Purpose. Predicting the stress-strain state (SSS) of the rock mass in the zone of stope operations influence using the selfcaving mining system and the calculation of the load-bearing capacity of mine workings support at the 10th Anniversary of Kazakhstan’s Independence mine. Methods. An engineering-geological data complex of the host rocks properties has been analyzed. Numerical modelling of the rock mass stress-strain state and the calculation of the load-bearing capacity of the support types used at the mine have been performed with the help of the RS2 software. This program, based on the Finite Element Method in a two-dimensional formulation, makes it possible to take into account a significant number of factors influencing the mass state. The Hoek- Brown model with its distinctive advantage of nonlinearity is used as a model for the mass behaviour. Findings. The values of the main stresses and load on the support have been obtained. According to the numerical analysis results of the rock mass stress-strain state at a depth of 900 m (horizon -480 m), the principal stresses are close to hydrostatic ones σ1 = σ3 = σz = 24.8 MPa. Predicting assessment of mine workings stability margin is performed before and after stope operations. Based on its results, it can be assumed that the stability margin of the mine workings driven in the stope zone is below the minimum permissible, therefore, caving and an increase in the load on the support are possible. Abutment pressure on mine workings support at a mining depth of 900 m (-480 m) has been calculated. The parameters of support in mine workings driven at the horizon -480 m have been calculated. Originality. The nature and peculiarities of patterns of the stress-strain state formation within the boundaries of various stope operations influence in blocks 20-28 at the horizon -480 m have been determined. The quantitative assessment of the values of loads on the support of haulage cross-cuts of the horizon mining is given. Practical implications. The research results can be used for creating a geomechanical model of the field and to design stable parameters of mine workings support.

Purpose. Determining the deformation properties of backfill mass used to preserve the continuity of the coal-rock stratum enclosing mine workings. Methods. To achieve the purpose set, laboratory studies have been performed on crushed rock samples with different granulometric composition, which are exposed to uniaxial compression in a steel cylinder. The experimental data are processed using the mathematical statistics methods. Findings. As a result of performed laboratory studies, it has been determined that during compression pressure of the backfill material from crushed rock, the deformation modulus is a variable value and depends on the value of the applied load, which means that it cannot be used as a physical characteristic of the backfill mass. It has been proven that the deformation modulus characterizes the backfill mass rigidity, that is, its ultimate stress state. The rigidity value under a constant external load, can be regulated using the granulometric composition of the crushed rock. It has been revealed that the maximum shrinkage of the backfill mass is achieved when repacking crushed rock fractions of different sizes under volume compression of the backfill material. In the case when the backfill material is a homogeneous fraction of crushed rock, when increasing the constrained modulus, the backfill mass rigidity increases, and shrinkage decreases. Originality. It has been proven that the values of the crushed rock compaction coefficient, which characterizes the shrinkage of the backfill mass, are correlated with a parabola and depend on the granulometric composition of the source material. With inhomogeneous granulometric composition, the compaction coefficient values are maximum, and for backfill material with the similar fraction, they decrease with a change in the bulk density of the crushed rock. Practical implications. To ensure the side rocks stability and to maintain mine workings in an operational state, it is necessary to ensure a uniform by volume granulometric composition inhomogeneity of the crushed rock. This determines the ability of the roof and bottom of the coal seam to effectively respond to the impact of external factors that are manifested in the mass of sedimentary rocks during mining operations.

Purpose. To substantiate changes in stress-strain state of rock mass in the process of long-pillar mining with the help of double-unit longwalls while evaluating stress of a mine field in terms of Lvivvuhillia SE mine. Methods. Analysis of the plans of mine workings has become a basis for the evaluation of physical and geometrical parameters of a support pressure area of the double-unit stopes depending upon mining and geological as well as engineering conditions for n7b coal seam extraction. 3D model of the rock mass has been rendered using SolidWorks 2019 software. The geomechanical model of the rock mass is based upon the specified output data concerning actual operating schedule of 1018 and 1019 double-unit longwalls (numbers of the longwalls are changed as it has been required by the authorities of Lvivvuhillia SE) in terms of n7b seam and support patterns of the development mine workings in Lvivvuhillia SE mine. Each component of the support was modeled as a separate part with the relevant geotech data. Behaviour of the expansion of the rock mass stress-strain state within the selected point has been analyzed by means of sections at the specified plane. Findings. Rendering algorithm of 3D model of rock mass in terms of long-pillar mining of a coal seam using double-unit longwalls has been developed. A geomechanical model of the rock mass has been substantiated depending upon the mining and geological mode of occurrence and engineering parameters of coal mining process. Originality. Nature of the support pressure area formation in front of a stope as well as along the extraction pillar length has been analyzed. It has been identified that if stopes are within one and the same plane, interconnection of their frontal support pressure areas as well as walls of the development workings take place. In this context, adjoining entry acts as the extra destressing technogenic cavity in addition to its proper functions. Practical implications. Output data to make recommendations concerning the efficient mining parameters and methods for rock pressure control have been identified relying upon the analysis of stress-strain state of rock mass in the process of the operation of double-unit longwalls. Visualization of the principles of formation of the stress-strain state of support pressure area and evaluation of the rock mass condition have shown that the maximum reduced stresses reach 70 MPa in terms of 18 m width of the support pressure area.

