Purpose. Determination of the rock stability along the strike of the mass, where the drift mining of the horizon -480 m is conducted, considering the possibility of using the improved types of supports in the conditions of the 10th Anniversary of Kazakhstan’s Independence mine at the Khromtau field with the substantiation of using the effective type of fastening that increases technical and technological, operational and economic indicators of the mine. Methods. Numerical modelling of the stress-strain state of the rock mass applied at the mine have been performed using the RS2 software in a two-dimensional formulation. The rock mass state, as well as the physical-mechanical properties of mine rocks are determined according to building codes and regulations (SNiP II-94-80), depending on the category of the rock stability. Findings. It has been revealed that the combined supports from rock bolts and shotcrete are the most rational type of fastening in the studied mine. The efficiency and prospects of using the combined supports have been determined, which ensure a decrease in their material consumption and cost while increasing the reliability of mine workings and the labor productivity of miners. The use of combined support allows to increase the economy of materials for support by 1.7 times, as well as to increase the drifting rate by 1.6 times in comparison with the metal support. Originality. The paper proposes a new approach to substantiation of an effective fastening method by comparing the costs when driving horizontal underground mine workings in the mining-and-geological conditions of the 10th Anniversary of Kazakhstan’s Independence mine. Practical implications. The research results can be used when planning mining operations, in particular, stable fastening methods at the 10th Anniversary of Kazakhstan’s Independence mine of the Khromtay deposit, as well as other mining enterprises with similar mining-and-geological conditions.

Purpose is to improve a methodology for considering the influence of scale effect by transferring to the evaluation of rock strength immediately within the rock mass. Methods. The research involves methods of critical analysis, theoretical and experimental research methods in the laboratory and full-scale conditions. In particular, there are statements of probabilistic and statistic theory, standard strength tests of rock specimens, laboratory studies of coal cutting resistance, and evaluation of rock strength by impact pulsing within the rock mass. Findings. It has been determined that rock strength depends considerably on the sizes of specimens being tested. That is stipulated by high porosity and fissility of the material. Measurement error decreases along with the increasing specimen size. There is the ultimate size, beginning from which its following increase does not results in considerable changes in the strength indices. For instance, in terms of Western Donbas coals, such an ultimate size is represented by a cube with the faces of not less than 100 mm. It has been shown that despite its high density, considerable scale effect is observed in hard rock as well; the effect is stipulated by the available zones with anomalously high porosity and coarse grains. It has been specified that minimum sizes of specimen faces for hard rock should be not less than 150-200 mm. Tests of such specimens are rather labour-intensive; they are often beyond the capacities of standard equipment. It has been concluded that structural anomalies of rocks require application of the methods which help evaluate their strength immediately within the rock mass; impact pulsing is one of those methods. Originality. Minimum sizes of hard rock specimens and rock formations, making it possible to exclude the influence of scale effect of strength, have been identified. Correlation dependences, connecting the informative parameter of the impact pulse method with the strength of different rock lithotypes, have been obtained. Practical implications. Methodologies for both considering scale effect of strength during laboratory studies and evaluating rock strength within the rock mass have been improved.

Purpose is to develop mathematical model of nonisothermal inflow and lifting of the recovered gaseous mixture (i.e. geothermal fluid) of a well taking into consideration dynamic coefficient of heat transfer and thermal diffusion coefficient; fluid expansion coefficient in terms of nonadiabatic process; effect of average integral environmental temperature on the heat transfer coefficient; changes in molar mass of the fluid during the well operation; and a process of the productive seam cooling during initial development stages (i.e. months-years). Methods of material and energy balance of fluid-heat flows within a productive formation and within a well as well as forecasting of geothermal fluid production; numerical methods of fluid thermal gas dynamics; Runge-Kutta 4th order method; and Quazi-Newton method to solve nonlinear equations have been applied. Findings. It has been demonstrated that thermal gradient of rocks and thermal carrier-rock heat exchange vary depending upon operation modes of the formation and the well in terms of temperature effect, temperature difference in humidity, viscosity, compressibility, and other rock characteristics determining efficiency of thermal diffusion as well as coefficient of heat exchange between the fluid and rocks. Originality. The specified equations of thermal energy balance in terms of radial filtration and well product lifting have been developed. The equations are more preferable to compare with the current calculation technique, where a coefficient of fluid is expanded in a seam in the context of nonadiabatic process, and consideration of effect of average integral environment temperature of the heat transfer strength (the known methods takes into account geometric mean of the formation temperature). Actual changes in molar mass of the produced geothermal fluid during the whole period of the well operation (i.e. up to 50 years) are involved. Thermal gas dynamic model well inflow-lifting has been improved owing to the consideration of a transient process of the productive formation cooling during the initial stage of the geothermal fluid production (i.e. months-years). Practical implications. The developed mathematical model helps specify calculation of a well yield by 10-15%. To compare with the standard methods, the model makes it possible to perform 20-30% specification of heat output by a gas condensate well in terms of thermobaric intensification of the fluid production as well as in terms of binary techniques of fluid-geoheat generation.

