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By S. D. F. Rocha

The influence of surfactants on the crystallization of calcium sulfate was investigated in both hatch and continuous systems. The investigation was per formed at the following conditions. 343 °K, 28% P205 and with a sulfate level of 2.0%. At concentrations of 5 and 200 µgig, respectively, dodecylbenzene sulfonic acid (DBSH) and sodium diisooctil sulosuccinate (SSNa) promoted both an increase in the size and a reduction in the length/width (L/W) ratio of the calcium sulfate hydrates produced in the hatch and continuous crystallizers. Unique effects were observed in the batch system at higher DBSH concentrations. At 10 µg/g, the precipitation of hemihydrate crystals with a distinct morphology and texture occurred under conditions where dihydrate precipitation was expected. Above 50 µg/g, the precipitation of calcium sulfate hydrates was completely inhibited.

Jan 1, 1996

By M. Li, J. D. Miller

Recently water insoluble alcoholic solutions of alkyl hydroxamic acid collectors have been shown to be particularly effective in the flotation of coarse feed material sampled from phosphate operations in Florida, North Carolina and Utah (Miller et al., 2000). The experimental results indicate that high separation efficiencies can be achieved in single stage flotation with these new collectors. In some cases the concentrate grade reached 34% P2O5 with 93% recovery from single stage bench scale flotation experiments. Critical aspects of the composition and structure of these new collectors are discussed with respect to their effectiveness in phosphate flotation. The wetting characteristics at fluorapatite, francolite, dolomite and quartz surfaces are being investigated with the new collector. Finally, other surface chemistry considerations in the development of these new collectors for phosphate flotation are discussed.

Jan 1, 2002

By Roy M. Fleming

During the decade of the 1970's, a new emphasis was placed on assuring a safe and healthful workplace for all American workers. Much of the basis for this national effort was federal legislation: the Occupational Safety and Health Act of 1970 and the Federal Mine Safety and Health Act of 1977 (amended from the 1969 Coal Mine Act). One of the agencies involved in this protection effort is the National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control (CDC) in the Department of Health and Human Services (DHHS). In fulfilling its mandates under the 1970 and 1977 Acts, NIOSH conducts research, experiments, and demonstrations to support and stimulate advancements in health and safety practices. Priorities for NIOSH research are established primarily through congressional mandates, requests from the Department of Labor, needs as defined by NIOSH researchers, and surveillance information. Emphasis is placed on research in the areas of toxicology, industrial hygiene, physical and chemical sciences, physiology, ergonomics, engineering, psychology (behavior and motivation), and epidemiology (industry-wide studies). The framework of the current Institute program to identify, evaluate, and control occupational hazards includes activities in surveillance, research, evaluation, and training. These activities are planned and evaluated through a system that coordinates the efforts of eight research and scientific divisions. Each division develops projects to address program areas that have been identified by NIOSH management as having highest priority. In surveillance programs, the objectives are to identify substances and agents found in a representative sample of workplaces and to collect and evaluate information on rates of disease and injury in occupational groups. Information is also collected on occupational safety and health programs implemented by industry. Estimates of worker exposures and the potential for adverse health effects are considered in setting priorities for further investigations. A related activity, which also serves to provide technical assistance to industry, is NIOSH's Health Hazard Evaluation program. On-site investigations of workplaces are made in response to worker, employer, or government agency requests. Both industrial hygiene and medical examinations are conducted, and the results contribute to identifying new problems and evaluating their significance which may have public health implications beyond the particular worksites that are investigated. Field and laboratory research projects are performed to meet several objectives: - Characterize the working environment by evaluating current and past exposure levels for workers who are included in epidemiological or medical investigations. - Develop epidemiological information to define the association between the substance or agent under investigation and the acute and chronic health effects on workers. - Determine through animal studies the parameters of an association between exposure and effect. - Investigate the etiology of disease. - Develop sampling and analytical instruments and techniques and demonstrate their application for measuring toxic materials in the workplace. - Formulate sampling strategies that will accurately and precisely indicate exposure levels. - Develop medical procedures to prevent disease and to detect the presence of disease and early indicators of disease. - Assess the technology for control of exposures, including engineering and administrative techniques, personal protective equipment, and work practices. Presently, the research program is focused on reproductive effects, neurotoxic effects, injury/trauma, lung disorders, cutaneous disorders, cardiovascular disorders, cancer, stress-related disorders, effects of physical agents, digestive disorders, and renal and other organic disorders. In studying these issues, priorities are determined by the seriousness of possible adverse health effects resulting from occupational exposures, the feasibility of studying existing records or obtaining new data, and the size of the population which is potentially affected. Where there is low level of suspicion concerning adverse health effects or where an occupational disease occurs in a variety of industrial environments, investigations are limited to gross analyses of health effects such as review of mortality patterns. In such studies, the industrial populations selected are those for which existing data resources can be utilized. Such data consists of records of occupational exposures or health status which have been maintained by the employer, the union, or Government agencies. Where a review of the available information suggests that serious health hazards exist and the existing data resources are inadequate for quantifying the relationship between the specific biological response and type and degree of exposure, prospective studies are initiated. Information derived from such research is essential for the development of sound criteria for control of industrial exposures to noxious agents. Other input to the criteria documentation process comes from searching and evaluating the literature. Criteria documents contain the recommendation of an environmental limit where information is available to support it, as well as the recommendation of work practice controls, medical evaluation, information for workers to recognize and avoid the hazard, and identification of specific research gaps. In some cases, during the criteria document preparation, gaps in knowledge are found which necessitate further research before an occupational standard can be recommended.

