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The coal freezing adhesion tests on typical substrates including metal, rubber and plastic substrates were carried out, the steady and separated interfacial structures between coal and substrate surfaces were investigated, and the strength characteristics of coal freezing adhesion on substrates were analyzed in depth. At the stable interface of coal freezing adhesion, the frozen coal slime area is formed in some areas, while the direct contact area as well as the void area may appear between the frozen coal and substrate surface in other areas. The surfaces of metal and rubber substrates have small water contact angle and good wettability, and the separation failure of freezing adhesion occurs at the interior of the frozen coal slime area or the frozen coal itself, thus the coal freezing adhesion strength is reflected by the freezing strength of the frozen coal slime or the frozen coal itself. The surfaces of plastic substrates have large water contact angle and poor wettability, and the separation failure occurs at the bonding interface between the frozen coal slime area and substrate surface, thus the coal freezing adhesion strength is reflected by the bonding strength. The coal freezing adhesive strength on plastic substrates is 4-12 time less than on metal and rubber substrates.

In this study, the rebound hardness values (Shore-Schmidt-Leeb) were calculated for 12 different carbonate rocks using three different devices. The relationships between hardness values and rock cuttability properties (specific cutting energy and noise level) were investigated by simple and multiple regression analyses. It is determined that the Leeb hardness of the rocks can be an alternative to the Shore hardness and Schmidt hardness and that both the specific cutting energy and the noise level can be estimated with the Leeb hardness values.

This study examines the usability of concrete wastes generated from buildings demolished for various reasons in shotcrete. The strength properties of shotcrete produced from recycled aggregates (RA), cylinder specimen and plate specimen were tested. it was observed that as the ratio of RA used instead of natural aggregate increases, the strength of the cylinder specimen decreases, ultrasonic pulse velocity increases. The toughness value has increased in the concrete samples prepared by replacing the natural aggregate with 50% or more RA. It was observed that the fiber amount and load carrying capacity were proportional in fiber reinforced plates prepared using RA. As a result, it has been observed that the interaction of RA with fiber is positive and it can be used in shotcrete. It has been revealed that RA can contribute to the reduction of environmental pollution caused by construction and wreckage wastes and can be presented as an alternative to natural aggregate.

The authors discuss the mechanisms of gas transfer in exposed coal on the strength of the phenomenology of coal gas content. The phenomenon of gas transfer is divided into flow and diffusion, and the major characteristics of these processes in the overall gas travel are revealed.

The authors make a geomechanical assessment of undermined rock mass before and after formation of a sinkhole on ground surface during blind orebody mining on Podruslovy site. The geophysical surveys allowed finding the pillar size dynamics above the mined-out void. The borehole gravity measurements in integration with an orthophotomap made it possible to determine the boundaries of the mined-out void and the parameters of the sinkhole. The mathematical modeling estimated the zones of stress concentration and fracture in enclosing rock mass in the neighborhood of the test boreholes. The safety precautions are designed for the further mining operations on Podruslovy site at Sheregesh deposit.

The usability of salt mine water with high content of chloride-ions in preparing cemented paste backfill is studied. The rheological and mechanical properties of experimental backfill mixtures at different cement consumption are analyzed at uniform and compound aggregate hydrated with tap and mine water with the content of chloride-ions up to 0.75% of the mass of cement. The strength, elasticity modulus and Poisson’s ratio are calculated in cemented paste backfill with tap and mine water after curing for 28, 60, 90 and 360 days. It is found that the strength, elasticity and deformation characteristics of the test cemented paste backfill made of mine water change similarly to the backfill made of tap water, at deviation of ± 10% and ± 4% in terms of strength and deformation, respectively. Chloride-ions contained in mine water have no adverse effect on rheological properties of backfill or hydrated cement, and on dynamics of development of strength in the mixture.

It is examined how convergence of roof and floor affects condition of temporary roadways during extraction of coal series in Kuzbass. The geological and geotechnical factors that can cause deformation in roadways are identified. Roadways are classified in terms of their location relative to a coal seam being mined and a coal seam being overmined in a coal series. The parameters and phases of deformation of rocks are analyzed as primary and secondary convergence of roof and floor rocks in temporary roadways. The primary convergence is observed in temporary roadways located in parallel to the mined-out void and driven in the bottom layer of a thick coal seam being overmined. The secondary convergence takes place in temporary roadways in the abutment pressure zone induced by the earlier mined-out extraction site.

The authors perform the aerodynamic design of axial fans with impeller and inlet guide vane to reverse air flow direction via killing rotation of the impeller while putting the guide vane into rotation. This approach can substantially enhance fan efficiency in reverse mode. The newly developed blade angle analysis procedure allows finding air flow parameters in reversal. The parametric regions in aerodynamic designs of axial fans, where the proposed approach of reversal is effective, are delineated. Design of a fan having similar aerodynamic characteristics in the forward and reverse air flow is undertaken. The swirl ratios of flow in the guide vane are correlated with the axial velocity ratios toward geometrical similarity of blade profiles of impeller and guide vane at an average radius.

A brief review of machines for pit wall scaling is given. The inertial impact technique is compared with the surface miner operation. The authors describe an inertial impact machine with a hammer rotor for pit wall scaling. The procedure and data of the numerical and lab-scale testing of the machine are presented. The tests produced the rational range of lip angles for hammer plates and the preferable impact frequency, which ensure the minimized energy intake of the rotor motor and the least counterforce of rock mass to the bearing seat of the rotor at the preserved efficiency of fracture process.

The found interaction mechanism between a mineral-diamond mixture and a modifying agent includes the stage of adhesive attachment of luminophore at grains of diamonds and kimberlite. The selected compositions of modifying agents and the modification process parameters ensure efficient attachment of luminophore-bearing compositions at diamonds. The proposed criterion of selective action of modifying agent on spectral characteristics of diamonds enable choosing modes of recovery of weak and high luminous diamonds from kimberlite ore in X-ray luminescence separation. The rational variation parameters are determined for the organic collector composition, water phase of a modifying agent and for the process of modifying treatment of diamond-kimberlite products before the X-ray luminescence separation. The test of the selected compositions of modifying agents and the diamond-bearing product treatment modes proved almost complete extraction of weak and high luminescence diamonds to concentrate at minimized yield of kimberlite.