• Energy Research

Being one of the world’s largest uranium producers(about 2% of the world’s production), the state enterprise “Vostochnyi Mining and Processing Works” (“VostGOK”) provides about 40% of Ukraine’s nuclear power stations with uranium raw materials. Considering the conditions of uranium deposits exploitation (location in densely populated areas, protected sites etc.), to protect the environment from possible emissions of radioactive elements room mining is applied with subsequent backfilling of the dead area with consolidating mixtures. This technology is economically reasonable at deposits with the increased uranium content. To exclude a number of labour-consuming and environmentally dangerous operations from the production process, lean uranium-containing ores are reasonable to be mined applying underground block leaching. This enables reaching maximum values of mineral extraction and avoiding considerable material expenditures on backfilling mixture preparation and backfilling dead rooms, as they are almost completely backfilled with the muck pile, and on utilization of waste after the mined ore primary processing (barren rocks and off-balance ores) on the daylight surface.

The work aims at studying and developing an efficient option of layer-by-layer muck drawing from the “dead area” of the footwall for the account of forming an inclined limiting contact of the muck ore with the unmined ore massif. The paper presents a detailed technical and economic analysis of factors and conditions impacting efficiency of muck drawing from the footwall “dead area”. The conducted studies of muck drawing on laboratory models considering a modeling scale enable determining optimal parameters of the layer-by-layer ore breaking and, further on, conduct a layer-by-layer muck drawing from the footwall “dead area” with minimum losses and dilution. The article determines regulations of the broken ore layer width considering possible obtaining of maximum muck values. On the basis of the conducted studies there are suggested optimal options of the technology of layer-by-layer breaking and drawing of the muck when forming an inclined limiting contact of the muck ore with the breakage face. The article proves practicability of breaking by inclined layers with formation of a limiting contact of the muck ore with the breakage face and suggests implementation of layer-by-layer muck drawing by an inclined flow.

The authors express their sincere gratitude to the management of the SE “VostGOK”, as well as to the employees of the Industrial Ventilation Laboratory at the State Research Institute for Labour Safety and Ecology in Ore Mining and Metallurgic Industry of Kryvyi Rih National University for their help and assistance in conducting this research.

Данные исследования выполнены благодаря исходной информации, представленной горнодобывающими предприятиями Криворожского железорудного бассейна, в частности “Евраз Сухая Балка” и “Центральный ГОК”.

Purpose. The present paper aims to enhance methodology for determining the safety and stability parameters of room mining systems with backfilling of the mined-out area when mining uranium ores in underground mines of the State Enterprise “Skhidnyi Mining and Beneficiation Plant” (SE “SkhidGZK”). Methods. The analytical research method used in the presented paper includes the analysis of previous relevant instructions and reports on the research performed at the SE “SkhidGZK”, as well as publications on the subject, operational geological survey documentation containing monitoring data on the stress-strain state of the rock mass surrounding the formed cavities and the actual state of the mined-out blocks in all underground mines of SE “SkhidGZK”. Findings. The research performed enables development of a new instruction for determining the safety and stability parameters of the room systems with backfilling when mining uranium ores in the SE “SkhidGZK” underground mines. Based on the developed new instruction, the stability of outcrops in mined-out rooms has been calculated, considering the actual time of their life. The obtained parameters fully correspond to actual stability of rooms in blocks of all underground mines. This indicates that the new instruction is more advanced as compared to the current Instruction and its implementation will contribute to mine safety enhancement. Originality. The increased depth of mining uranium ore in the SE “SkhidGZK” underground mines and the increase in lifetime of mined-out rooms require regular adjustment of the methodology for determining their safety and stability parameters. Based on the accumulated production experience, the observations conducted and a thorough analysis of the actual state of cavities, new and adjusted current dependences have been obtained that more accurately consider the impact of both determined factors and those unprovisioned in the current Instruction for determining the safety and stability parameters of rooms. Practical implications. The advanced methodology for determining the safety and stability parameters of room systems in comparison with the methodology described in the current Instruction at the “SkhidGZK” underground mines provides higher accuracy when determining the design parameters of rooms in the stoping blocks and greater reliability of predictive stability of both individual outcrops and rooms in general.

The purpose of research is to increase the ore mass extraction ratio when mining rich iron ores by changing the shape of the stope chamber, as well as to substantiate its stable parameters under the conditions of the rock pressure manifestation. Used in mines existing methodologies for determining the structural elements of mining system are based on calculated equivalent spans of outcropping the stope chambers, which have a rectangular or tent shape. For the first time using the ANSYS software package, it has been determined that the formation of a compensation chamber of quasi-parabolic shape can significantly reduce the stresses concentration around the stope block. Thus, the formation of a stope chamber of a quasi-parabolic shape makes it possible to reduce vertical stresses as compared to horizontal ones without increasing horizontal pressure. When mining the extraction block, it is proposed to form the stope chamber of a quasi-parabolic shape with geometric parameters that directly depend on the parameters of the deposit, the depth of mining, and the direction of main stresses action. Dependences have been determined of the stresses value on the depth of mining and the physical properties of rocks, as well as on the length along the strike of the ore deposit. Thus, depending on the mining depth and length along the strike, rock pressure on the stope chamber of a quasi-parabolic shape decreases under non-uniform loading. The formation of a stope chamber of a quasi-parabolic shape will increase by 1.2 – 1.5 times the volume of pure ore that is recovered from the block.