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A boundary value problem is formulated for the stress-strain modeling of rock mass with regard to nonlinear deformation of rocks in the influence zones of mine roadways. Different variants of boring patterns for the directional hydrofracturing of hard roof, such that reduce the risk of geodynamic events in longwall mining of flat coal seams, are discussed. Numerical modeling shows that the most effective variant is arrangement of an initiator-notch in the seam roof in parallel to natural bedding in coal-rock mass. It is found that initiators-notches ensure a substantial decrease in roof rock displacements above production faces because of stress relaxation in rocks between induced fractures and coal seam. This effect grows when the length of an initiator-notch is increased to 10-20 m.

The article describes numerical investigation of usability of fracture propagation pressure in stress assessment of rock masses. Development and testing of the proposed approach involved 3D numerical experimental modeling of hydraulic fracturing nearby a cylindrical cavity. The main equations in the model were solved using the extended finite element method. The patterns of variation in the fracture propagation pressure nearby the cylindrical cavity are obtained. The relations are presented to find stresses in uniform compression and in a nonuniform field when the minimal stress acts in perpendicular to the axis of the cavity. It is studied how the error of the method changes depending on the ratios of the model parameters. It is shown that in some cases, it is possible to assess direction of the minimal stress by the hydraulic fracture trajectory, its exposure and propagation pressure.

Using the discrete element method, the scalar and vector properties of a granular medium subjected to loading along two-link broken trajectories are analyzed numerically. The calculations of loading samples of a granular medium by cyclic alternating shear and broken trajectory shear are performed. The issue of the value of Ilyushin’s delay trace is discussed. Based on the dilatancy analysis, the trace of delay in the scalar properties of a medium is estimated. The delay in the vector properties is assessed by comparing the stress and strain tensor components during loading. It is found that the trace of delay in the scalar and vector properties in granular media is higher than in metals by one-two orders of magnitude.

Rockburst hazard of mining operations under an open pit bottom at Sayak-1 deposit is assessed. Mining practices use the room-and-pillar system down to a depth of 295 m below the pit bottom. At the present time, pit bottom rock mass of the Central Sayak deposit holds reserves mostly in ore pillars. Single events of dynamic behavior due to the action of rock pressure were recorded in the course of mining. The strength and deformation characteristics of rocks are determined in a laboratory environment. It is found that core samples are prone to rockburst hazard. The natural stresses at the deposit are measured using the hydraulic fracturing method. RQD index of rock mass is determined. The rock mass is of fair and good quality. The average uniaxial compression strength of rocks is 95.85 MPa. By Kaiser’s criterion, rockburst hazard is absent at the deposit and dynamic failure events are unlikely as a consequence. For all rockburst-hazardous types of rocks at the deposit to the depth of 295 m, the coefficient K characterizing rockburst hazard is lower than the critical value. The level of the maximal stresses induced by mining operations is insufficient to provoke dynamic events in rock mass.

The article describes the research findings on slope stability in open pits and quarries Transbaikalia, at the stages of exploration, mine planning, design and redesign. The feature of the test surface mines is tectonic disturbance of rock masses, including zones of faulting, crushing and compression. Earlier, such geomechanical assessment was carried out using traditional approaches, and the conclusions lacked estimates of probability of slope failure in open pits. Modern regulations on pitwall stability recommend quantitative estimation of slope failure probability using the probabilistic analysis and statistical testing, for example, the Monte-Carlo method. Owing to the statistical testing and its results, it is possible to quantitatively assess probable risks of slope failures in open pits and, also, to offer better defined requirements on the input data accuracy.

The authors used numerical modeling and physical simulation techniques to study influence exerted by the discontinuity zone width in rock mass and by the size of a crushed rock fraction on the parameters of ground penetrating radar signals. The discontinuity zone represented a layer with rough boundaries. The correlation is found between the measurement error of such layer width and the size of the crushed rock fraction.

In order to study the formation mechanism of the high-cold and high-altitude mountain collapse disaster caused by underlying complex goaf group, the lithology, occurrence of structural planes in rock mass and hydrological conditions of overburden in goaf were obtained through field investigation. Combined with the field investigation results, the landslide disaster mechanism was comprehensively analyzed. The stability of the mountain slope in the underlying goaf and the potential slip arc surface of the collapse body are analyzed by the two-dimensional finite element analysis method. The main causes of surface collapse of mountain slope are: the steep structural plane of rock mass, rainfall and fissure water erosion, freeze-thaw cycle, underground ore body mining disturbance, etc. Geological conditions are the internal cause, while underground mining is the inducement. The combined action of the internal and external causes leads to the special formation mechanism of collapse.

Electric disintegration of spodumene pegmatites is investigated. It is found that treatment with electric pulses ensures partial dissociation of monomineral spodumene, and the best extraction of spodumene crystals, either with or without concretions, takes place when initial rock is ground to a size of 1 to 4 mm. The crystals of spodumene remain unbroken, as in mechanical treatment, and represent whole pieces. The gravity separation later on allows production of spodumene concentrate for the subsequent lithium extraction.

The article presents the method of location of heavily fractured zones in rock mass. The method uses a geophysical model of electromagnetic radiation which accompanies discontinuity of rock mass. It is shown that for the location of a rock mass area with the change in the stress-strain behavior in the neighborhood of mine openings using the electromagnetic radiation method, it is required to assess the power of a source of rock failure by means of recording signals from sensors of electromagnetic radiation. An approach to building a software architecture to predict dynamic events induced by rock pressure is proposed.

The article discusses in-situ seismic tests carried out during operation in the mines Kazakhstan, Abay and Kuzembaev in the Karaganda Coal Basin for studying and predicting geological faults in coal seams. Seismic testing used the methods of reflection survey, transmitted waves, seismic location, as well as their combinations. The practical results of the in-situ seismic testing in complex geological conditions proved the efficiency of the listed methods, and enabled adjustment of the presence, position and stretch of expectable faults, revealed the absence of unpredictable faults, and detected the zones of change in hypsometry of coal seams, as well as other anomalies.