Ground control, one of the key elements in mine safety, is an issue that warrants continuous improvement in the underground coal industry. The United States experienced over 3,300 injuries and 42 deaths between 2006 and 2012 from the fall of a roof or rib (MSHA, 2015). Out of the underground coal mining methods, room and pillar retreat mining lacks significant research to adequately understand the rockmass behavior associated with the process. A microseismic monitoring system was installed in a retreat mine in Southwest Virginia to provide more information about the changing stress conditions created by retreating and ultimately reduce risk to miners. Microseismicity has been proven to be an acceptable method of monitoring stress redistribution in underground coal mines and assist in explaining rockmass behavior (Luxbacher, et al, 2007). An array of geophones was placed underground along a single retreat panel to record failures due to stress redistribution throughout one panel of retreat. These microseismic events were located, and their moment magnitudes were found. An analysis was completed to observe the redistribution of stress and related gob formation throughout the panel's retreat. Expectations for the gob formation were consistent with the distribution of microseismic events. Over 13,000 microseismic events were found in 1.5 months of monitoring. Approximately 2,800 of these events were well enough located to provide analysis of the changing underground stress conditions from the retreat process. On average, recorded microseismic events during retreat produced a moment magnitude of -0.9, with no events higher than a magnitude of 2.0. / Master of Science

A study or the possibility of a modern mining operation in the Valley Coal Fields of Virginia begins with a brief history of previous mining operations in the area. Following this is a study of the geological occurrence and a geographical description of the site selected. The deposit is studied from various angles - physical characteristics of the seam in place, chemical characteristics and washability are all included. After the amount and type of impurities present in the deposit are ascertained, a coal preparation plant is proposed to clean the coal to the desired level. Leaving the surface problems, the underground problems of hoisting, mining methods, ventilation, haulage and drainage, and power are taken up separately and a solution recommended for each problem. To operate the mine an organization is designed to fit the solution of the various problems. The estimate of the cost of equipping and providing the labor and supervision to operate such a mine is included in the study. This cost is compared with the expected income. / Master of Science

Thermodynamic calculations are used to study the alkali reactions in coal gasifier atmospheres. The reactive alkali and sulfur species released from coal are first calculated at temperatures from 800 K to 1900 K and pressures from 1 atm to 100 atm. Four P-T diagrams are constructed for the stable alkali and/or alkali-sulfur species at differ-ent temperatures and pressures. Alkali vapors are generated by the reactions Na₂CO₃_(s) + 2C_(s) = 2Na_(g) + 3CO_(g) Na₂CO₃_(s) + H₂O_(g) + C_(s) = 2NaOH_(g) + 2CO_(g) or K₂CO₃_(s) + 2C_(s) = 2K_(g) + 3CO_(g) K₂CO₃_(s) + H₂O_(g) + C_(s) = 2KOH_(g) + 2CO_(g) The phases formed from alkali-cement, and alkali-sulfur-cement reaction are also predicted. For both 53% and 72% alumina cement, calcium aluminate (CaO•Al₂O₃) is decomposed by the reactions CaO•Al₂O₃ + 2Na + 1/20₂ = Na₂O•Al₂O₃ + CaO CaO•Al₂O₃ + 2K + 1/20₂ = K₂O•Al₂O₃ + CaO or CaO•Al₂O₃ + 2Na + l/2S₂ = Na₂0•Al₂O₃ + CaS CaO•Al₂O₃ + 2K + 1/2S₂ = K₂•Al₂O₃ + CaS / M.S.

The use of anthracite as a filter medium is gaining popularity throughout industry as evidenced by the fact that in recent years 1100 filter plants have been installed for clarifying water and other chemicals (51). Since little information is contained in the literature as to why anthracite has become so popular replacing the much used sand filters, this investigation was undertaken in an effort to determine the reason, if any, tor this popularity of use. A number of factors such as rank, chemical composition, size, shape, and surface condition or coal could possibly affect its adsorptive properties. Tests were made in an effort to determine if any relationship existed between these factors and adsorptive properties. In the experiments tannin extract solution and viscose spinning bath solution were used as the adsorbate and coals varying in rank from anthracite to high volatile bituminous C, in sizes of -4 +8, -8 +10, -8 +16, -10 +16, -16 +20, -20 +30, and -30 +40, as the adsorbent. The tests were made with the coal in the form of the conventional filter bed (10 ± l in. depth) in l¼ diameter by 12" length Liebig condenser jackets with the direction of flow of the adsorbate, in the case of the tannin extract solution in an upward direction, at a rate of coverage of 500 to 2600 cm.²/min., at 24 ± 4°C, and the viscose spinning bath solution in a downward direction, at a velocity of 19 to 44 ml./min., at 35 ± 6°C. The results of the experiments indicated that in the case of the tannin extract solution the coals were not effective to tannin extract solution clarification; while in the case of the viscose spinning bath solution the following conclusions were drawn: l. As the size of anthracite was decreased from -4 .+8 to -30 +40 mesh (U. S. Standard Screen), thus decreasing the pore space diameter and increasing the surface area in the coal bed from 2740cm.², to 22,940 cm.², the amount of insoluble solids adsorbed was increased from 10.3 p.p.m. or 27.9% to 34.1 p.p.m. or 92.4% of insoluble solids in the testing solution. 2. In testing all coals in the size range of -8 +16 mesh (U. S. Standard Screen), the solids adsorbed per 1000 cm.² of coal surface increased from 9.7% to 14.7% as the porosity of the coal beds decreased from 52.3% to 47.2%. 3. In testing all coals in the size range of -8 +16 mesh (U. S. Standard Screen), no correlation of proximate chemical analysis or relative roughness with adsorptive power could be obtained. 4. The method of determining surface area used in this investigation is a satisfactory means of obtaining relative external surface area of coal particles of the sizes tested. / Master of Science

