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The article describes experimental studies on water saturation of samples of major rock types typical of Donbass. The alterations of deformation properties of moist rocks are generalized. The procedure of modeling with regard to the effect of flooding on displacement parameters in different rocks is presented. Using laboratory data, a finite-element model of activation of geomechanical processes initiated by rock mass undermining and flooding is constructed. It is found how rock mass lithology influences displacement parameters in flooding of underground roadways in coal mines being closed. The research results can help improve effective regulatory documents on ground surface displacement prediction in coal mining and mine closure through lithological analysis of coal-rock mass.

To investigate the slip mechanism of the slope with weak interlayer, the location of the weak interlayer within the slope was determined by on-site monitoring using the Hequ open pit mine as the engineering background, and a three-dimensional numerical model was established based on this, and the study of the potential slip surface and key units of the slope containing weak interlayer was carried out. The potential slip surface inside the slope with weak interlayers is determined from the perspective of displacement contour and maximum shear strain increment. The principle and method of key unit identification for the slope with weak interlayer is proposed. The initial key unit on the potential slip surface of the slope with weak interlayers is identified, and the dynamic breaking path of the key unit on the potential slip surface of the slope with weak interlayers is determined.

The difference in energy accumulation in coal and rock under the same stress level is analyzed, and it is found that the difference of energy accumulation of coal rock under the same stress level mainly depends on the elastic modulus of coal rock material. Based on the structural characteristics and mechanical properties of coal-rock, the mechanical model of combined coal-rock body was constructed and analyzed, and the calculation formula of partition energy storage of combined coal-rock body was deduced. The axial compression test of combined coal-rock body under different loading rates was designed and carried out. Finally, the differential energy instability model of the combined coal-rock body was constructed. An evaluation index of the impact tendency of the combined coal-rock body considering the elastic energy difference and the release time is proposed, which provides a multi-scale criterion for accurately evaluating the impact propensity of the combined body.

The authors design and estimate a room-and-pillar method for mining inclined orebodies with combination of two approaches to ground control: through natural stability of rock mass and by means of overlying rock caving. It is shown that in rock mass under tectonic stresses, it is safe to extract ore reserves from rooms and from temporal ore pillar under protection of rock overhang. Due to inclination of an ore body, rocks in the pillar and in the block bottom fail mostly by way of shearing. The efficient ratios of a minimal width of a temporal ore pillar to a span of a stope are determined.

Fundamental considerations like drillability and tool wear may be pondered for development of deep well drilling for oil and gas, and tunneling projects. Careful considerations of key parameters may enhance the advance rate, operational costs, activity completion timeline and inventory control for spares. NTNU/SINTEF developed drilling rate index (DRI), bit wear index (BWI) and cutter life index (CLI) to quantify drilling and TBM related parameters. Until now, most of the research work has been carried out to develop models in order to recognize the effects of rock properties on drillability. However, very little if no studies have been conducted on the prediction of bit wear using BWI. This work deals with the effects of different geo-mechanical parameters of rocks on the drillability and the bit wear. The work shows that both drillability and bit wear are affected by physical and strength parameters of rocks. Moreover, various statistical models (with R² ≥ 0.83) have been developed through simple linear regression analysis (SLRA) and multiple linear regression analysis (MLRA) for the prediction of NTNU/SINTEF indices (DRI and BWI).

The authors propose an approved integrated approach to assessing influence of coal-rock mass on coal faces by a gas-based criterion through the isotope analysis of coalbed methane. The quantitative ratios of carbon isotopes of methane are determined in coal samples and in mine air samples from seven operating mines in Kuzbass. The geometrical parameters of such zones are assessed, and the maximal methane volume capable to affect a coal face during its operation is found. It is emphasized that the gas volumes and the methane migration zone parameters differ greatly when found using a traditional method and the integrated approach with the carbon isotopic analysis of methane in mine air and in coal.

Gas emission during destruction of coal samples in a mill is measured experimentally. Using the Skochinsky Institute’s procedure, emmitable gas amount is calculated as function of coal particles. Coal samples for the tests were taken in an outburst-hazardous seam. It is found that the decrease in the size of coal particles to 0.1 mm increases gas emission by several times. The authors developed a model of force interaction between methane molecules in micro-porous coal structure and surface of coal macro-molecule, and a calculation procedure for gas emission in coal as function of its degree of breakdown.

The authors developed a resource-saving and energy-efficient technology for integrated processing of eudialyte concentrate. It is found that the main losses of valuable components (Zr and REE) are associated with leaching cake. The effective methods and modes of processing of pregnant solution are determined to ensure high recovery of Zr and REE owing to conversion of silica gel and thanks to successive extraction of zirconium phosphate and rare earth carbonates from pregnant solution. The proposed complimentary methods of regeneration of reagents and shutting off of water circuits ensure recovery of zirconium and rare earths from eudialyte concentrate. The developed technology provides additional marketable products (sodium metasilicate and ammonium nitrate), as well as economic expediency and improved ecological safety of eudialyte concentrate processing due to regeneration of calcium carbonate.

The research focuses on the specificity of flotation of carbonate-fluorite ore waste at Yaroslavskaya Mining Company. The waste composition and process properties are examined. Fluorite in the test waste occurs in mineral concretions and in slime. The problems in flotation of old mining and processing waste are governed by specific surface properties of particles, film coatings and structural transformations. The promising methods to induce conversion of components in flotation pulp are discussed. It is found that ultrasonic and electrochemical treatment of waste components promote selectivity of their separation. The indicators of processes at fixed time intervals and under special effects are analyzed. Flotation with ultrasonic and electrochemical pre-treatment of pulp substantially increases fluorite concentration in froth and enhances selectivity of fluorite separation from calcite. Recovery of fluorite in concentrates with CaF₂ content more than 94% rises by 2.97-4.58%. It is demonstrated that it is possible to reduce mass fraction of silicon dioxide in concentrates by 0.3-0.5%.

The studies on vanadium production are generalized, and the promising nature of flotation is demonstrated in this regard. The prognostic selection of fulvic acid FulvAc as a selective collecting agent relative to vanadium occurred as vanadyl VO²⁺ in acidic pregnant solutions is justified. The analysis of chemical reactivity studied the mechanism of vanadyl extraction and concentration using chelating agent FulvAc. Computer modeling is performed for a flotation system representing a slightly soluble metal complex of vanadyl fulvat [VO²⁺ - FulvAc]_n . Efficiency of FulvAc is proved by lab-scale flotation tests with recovery of vanadyl not less than 92%. Vanadium oxisols are demandable by different industries, and [VO²⁺ - FulvAc]_n is usable as complex mineral supplements for fertilizing mixtures for urban greening.