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The authors discuss concentration of chemical elements in underspoil water subject to a season and to climatic conditions. The features of underspoil water composition are analyzed with respect to chemical composition of spoil rocks in water and acid extracts. Majority of the test elements correlate well with their composition in the acid extract and with the spoil rocks composition. The water extract is assumed to be unreliable to predict composition of underspoil water.

The article analyzes the impact of water inflow in a mine on the efficiency of the main mine water drainage system as a case-study of Udachny Mine, ALROSA. It is found that the content of solid particles in mine water grows with the increasing water inflow in the mine. A method is proposed to eliminate excessive water inflow in the mine in warm season in case of a pumping station teardown because of the spoil bank slide. The expected payback time of the proposed engineering solution is calculated.

The authors attempt the numerical modeling of the geomechanical behavior of a rock mass in the course of single unit face longwall mining. The calculation models are constructed for the rock mass geomechanics from ground surface down to mining depth. The model problems are solved in two and in three dimensions. The resultant characteristics of a trough subsidence on ground surface were compared with the data of engineering analysis. The modeling results are verified using actual in-situ observations of check point subsidence. The comparative analysis of the trough subsidence characteristics on ground surface from the geomechanical modeling and engineering analysis show their correlation in case of all test alternatives.

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.