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The authors propose a new approach to processing multichannel data on surface waves to enhance interference immunity of dispersion curves of the Rayleigh wave phase velocities determined from the analysis of motion paths of particles in the time-and-frequency domains based on the S-transform applied to the two-component seismic records. Efficiency of the approach is demonstrated as a case-study of processing of the synthetic and field data of shallow seismic investigations.

Rock testing data are used to determine proper bases of tensors where strains along the unit vectors are only governed by stresses along them. The obtained curves along the unit vectors-one curve is proportional and the other curve is nonlinear, and both are independent of loading history and mechanism-are used to solve geomechanical problems. In planar post-limit deformation, these curves lead to a hyperbolic system of differential equations with four real functions and four relations to find four unknown functions: average stress, maximum shear stress, rotation angle and angle of directions of principal stress tensor axes. For finding their boundary values, the Cauchy stress vector and the displacement vector are assigned simultaneously at one and the same boundary. The authors propose an algorithm of finding these four functions within the post-limit deformation domain.

Chagan Aobao Iron-Zinc Mine is taken as the research case, and the characteristic angles of overlying strata collapse caused by underground mining are recommended. The research results can provide guidance for disaster prevention and control of rock collapse.

The authors have developed a regression model of coal freezing adhesive strength in transportation on equipment made of steel and rubber. The model uses the response surface methodology and the coal freezing adhesive strength tests. The influence exerted on the adhesive strength by the external conditions, as well as by the coal and transportation surface properties is analyzed.

The authors describe numerical investigations of hydraulic fractures in boreholes with branches (intersecting boreholes). The directions of growing fractures were determined in the static problem solution by the criterion of maximum tangential stresses and in the quasi-static three-dimensional formulation with the analysis of fracture of an elastic uniform medium using the cohesive failure mode and the extended finite element method. It is found that some geometrical parameters of the starter fracture and the stress state nonuniformity have influence on the growth direction and shape of the created fractures. The X-shaped starter fracture, which simulates branching and intersections of boreholes, is preferable over the disc-shaped starter fracture in local control of hydraulic fracture orientation in rock mass under nonuniform compression.

The spotlight is on the stress patterns in oil and gas reservoirs and in enclosing rock mass containing displaced fractures (disjunctive cleavages). The mathematical modeling finds out that with the decreasing reservoir pressure in rock mass subject to elastic deformation, the shearing stress raisers arise on the surfaces of displaced fractures and can make an initially impermeable fracture to become fluid-conductive. Creeping widens the fractures, which also contributes to hydrodynamic connection between a pay zone and the upper- and low-lying permeable strata. This process of formation of the permeable channels in rock mass can be an explanation for the mechanism of oil and gas reservoir infeed with fluid flows from the lower-lying fluid-bearing strata.

Description of formation of a manmade backfill made of frozen briquettes using the cryoresource of the permafrost zone involves the phase transfer theory. The seasonal dynamics of the regional temperature is included in the closed life cycle of a solid substance as the main component of the geotechnology. A Stefan problem is adapted to heat processes in formation of a manmade frozen rockmass in the permafrost by filling a mined-out void with briquettes frozen on ground surface, with further injection of processing slurries having a positive temperature in remaining cavities. The numerical implementation program is developed for the set problem in 3D formulation. The freezing time of the artificial rockmass made of the frozen briquettes is related with the size of the briquettes, and with the temperature of the permafrost and the slurries. The frozen backfill in underground mined-out voids is a favorable decision in terms of ecology in mineral mining in the permafrost zone.

The authors implement a new model of calculating temperature field and stresses in frozen rock mass at all successive stages of sinking: rock freezing, shafting, concrete lining and thawing. The model allows assessing dynamics of temperatures and stresses in rock mass, in frozen wall and in concrete lining at the freeze and thaw stages with regard to the thermophysical and mechanical properties of the materials. It is found that functioning of the freezing pipes in the same mode in depth is nonoptimal and leads to excessive energy consumption.

In this study, combustion properties such as thermogravimetric analysis and differential thermogravimetric analysis, combustion profile, ignition temperature and peak temperature were analyzed for 3 lignite samples obtained from different regions of Konya in Turkey. In the kinetic analysis, activation energies were calculated separately for four different reaction sequences using the Coats-Redfern method. As a result, when the calculated activation energies, thermal and kinetic properties of the coal samples are evaluated together, it is seen that Beyşehir coal is more prone to combustion than other coals.

The article describes the studies into the current flow charts available for processing diamond-bearing kimberlites of complex material constitution. The theoretical and experimental substantiation is given for the methods to modify properties of the mineral components to enhance selectivity of their separation. Efficiency of luminophore-containing compositions is proved for weakly and abnormally luminescent diamond. Luminophores modify the spectral and kinetic properties of diamond crystals to the values at which diamonds become recordable and recoverable in the current flow charts of X-ray luminescence separation. Efficiency of integration of ultrasonic, thermal and electrochemical methods in removal of hydrophilic impurities from diamond surface toward enhanced recovery of diamonds by grease technology and froth separation is demonstrated. The method is developed to increase the corrosion resistance of ferrosilicon by means of its nitride coating which unsupports interaction with corrosive components of the water environment. Experiments justify that magnetic separation improves the quality of preconcentrates of float-and-sink separation owing to removal of up to 95.8% of magnetic minerals from the diamond-bearing material.