Simulation testing and theoretical analysis were made to study generating mechanics and moving evolutionary process of "granular arch" structure of upper immediate roof in top coal caving.

通过相似模拟实验和理论分析，研究了综放条件下上位直接顶“散体拱”结构的形成机理和移动演化过程。

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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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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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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.

WSJ: Indonesian Mine Death Toll Rises, Miners Still Trapped