Vol 55, No 5 (2019)

The applicability of calculated information entropy to quantification of coal structure nonuniformity at a microlevel is demonstrated. The calculations used digital images of coal surface from scanning electron microscopy after thousandfold increase. The calculated statistical entropy-complexity values enable comparing structural nonuniformity of coal sampled from outbursts, as well as from outburst-hazardous and outburst-nonhazardous zones. It is found that coal from outburst-hazardous zones contain areas of highly chaotic structure as against the ordered structure of coal from outburst-nonhazardous zones. Outburst coal is free from chaotic structures though its structure is less ordered than in coal from outburst-nonhazardous zones. The proposed method allows detecting the certainly outburst-nonhazardous zones in coal seams using digital images of coal samples.

The flow of pore fluid is modeled on a lab scale with samples of man-made substance from tailings ponds. The data obtained in the gravimetric and apparent resistance tests are presented. It is found that capillary forces make the main contribution to flow of solutions from a pollution source. This allowed estimation of nature and velocity of the process. The experimental results show high-rate vertical and lateral spreading of solid waste substance from sources of drainage solutions, which has detrimental effect on ecology of the nearby lands and water bodies.

The main purpose of this research is to evaluate the effect of coal seam dip on the front abutment and side abutment stresses distribution around the longwall panels by FLAC3D software. For this purpose numerical modeling of five longwall panels in coal seam with dip angle of 0, 12, 22, 32 and 42 degree have been done. The results of numerical modeling have been shown that in all models, peak value of front abutment stress was found to act at a distance about 1–3 m in front of the panel face and the difference between this stresses in front of the working face is about 9.7 MPa. In this distance, the peak vertical stress is in the order of approximately 4–5 times the in-situ stress and then gradually decreases toward the initial field stress. Moreover numerical modeling results have been shown that increasing coal seam dip has no significant effect on the peak value of side abutment stress at the edge of pillar, but the side abutment stress concentration is nearer to the edge of pillar. At coal seam dip of zero and 12 degrees, maximum vertical stress occurs at a distance of 5.4 m from the pillar edge, whereas at the coal seam dip of 42 degrees, this stress occurs within 3 m of the pillar edge. However, increasing the dip of coal seam caused to increase entry roof displacement. The results are in good agreement with field observation.

The criteria of failure and limiting state, widely used in strength assessment of rocks and building materials, are considered. The two-dimensional computer model is presented for deformation of cement lining in a cemented cased hole in rock mass under the action of internal pressure from the casing and external pressure from rock mass. The model has a number of science-based and experimentally proved strength criteria for determination of failure behavior and potential damaged zones in cement lining. A series of stress-strain analyses of cement lining is performed with varied geometrical parameters and stresses. The criticality of local and nonlocal failure criteria is analyzed. By comparing equivalent stresses, six failure criteria are selected and recommended for estimation and prediction of load resistance of cement lining.

High production rates and low operating costs highlight block caving as one of the favorable underground mining methods. However, the uncertainties involved in the material flow make it complicated to optimize the production schedule for such operations. In this paper, a stochastic mixed-integer linear optimization model is proposed in order to capture horizontal mixing that occurs among the draw columns within the production scheduling optimization. The goal is to not only consider the material above each drawpoint for extraction from the same drawpoint, as traditional production scheduling does, but also to capture the horizontal movements among the adjacent draw columns. In this approach, different scenarios are generated to simulate the horizontal mixing among adjacent slices within a neighborhood radius. The best height of draw for draw columns is also calculated as part of the optimization. The model is tested for a block-cave mine with 640 drawpoints to feed a processing plant for 15 years. The resulting NPV is 473M$ while the deviations from the targets in all scenarios during the life of the mine are minimized. Using the proposed model will result in more reliable mine plans as it takes the horizontal mixing into account in addition to achieving the production goals. Using different penalties for grade deviations shows that the model is a flexible tool in which the mine planners can achieve their goals based on their priorities.

The results of modification of the Middle Timan high-iron bauxite by thermal radiation, including the earlier unknown phenomenon of phase heterogenization—formation of intrinsic minerals by originally endocryptically disseminated noble, nonferrous, rare and rare-earth micro-elements—are presented. It is possible to utilize this phenomenon for the purpose of commercial application of low-grade bauxite, red mud and other difficult ore.

The occurrence form of sodium dibutyl dithiocarbamate on chalcopyrite is defined by IR spectroscopy. A stable compound of lead dibutyl dithiocarbamate forms on galenite. Fat acids of tall oil are adsorbed at the surface of cassiterite as chemically adsorbed oleate and physically adsorbed calcium dioleate. Sodium oleate adsorption at quartz surface is unfound in the mineral spectra after contact with fat acids, which proves selectivity of this agent relative to cassiterite. Applicability of 1,3,5-triazine-2,4,6-triamine agent to flotation of silver-bearing minerals is studied. The output of ultrasonic treatment aimed to remove slime material which deteriorates gravity separation of tin tailings at Solnechny Mining and Processing Plant is described.

Grinding, as an important preparation step for beneficiation is very necessary to study for the finely disseminated extent, vanadium-bearing stone coal with complex chemical composition. In this paper, grinding medium, time, degree and monomer dissociation degree were investigated in detail. The results show that the efficiency of rod milling is better than that of ball milling, especially the proportion of −0.038 mm size fraction obtained by rod milling is 10.89% higher than ball milling. The grinding degree of 8 min rod mill is −74 µm 73.19%, then the proportion of monomer is 70.68%. MLA measurement shows that roscoelite can not be dissociated by fine grinding. Vanadium concentrate with 0.97% of the grade and 89.88% of recovery was obtained by classification and shaking table technology. Tailing rate is 18.82%. The enrichment of vanadium can be realized by reasonable grinding and classification.