is the pattern of iron filings on a sheet of paper when a magnet is placed underneath. Lines of flux2 are measured in Gauss (1 line/cm2) or Tesla (10000 gauss). Regions of high field strength have a greater number of lines. Field direction is indicated by a convergence of lines. When a particle is placed in a magnetic field it cuts the lines of flux and alters them in one of three basic patterns. These patterns are referred to as diamagnetic, paramagnetic and ferromagnetic. Diamagnetic materials have electronic structures which react to oppose an applied magnetic field. This opposition acts to locally reduce the applied field slightly. The visualization is that lines of flux diverge and go around the particle. Because of this divergence or opposition, a diamagnetic particle will tend to move towards regions of lower flux density. That is to say that the particle will be repelled by a magnetic field. Aluminum oxide and napthalene are examples of diamagnetic materials. Paramagnetic materials have an electronic structure which increases an applied magnetic field. Although these materials also exhibit diamagnetism, they have randomly oriented impaired electrons which align with the magnetic field. The resultant local field enhancement is significantly larger than the diamagnetic opposition. The visual-

Jan 1, 1986

"A carefully planned laboratory test program is the foundation for the successful development of a sulfide flotation process. In this paper, the development of a copper-molybdenum flotation process is described. However, the concepts discussed can be applied to most sulfide flotation systems and to many industrial minerals projects as well. Each step is examined, beginning with sample procurement and covering sample preparation, flotation test preparation grinding, scoping flotation tests for reagent scheme selection, rougher flotation parameter evaluation and cleaner circuit evaluation, through to locked-cycle testing and pilot plant design and operation. Ore variability and modeling to determine the response of various ore types to the optimum conditions established is also examined.IntroductionA carefully planned laboratory test program is essential for the successful development of any sulfide flotation process. These programs usually begin with a series of batch tests on several ore type composites to evaluate appropriate reagent schemes and delineate optimum rougher flotation conditions, such as primary grind size, flotation pulp density, flotation pulp pH and retention time. Cleaner parameters such as regrind size requirements, cleaner pH, pulp density and number of stages are then defined. Semicontinuous locked-cycle tests are performed using the parameters established in the batch tests to determine the effect of middling streams recirculation on flotation performance. The data generated and the experience gained in the locked-cycle tests may be used to design and operate a continuous pilot plant if relatively large amounts of concentrate are required for further process development, such as optimization of byproduct molybdenum production from bulk copper-molybdenum concentrate.A comprehensive ore variability program is undertaken to determine the response of various ore types to the optimum conditions established. These ore variability programs often test hundreds of samples in standardized batch rougher and cleaner tests to ensure that the orebody is well understood.This article describes the development of a copper-molybdenum flotation process, but the concepts discussed can be applied to most sulfide flotation systems and many industrial minerals projects. The block flow diagram in Fig. 1 provides an overview of the development process."

Jan 1, 2016