Jan 1, 1981

By J. H. Tu

The technical paper correctly points out that the kriging variance is not a good measure of the uncertainty of the estimated (i.e., kriged) value of individual blocks. The au thors claim that their proposed jackknife method, which is a rekriging of each block by eliminating, in turn, one sample from the original sample set and then taking the average of the rekriged estimates, not only gives good block estimates, but the resulting jackknife kriging standard deviation is a useful indicator of the "true uncertainty associated with block estimates." However, they immediately abandon the idea of using the block-by-block standard deviations, reasoning that these standard deviations are not independent and that there is no easy way to utilize them. There may be another reason for not using them. The jackknife standard deviations for individual blocks given in their example are mostly in the range of 0.004 to 0.005 oz/st (0.14 to 0.17 g/t) with only one block having a high value of 0.012 oz/st (0.41 g/ t). These individual block standard deviations are as low as the jackknife standard deviation for the mean grade of the entire shape, i.e., 0.0041 oz/st (0.14 g/t). Do they represent the "true uncertainty" of the individual block estimates? Could the authors explain this? In a global shape consisting of a large number of blocks, any given sample will affect the kriged estimate of only those few blocks within its vicinity. This is the rationale for the authors' selective rekriging, making the jackknife algorithm more efficient. On second thought, why not do away with jackknifing altogether? Just cumulate and normalize, if necessary, the kriging weights of each sample used during the ordinary block kriging process, and then compute the global variance from these kriging weights and their respective sample grades? After all, isn't the global mean grade nothing but the weighted average of the samples used in the estimation? Reply by G.S. Adisoma and M.G. Hester The jackknife is one of the many tools in a practitioner's toolbox to solve estimation problems. The strengths of the technique lies in its simplicity, i.e., it uses the concept of mean and standard deviation and the fact that it can be easily combined with other tools, in this case kriging. Because the jackknife kriging (JK) estimate is also the mean of the pseudovalues, the JK standard deviation is attractive just as the standard deviation of the mean explains the variability of the data. The difference is that the pseudovalue calculation in jackknife kriging uses the ordinary kriging (OK) weighting scheme instead of simple arithmetic averaging. The data used to illustrate the jackknife technique in the paper consist of high values that are roughly three times the low values. The resulting JK estimate of the block grades show that the highest estimate is roughly twice the grade of the lowest estimate. The contrast between the low and the high estimate is more evident in the JK estimate than in the OK estimate, even though the mean grades of the blocks for the two estimates are very similar. Nonetheless, in this paper, we are concentrating more on the need for a more realistic measure of uncertainty, or precision, for the estimate. Unlike its OK counterpart, the JK standard deviation of the blocks clearly reflects the original data variation. The highest JK standard deviation of the blocks is three times its lowest value. This follows our intuition that, when the samples used to estimate a block is more variable, the resulting estimation variance (or standard deviation) should be higher than the case where the samples are more uniformly valued. However, block-by-block standard deviation or variance is of little practical value in reserve estimation and classification, as well as in mine planning. One is usually more interested in quantifying not the variance of the individual block estimate, but the uncertainties associated with a much larger dimension, such as the minable reserve. Thus, the thrust of the paper is to find a simple way to obtain a single estimation variance or standard deviation associated with the reserve grade estimate. The discussion by J.H. Tu did not mention how one would obtain the global variance from the OK weights and the sample grades. As a technique that offers a data valuebased measure of uncertainty for its estimate, the "leave-one-out" jackknife fills this need nicely through the block kriging shortcut approach described in the paper. Note: The first column and the last two columns of Table 3 in the paper should have contained a single number each, namely, an OK estimate of 0.0317, a JK estimate of 0.0333 and a JK standard deviation of 0.0041 oz/st, respectively, for the shape, as are obvious from the text. ?

