Analyses factors that affect cover caving ability of roof coal in sublevel caving mining method.

分析了放顶煤开采顶煤冒放性的影响因素。

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The paper discusses the roof coal breakage principle, deformation breakage and retrieval law and analyzes factors affecting cover caving ability.

论述了综放开采的顶煤破碎机理、变形破碎及回收规律；

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The loading affection on supports in process of transformation. the roof coal behaviour on the face zone and its caving character at cavity edge are expounded.

论述了顶煤介质状态转化对工作面支架的作用，不同强度顶煤在工作面控顶区上方的性态分布和放顶煤线处的垮落特点；

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But most days, I make enough roof top PV solar power at home to avoid buying coal-based utility power.

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Energy Secretary Steven Chu, speaking here this morning, touted gas as a bridge fuel to get us between coal and a wonderland of solar panels on every roof and windmills in your backyard.

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Thamrin Sihite, director general of minerals and coal at the Indonesian energy ministry, said workers were in the underground training room when the roof collapsed, caving in most of the room.

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