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The paper discusses the features of the development of pit reserves of the Udachnaya diamondiferous pipe which consists of two closely spaced ore bodies under the protection of a moving ore-rock massif (a safety cushion). Low stability of the rock massif located between the ore bodies is indicated. Such low stability is caused by the presence of areas of increased intensity of fracturing and low coherence zones in the massif; it is also caused by the mutual impact of mining operations carried out in closely located ore bodies. A conclusion is made about the danger of collapse of sizeable rock blocks from the edge zones of the rock massif located between the ore bodies onto the safety cushion. In this case, individual rock blocks can be 0.4-0.6 tons or more, the drop height is up to 600-700 m. Impact blows on the safety cushion when rock blocks collapse onto it can cause a disruption of underground mine workings stability and occurrence of dangerous pressure drops at the outlet of air waves from the safety cushion into the underground mine workings. A method for preventing dangerous impact blows is proposed, which consists in the forced collapse (with certain parameters) of the edge part of the rock massif located between the ore bodies, onto the safety cushion.

Substantiation of the method ensuring the safe development of the pit reserves of kimberlite ore deposits in the conditions of the Udachny mine