Purpose. The study of mechanisms of the overworked slightly metamorphosed massif stability around mine working using the example of laminal rocks in the Western Donbas (Ukraine). Methods. The analysis of the overworking influence when planning mining operations on the underlying horizons has been made based on the studies of the stress-strain state on the overlying horizons. Attention was paid to the conditions of a slightly metamorphosed coal-bearing rock massif, which has specific mechanical properties and structural peculiarities. A computational experiment by the finite element method has been performed. The model adequacy and the calculation accuracy of the stress-strain state have been proved. The research results have been confirmed by a mine experiment. Findings. The geomechanical model of the computational experiment has been substantiated, in which the real massif structure, factors of stratification, fracturing, and moisture saturation, which weaken the strength and deformation properties of the rocks, are reflected. The zones of uncontrolled collapse, hinged-block displacement, and smooth deflection of layers without discontinuity have been studied. Originality. The patterns of the overworking influence on the state of mine workings in the laminal massif of soft rocks have been determined. Therewith, three areas of lithotypes discontinuity throughout a height of a parting have been identified and the stresses components parameters, as well as their compliance with real mining and geological conditions have been analysed. Practical implications. It has been proved the absence of the overworking influence on the underlying mine workings state in a slightly metamorphosed massif. A comparative analysis with the mine experiment results has been made. The possibility of mining the protecting pillar reserves is shown, which will allow to extract additional coal without attracting significant material resources.

Purpose is to determine factors of effect of mechanical parameters and geometry of packs, constructed using the undercut rocks in the process of selective coal mining, on the state of geomechanical system within a mine working-stope junction during a computational experiment. Methods. The computational experiments involved finite-element method to simulate three-dimensional analytical area of the geomechanical system. Rock mass was represented by twelve rock layers and a coal seam. In the process of the computations, neighboring rock layers displace freely relative to each other. Stresses and deformations have been calculated within a full-size 300×160×50 m block involving undisturbed rock mass, a stope and two development workings. Mechanical characteristics of packs were simulated using additional analytical calculations. Findings. The calculations of a geomechanical system of a mine working-stope junction have helped determine typical areas of the disturbed rock mass identifying a propagation mechanism of the stope roof fall taking into consideration the effect of backfilling parameters. Analysis of stress-strain state (SSS) of the geomechanical system within the stope roof, using the selected cross-sections, made it possible to define conditions of interaction of the rock layers resulting in the roof lowering on the packs. Originality. The identified regularities of interaction between a stope roof and backfilling components determine optimum conditions to control a stope roof during selective coal mining. It has been substantiated scientifically that consideration of longitudinal horizontal stresses to identify optimum backfilling parameters makes it possible to define unambiguously both a type, and geometry of protection schemes for the mined-out area of a stope in terms of different strength parameters and geometrical parameters of the disturbed rock mass. Practical implications. The results have helped determine a mechanism of a stope advance velocity as well as a type and geometry of the packs being constructed. The abovementioned makes it possible to minimize expenditures for internal logistics; to cheapen prime cost of mining; and to improve safety of stope miners.

Purpose. Determining the conditions and parameters for ensuring the stability of the coal seam roof with a yielding support in the area adjacent to face and behind it under the influence of dynamic loads based on the analytical and laboratory studies. Methods. To achieve the purpose set, analytical studies have been carried out using the basic principles of the theory of elasticity and vibrations, the hypothesis of girders and the hinged-block displacement of the stratified rock stratum. Also, the laboratory studies of models from equivalent materials have been performed, in which the coal seam roof is presented in the form of a girder having a yielding support with variable rigidity from the filling material under dynamic load. Findings. As a result of performed studies, the phenomenon has been determined that the condition for the stability of the coal seam roof is a geometric parameter that reflects moving of the girder with a yielding support, under the force impact of a falling load with a known mass and the physical-geometrical characteristics of the deformable system. It has been determined that as a result of a change in the spans length, a change in the flexural rigidity of the girder occurs, which means that the yield influence of the same supports on the stability of the coal seam roof is different. The values have been set and the relationship has been studied of the physical-mechanical characteristics of the filling mass as a yielding support. Originality. It has been proven scientifically that the stress-strain state (SSS) of a system in which the coal seam roof is studied as a girder depends on the physical-geometrical characteristics of the system, as well as the type and place of applying the external load, in case when the law of the girder movement in time is determined. Practical implications. The effective supporting of the undermined rock stratum in the working part of the longwall face and behind the face is achieved by placing the yielding supports in the mined-out space or by using the backfill in the mined-out space while conducting the stope operations, thus, increasing the efficiency of measures to protect the labour of miners in coal mines.

