| This thesis quantitatively and qualitatively studies the influence on the top coal caving characteristics from the depth of seams embedding, the strength of coal-rock mass, crack scale distribution in coal mass, the locality and thickness of dirt band, the thickness of coal seams and the conditions of roof and their relativities. Based on the embedding of 6# seam of Suancigou mine, top coal caving characteristics are evaluated synthetically. The fuzzy mathematical method is employed to forecast top coal caving characteristics. Under the similiarity theory, by virtue of the existing testing equipment of large-scale 3000mmx3000mmx200mm plane strain flexible loading in the laboratory, experiments are carried out comparatively on the laws of top coal and overlying strata distortion, movement and failure for entirely caving and layer-divided caving. The laws are discovered concerning main roof span, the caving angle of top coal and roof, the laws of abutment pressure distribution, recovery ratio of coal and its variation with the distance of coalface advance and the variations of support resistance in the end of cutting and caving periodic. Combined with the the effect of similar material testing, the numerial simulation method is employed to study the variations of abutment pressure and top coal failure units with the distance of coalface advance fordifferent width of coalface, and distributions of abutment pressure and its variation along width of coalface difference distance to it center for different width of coalface. Two natural conclusions are reached at the end of the thesis: one is about the rational width of coalface for different mining; the other is the rational mining technology parameters for entirely and layer-divided caving about Suanchigou mine through orthogonal experiment of numerical simulation, the influence on the effect of fop coal failure from mining height, cutting-caving ratio, support resistance and recovery ratio etc . |
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