Based on theoretical analysis, similarity simulation tests, numerical simulation analysis and field observations, we analyzed rock collapse and rules of fraction evolution of overlying rocks and studied the rules in controlling the effect of an extremely thick igneous rock, found above a main mining coal seam in an area prone to coal mine disasters in the Haizi Coal Mine. The results show that this igneous rock, called a "main key stratum", will not subside nor break for a long time, causing lower fractures and bed separations not to close. The presence of igneous rock plays an important role in rock bursts, mine floods, gas outburst and surface subsidence in coal mines. By analyzing the rules in controlling the effect of this igneous rock, we provide useful references for safety and high efficiency mining in coal mines under special geological conditions.
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