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Under consideration is the principal diagram of a percussive tool with a ring-shape elastic valve installed in the air distribution system: the valve closes when contacting the housing and opens under action of elastic forces. The operability conditions and basic design parameters of the valve are determined. The authors characterize contact interaction between the ring-shape valve and the side slide surface when the valve is closing. The balance of forces affecting the ring-shape valve is shown.

The authors determine basic parameters for elements of axial tunnel fan VO-21(t) with direct annular diffuser. The algorithm is proposed for calculating aerodynamic parameters of the axial fan using ANSYS CFX program, which allows modeling, computation and analysis of effect exerted by various parameters of the fan air section on the fan aerodynamics. It is found that it is possible to reduce the fan impeller metal consumption and inertia moment by redistributing normal inertia force of blades from the boss to the disks. The admissible impeller velocity is related with the thickness of the impeller disks.

The authors substantiate new engineering designs for selective heading machines and cutter-loaders fitted with screw-type cutters. It is proposed to use biconical and conical disc tools and their attachment units to polygonal prisms to equip both bits of heading machines and screw cutters of cutter-loaders to cut structurally heterogeneous rock mass. It is recommended to practise reverse-mode operation of universal radial-type drill bits fitted with disk tools mounted on triangular prisms with a view to widen the front of loading to be imposed on sidewalls. The presented data on modeling stress sate of disk tools and variants of their attachments to polygonal prisms show the mechanisms of loading of related parts in the course of rock cutting.

Using numerical modeling of rock mass stress-strain state to estimate and predict stability of structural elements of a mining system in combination with the in situ observation data on deformation of rocks in sidewalls, roofs and floors of underground excavations, the authors perform geomechanical analysis of overcutting scenarios in top-down mining in Internatsionalny Mine, ALROSA. Various overcutting flow sheets are considered, and the optimal sequence of overcutting towards higher stability of stopes is determined.

The article gives the analysis of basic mechanisms in variation of output of production heading versus its length in the cutter-loader and scrape conveyor system in underground mining of flat-lying coal beds. Based on the analysis of interaction between cutter-loader and scrape conveyor, the dependence between the maximum capacity of production heading and the longwall length is determined.

The authors investigate modes and parameters of mining operations with a view to create conditions for transmission of geotechnologically produced kinetic energy of rocks to electric generators. The features of application of energy harvesting equipment in underground mining of hard minerals are discussed. The low-frequency energy trap designed to entrap elastic energy of rock mass oscillations operates in a wide range of amplitudes and frequencies of rock mass vibration, and is composed of three nonlinear oscillators having preset mass and elastic characteristics.

The article presents the applied research on formation of science-and-technology basis for commercial introduction of a technology that ensures cardinal reduction in loss in underground mining at unique Kyshtym quartz deposit. Based on the theoretical analysis of the minimum loss criterion, the authors determine rational variants of combination mining system and quartz breaking pattern of planar charges for in situ experimentation.

Currently coal is extracted from highly gaseous beds using preliminary degassing. To estimate efficiency of measures aimed to reduce residual gas content of coal beds, an original approach is offered based on measuring methane content of coal samples taken directly in mine using deep horizontal holes. The authors describe the purpose-designed core sampler and the methane drainage efficiency estimates obtained using the core sampler.

The article sets methodological basis for selecting support for preparatory drives in copper-nickel ore mining by Transpolar Division of Norilsk Nickel. The authors present a case study of selecting support for preparatory drive in the influence zone of top-down multi-slice breast stoping.

In focus is selection of load-haul-dump machines for hard mineral mines. The authors offer substantiation procedures for tuck-and-shovel systems of mining in difficult ground conditions. In terms of Kyrgaisky Sredni open-cut located in the Erunakovo coal district in Kuzbass, using the Lerchs-Grossman algorithm, the principles and sequence of forming efficient application domains for different specification trucks and shovels within a mine field are presented.