The hedonic approach involves determining the characteristics of a good or service that have a market price. Simultaneously, estimates of those prices are made using regression analysis. Both delivered and FOB mine prices are examined in regional U.S. markets. The steam coal contract terms examined include Btu, sulfur, and ash content; transportation cost, average annual tons delivered, start year of the contract, length of contract, buyer controlling interest in the mining operation, coal mine locations, and the individual buyers. Data for about eighty-five percent of all 1978 steam coal deliveries is utilized. The major findings were that coal price structure varies substantially across markets, from year to year, and for delivered prices and FOB mine prices. Btu is usually, but not always, the most important characteristic in explaining coal price variations. Length of contract is occasionally more important. Transportation cost and sulfur content are usually of high importance. Some buyers have a substantial impact on price because of market imperfections and poor buying practices. The regression results were robust. / Master of Arts

The sensible heat losses in the flue gases was exceeding the best economical operating ranges of the Boiler No. 6. This was done to study the adverse effect on the flue dust carryover in the furnace. / Master of Science

A reliable estimate of minable coal reserves is essential for long-term planning and for conservation of energy resources. In the majority of the world's coalfields, seams are found on multiple horizons, and coal recovery may be significantly reduced depending upon the magnitude of seam interaction. In order to evaluate the effects of interaction in terms of coal losses, a hazard technique has been developed. The first stage in this technique was to develop an efficient and accurate system to grid spatial geologic and structural information developed from randomly placed boreholes. The second stage was to utilize these gridded values to determine total available coal tonnage and chemical compositions of the seam. Depending on whether over or under mining effects are to be assessed, spatial geologic and structural conditions between the seams, are evaluated to determine if interaction is possible. Where interaction will occur, recoverable reserves are reduced accordingly. To demonstrate application of the hazard approach, potential interaction in a lower seam has been evaluated. To facilitate implementation of this reserve evaluation method under multi-seam conditions, a user-friendly computer design program, HAZARD, has been developed to calculate the recoverable coal reserves in an affected seam. / Master of Science

The problem of degasification of coal beds is important because it is desirable to reduce the inflammable gas in coal mines as well as to recover economically the gas for use as a fuel. Permeability of coal is defined as a measure of the ease with which a gas flows through coal under a given pressure gradient, and it is of practical importance in the problem of degasification, The factors that affect the permeability of coal are also important in order to develop a more effective way of degasification. This study is concerned with the factors that affect the permeability of coal. Some of the major factors which affect the permeability of coal are the property of coal, properties of the natural coal gas, physical and chemical correlations between the coal and the gas, overburden pressure, and direction of the gas flow and other factors. In the case of these factors it is usually necessary to assess their effects in a qualitative way rather than in a quantitative one. For this reason, it would be impossible in the time allotted to this paper to present anything more than a brief discussion of their interrelationships. By experiment conducted for this thesis, it has been determined that (1) the permeability of coal differs from place to place, (2) the permeability of coal may or may not differ from bench to bench in the bed of a given location, (3) the permeability of dry coal does not differ significantly from that of wet coal, and also (4) in general, no significant difference in permeability was found when the gas flowed parallel to the coal bedding and when it flowed perpendicular to the coal bedding. / Master of Science

Performance of Southwest Virginia coal: The results of the 24-hour tests herein recorded indicate that nut and slack coal from Southwest Virginia can be burned economically at burning rates of from 15.36 to 27.20 pounds of dry fuel per square foot of projected grate area per hour with an average efficiency of 75.12 per cent, with extremes of 73.21 and 77.28 per cent. / Master of Science

M.S.