| It is well known that improving coal recovery rate of fully- mechanized caving mining is one of the topics in the study of mining technology all the time. under the condition of fully- mechanized caving mining in super high coal seam with 14~20m, caving flowing law of top coal, structure effect of forming arch in the process of coal and gangue caving and top coal loss law have important significance on determining reasonable coal caving parameters and related technical measures and further improving top coal recovery rate. So the paper based on geological conditions of Tashan coal mine 3-5 coal seam in Datong mining area, the method of theoretical analysis, numerical simulation and field measurement were applied for in-depth analysis the variation of coal gangue flow filed, especial the arch structure of the flowing field, which formation and destabilization law and affection of coal gangue flow patterns and top coal loss on the condition of special thick seam. It has supported basis of determined reasonable caving technology parameters and reduced the loss of coal.(1) Reveals the fractured state and block distribution characteristics of the special thick seam top coal. Measurement analyzes fractured state of Tashan coal mine in 8103 fully- mechanized caving face with three layers which is 0~4m, 4~8m and 8~12m top coal to obtain distribution characteristics of the top coal in super high coal seam: the upper top coal block is minimum, hypogynous top coal is second and the middle top coal is largest. It shows that the extent of damage in the middle top coal directly determines the effect of the release of top coal.(2) Proposes concept of dynamic random arch in the process of coal and gangue caving and flowing in fully- mechanized caving mining. Dynamic random arch is formed in the process of and broken top coal and gangue caving and flowing during fully- mechanism caving mining, and its forming time, position and shape are formed with random properties. So it can define coal gangue structure that has random characteristics called dynamic random arching effect, which is format as the difference of block and support cover beam boundary restrictions on the process of dynamic caving coal. Factors of dynamic random arch includes coal gangue degree, arch structure span, horizontal binding and so on, construc ting the mechanical model of dynamic random arching, analyzing the arching condition and stability characteristics of dynamic random arching.(3)It obtained that d ynamic random arch has three structure types such as the upper arch, and the median arch and the lower arch. And the stability of the three- layer structure was analyzed by numerical simulation, in which was descending order from the lower and the median and the upper arch structure, and those structure accounted for 70.1%, 25.2%, 3.94%respectively. With the influence rule of different arch structure on top coal loss analyzed, the top coal mobility decreased that caused by dynamic random arch and top coal losses due to the amount of coal caving above the arch were obtained. While after the support moving, what caused coal gangue boundary moving backward and top coal caving into the area where cannot be caving and coal and waste rock mixed which resulted top coal losses greater. Analysis obtained that the lower arch structure that full of coal and the lower arch structure that of coal gangue and the median arch that full of coal have the greatest impaction of top coal recovery rate, which is the key to control objects.(4) For classification of the controlled area of top coal loss of special thick seam using full mechanized caving mining, obtained that top coa l losses included the loss of caused by arch structure formation and waste rock invasive and non-release of the regional. According to the characteristics of arch structure layer and stability, proposed measure action of the dynamic random arch, including twitching flapper and strong disturbances of the support and fill the seats caving methods, etc. With the reasonable caving technology applied, the degree of mixing of coal and rock was decreased and top coal recovery rate was improved. For the area of non-release, applied guide coal unit the losses of top coal decreased and top coal recovery rate improved.(5) Field measurement analysis concluded that these three broken arch ways such as the swing tail boom and support strong disturbance and fill the seats caving can broken arch structure at an average of 78%, and 68% and 91% respectively, which is a more effective way of broken the arch. At the same time, after top coal pre-split blasting technology used, the average degree of chunks was decreased around 9%, and the number of arch formation was reduced 30% and top coal recovery rate was increased 1.8%.And caving technology is determined, which the apheres height is 3.5m and the caving step distance is 0.8m and two-wheeled order of caving. Field test showed that the top coal recovery rate is achieved 84.16%, and field application has got better results.This paper includes 54 graphs,13 tables and 129 references. |
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