Abstract
This paper is dedicated to research into the geological peculiarities, shape of the ore body and the occurrence of the host rocks in the hanging wall of the Pivdenno-Biloz- erske deposit , as well as their influence on the degrees and quality of high-grade iron ore extraction. It is noted that in the interval of 480 – 840 m depths, a decrease is observed in the stability of the natural and technogenic massif, which is caused by the increase in rock pressure with depth, the influence of blast- ing operations on the massif and the difference in geological conditions. This has led to the collapse of hanging wall rocks and backfill into the mined-out space of chambers in certain areas of the deposit, the dilution of the ore and deterioration of the operational state of the underground mine workings. Attention is focused on the causes and peculiarities of consequences of the collapse of the hanging wall rocks during ore mining, which reduce the technical and-economic indexes of the ore extraction from the chambers. A 3D-model of an ore deposit with complex structural framework has been developed, which makes it possible to visually observe in axonometric projection the geological peculiarities and the shape of the ore body. The parameters have been studied of mining chambers in the 640 – 740 m floor under different changing geological conditions of the ore deposit and hanging wall rocks occurrence – the northern, central and southern parts. The difference in the iron content in the mined ore relative to the initial iron content in the massif has been defined as an indicative criterion of the influence of changing conditions on the production quality. The reasons have been revealed which contribute to the collapse of the rocks and the subsequent decrease in the iron content of the mined ore in ore deposit areas dif- fering by their characteristics. It has been determined that within the central and half of the southern ore deposit parts with a length of 600 m, an anomalous geological zone is formed, the manifestation of which will be increased with the depth of mining. It was noted that within this zone, with the highest intensity and density of collapse of hanging wall rocks, the influence of decrease in the slope angle and change in the strike direction are of greatest priority, and such geological factors as a decrease in hardness, rock morphology, deposit thickness increase this influence significantly. To solve the problems of the hanging wall rocks’ stability, it is recommended to study the nature and direction of action of gravity forces on the stope chambers in the northern, central and southern parts, as well to search for scientific solutions in regard to changes in the geometric shapes of stope chambers and their spatial location, improving the order of reserves mining in terms of the ore deposit area, the rational order of breaking-out ore reserves in the chambers with changing mining and geological conditions of the fields’ development.
Highlights
Ukraine holds the first place in the world in terms of geological reserves of iron ores, which are assessed at 30 billion tons, and per pure iron content it holds the fourth place after Russia, Brazil and Australia (Peregudov, Gritsina, & Dragun, 2010; USGS, 2018)
The difference in the iron content in the mined ore relative to the initial iron content in massif of the chamber, according to the geological exploration data, has been defined as an indicative criterion of the influence of changing conditions on the production quality.The analysis provided for a comparison of the dynamics of changes in the average parameter of iron content (Fe, %) in the mined ore of 5 mined-out chambers in the ore deposit parts with different geological conditions
We have studied the parameters of mining chambers under different changing geological conditions of the ore deposit and hanging wall rocks’ occurrence – the northern, central and southern parts
Summary
Ukraine holds the first place in the world in terms of geological reserves of iron ores, which are assessed at 30 billion tons, and per pure iron content it holds the fourth place after Russia, Brazil and Australia (Peregudov, Gritsina, & Dragun, 2010; USGS, 2018). Despite the use of an effective mining system with a consolidating backfill, when developing the ore reserves in the range of 480 – 840 m depths, serious problems of the natural and technogenic massif stability have arisen, caused by the increase in rock pressure with depth, the influence of blasting operations and the difference in geological conditions This leads to the collapse of rocks and backfill into the minedout space of chambers in certain areas of the deposit. This testifies to the collapses of the hanging а wall rocks into the excavation chambers, which dilute the ore, and the formation of an increased stress state in the hanging wall rocks, which leads to deterioration of a state of the drift of the 740 m horizon (Chistyakov, Ruskih, & Zubko, 2012). Hardness of rocks, f Angle of slope of the ore body, degree Angle of slope of the hanging wall rocks, degree Characteristic and thickness of the ore body, m Fracturing Stability
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