The coal fields of Appalachia of many contiguously mineable coal seams. Common practice in mining multiple seams is to extract the seams in a descending order. However, the mining sequence may still be based on seam ownership, availability of the seam and the general economic situation, net on ground control considerations. One of the major ground control mechanisms that must be considered in the design of a mine is the arching of stresses around a previously mined lower seam. This investigation deals with the extent and magnitude of the stresses above an underground opening. The finite element approach was utilized to determine the extent and magnitude of stresses for various widths of mine opening, depths of cover and overburden material. This information can then be used as an approximation of the stresses that may be encountered in an actual mining situation. / Master of Science

Roof and rib failures in underground coal mines are one of the major problems facing the industry today. In addition to safety considerations, the resulting economic impact of such failures is staggering. Uncovering and replacing buried and damaged equipment and clearing entries can account for a large expenditure in lost man-hours and machinery. Yet, because of the complex nature of their formation, geological variability, and structural characteristics, coal mine roof strata are one of the least controllable of all mine design parameters. This is especially true along the leading (southeastern) edge of the Appalachian coalfields where considerable faulting and movement have contributed to hazardous coal mining roof conditions. For this research, a detailed study of several mines, in the southern Appalachian coalfields, was undertaken to determine the most prominent geomechanical factors affecting roof stability and to evaluate their influence in promoting unstable ground conditions. In order to accomplish this task, the major geological and geomechanical features found to be detrimental to the coal mine roof within the Appalachian basin were identified and mapped in four Virginia mines. Statistical processing by chi-square and linear regression analysis as well as analytical analysis by the finite element method were used to determine the influence of geology, mine-layout, and support methods on roof stability. It was found that some easily determined parameters can be successfully used to predict potentially unstable areas. A simplified roof classification system was developed based on the geomechanical parameters, which can be used to assess the stability of a particular roof type. A Roof Rating Index was also devised capable of expressing the probability of failure under a given set of geomechanical conditions. / Ph. D.

The geological disposal of nuclear waste, in underground openings and the long-term performance of these openings demand a detailed understanding of fundamental rock mechanics. A full scale field experiment: Äspö Pillar Stability Experiment was conducted at a depth of 450 m in sparsely fractured granitic rock to examine the rock mass response between two deposition holes. An oval shaped tunnel was excavated parallel to the σ3 direction to provide access to the experiment and also provide elevated stress magnitudes in the floor. In the tunnel floor two 1.75-m diameter 6-m deep boreholes were excavated so that a 1-m thick pillar was created between them. In one of the holes a confinement pressure of 700 kPa was applied and in the other displacement transducers were installed. The pillar volume was monitored by an Acoustic Emission System. Spatially distributed thermocouples were used to monitor the temperature development as the pillar was heated by electrical heaters. The excavation-induced stress together with the thermal-induced stress was sufficient to cause the wall of the open borehole to yield. The temperature-induced stress was increased slowly to enable detailed studies of the rock mass yielding process. Once the rock mass loading response was observed, the rock mass was unloaded using a de-stress slotting technique. This thesis focuses on the in-situ study of the rock mass response to coupled mechanical thermal loading and thermal-mechanical unloading. The experiment, its design, monitoring and observations are thoroughly described. An estimate of the yielding strength of the rock mass is presented and compared with laboratory test and results from other rock mass conditions reported elsewhere in the open literature. General conclusions about the effect of the confining pressure and the observations from the unloading of the pillar are also presented. Important findings are that the yielding strength of the rock mass has been successfully determined, low confinement pressures significantly affects the onset of yielding, the primary mode of fracture initiation and propagation is extensional, no significant time dependency of the yielding process was observed. The unloading studies also indicated that what appeared to be shear bands likely was a propagating zone of extensile failure that weakened the rock so that displacements in the shear direction could occur. / <p>QC 20100622</p>