Purpose. The substantiation of accounting the deformation-strength characteristics of the collapsed rocks and the rocks consolidating near the reusable preparatory mine working of the mined-out space to optimize the loading parameters of its fastening and security systems. Improving the research adequacy and recommendations reliability. Methods. By means of computational experiments based on the finite-element method, the influence has been studied of rigidity of the collapsed rocks and consolidating rocks in the mined-out space on the level of intensity of the load-bearing elements of the fastening and security systems of mine working. The analysis has been performed of the stress-strain state of the geomechanical system load-bearing elements, as well as comparative mine research. Findings. The research results and analysis are represented of the stress-strain state of the fastening and security systems elements in the preparatory mine workings with different degree of rigidity of the collapsed and consolidated rocks of the mined-out space. The patterns of the rigidity influence of the collapsed roof rocks on the stable state of preparatory mine workings have been assessed. Originality. A different-valued relation has been established between the deformation-strength characteristics of the collapsed rocks in the mined-out space and the elements of fastening and security systems of mine working, which should be considered when optimizing the modes of their operation. It has been revealed that the increased loading on the combined roof-bolting system elements protects the frame support from the increased rock pressure, which contributes to reducing the section losses of mine working. Practical implications. The research performed is the basis for the parameters optimization when maintaining the preparatory mine workings for their repeated use and also for the rational parameters search of the combined roof-bolting system in order to develop a method for choosing its parameters depending on mining and geological conditions.

Purpose. To create a model allowing integration of the diverse features identified for the rock massif behavior by differentiation of various theories and real phenomena into a single information-analytical flow. Methods. System analysis of computational experiments’ results was based on the use of recursive calculation methodology for assessing accuracy of the obtained results with different methods of geometric and physical description applied to individual elements of simulation in the computational domain. Findings. Sample tables were obtained containing the acceptable values of weight characteristics for the various simulated elements in the generalized computational domain. A recursive algorithm for the analysis of the studied objects description’ efficiency in the solution of geomechanics problems by grid numerical methods was formulated and implemented as a computational module. The authors created a system for the assessment of the results obtained via computational experiment at the time of full-scale investigation, which provides a comprehensive analysis of changes in the rock massif state during the operation of the selected support system. The conditions of combining the design characteristics of the simulated support elements functioning in a single load-carrying system under dynamic redistribution of forces were obtained. Originality. The resulting generalized model of mine working and elements affecting its condition allows to determine most accurately the nature of changes in the stress-strain state of geotechnological system regardless of the originally a priori specified limitations. Practical implications. The unified approach can be used in the search for the optimal parameters of implementing combined working supports in the area of mining operations and beyond.

Purpose. To determine the effect of rock overworking and underworking on massif stress-strain state while extracting the series of flat coal seams. Methods. Mining, geological and technical conditions; current approaches to solution of the related problems were theoretically analysed on the basis of the developed calculation algorithm with the help of the boundary element method. We calculated maximum coefficients of stress concentration in the roof and floor of the working seam in the zones affected by pillars and contiguous seams. Findings. Boundaries for areas of increased rock pressure in the roof and floor of the extracted seam at mining enterprise “Lvivvuhillia” were determined. Values of maximum coefficients of stress concentration were derived. The load acting on the section of powered support was calculated considering the weight of rocks located in the area of boundary stress state in the roof above the longwall face. It was stated that during stope workings in areas affected by contiguous seams’ selvage, the period of longwall face exposure from under the selvage of the low seam is the most hazardous in terms of rock pressure manifestation. Originality. Analysis of stress-strain state of stratified heterogeneous massif around the stope was conducted considering overworking and underworking. Actual values of the force and geometrical parameters of the powered support were derived; rational velocity of stope advance in the given mining and geological conditions was determined. Practical implications. The results of the study allowed to obtain the data necessary to choose the type of standing support and estimate rational force parameters for the powered support during its operation in the areas of high and low rock pressure as well as to determine the velocity of longwall face advance and permissible distance between stopes of contiguous seams for the mines of Lviv-Volyn basin.

Purpose. To estimate the probability of interstratal rocks stability loss during simultaneous mining of two seams in series in the descending order. Methods. Methods of a computing experiment and mine observations were used for conducting the research. Findings. Recommendations for the improvement of 914 bolting system parameters of complex roadway for possibility of its reusing are developed. Originality. Regularity of stress-strain state change of parting during simultaneous mining of coal seams with the purpose to reveal the constituent of rock pressure manifestations during the top seam mining is studied. Practical implications. The received results can be generalized for the purpose of providing recommendations concerning bolting and supporting of mine workings during simultaneous mining of seams in series.