Coal pillar’s breaking and fracture development mechanism and numerical simulation
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This study explores the influence of a repeated mining process on an upper coal pillar in a close coal seam group. The pillar's breaking and instability processes are emphasized, and the influence of fracture development on the oxidation and spontaneous combustion of coal pillars is revealed. A numerical simulation is used to simulate the dynamic evolution characteristics of stress, displacement of the upper coal pillar, and the numerical results elucidate that the mining of the lower adjacent coal seam is a pressure relief process for the upper coal pillar. The theoretical length of the fracture along the strike of the upper coal pillar is also obtained for the upper coal pillar.Keywords:
Pillar
Spontaneous Combustion
The paper introduces the application of the thermometry for the research of spontaneous ignition in Jianxin Colliery,and makes a further study on the regularity of temperature change in the goaf behind the working face in the process of advancement,which has provided the scientific basis for the colliery against the spontaneous ignition.
Spontaneous Combustion
Autoignition temperature
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Through the determination of spontaneous combustion three zones in 12# coal seam and 13# coal seam mining area of MeiHe Coal Mine,it provided the powerful basis and reliable data for taking the specific measures of fire prevention and extinguishing in the coal seam mining area.
Spontaneous Combustion
Longwall mining
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The paper advances a Four Pillar Trades theory and argues that tourist commodities, instead of Scenic Areas, must be seen as one of the four pillar trades that support tourism industry. Traditionally, transportation, hotels, and travel agencies have been regarded as the Three Pillar Trades supporting tourism.
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Abstract Pillar saints were anchorite recluses, also called Stylites from the Greek word stylos : pillar, who lived on pillars and remained on them until the end of their lives. The pillar became their hermitage which, by being on top of it, helped them to spend days and nights in prayer and fasting.
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Spontaneous combustion of coal seriously threatens mines safety.The determination of three-zone in mined-out areas is significant for the fire control and extinguishing.Based on the characteristics of mined-out areas in Zijin Mine,the FLUENT numerical simulation were used to determine the distribution law of three-zone in 1203 fully-mechanized working face,which could provide theoretical evidence for the fire control and extinguishing.
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Abstract Together with Gilbert Murray and Francis Cornford, Harrison dreamed of a new way forward in the study of religion, exploring the relationship of religion to philosophy, ethnology, and literature. Her idiosyncratic approach to teaching is described, with her relationship with students and her love of languages. A pillar shrine at Chartres demonstrated for her the continuity with the pillar worship in Minoan art and led her to conclude that the earliest forms of religion had no god — ideas that were published in an article entitled ‘The Pillar and the Maiden’. Meanwhile, without the sane counsel of her ‘pillar’ Murray, who was lecturing in America, the ‘maiden’ Harrison became embroiled in an academic row with Lewis Farnell.
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Based on market standards and demand standards, this paper points out the chosen pillar industries in Chongqing and their direction of development by means of the new approaches of choosing pillar industries, which is of great significance to the modification of industrial structure and economic development of Chongqing.
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Spontaneous combustion of coal occurs in the longwall (LW) goaf during mining cycles due to coal oxidation at low temperatures and air ingress. Coal seam orientations, dictated by the elevations of maingate (MG) and tailgate (TG) and the height of working face and starting-up line, significantly impact the gas distribution in the goaf. Despite this, there has been limited study on the effects of coal seam orientations on spontaneous heating management. To fill this knowledge gap, extensive computational fluid dynamics (CFD) modeling was conducted based on the actual conditions of an Australian underground coal mine and verified with onsite gas monitoring data, after which extensive parametric studies of how coal seam orientations influenced gas distribution were conducted. Simulation results indicate that coal seam orientations significantly impact spatial gas distribution in the LW goaf and the development of proactive goaf inertisation strategies. Regardless of coal seam orientations, nitrogen performs better than carbon dioxide in reducing the oxidation zone area. In addition, at least 1.5 m3/s of nitrogen is required to effectively prevent spontaneous heating, and the area ratio of oxidation zone to active goaf is approximately 10%, reducing by about 15% compared to scenarios without inertisation. The modeling results shed insight into the goaf gas distribution characteristics under various coal seam orientations and provide guidance on developing corresponding proactive inertisation strategies for managing spontaneous heating in the goaf, thus improving mining safety.
Spontaneous Combustion
Longwall mining
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At Akabira Colliery, the instance of fire fightings for mine fire tells one side of the history of the colliery since the mine was opend. Six mine fires which have occured in the colliery in the past seven years resulted from spontaneous combustion of the residual unmined coal around operating areas. In every case such as the fire could not be detected in early stage and was not extinguished by direct water spraying, the firing zone was immediately sealed off from the other area. The accumulated experiences in our mine have suggested that the early detection of spontaneous combustions of coal is important countermeasures and is able to minimize the trouble.This paper gives an account of early detection methods of spontaneous combustions and typical countermeasures applied at Akabira Colliery. It reports, in addition, the most up-to-date methods for early detection in spontaneous combustion and the prospect for the development of underground integrated monitoring system.
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1. Getting Started 2. Introduction and Overview 3. The First Pillar: Sort 4. The Second Pillar: Set in Order 5. The Third Pillar: Shine 6. The Fourth Pillar: Standardize 7. The Fifth Pillar: Sustain 8. Reflections and Conclusions
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