O COMEX Lab-Sorter MSX-400-VL-XR-3D (Sorter) foi avaliado, sob diferentes condições operacionais em relação a sua capacidade de realizar testes de pré-concentração em escala laboratorial, visando o uso dos resultados gerados para aplicação industrial. Para tal, 24 testes de separação (bem como mais testes de calibração) foram realizados para dois minérios diferentes (a base de ferro e zinco). Nesses testes, aproximadamente 73 kg de minério foram avaliados para fins de separação no equipamento acima citado. Este mostrou a capacidade de aumentar o teor do minério de ferro acima de 60% Fe, aproveitando assim de 46% da massa do material no tamanho Lump (-31 +12,7mm) que era anteriormente classificado como rejeito pela mina e tinha um teor de apenas 53% de Fe. Com respeito do Zinco, o equipamento recuperou 93% do minério de zinco, aumentando seu teor acima de 27% Zn. Dessa forma, o Sorter eliminou 27% da massa do ROM a ser alimentado na planta de benefíciamento da mina de zinco. As configurações de porcentagem ideal para o ferro eram de 150-220 threshold e 75% porcentagem, e para o zinco as configurações ideais eram de 0-100 threshold para a granulometria maior (-50 +19 mm) e de 0-150 para a granulometria menor (-25 +8mm), ambos com 75% porcentagem. / The MS-400-VL-XR-3D COMEX Lab-Sorter (Sorter) was evaluated under different operating conditions for its ability to carry out pre-concentration tests at the laboratory scale, with the intention of using the results generated for industrial application. To this end, 24 separation tests (and many more calibration tests) were performed for two different ores (iron and zinc). In these tests, more than 73 kg of ore was passed, particle per particle in the equipment. The Sorter showed the ability to increase the iron ore content to over 60% Fe, thus taking advantage of 46% of the mass of the Lump size material (-31 + 12.7mm) that was previously classified as waste and had a grade of only 53% Fe. With respect to Zinc, the Sorter recovered 93% of the zinc ore, increasing its content above 27% Zn. In this way, the Sorter eliminated 27% of the ROM mass to be fed into the zinc mine beneficiation plant. The ideal percentage configurations for the iron were 150-220 threshold and 75% percentage, and for zinc the ideal configurations were 0-100 threshold for the large particle size (-50 +19 mm) and 0-150 for the small particle size (-25 + 8mm), both with 75% percentage.

This ethnographic study was designed to explore the phenomenon of corporate social responsibility (CSR) in the mining industry. The research addressed the impacts of a problematic, systemic, and ethnocentric (top-down) CSR approach driven by a transnational mining company, and proposed a novel cultural relativist (bottom-up) CSR approach looking at the social needs of the community. Solving the problem stemming from the ethnocentric approach is important for both the mining company and the community affected by the CSR program, as it will alter dynamics between actors and mitigate social conflicts. The purpose of this study was to investigate factors that improve the fractured relationship between the community and the mining company and put its social license to operate at risk. The mitigation of social conflicts is needed for the mining corporation to maintain its social license to operate in a harmonic and collaborative mining-community relationship. The research question was designed to gather the perceptions of corporate leaders and community members in Chile's Andacollo mining area regarding the imbalance between the ethnocentric and cultural relativism perspectives adopted in CSR policies and practices. A purposive sample of 30 subjects was interviewed to collect data regarding their perceptions that were then categorized, coded, and interpreted using an inductive approach and thematic networks. The research findings showed that improvements in CSR practice are likely to result from the mining company placing emphasis on the social dimension. A shift from a top-down to a bottom-up CSR approach will contribute to the reduction of social conflicts, build a socially sustainable setting, and foster positive social change with benefits for the society.

Heavy industries, such as mining, generate dust in quantities that present an occupational health hazard. Prolonged exposure to the respirable dust has been found to result in many irreversible occupational ailments in thousands of miners. In underground mining applications, a variety of scrubbing systems are used to remove dust near the zones of generation. However, the wire-mesh type fibrous screens in the flooded-bed dust scrubbers used on continuous miners, are prone to clogging due to the accumulation of dust particles. This clogging results in a reduced capture efficiency and a higher exposure to the personnel. This research establishes the Vortecone, an inertial wet scrubber system, as a suitable alternative to the existing filters. The Vortecone accelerates its inlet fluids into a rapid circulatory motion into a vortex chamber, preferentially moving the heavier particles towards the impermeable surface to be trapped by the circulating water film. Vortecones are used on automobile painting lines and capture over-sprayed paint particles with cleaning efficacies exceeding 99 % while requiring only infrequent maintenance. The existing design of the Vortecone could also be altered to control the flow patterns. This dissertation presents detailed computational fluid dynamics (CFD) models to describe air flow patterns in the Vortecone in steady and transient states. Multi-phase spray models were generated to simulate injection of water into the Vortecone. The volume of fraction (VOF) approach was adopted to mimic the air-water interface. The Lagrangian particle tracking method was used to model particle capture on the interface described by the VOF. The CFD models indicate excellent cleaning efficacies, especially of larger particles. Laboratory experiments with optical measurements of aerosols in a reduced scale model of the Vortecone validate the computer models. These experiments which were performed on dust samples with particle sizes 0.3 μm and above, show that the Vortecone captures 90 % particles by mass exceeding about 5.20 and 3.20 μm at air flows of 0.28 m3/s (600 cfm) and 0.38 m3/s (800 cfm), respectively. The development of detailed large eddy simulations (LES) of air flow in the Vortecone provides a novel contribution to research by better resolving the flow patterns. An impactor-type, self-cleaning, non-clogging impingement screen system was designed as a substitute for conventional screens used in continuous miners. The screen could further be used as an efficient dust capturing mechanism with a demister in general mining applications. CFD models and laboratory experiments are presented to establish the cleaning efficacies of the system. Laboratory experiments to investigate the cleaning efficiency of a fibrous-type conventional screen is also discussed. The parameter, filter selection factor, is proposed to compare the performance of the three systems (Vortecone, fibrous screen, and impingement screen) under similar flows. The Vortecone has been found to be the most efficient dust-cleansing system, although it is the most power intensive fillter. The impingement screen shows a similar cleaning efficiency and a much higher availability compared to the conventional fibrous screen. Because of its minimal maintenance requirement, the impingement screen shows significant promise in dust-control applications in mining.

