Home – Home – Jornals – Fundamental and applied issues of mining 2021 number 1

The set of complicating natural and technogenic factors affecting the formation of geomechanical processes and sustainability of mine workings during intensive mining of coal deposits by an underground method was classified. An assessment of their influence was carried out on the basis of a probabilistic-statistical method using total probability formula of Bayesian hypotheses.

A scientific approach to determining the width of stable coal pillars during the preparation and mining of extraction panels with a load of more than 15 thou t/day has been substantiated. The proposed procedure differs from the traditional one by taking into account the advance rate of stoping and development faces, the time of maintaining the development workings, the effect of dynamic support pressure during the hanging and caving of undermined roof rocks of neighboring extraction panels.

The technology of laying rubble concrete filling masses is considered. The properties of artificial pillars have been determined depending on the enclosing rocks extracted during the excavation of mine workings at the Veduginskoye and Perevalnoye deposits. Based on the results of numerical modeling of stress-strain state of the rock mass during the development of chamber mining system with ore breaking from sublevel workings and formation of rubble concrete pillars, main design features of the technology of ore deposit extraction are determined. Safe parameters of the mining system with a combined backfill for the development of the Veduginskoye field are recommended, taking into account the depth of stoping.

Two-component compositions based on polymersilicates and polyurethanes, developed to strengthen destroyed rocks and create impermeable inclusions in the rock mass, were studied in laboratory conditions. The rheological properties of liquid components of polymer compositions for the temperature conditions of underground mining of solid minerals, physical and mechanical characteristics of hardened polyurethane and organomineral compositions have been determined.

This paper presents the results of testing prismatic samples made of mudstone with a hole in the center under uniaxial compression before destruction using the test-measurement complex designed for synchronous recording of stresses, strains, temperature field and microseismic emission parameters. The changes in these physical parameters have been analyzed at different stages of sample deformation. Evolution of the deformation process - the appearance of micro-damages, their localization in the area of future destruction and the appearance of a main crack - leads to a significant change in the spectral composition of microseismic emission signals, micro-deformation field and the temperature field. A temperature increase in the region of the future main discontinuity and generation of powerful low-frequency harmonics under loads approaching the peak can be a forerunner of discontinuity on the surface and, as a consequence, of geomaterial destruction.

A technique for studying the movement of the body of a percussion device under the action of a shock load is presented, during which its displacement was recorded simultaneously with an accelerometer and a displacement sensor. The results of double integration of acceleration and their comparison with the displacement recorded by the displacement sensor are presented. The incorrectness of the acceleration graphs of the body displacements in amplitude and direction obtained with double integration of oscillograms is noted. When displacing along the ordinate axis of the first half-wave of the acceleration oscillogram recorded upon impact, it is possible to significantly improve the integration result. The value of displacement is selected in such a way that displacement of the body after the end of striker impact remains unchanged.

The paper presents main features of a laboratory setup for modeling hydraulic fracturing in large-sized cubic samples with independent triaxial loading and prototypes of downhole tools for its implementation. The test cell of the setup is demountable, which allows for easy access to the sample after the end of the experiment. The design of a fracturing tool with compression packers and adjustable interpacker interval for creating longitudinal and transverse cracks has been developed. Three variants of non-removable fracturing tools installed in a sandcrete block during its pouring have been tested.

The possibility of using pneumatic percussion machines for the implementation of adaptive technological processes and operation as part of robotic systems is considered. Taking into account the analysis of existing pneumatic percussion machines, a design diagram of pneumatic impact device with an elastic valve and a movable branch pipe is developed. A simulation model of the new pneumatic impact system is constructed and the operating cycle is investigated.

The dependence of the simulation pulse removal from the primary transducer with respect to the values of amplitude and duration parameters has been determined. This dependence can be used to calculate the energy component of an acoustic emission event and to develop an additional criterion for a more reliable assessment of rockburst hazard level in local sections of the rock mass using a local control device Prognoz- L.

The relevance of using pneumatic hammers in the construction of underground structures is justified. The dependence of the energy value of a single blow of a pneumatic hammer on the diameter of a pipe to be driven is proposed. The resistance forces from the side that occur during hammering the steel pipe are determined. As the main technical parameter of a pneumatic hammer, the weight of its striking part is proposed. The features of the device and technical characteristics of pneumatic hammers with a variable power structure are given. The practical experience of vertical pipe driving in the construction of piled foundations is described. Technological operations for the construction of retaining walls in the ground based on the use of steel sheet piles, pipes, channels, I-beams, etc. are considered. Methods of placement and arrangement of technological equipment for fixing a pneumatic hammer on a steel pipe driven into the ground are given.