The harmfulness of the strong air wave accompanying a rock roof collapse is tremendous. It is vital to analysis the damage scope and degree caused by blast so as to plan the mining scheme under the condition of mined-out area and preserve safety mining operation. However, no effective calculation method is presented on this aspect by now. The roof collapses could be classified to two fundamental falling patterns, namely mass fall and single boulder fall. The former describes the situation while the roof rock falls as a whole almost at the same time and compressed air is forced to erupt through the passage at a high speed. The latter describes the situation when the roof rocks fall gradually. Based on site investigation, we conclude that the main falling pattern is single boulder fall. Further more, a mathematical model about air flow of single boulder fall is set up.
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