Abstract
The article studies stability of intervening pillars at underground selective mining of complex structured ore bodies of Kryvyi Rih iron ore basin applying open stope systems that will enable the increased useful mineral component content in the mined ore mass. When calculating an exposure span, the current methods of determining room system constructive elements do not consider dirt thickness. So, it is essential to develop methods of determining room system constructive elements for mining complex structured ore bodies to provide stability of stope exposures. When mining a mine block, stoping is suggested to be fulfilled gradually from the footwall to the hanging wall of the ore body by room-and-pillar methods leaving a dirt or ore inclusion in the block. This enables decrease in concentrating tension and compression stresses in the middle part of the dirt or ore inclusion resulting in its 1.5 – 2.0 times greater stability. There is also determined that the stope stability is impacted by the horizontal thickness of the inclusion, the hardness ratio and the order of stoping in a mine block. Application of open stope methods in selective mining of complex structured ore bodies of Kryvyi Rih iron ore basin enables increased quality of the mined ore mass without significant capital and operating costs and results in better environment of the region.
Highlights
Kryvyi Rih iron ore basin is represented by thick deposits of rich and lean ores with dirt or ore inclusions (DOI) of 2 to 15 m [1 – 3]
Underground mining of complex structured ore bodies (CSOB) is conducted by bulkcaving and open stope methods resulting in 3–6% less iron content in the mined ore and 1.2 – 1.5 times greater than standard ore losses
To increase mined ore volumes that directly impact economic indicators, it is reasonable to mine complex structured ore bodies by the selective open stope method according to the developed classification [4, 24, 37]
Summary
Kryvyi Rih iron ore basin is represented by thick deposits of rich and lean ores with dirt or ore inclusions (DOI) of 2 to 15 m [1 – 3]. To increase sales, mining enterprises apply resource-saving technologies enabling increase of volumes of mined ore with the iron content of 60% to 80%. In most cases, when developing nondestructive control methods, electromagnetic, ultrasonic and radiometric techniques are used. All these approaches result in greater mining costs and deterioration of the regional environment
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