Purpose is to substantiate intensification of dozer dump reclamation in the process of open pit-mining. Methods. Analysis of methods intended to intensify reclamation activities in the context of open-pit mineral extraction under different mining and geological conditions has been applied. Innovative operation schedule of dump reclamation has been developed on the basis of critical analysis and proper analytical research. Findings. Operation schedule to form a dozer dump has been substantiated taking into consideration rock suitability for reclamation making it possible to mitigate impact of mining on the environment. Algorithm to calculate dozer dump parameters has been developed as well as a digital topographic model of selective dump formation. Originality. The developed operation schedule for selective formation of the external dump differs from the available one in the simultaneous layer dumping to intensify surface of its dumped share in the process of open-pit mining. Practical implications. Use of the method of selective surface formation in terms of a dozer dump, taking into consideration overburden suitability for reclamation, helps intensify reclamation of the soils disturbed during field development.

Purpose. Consider possible series methods of Mohr-Coulomb nonlinear criterion that takes into account stresses in the plane of fracture. Investigate the influence of the average principal stress on rocks destruction when cylinder modeling under axial and side load conditions. Determine the weakening effect on the internal friction angle in the rocks under study using the examples of sample testing simulation. Methods. To study the processes in rock samples, we used a finite-element method DESTROCK-FE for modeling the deformation of rocks decomposes. The parameters of the deformation and fracture model are determined by comparing the deformation curves obtained by the modeling and experimental approaches. Findings. Modeling of rocks deformation under various loading conditions with a nonlinear criterion of fracture variants, in which destructive stresses can grow limited or unlimited or even decrease with increasing pressure, is performed. The design charts of axial and side deformations of the samples with a good approximation coincide with the experimental ones. The model parameters, including those for triaxial load conditions, are determined with a mathematic method using simulation laboratory tests under axial compression. Modeling with an upgrade fracture criterion showed that the load-bearing strength of salt rock samples under side load is greater than with axial pressure. Internal friction angle reduction with loss of strength reaches 15%. Originality. The Mohr-Coulomb series criterion is proposed, which makes it possible to set the nonlinearity in accordance with experimental data. Mechanical model parameters of rocks can be determined according to the results of single sample testing using the finite-element method DESTROCK-FE of decomposed rocks. The simulation was performed taking into account microdeformation, the influence of which is described by equations for a nonlinear-elastic condition. Practical implications. Cylinder modeling showed that the load-bearing strength of samples under side load is 10% for sylvinite and 20% more for rock salt than at axial loading. The obtained results indicate the ability of the finite-element method DESTROCK-FE of rocks destruction modeling while geomechanics survey conducting. Using this method, based on single sample simulation results, tested at simple compression, the parameters of elasticity, plasticity, viscosity, crisping can be obtained, suitable for deformation and fracture processes studies under various loading conditions.

