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The authors analyzed some reagent regimes in flotation of nepheline from loparite ore tailings: mixture of tall oils, hydroxamic acids in combination with distilled tall oil; mix of tall oils with addition of polyalkyl benzene sulfonic acids or amine-containing collectors. The nepheline concentrate produced in the optimized reagent regime contained Al₂O₃ 27.18-27.57%. With addition of tall oil polyalkyl benzene sulfonic acid, activity of the collecting mixture reduced, and the produced concentrate quality lowered to Al₂O₃ 26.33%. Two methods to bring flotation concentrates to a standard quality are discussed. The use of magnetic separation allowed production of nepheline concentrate with Al₂O₃ 28.0-28.3% at the recovery of 72-76% compared to the initial product. Direct cationic flotation with agent Flotigam-2835 in an acidic medium with рН 4.5, created by sodium silicofluoride, produced nepheline concentrate with Al₂O₃ 29.63% at the recovery of 65.9% compared to the initial product.

The authors theoretically substantiated and, using in-situ measurements, proved the method of determining kinetic characteristics for coal bed gas: content, diffusion factor, mass exchange and rate of desorption. These data are required for the development of technologies of coal mining and methane utilization. The method involves solution of an inverse problem within the framework of a nonlinear model of gas emission from a particle placed in an isolated container, using the data on time change in thermodynamic parameters (pressure and temperature) in a sealed canister with coal chippings. The model analysis shows that ratio of methane concentrations at different moments of time is independent of gas content. This enables development and numerical implementation of a two stage algorithm: first, by solving an inverse problem with time-dependent coefficients, the factors of diffusion, mass exchange and desorption are found; then, with minimization of a special function, the gas content is determined. The in-situ data are obtained using coal chippings from drilling in an operating mine in Kuzbass, by means of measurement of pressure and temperature in five canisters for 10 days. The interpretation of the data made it possible to assess the methane content in the test coalbed site as 4 kg/m³.

The field research of the geomechanical behavior of rock mass was carried out in the neighborhood of an abandoned railway tunnel by means of multi-channel analysis of seismic surface waves. For the interpretation of the results, the spectral dispersion images of waves along the tunnel were selected and analyzed. That made it possible to obtain the velocity patterns of waves in enclosing rock mass, and to identify the low-velocity zones in it. The results prove the applicability of the method of determining structure and condition of adjacent rock mass surrounding underground structures.

Open mining operations generate deep open pits, and the industrial infrastructure and buildings become closely spaced with the open mining zone as a result. The situation requires implementation of integrated monitoring and periodic assessment of pitwall stability considering up-to-date data on properties and condition of rock mass. This article describes an approach to monitoring and assessment of pitwall stability on a hazardous site. The periodic seismic profiling reveals great disruption of the test site. The stability assessment of the test site using the limit equilibrium method shows the slope instability. It is concluded that prediction of failure zones on the test site is advisable to carry out by integrating the field inspection and computational methods of slope stability control.

The static and dynamic wedge indentation resistance tests involved plexiglass and marble samples. The static tests recorded the indentation resistance force as function of penetration depth. The dynamic tests included a rope gravity drop hammer. The tests focused on the dynamics of penetration of a dropping massive wedge into a plexiglass sample. The indentation resistance was determined using an accelerometer mounted on the wedge. Plexiglass as a model material allowed finding the shape and size of the main cracks generated by wedge indentation. The test data on the wedge indentation resistance and on the main crack size were compared with the theoretical values. The comparison showed a good agreement of theory and static experiments with plexiglass samples. In the dynamic tests, the theoretical indentation resistance appeared to be less than the test values by 25% at the most, at a good agreement between the sizes of the main cracks.