Jan 1, 1998

By Erich U. Petersen, J. B. Hiskey, William J. Tafuri, Donald M. Hausen, X. H. Jiang, Douglas N. Halbe, G. Ramadorai

The extraction of gold from chloride solutions with activated carbon is examined. It is shown that the uptake of gold by activated carbon from chloride solution follows a mechanism whereby gold is reduced to the metallic state. Metallic gold appears as deposits both on the carbon surface and in pore space within the carbon particle. The deposition rate is dependant on the carbon particle size and pH. At low initial gold concentrations, the initial rate is insensitive to gold concentration. Sodium hypochlorite exhibits an adverse effect on the reduction reaction. The overall loading and initial rate of reduction are both decreased in the presence of NaC10. The effect of iodide on the loading of gold was also examined in an attempt to overcome the superficial deposition of gold on carbon.

Jan 1, 1990

By Edward K. E. ] [Williams

Conditioning is any treatment of an ore with or without reagents which affect its floatability. While it can start in crushing or grinding circuits and continue into the flotation circuit, conditioning will refer here only to reagent treatment in an agitated tank designed for the purpose. Such treatment is often unnecessary with sulphide ores and collectors or with amines,* but it has long been recognized as essential with fatty acid collectors in the flotation of non-sulphide minerals, The requirements can be extremely variable, depending upon ore alteration, the presence or absence of slimes, and 1 the minerals to be separated. The study described here was concerned with the recovery of oxidized molybdenum minerals from an ore containing the element in both sulphide and oxidized form. Flotation of the iron minerals with which the oxidized molybdenum was associated was the basis for the process. Recovery and optimum concentrate grade without desliming depended upon a twenty to thirty minute conditioning of the pulp with flotation reagents at forty to fifty percent solids and at high turbulence. The objective in the study was the determination of design and operating criteria for conditioners in order to permit scaling-up of the results without repeating the entire study on a larger scale.

Jan 1, 1968

By Neil B. Prenn

Drill-hole contamination has been a problem for many years. Contamination of rotary drilling has been well documented. More recently contamination in wet reverse circulation drilling has been noted by Echo Bay and others at the 1991 AIME annual meeting. Mine Development Associates (MDA) has worked on a number of projects at which contamination of drill-hole samples has occurred. Properties are commonly acquired with drilling accomplished by other companies and at times the only records of the drilling program are the drill-hole logs and assays themselves. Identification of contaminated zones is sometimes difficult to determine. Most geologists and engineers in the industry are aware of the magnitude of the problem, as contamination is a relatively common problem with wet reverse circulation drilling. MDA has developed a computer program to help determine if contamination has occurred when using reverse circulation drilling, based on cumulative distribution curves and by a process we call decay analysis. Most deposits are not homogeneous throughout the deposit, but exhibit a characteristic drop-off or decay of assay values around higher-grade drill-hole intercepts. Using graphs of this characteristic decay and cumulative frequency distribution, we can use the program to help determine contamination in several ways. This paper will discuss the use of decay analysis at three gold deposits where contamination is known to have occurred. In one of the deposits decay analysis was used, successfully to determine if contamination had occurred, while in the other two the decay analysis was used to verify our decay analysis procedure.

