Abstract
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.
Highlights
As of 2020, the intermediate stage of the combined development of the deposit has been completed at Udachnaya kimberlite pipe
To ensure the safety of underground mining operations at the Udachny Mine, it is recommended to implement a set of activitieson the forced collapse of the rocks of the edge part of the massif located between the ore bodies, onto the safety cushion by drilling and blasting operations
The factors that significantly increase the risks of underground mining of the Udachnaya pipe pit reserves with the use of forced caving and areal ore drawing under the safety cushion, include: 1.Low stability of the rock massif located between the closely spaced Eastern Ore Body and Western Ore Body, and the high probability of collapse of sizeable rock blocks from the edge zones of this rock massif onto a safety cushion
Summary
As of 2020, the intermediate stage of the combined development of the deposit has been completed at Udachnaya kimberlite pipe. To ensure safe underground mining, a safety cushion was formed at the bottom of the open pit (Fig. 1) [1]. According to the solution specified in the Technical Regulations, the following mining methods for the pit reserves extraction were adopted: 1.Method of level caving with one-stage excavation and areal ore drawing for development of the deposit reserves to the level of -580 m [2, 3]; 2.Method of sublevel caving with side ore drawing for the completion of the pit sides mining and formation of the necessary volume of safety cushion rock [4]. It is planned to develop mining of the main ore reserves under the pit bottom under the protection of this safety cushion [5, 6, 7]. The main workings ofproduction horizons(-380, -480 and -580 m) pass through this rock massif [10] This rock massif has a deformation structure in the zones of contact with kimberlite. The purpose of the study is to develop organizational and technical measures for ensuring the safety of the underground mining under the safety cushion
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