The article describes the stability testing and calculation results for a heavy column set on the surface of a granular medium, and for a plate buried in the granular medium. The column and plate were exposed to a pre-limiting static load. The granular medium was subjected to multiple weak impacts. The lab-scale tests determined that under such loading, the granular medium evolved gradually to the critical condition and lost the shearing strength. The rate of approaching the critical condition grows with the number of impacts. The critical number of impacts before failure of the medium obeys the log-normal distribution. The most probable value of the critical impact number increases exponentially with the decrease in the static load. The DEM-based modeling of the stability loss in the plate buried in the granular medium yielded the results that qualitatively coincided with the test data.

It is investigated how the content of basalt fiber with a diameter of 23 µm influences specific energy intensity of failure in concrete D2000 and in light heat-reflecting concrete D1000. The mechanisms of alternating temperature effects on dynamic impact resistance of fiber-reinforced concrete are determined. After 12 cycles (freezing temperature - 50 ± 2 °С), the energy cost of failure in the samples of concrete D2000 at the fiber volume ratio of 2.7% totals 1962 J/m², which is 3.6 times higher than the energy intensity of failure in the samples of non-reinforced concrete. It is found that concrete with a porous absorbing aggregate made of expanded vermiculite possesses higher dynamic impact resistibility than high-density concrete. The energy intensity of failure was 5038 J/m² in vermiculite-containing heat-reflecting concrete and 2326 J/m² in fine-grain concrete D2000. The failure energy intensity in vermiculite-containing non-reinforced concrete after three freeze-thaw cycles drops by 71%, from 5038 to 1473 J/m². At the fiber volume ratio of 2.4%, the energy intensity of failure in fiber-reinforced concrete decreases by 9%, to 4608 J/m². These results can help increase the impact resistibility of shotcrete lining, including situations after the adverse effect of cyclic freeze-and-thaw.

The geodynamic research of coal-rock mass in mines in the Donbas uses composite seismic signals which appear on ground surface during coal mining. The search of regular patterns in geological response of rock mass to seismic waves is based on the main physical principles of elasticity: dependence of the signal energy on the proximity to the vibration source and dependence of P-wave velocity on the density of the medium. The authors of the article discuss the results of seismic monitoring in the mine fields in the Donets-Makeevka region of the Donbas. The energy and spectrum characteristics of seismic signals are correlated with the geodynamic processes and with the geological section parameters. The direct proportional dependence is found between the total thickness of jointed rock mass and an integrated parameter including azimuth of any component of seismic waves. The analysis of spectra of composite signals shows that their frequency characteristics allow differentiating areas of maximal softening and compaction in coal-rock mass and eventually enable delineating faulting influence zones which are the anomalous accumulations of methane.

Density, porosity, P-wave velocity and Leeb hardness were determined for travertine samples from different quarries in Turkey, and the relationship of these properties with uniaxial compressive strength values was evaluated. Exponential relationships were obtained between UCS and physical and mechanical properties of test samples. The strongest relationship was obtained between UCS and the Leeb hardness, at the correlation factor R² 0.91.

Inspection of underground openings in the Taimyrsky Mine, in the previously flooded areas, revealed increased jointing, rock falls in roofs and sidewalls, dome folding in roofs and fracturing of shotcrete lining. The main cause of failures is dissolving of loose material in cracks in gabbro-dolerite rock mass, with its leaching out later on. The complex mode of the Oktyabrsky deposit ore occurrence is revealed within the Taimyrsky Mine field. Mining is greatly complicated by faulting, heavy jointing, low stability of rock mass and dynamic events induced by rock pressure. Condition of mine openings was analyzed, and samples of rocks taken in the flooding zone were tested: in uniaxial compression, the strength, deformation modulus and lateral deformation coefficient were determined; in tension, the strength was determined; the failure curves (cohesion and internal friction angle) were plotted. Stability of rock mass enclosing the Oktyabrsky deposit, including jointing, was estimated. Videoimage endoscopy was carried out in exploration and destressing boreholes in order to detect stratification and fracturing in moist zones in rock mass. The ground penetrating radar inspection of adjacent rock mass was performed. It is found that mine water and mine air have the corroding influence on metal and concrete elements of mine support. The ways of improving the mine support technology in moist rock mass areas are proposed. The recommendations on safe roadheading are made.