Jan 1, 1992

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 Roger B. Jr. Herbert

Surface water samples were collected from water accumulations at the surface of a neutral pH mine tailings deposit in Kristineberg (Sweden) where algal growth and iron hydroxide precipitates were observed. Ferric iron in the aqueous samples was determined by (adsorptive) differential pulse - cathodic stripping voltammetry. The analyses indicated that labile Fe3+ concentrations were in the range <20 to 337 nM, while total Fe3+ levels were much higher at 0.9 to 8.3 uM. The labile Fe3+ levels are more than two orders of magnitude greater than would be expected based on equilibrium with ferrihydrite. These results suggest that iron complexation with strong ligands in the surface water competes with iron hydrolysis, and that these ligands may be of algal and/or bacterial origin.

Jan 1, 2000

By Hassan El-Shall, Abbas A. Zaman, Brij M. Moudgil

The addition of organic and inorganic dispersants to aqueous suspensions of heterogeneous particles (kaolin) was found to significantly affect the solubility of metal ions from kaolin particles and stability of the dispersion. In most of the industrial applications of kaolin, highly concentrated slurries of controlled stability and fluidity are required. The solubility of kaolin particles in terms of aluminum and silicon ions and its effect on the stability of the slurry was investigated. The main objectives of this study were (1) to study the effect of the extracted metals on the properties and performance of the slurry, (2) to understand the reaction mechanism of dissolution of metals from kaolin, and (3) to understand the interaction mechanism of dispersants with kaolin particles. The controlling variables were dispersant dosage, slurry pH, solids loading, and aging.

Jan 1, 2003

By Gordon F. Revey

In underground construction and mining work, situations occasionally occur where hard rock or concrete must be excavated at locations near critical structures or utilities. Fearing damage from blasting, contractors and engineers often explore the viability of using mechanical methods or expansive concrete to facilitate the excavation work. However, for moderate to large excavations, the prolonged duration and high cost of using these methods is often impractical. In these situations, under the right conditions, controlled blasting and blast-management methods can be used to speedup the work and lessen costs. The process of determining whether or not blasting is practical is often complex, particularly when risks are high. In this paper, general methods of conducting blasting risk evaluations and outlined and considerations for blast design and risk management are reviewed. This paper also includes three blasting case histories demonstrating how these techniques were used at recent projects. In the first case, a cautious blasting program was developed to facilitate the removal of concrete and rock within a large section of an active mineshaft. The second case involved critical blasting to excavate a dry lake-tap connection between a tunnel and a shaft at the Southern Nevada Water Intake No. 2 project in Henderson, Nevada. The third case history describes how novel blasting methods were used to carefully drop a 2,721,500-kg (6,000,000-lb) concrete caisson into a1.2-m (4-ft) rock socket at the Detroit Outfall No. 2 project in Detroit, MI.

Jan 1, 2001

By Regina N. Tempel, Mae S. Gustin, Mark A. Engle

This study characterizes the hydrogeochemistry of groundwaters near opalite-hosted epithermal hot-spring type mercury deposits in the Ivanhoe mining district, Elko County, Nevada. Local groundwaters generally range from Ca-HCO3 to Ca-Mg-Na-SO4 type waters with background mercury concentrations ranging from 0.014 to 0.32 ug/l. Leaching experiments conducted on mineralized rocks, using typical water chemistries to represent local groundwaters, yield total mercury concentrations ranging from 6.3 ug/l to 27.4 ug/l after one year of reaction. Geochemical modeling indicates dissolved mercury is dominated by HgO(,) and that precipitation of quicksilver controls mercury concentrations to an upper limit of 63 ug/l.

