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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.

Transition from the specific energy analysis to optimizing process variables in drilling and blasting is discussed as a case-study of the Koktasjal copper-porphyry deposit. The proposed rock hardness determination procedure, as compared with the same-purpose laboratory testing, provides preventive information on rock mass, in real time and without significant expenditures, which is beneficial for practical problem solving, in particular, drilling and blasting optimization and control. Adjustment of a mass blast project in block no. 18-19 at Terekty Mining and Processing Plant is carried out. The powder factor was calculated per each blasthole using the conventional approach and the proposed procedure with regard to the specific energy of drilling. The experimental research with the determination of the drilling specific energy as an optimization criterion of drilling and blasting yielded a positive result and a substantial economic effect. The saving totaled more than 10% of the overall explosive amount put in the mass blast project. The quality of rock fragmentation by blasting was improved as well, which was favorable for the performance of the crushing and sizing facilities.

The authors substantiate the use of the cushion blasting method and decoupled explosive charges to soften large-block (pebbly alluvium) permafrost rock mass at open pit coal mines in the cryolithic zone of Russia’ Far East. The key feature of the method is the decoupling of a borehole charge with separate initiation of the top and bottom portions at a delay not less than one day. This allows an artificial quasi-greenhouse effect owing to blocking of detonation products of the bottom charge. The introduction of the method at the Bureya Open Pit Mine in the Khabarovsk Krai ensured reduction of the powder factor more than by 1.5 times, increased underdrilling of up to 2 m to the design bench toe and enhanced level of safety due to a larger volume of mass blasts over 2 times.

The process of rock arching in top coal caving with powered roof support systems is investigated. A direct proportional dependence between top coal flow duration and probability of static arching of rocks above an outlet hole, which prevents caving, is revealed. The new-developed method allows more accurate determination of the conditions and zones of rock arching in a model with one unit of powered roof support. When a number of powered roof support units operate in simultaneous top coal caving, the probability of arching may reduce greatly owing to the creation of a common zone of top coal flow.