Purpose of the paper is to develop mathematical model describing nature of argillous and salt samples under compression and to make available microdefects using finite-element method. Methods. To simulate behaviour of cylindrical rock samples under axial strain, finite-element model of rocks, being broken, is applied. In terms of the assumed model, components of medium with the disturbed continuity are calculated as those being continuous with anisotropic deformational and strength properties. Failure is considered as strength loss in terms of displacement and tensile on the anisotropy planes of the element. Within each point of the medium (if finite-element method is applied, then each element is meant) the limited number of planes of possible failure with 45° pitch is considered; they are used within each stage to evaluate potential failure resulting from displacement stresses or tensile ones. Coulomb-Mohr criteria as well as tensile strength are applied to determine potential failure on sites. Findings. It has been determined that mathematical modeling enables observing the process of disturbances within the sample. Stress-deformation diagrams, being a result of the modeling, demonstrate features of the sample behavior during different loading stages (i.e. nonlinear nature up to the peak load; decrease while breaking; residual strength; and hysteresis loops in terms of cyclic loading). It has been proved that if the model parameters are selected adequately, acceptable coincidence of both calculated and laboratory curves describing connections of axial strains and side strains with pressure on the samples of clay, sylvinite, and rock salt can be achieved. Originality. Finite-element has been developed. The model makes it possible to describe processes of strain and failure of rock samples in the context of laboratory tests; moreover, the model differs in the fact that it is added by the description of deformation processes taking place in microfissures and pores. Practical implications. Modeling with the use of finite-element method for rocks under breaking helps reach sufficient coincidence of the calculated diagrams of sample tests with graphs of stresses-deformations connection resulting from the laboratory studies. The obtained positive results confirm applicability of finite-element model of rock deformation and failure in terms of rock pressure problems.

Purpose. To define peculiarities related to the formation of the dynamic and stationary half-troughs under the influence of anthracite seam extraction by adjacent faces. Methods. To establish the parameters of the surface displacement during the consecutive extraction of adjacent faces. Analysis of experimental data. Findings. The effect of rocks displacement activation on the formation of the dynamic half-trough on the surface is established. Originality. It is established that the length of the stationary half-troughs is almost functionally related to the total width of the goaf. The correlations between the stationary half-trough parameters and the degree of stoping development are determined. Practical implications. The obtained results contribute to the improvement of measures for the rational protection of objects on the surface.

Purpose. To develop the technology for explosive destruction of solid inclusions in the mass of rocks with different hardness on the basis of established correlations between changes in the radius of hard streaks fragmenting, fracturing density and relative distance to the free surface during various initiating techniques in rocks of different hardness. Methods. Theoretical and experimental research into the development of scientific and technical fundamentals of explosive destruction of the mass of rocks with different hardness, which allows to determine the zone of hardening soft rocks located between solid inclusions. Findings. The developed technology for explosive destruction of mass of rocks with different hardness was implemented in the Tashkura quarry of Dzheroj-Sardara phosphate deposit of Navoiy MMC resulting in the economic effect of UZS 581.7 mln per 10.5 mln m3 of the extracted rock, while the economic effect in the free industrial and economic zone “Navoiy” was more than UZS 12 mln per 17000 m3 of the extracted rock. Originality. The conducted complex research resulted in the new technology for explosive destruction of the mass of rocks with different hardness, including hole boring, determination of the number and capacity of hard streaks in the process of boring, placing of the explosive charge in the hole, stemming. and blasting. Practical implications. Implementing the research results in the open quarry of Navoiy MMC allowed to make a significant contribution to the solution of the topical scientific and practical problem: efficient blast energy utilization during industrial explosions on hard streaks.

Purpose. The need for new technologies and techniques for the efficient development of thin coal seams. Methods. Mathematical and experimental modeling of the contact interaction of multipoint cutter with the rock. Findings. A mathematical model describing contact interaction of multipoint cutter with the rock and the kinetics of its cutting elements wear has been developed. Departing from the results of the performed analysis and experimental research, we created a number of innovative designs of a drilling tool, taking into account peculiarities of the load distribution on its cutting elements in the process of work, which allowed to develop new tool designs, including those for auger machines. Originality. A mathematical model of contact interaction of multipoint cutter with the rock and the kinetics of its cutting elements wear has been developed. Practical implications. For auger machines “BSHK-2DM” produced by “Buran” plant, we have developed innovative effectors of 650 mm and 750 mm which reduce energy consumption of the drilling process, lessen the load on the main drive, increase the speed of drilling, and also improve the grade of coal mined.