Jan 1, 2000

By Irving Hoch

INTRODUCTION The demand for tunnelling can be related to urban population size and density; often, tunnelling occurs when a certain city size and density threshold is reached, and increases thereafter as a function of those population characteristics. Subways for rail mass transit are the most notable example, of course, but tunnels for water supply and perhaps for sewerage can also be related to size and density. As cities grow large they sometimes outgrow their local water supply and have to import water from distant places via tunnels; witness New York City, Los Angeles and San Francisco. And it has been suggested that Chicago use deep tunnels for storm water storage because tertiary treatment to meet water quality standards will require treating storm water runoff.(1) Other uses of underground space also increase with urban density, e.g., underground parking, concourses and shopping centers such as Rockefeller Center in New York City and the Place Ville-Marie in Montreal. These examples can be viewed as illustrative of the central point of urban land economics. As the number of people locating in a place increase, they bid up land values and make the more intensive use of land economic, with land defined to embrace the space both above and below the surface. Hence, we are led to think about the city, and of urban land use, in three dimensions. Now, if we accept the relation of underground space use to urban size and density, recent demographic trends seem anything but hopeful for future tunnelling demand: urban density is declining, population growth is slowing down generally, and there

Jan 1, 1974

By Krystyna Raszka, Jerzy Iskra

The paper presents results of spectrophotometric investigations concerning the adsorption of sodium oleate on silicon carbide in the presence of the cations of multivalent metals, applying the ATR IR technique with computer-aidedprocessing of the spectrum. The analysis of these spectra indicates the occurance of distinct OH and COOH bands in the pH range in which the hydroxy complexes of metals of the type MeOH+ and MeOH++ reach in the respective cases the highest concentration in the solution. The correlation of these results with those of flotation, measurements of the zeta potential confirms the proposed mechanism of activation of the flotation of silicon carbide, applying sodium oleate as a collector, the collection taking place over the adsorption of hydroxy complexes of the type MeOH+ and MeOH++

Jan 1, 1995

By Robert H. Oliver

Flowsheet flexibility in new 750 TPH coal cleaning plant provides three unusual capabilities. Two compartment drum coarse H.M. washer can be adapted to provide two stage separation. Coarse section of plant can be operated without fine section when washing surface mined coal. Fine section can operate with flotation cells bypassed if strip coal oxidation kills the froth. Plant can be fed by belt from bulk storage, front end loader from storage piles and truck from the mines. Raw coal and each of four washed products can be fed by belts to three separate loading points on two separate railroads.

Jan 1, 1979

By R. B. Lawrie

Diesel powered underground mining equipment is presently the most productive, safest and efficient equipment used in underground mining operations. The widespread application of this equipment to underground mining is restricted, however, largely because of the difficulty of controlling the diesel engine exhaust emissions. This paper briefly examines control devices currently available for underground application, and also discusses the theory and mechanics of controlling diesel missions with particulate traps and filters.

