Institute of Mining, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia:
E. Yu. Efremov, Researcher, efremov-eu@mail.ru
D. E. Melnik, Researcher

The collapse zone formed on the earth’s surface over underground mines is a territory excluded from economic activity. Depending on the size of a mine, this zone can be considerable, with an area of up to hundreds of thousands square meters. It is possible to dump overburden and other mining wastes on this territory taking into account the necessary safety measures for the relevant technological processes. The paper proposes solutions for dumping hard overburden rocks from an open pit in the collapse zone over the existing underground mine. The decisions are aimed at the safety of operations in the hazardous zone. The measures are aimed at the implementation of two tasks: stability of the dump body on the weak base, which is composed of clay sedimentary rocks and disturbed by sinks; safety of personnel and equipment in the collapse zone. To solve the first problem, the stability parameters of the overburden dump are determined. The calculations were performed by two methods: finite element modeling and limit equilibrium. To solve the second problem connected with safety of personnel in the collapse zone, the sinking termination criterion defined as the maximum volume achievable by a sink is developed. The final volume of a sink is determined by the mined-out void size, mining depth and by the parameters of rocks in the collapse zone. The actual volume of the sinks is measured using geodetic methods (UAV survey, laser scanning) The separation of the technological process into the advanced filling of sinks and segmented dump formation is proposed. The sink filling should begin when the sinking termination criterion is met. The formation of the dump should be carried out in segments, in the prepared areas with the filled sinks. Planning and segmentation of dumping operations is carried out in accordance with the schedule of underground work; no personnel or operation are allowed over active extraction blocks.

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