Vol 55, No 3 (2019)

The solution is presented for the problem on oil percolation in a reservoir at the present and time-varying pressure difference between the injection and production wells. The area of water blocking under capillary pressure in the well bottom zone is determined. The algorithm is proposed for calculating fluid pressure on the well bottom by readings of echo sounder installed at the well mouth. The penetration zone of pressure fluctuations in the reservoir is estimated, and their effect on enhanced well production is shown.

The results of physical modeling of deep pit slopes with equivalent materials are presented. The checking calculation is preformed using the limit equilibrium method. The displacements in the model are determined, and the safety factors of stable slopes are calculated at all stages of modeling. The pattern of deformation and failure of pit slopes is analyzed starting from the first manifestations till total instability at different strength characteristics of bedding interfaces. It is found that failure mechanism of pit slopes with steep bedding is governed by shear strength of interfaces. When the interfaces and rock mass have similar strength characteristics, pit slope deforms along a smooth curved sliding surface by the similar mechanism of an isotropic slope. In the presence of interfaces with much lower strength characteristics than the rock mass strength, the slope deformation has the mechanism of flexure toppling. In an intermediate variant, it is most probable that failure follows the mechanism of bending with subsequent shear of the layers along a curved surface.

In order to determine the slope stability of an open-pit mine effectively at Dorli Opencast Project-II (Dorli OCP-II) of M/s Singareni Collieries Company Ltd. (SCCL), India, from available geotechnical data, this paper proposes analytical and numerical models. Physico-mechanical properties of the rock materials required for establishing these models were obtained by laboratory tests conducted on core samples taken directly from the mine. In this research, the influence of 6 discriminant factors on the pit stability by changing one-factor-at-a-time (OAT) and keeping all other factors fixed is studied. The study utilizes Limit Equilibrium Method (LEM) based software (SLIDE), Finite Element Method (FEM) based software (RS²) and Finite Difference Method (FDM) based software (FLAC/SLOPE) to analyze the sensitivity of each factor on the Factor of Safety (FoS) of pit slope for high accuracy and validation of models. The results from these methods of analyses are compared and comparison of the outputs of analyses shows a very good agreement with nominal difference (<1%) in the FoS.

The method of determining strength characteristics of rocks subjected to tension is tested; the method is based on processing of data from fracture tests of specimens with axial holes of different diameters subjected to loading along diameter. The test data of specimens of rocks and simulating media in the form of cores with axial holes and fractured along diameter are processed based on the integral strength criterion of Novozhilov. The comparison shows good agreement between the fracture toughness and tensile strength values obtained using the proposed method and in standard measurements.

The problem of finding ways of overcoming antagonistical contradictions between the techno-and bio-spheres in development of mineral resources in the Arctic is discussed. It is shown that one of the main avenues of advancement under these conditions is creation and application of nature-like mining technologies. It is found that the hierarchical peak influence on natural biota destruction in permafrost zone is connected with accumulation of solid mining and processing waste on the ground surface, which predetermines the principate of the closed-cycle circulation of solid in lithosphere within the cluster of a nature-like mining technology. The idea is developed and proposed to accord the functional structure of a mining technology with the internal structure of a cryo-georesource and with relation of its components in space and time.

In order to evaluate water inrush risk from the deep coal floor by mining above the confined aquifer in mining area, the structural complexity of the study area was partitioned by fractal dimension method. Moreover, the water inrush coefficient was calculated. Quantization partition was also carried out using the distribution law of the water inrush coefficient contour. It is found that the structural complex area and the water inrush danger zone have good coincidence in parts of study area, which increases the estimating reliability of the water inrush risk. The research results have an important reference value for realizing safe and efficient mining of the second level coal seams.

The results of the experimental studies into formation conditions of gas dispersion during electrolytic flotation are presented. The facing factors of electrolytic bubbling are considered. The influence exerted by the electrolysis process parameters and electrolytic compositions of water solutions on the dispersion state and gas content of electrolysis solutions is analyzed. The effects on the electrical state of the bubbles during electrolysis are studied.

The research results on gravity concentration of the Shalkiya deposit lead-zinc ore are presented. Using the float-and-sink analysis data, the Henry-Reinhard-type washability curves are calculated and plotted for separation size grade 40–8 mm. The separation density required for recovery of light fraction at minimum possible loss of lead and zinc, as well as the gravity washability indices are determined. It is found that the overhead product of the gravity concentration of coarse ore is tailings containing silicon, calcite and carbon black dioxides. The loss of lead and zinc is minor. Processing of coarse crushed ore should be carried out in heavy medium.

The research results are presented for dressability of quartzites from the Garga quartzite region of the East Sayan. From the detailed analysis of the structure, texture, mineral and fluid inclusions in the chemical constitution, bright veined quartzites and coaly veined quartzites were distinguished in the Urda-Gargan block. Both kinds are readily dressed up quartz concentrates of deep concentration. The fist quartzite kind can be used in manufacturing of transparent optical quartz glass, whereas the second variety is a promising feedstock for carbothermal production of silicon.

In this paper, the influence of alkali on the flocculation of starch on fine hematite was investigated through a series of tests, like turbidities, paste titration, adsorption, conductance, scanning electron microscope (SEM) measurement, and Fourier transforms infrared spectroscopic analysis (FTIR) as well. The results pointed out that alkali concentration has a strong influence on physicochemical changes of starch granules, inducing different adsorption densities on mineral surfaces. A maximum amount of adsorption density on mineral particles was harvested for the starch digested with sodium hydroxide at a concentration of 0.4 N/g starch. It is worthy to note that starch is not fully digested in the presence of alkali at a concentration of less than 0.4 N/g starch. Higher concentration of hydroxide ions, however, tends to obtain less adsorption density of starch on hematite because too small remnants in the starch gel have inverse effects on adsorption capacity.

The article substantiates the retrofit method for two-stage axial flow fans including an impeller and a flow straightener in each stage. In this method, the two-stage rotor is replaced by a high-rate one-stage rotor within the inlet guide vanes-impeller-flow straightener circuit. As a result, the air flow at the impeller input is uniform per standard, the operational life of the rotor bearing assembly is extended while the rotor mass is largely reduced. The procedure is developed for design and selection of aerodynamic and structural parameters of the remodel axial mine fans. The procedure takes into account the influence of the variable frequency drive and gyroscopic moment of the impeller, as well as the rigidity of the bearing assemblies and ratio of mass-inertia properties of the rotor, which allows determination of critical rotor speeds at early stage of design.

The experimental procedure is presented for range test of critical flame spread in the conditions of uniform distribution of particles in dust cloud under varied temperature of the ignition initiation source. Fire and explosion hazard of coal dust is estimated by the method of successive approximations. The feasibility of studying the cold flame effect in inflammation of coal dust suspension in air and its transition to the hot mode burning when dust concentration grows is demonstrated, which is of importance for the theory of safety technology.

Wireless sensor networks WI-Fi ad hoc have been proposed information transmission between data loggers and mobile station (smartphones). The wireless data transmission follows from an underground station to a worker’s smartphone and, then, after the worker has left the mine, to a data logger on the surface. The serviceability of this system was tested by measurement of communication quality indexes in various environments. The tests show that wireless communication between a stationary point and a mobile devise is possible at transfer speeds up to 2 MB/s with a packet error rate (PER) below 25% either at a maximum distance of 110 m in a straight path or at a distance of 20 m in case of a corner or turn of the path. The proposed system allows the transmission of 39.6–79.2 MB of monitoring data to a worker moving at 20 km/h.