Jan 1, 1985

By Sertaç Dündar, Bilgehan Kekeç, Arif Emre Dursun, Niyazi Bilim

"Estimation of rock drillability is vital for mining and boring operations. For this purpose, many researchers have developed various models and equations to estimate rock drillability. Most of these models aim to determine the drillability of rock and the penetration rate by using the physical and mechanical properties of rocks. Although drillability primarily depends on rock properties, other parameters have an impact on drillability as well. One of these parameters is the rotation speed of the bit. This study investigates the effect of rotation speed of the bit on drilling performance. Drilling tests were performed in the laboratory using rotary core drilling and a diamond drilling machine. The relationships between the physical rock properties and the penetration rate were investigated on 15 different rock types and four different rotation speeds were applied to determine the effect of rotation speed of bit on drilling. The uniaxial compressive strength, density, and P wave velocity show strong correlations with the penetration rate. In addition, if the values of the physical and mechanical properties of the rock increase, the effect of the rotation speed on the penetration rate decreases, i.e., increasing the rotation speed of the bit slightly affects drillability on hard and solid formations. 1. Introduction Drilling is one of the most essential operations in the mining industry, beginning from the exploration phase and continuing throughout all stages of production to the end of mine life (Taheri et al. 2016). In addition, drilling is widely using in the construction industry and other engineering operations. Various drillholes (blastholes, injection holes, borehole, diamond wire holes in natural stone mines, etc.), are needed during development and production activities in underground and open-pit mines as well as in dam, tunnel, road construction and sewage systems. For effective drilling operations, it is first necessary to gather information about the formation to be drilled. Drilling should then be performed after selecting appropriate drilling equipment and drilling parameters (thrust, pressure, rotational speed, flushing). Prediction of the drillability of rocks is vital for planning and performing the drilling process. Although, drilling is affected by several factors, the most important ones are related to the geological and mechanical properties of formation (Protodyakonov 1963, Paone et al 1969, Tandanand and Unger 1975, Pathinkar and Misra 1976, Rabia 1985, Perrin et al 1977). Determining the penetration rate is vital for planning a project and calculating the operation costs. The prediction of drilling affects the selection of drilling equipment, the efficiency of drilling equipment, project costs and the process of drilling operations."

Jan 1, 2017

By M. E. Poad, Donald Ross, G. G. Wadell

Because of the "energy crisis" emphasis has been placed on bringing coal mines into full production faster. To accomplish this, more is involved than a rapid excavation system. Mine design should have the freedom within the law to customize as mining conditions dictate as long as the maximum safety of the miner is insured. A year ago, safety was the most prominent "social-human factor"--now, safety and energy self-sufficiency are primary to our national policy. The Single Entry research program as designed satisfies both. It investigates the hypothesis that a single-entry system, for longwall development, supported in the center by open cribs and divided by a fire-resistant partition, can be regarded as being equivalent to or better than a multi-entry system. This paper provides an explanation for the use and advantages of a single entry system in development for longwall mining, explains the problems anticipated with single entries and presents the research approach needed to evaluate and solve the problems. Under study are ground control, ventilation, fire and explosions, emergency procedures, and industrial hazards. Described are measurements data on crib and roof bolt loads as entry heading advances and longwall abutment load is superimposed, stress field determinations and preliminary structural analysis of the double and single entry, and methane liberation and ventilation records as entry advances. Some of the mine operation problems and waivers of mining laws will be discussed. This project is a complete system study having progressed approximately two years in a five-year program.

Jan 1, 1974

By V. Galla

In the present paper, two large diameter columns 2 m tall and 1.3 m diameter filled with crushed (finer) and run off mine (coarser) heap leach materials respectively were used to perform unsaturated flow studies. Instruments measuring moisture content and matric suction were placed in the columns at different depths as water was applied at calibrated flow rates from the top of the columns. The outflows from the columns were recorded using tipping bucket rain gauge placed at the bottom of the columns. Unsaturated hydraulic parameters were also obtained for the heap leach materials, scalped (passing 4.75 mm sieve size) and whole (passing 37.5 mm sieve size) sample. The measurements obtained from the columns were later compared with unsaturated flow modeling results. The comparison indicated sensitivity towards the sample size selection for unsaturated hydraulic parameters, and initial conditions considered in the model.

Jan 1, 2009

By Martin F. Grier

The Mt Todd Gold Project is located 300km to the south of Darwin in the Northern Territory of Australia. The identified resource comprises 46 million tonnes at 1. 65g/t using a 1. 0g/t cut-off ( 50 million short tonnes at 0.05oz/st). The resource is open to the north and at depth. Mineralisation comprises easterly dipping sheeted quartz/sulphide veins, typically 10 to 20 millimetres in thickness, hosted by hornsfelled greywackes. The majority of the ore body is primary ore with only 10% classified as oxide ore. Early testwork showed that the ore was not suitable for heap leaching, giving only 50% recovery at a -3mm crush size. Acceptable recoveries were obtained at a P80 of 75 micron. However, the ore is extremely hard.

Jan 1, 1992