<p> Case histories in mining have long described pillars or faces of rock failing violently with an accompanying rapid ejection of debris and broken material into the working areas of the mine. These unstable failures have resulted in large losses of life and collapses of entire mine panels. Modern mining operations take significant steps to reduce the likelihood of unstable failure, however eliminating their occurrence is difficult in practice. Researchers over several decades have supplemented studies of unstable failures through the application of various numerical methods. The direction of the current research is to extend these methods and to develop improved numerical tools with which to study unstable failures in underground mining layouts. </p><p> An extensive study is first conducted on the expression of unstable failure in discrete element and finite difference methods. Simulated uniaxial compressive strength tests are run on brittle rock specimens. Stable or unstable loading conditions are applied onto the brittle specimens by a pair of elastic platens with ranging stiffnesses. Determinations of instability are established through stress and strain histories taken for the specimen and the system. </p><p> Additional numerical tools are then developed for the finite difference method to analyze unstable failure in larger mine models. Instability identifiers are established for assessing the locations and relative magnitudes of unstable failure through measures of rapid dynamic motion. An energy balance is developed which calculates the excess energy released as a result of unstable equilibria in rock systems. These tools are validated through uniaxial and triaxial compressive strength tests and are extended to models of coal pillars and a simplified mining layout. </p><p> The results of the finite difference simulations reveal that the instability identifiers and excess energy calculations provide a generalized methodology for assessing unstable failures within potentially complex mine models. These combined numerical tools may be applied in future studies to design primary and secondary supports in bump-prone conditions, evaluate retreat mining cut sequences, asses pillar de-stressing techniques, or perform backanalyses on unstable failures in select mining layouts.</p>

Rotary drilling with roller cone bit is often accompanied by wide fluctuations of the weight on bit (WOB). In certain cases the WOB periodically reduces to null. It has been postulated that in these cases the bit lifts off from the formation surface. The present study models the interaction among the lift-off of the bit, the WOB variation, and the modulation of the amplitude of the lobes on the formation surface. The analytical model is used to obtain numerical results for a specific drillstring. From these results it is inferred that the rotary speeds corresponding to the axial resonant frequencies of the system, determined from the functions of the driving point mobility and impedance at the bit, are critical regarding the wide fluctuations of the WOB. They may be associated with the sustenance of the lobes with large amplitude.

Lime neutralization of acidic drainage is the most common process to produce an environmentally acceptable effluent. The process involves neutralization, precipitation of metal hydroxides, flocculation, settling and storage of the sludge. The sludge is not entirely stable over the long term due to the natural pH decline in the storage area that can re-solubilize metals. The use of activated silica sol could be an alternative to flocculants in the lime neutralization process. The nature of the metal hydroxide---silica bond could make the sludge more stable on short and long term. / It was observed that similar settling characteristics can be obtained with the standard flocculant and a low dosage of activated silica sol. Using activated silica sol, the settling rate is dependent on the concentration of magnesium and iron in the mine effluent. / There was an improvement in sludge stability when using a high dosage of activated silica sol. Two mechanisms have a role in the increased stability: the adsorption bond and the buffering capacity of activated silica sol. The tests suggested that a dosage of 0.1 gSiO2/gFe optimizes the settling characteristics and the sludge stability.

This study compares three mining taxation systems: royalty, profit tax and profitability tax, in a theoretical framework. It examines concepts and forms of taxation which are applicable to various nations, regions and/or commodities. / The study first reviews the economic characteristics of the mining industry and the principles of economic rent. Then, using a computerized model of a hypothetical project, the comparative impacts of the three tax systems are determined. / The following conclusions have been drawn from the study: (1) In general, taxes are a significant cost to a mining project. (2) A revenue taxation system (i.e. royalty) is easier to implement and enforce than either profit or profitability based systems. (3) The profit and profitability based systems are less discriminatory against low quality deposits and marginally profitable operations than a revenue taxation system.

This thesis is comprised of two analytical projects: (1) The results of an examination of the blue product formed during the interaction of wet lime with hydrogen sulfide gas are presented. Spectroscopic studies (FT-IR, FT-Raman, visible Raman, ESR, XPS and UV) indicate that the blue color is not due to a detectable impurity in the lime but is most probably a consequence of the formation of various polysulfide species, including S4 2- and S52-, although not the S3- radical. The use of the blue product as a precipitation agent for nickel and zinc in the treatment of acid mine drainage has been explored in a preliminary manner. (2) Diethylenetriamine is employed in the mining industry as a metal complexing agent in mineral flotation. A new analytical method for the determination of the concentration of diethylenetriamine (DETA) in aqueous mineral flotation solutions has been developed which is especially useful for plant situations.

