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A review of advanced equipment for automated interference measurements developed at the All-Russian Research Institute for Optical and PHysical Measurements is given. Three types of interference microscopes based on the Linnik, Twyman-Green, and Fizeau interferometers with the use of the phase stepping method are presented.

The article presents physical modeling of geomechanical processes in outer zones of coal beds with the main roof caveable with difficulty. The scope of the modeling embrace the effect exerted on gas release by gas temperature and pressure variation during stage-wise outlet of gas from a pressure bomb, which simulates cyclical mechanical impact on a coal bed in the zones of a gas pocket. It is found that the low-frequency (2.0-4.5 Hz) attenuating vibrations generated in the main roof can induce both secondary rock mass disintegration as well as methane desorption and decomposition of gas hydrates (if present) accompanied by an increases in gas pressure and in number of gas-dynamic events in outer zones of coal beds.

The author proposes a new analytical approach to the description of statics, kinematics and dynamics of interaction between mine support and enclosing rock mass in the course of stoping. Inclusion of the static component suggests the classical construction of a probable line of fracture. The kinematic aspect means accounting for the influence of the overlying rock weight on the process of failure. The dynamics of failure during growth of mined-out area is illustrated in terms of a unit event of production heading advance. These components of the damage accumulation process in rock mass allow more accurate monitoring of destructions due to rock pressure.

Mechanisms of change in the spectra of acoustic emission in specimens of mineral coal from Kuznetsk and Pechora Basins are experimentally determined in uniaxial and triaxial (Karman scheme) compression tests. It is shown that at the pre-failure stage in a specimen under uniaxial compression, the spectrum pattern of acoustic emission changes considerably, the amplitudes of low frequencies grow while the amplitudes of high frequencies reduce. Under the Karman scheme loading of specimens, the amplitudes of the low-frequency signals grow without the decrease in the high-frequency amplitudes, which is connected with the prevented opening of fractures under the influence of the hydrostatic pressure in the horizontal plane.

The object of the numerical study is the travel of pendulum waves in a blocky medium under nonstationary impact of deep-seated charge blasting on the surface of the expansion chamber. The blocky model is simulated by a two-dimensional lattice of masses connected by elastic springs along the axes and diagonals. The displacements and velocities of the masses at different half-space points are calculated using the finite-difference method.

The article describes the theoretical and experimental research into the strength of cylindrical specimens made of layered and anisotropic geomaterials exposed to axial compression and lateral pressure. The tests used INSTRON 8802 versatile servohydraulic fatigue testing system. The experimental results are the relationships between the ultimate strength and bedding angle in specimens of an artificial material, meta-siltstone and shale. The experimental data agree well with the theoretical calculations.

Fracturing efficiency of fluids in specific mining processes depends on reliability of data on structure and state of rocks, on pre-setting the location of fracturing origin, on choice of a fluid and its injection regime, as well as on the accepted engineering solutions. Fracturing by fluids are the processes that alter properties, structure, composition and state of rocks. Investigation of such processes offers a deeper insight into the multi-phase media (earth crust) and promotes advancement in nonconventional mining technologies.

In focus of the studies is the influence exerted by the radial displacement of the hammering unit on the air distribution in the air hammer drill with the ring-shape elastic valve. The minimal allowable volume of the backstroke chamber at the frontmost position of the hammering unit when it contacts the anvil is calculated with regard to the limited maximum pressure in the impact stroke chamber at the moment of the blow. In the capacity of the air hammer drill efficiency criterion, it is suggested to use the length of the powered closure of the elastic valve, that compensates rotation of the hammering unit in the body when the radial clearance between these parts grows. The parameters of the air distribution system are estimated for all sizes of air hammer drills with the ring-shaped elastic valves.

The article presents the procedure and algorithm for selecting basic characteristics of a positive-displacement hydraulic hammering system. The procedure is based on the dimensional analysis of equations of the system, selected similarity criteria and calculations of output characteristics in the space of the similarity criteria. The program offers a user the options of setting initial parameters and characteristics of hydraulic impact systems in the form of values and constraints and, then, table values for the dimensionless characteristics to be inserted in the similarity formulas for the selection of a hydraulic impact system. For a selected system, geometry of the hammer head is calculated. The Java-based program has a graphical multi-window interface, including menu, toolbox, windows for setting parameters, and limitations, input of source data and calculated data, computation of hammer head sizes and output of plotted dynamic characteristics of limit cycles of the hydraulic system.

The review of accidents connected with explosions in gently dipping and inclined coal bed mining with mechanized equipment is presented. It is shown that the most probable cause of the explosions is inflammation of methane-and-air mixture induced by the sources of coal self-ignition in mines. The explosion wave brings burning gas in the production heading and adjacent tunnels and causes blasting of coal dust. The mechanism of coal self-ignition in edge areas in inter-panel pillars exposed to high rock pressure is described.