Lack of effective occupational safety and health (OSH) strategies is a reason that workplace accidents in the mining and quarrying industry remain high, making the industry one of the riskiest operations worldwide. The purpose of this multiple case study was to explore successful strategies mining and quarrying leaders in Zimbabwe used to improve OSH. The key research question addressed successful strategies leaders in the mining and quarrying industry use to improve employee occupational safety and health in Zimbabwe. Six successful business leaders from 3 mining and quarrying mines in Zimbabwe demonstrated an exception to unsafe practices, particularly through their exceptional OSH improvement records. The conceptual framework of the study was Deming's plan-do-study-act cycle theory. Data were gathered through review of company documents, and in-depth interviews with 6 mining and quarrying leaders in Zimbabwe who had successfully improved OSH strategies in the workplace. Transcribed interview data were classified, coded, and analyzed. Themes that emerged included organizational culture, compliance with rules and regulations, and accident prevention. The results of the study indicate that successful OSH leaders designed the workplace, trained and developed employees, and empowered and equipped employees with the relevant skills and knowledge. The findings support positive social change by providing mining and quarrying leaders with knowledge and skills to improve OSH strategies in the workplace, thereby promoting a safe workplace and zero accident tolerance in the workforce and the community.

A new testing method was introduced and developed to determine Mode I fracture toughness of disc type rock specimens. The new method was named as Straight Notched Disc Bending and it uses disc specimens under three-point bending. 3D Numerical modeling was carried out with a finite element program ABAQUS to find stress intensity factors for both well-known Semi-circular Bending specimen models and Straight Notched Disc Bending specimen models for varying disc geometries. Both specimen types included notches where a crack front is introduced at the tip of the notch to compute the stress intensity factors. For stress intensity analysis, crack front-upper loading point distance and span length between the two roller supports at the bottom boundary of the specimens were changed. Fracture toughness testing was carried on Ankara G&ouml / lbaSi pink colored andesite for both specimen types / crack front-upper loading point distance and span length between the two roller supports at the bottom boundary of the specimens were changed during the tests. For both specimen geometries, notch lengths changing from 5 mm to 20 mm were used. For each notch length, two different roller supports with span lengths 60 mm and 70 mm were used. For both methods, fracture toughness values determined by using numerically computed stress intensity factors and failure loads obtained from the experiments were very close / the new method was verified by comparing the results. The new method had advantages of lower confining pressure at the crack front and lower stress intensities with a possible smaller crack tip plasticity region.

This study presents the results of probabilistic modeling of plane and wedge types of slope failures, based on the &rdquo / Advance First Order Second Moment (AFOSM)&rdquo / reliability method. In both of those failure types, two different failure criteria namely, Coulomb linear and Barton Bandis non-linear failure criteria are utilized in the development of the probabilistic models. Due to the iterative nature of the AFOSM method, analyzing spreadsheets have been developed in order to carry out the computations. The developed spreadsheets are called &ldquo / Plane Slope Analyzer (PSA)&rdquo / and &ldquo / Wedge Slope Analyzer (WSA)&rdquo / . The developed probabilistic models and their spreadsheets are verified by investigating the affect of rock and slope parameters such as, ground water level, slope height, cohesion, friction angle, and joint wall compressive strength (JCS) and their distribution types on the reliability index (&amp / #946 / ), and probability of slope failure (PF). In this study, different probability distributions are used and the inverse transformation formulas of their non-normal variates to their equivalent normal ones are developed as well. In addition, the wedge failure case is also modeled by using system reliability approach and then the results of conventional probability of failure and the system reliability approach are compared.

The expenditures resulting from work accidents is increasing every year. Among the other work accidents, mine accidents result important loss of time, money and lives. From the point of view of mine accidents, studies about cost of mine accidents need some contributions. In this thesis, cost of mine accidents to worker, employer, and total economy of country will be analysed in the light of data from Ministry of Labour, Social Security and Social Insurance Institution, and T&uuml / rkiye Coal Enterprises. General Analysis is carried out within all industrial sectors, Mining sector, and Coal Mining sector. Detailed analysis is carried out within Western Lignite Company (GLi). Occupational accidents have vital importance for the mines from legal, human and economic aspects. The goal of every mine should be to minimize occupational accidents. The top management of every mine should prove their commitments to the occupational health and safety policy to carry out this goal by means of preparing and implementing an accident preventing program.