The goal of this study was to verify if differences in respirable dust and respirable quartz concentrations exist with respect to the mines, the ore deposit types and the nature of workstations. / One hundred and seventy-nine respirable dust samples were collected in the six mines studied, in compliance with the method recommended by the Institut de recherche en sante et securite du travail du Quebec (IRSST). Then, samples were analysed using X ray powder diffraction technique to determine respirable quartz concentrations. / Results indicated statistically significant differences in the normalised exposure levels to respirable dust (p = 0.017), to respirable quartz (p < 0.001) as well as the quartz percentage in the respirable dust (p < 0.001) of the six mines studied. When grouped by ore deposit type, normalized exposure levels to respirable dust were not statistically different. However, statistically significant differences were noticed for normalized exposure levels to respirable quartz (p = 0.004) and respirable quartz percentage (p < 0.001) according to ore deposit types. / For all mines studied, respirable dust concentrations were all below the admissible exposure value whereas about 9% of the respirable quartz concentrations were equal or above the admissible exposure limit. Gold ore deposits hosted in quartz veins had the highest normalized respirable quartz exposure levels, as well as the highest percentage of quartz in the respirable dust when compared to gold ore deposits with sulfide lodes, the copper-zinc ore deposit and the disseminated gold ore deposit. / The study also revealed that workers who worked in the ore crushing and hoisting departments as well as loading and transport had higher normalised exposure levels to respirable quartz than workers who worked in the drilling and blasting or those who worked in the maintenance department. / In conclusion, this study stressed that quartz content in the mined rocks seems to be the most important factor influencing on respirable quartz concentrations in the mine worker's respiratory zone, but the relation between the two variables were not strongly correlated (Rs = 0.254, p = 0.005). Furthermore, the study showed that the gold ore deposits with quartz lodes had the highest normalized exposure levels to respirable quartz. Also, the workers assigned to ore crushing and hoisting departments as well as transport and loading had the highest exposure levels to respirable quartz. (Abstract shortened by UMI.)

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1922. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed April 7, 2010)

Purpose. The objective of this thesis was to examine work in mines. Specifically, part #1 performed in-situ time/motion analyses of common mining jobs and part #2 analyzed in-situ energy expenditures while working in a mine. Methodology. Part #1- task and sub-task duration and subjective work intensity were investigated for thirty eight subjects from six different mining jobs. These jobs were then organized into 4 groups for statistical analysis based on precedence: Group 1 (Bolting & Screening (attaching steel mesh to walls and ceiling), Group 2 (Conventional Mining (using a hand-held drilling carriage to drills holes in rock walls and ceiling)), Group 3 (Support Services (mechanic, welder, pipe layer)), Group 4 (Production Drill (using a machine mounted drilling unit), Scooptram(TM) (ore transport with no air conditioner), Shotcrete (concrete applied by spraying)). Part #2- In-situ metabolic energy expenditures were estimated through indirect open circuit calorimetry and deep tissue and skin temperatures were measured for those same groups. Results. Part #1- twenty three common mining tasks were identified with differences identified between various group for time and intensity. Part #2- metabolic requirements between groups were similar with one difference identified between groups 3 and 4 (P &lt; 0.05). Deep tissue and skin temperatures did not change significantly through the course of a work day. Conclusion. Part #1- a variety of tasks is performed by each group and there is no uniform work protocol. Part #2- each mining group's metabolic energy expenditure requirements to perform various mining tasks are similar.

Many of the scarcest metals are critical to future energy technologies. However, these metals often have limited supplies, and their current production and recycling methods are complicated and use toxic chemicals. In order to ensure the availability of these metals alternative methods for their recovery need to be explored. This thesis describes biological methods for the recovery of some of these metals, specifically the lanthanides and tellurium. It is one of the first investigations for the biogenic recovery of either of these metals, making it unique in the field. The lanthanides are critical elements in the high performance magnets used in wind turbines, electric vehicles, and other 'green' technologies, but they are difficult to separate from one another because of their chemical similarity. We demonstrate a biogenic method based on lanthanide adsorption to the bacteria Roseobacter sp. AzwK-3b, followed by subsequent desorption as a function of pKa using a semi-continuous flow process. The desorption behavior suggests that the basicity of the individual lanthanides is important in determining their biosorption and desorption behavior. Similar selectivity was also found using phosphatidic acid liposomes. It is possible to concentrate a solution of equal concentrations of each lanthanide to nearly 50% of the two heaviest lanthanides in only two stages of enrichment, surpassing existing industrial practice. This suggests that there is an opportunity to harness the diversity of bacterial surface chemistry and liposome chemistries to fine tune the separation and recovery of these technologically important metals, and to do so in an environmentally benign manner. Tellurium is used in photovoltaic (PV) modules and thermoelectric generators, however it is not abundant in the earth's crust and is difficult to produce. We show that the hydrothermal vent microbe Pseudoalteromonas sp. strain EPR3 can convert tellurium from a wide variety of compounds, industrial sources, and devices into metallic tellurium and a gaseous tellurium species. These include metallic tellurium, tellurite, copper autoclave slime, tellurium dioxide, tellurium-based PV material (cadmium telluride), and tellurium-based thermoelectric material (bismuth telluride). Despite the fact that many of these tellurium compounds are considered insoluble in aqueous solution, they can nonetheless be transformed by EPR3, suggesting the existence of a steady state soluble tellurium concentration during tellurium transformation. Insights from these experiments on the mechanisms of tellurium precipitation and volatilization by bacteria, and their implications on tellurium production and recycling are discussed. / Engineering and Applied Sciences - Applied Physics

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