Stress-strain State Of Rock Mass Research Articles

Investigation of the rock mass state in the near-wall part of the quarry and its stability management

Introduction: The research is aimed to identify the vulnerable areas of quarry slopes through the creation of a stress-strain state model for the rock mass at the Vostochny quarry, East Saryoba field of the Zhi-landy Group of cupriferous sandstones, as well as their subsequent strengthening.Methods: The research is based on the development of a database containing information on mining-geological, geophysical, geodetic and aerospace surveys. The authors of the research use modern geodetic, aerospace and geophysical technologies for scientifically based predicting of technogenic disasters and the rock mass stress-strain state modeling to ensure safe and optimal mining of fields in difficult mining-geological conditions.Results: The results obtained show that the strengthening of weakened quarry slopes based on the rock mass stress-strain state modeling contributes to the scientific-practical profitability of field mining and provides safe mining in difficult mining-geological conditions.Discussion: Novelty is in the scientific substantiation of the method for strengthening quarry slopes, which is based on the rock mass stress-strain state modeling. The research is of great practical importance, as the rock mass stress-strain state modeling increases the reliability of predicting the rock mass state during its mining. Strengthening of quarry slopes using the proposed method reduces risks and increases safety and economic efficiency of mining the solid mineral deposits in difficult mining-geological conditions.

Assessing stability of mine workings driven in stratified rock mass

Purpose.The research purpose is to assess the stability of mine workings driven in a stratified rock mass by studying the influence of the stratified rock bedding angle on the rock mass stress-strain state (SSS). Methods. The research uses both experimental and numerical methods. Experimental studies are carried out using rock samples with different angles of rock layer occurrence, while numerical modeling is performed using the RS2 (Geotechnical Finite Element Analysis) software based on the generalized Hoek-Brown failure criterion. The studies are carried out on models covering the border area of the mine workings driven in the mass with the angles of rock occurrence from 0 to 75°. Findings. Experimental and numerical studies have shown that when the rock layer inclination angle changes, significant changes occur in the stress concentration zones around the mine workings. An increased rock layer inclination angle is accompanied by a change in stress distribution, which is important for assessing the stability of mine workings. A particularly strong influence is observed at the angles of rock occurrence 30° and above. Originality. The research novelty is in revealing the patterns in the stress distribution in the stratified rock masses depen-ding on the rock layer inclination angle. Research results provide new data on the rock interaction mechanisms in difficult geological conditions. Practical implications. The results obtained can be used in the planning and operation of mine workings in difficult geological conditions. By taking into account the changes in stress zones caused by the rock layer inclination angle, it is possible to improve the safety and efficiency of mining operations.

Management of the longwall face advance on the stress-strain state of rock mass

Purpose is to study influence of a longwall face advance on the geomechanical situation in the neighbourhood of a mining site based upon determination of changes in standard and critical subsidence of the immediate roof rocks. Methods. To study a geomechanical situation in the neighbourhood of a mining site the authors have applied software product GeoDenamics Lite developed at Dnipro University of Technology. The software product relies upon a calculation procedure of stress-strain state of rocks by Professor O.V. Savostianov. Expediency of the software selection is based upon the supported control and adaptation of a coal mining technique to changes in geodynamic stress fields in the anisotropic rock-coal medium impacting temporal and spatial changes in the technological parameters. Findings. The basic problems have been singled out connected with certain changes in a longwall face advance. For the first time, an analytical scheme of tangential stresses within the immediate roof rocks has been developed for Lisova mine of SE Lvivvuhillia under the conditions of coal seam mining by means of the paired longwalls which makes it possible to determine both physical and geometrical parameters of standard loads within the formation. Originality. Dependencies of temporal and spatial changes in subsidences and horizontal displacements of rock layers of the immediate roof have been defined being 5.2 m for the upper rock pack and 3.9 m for the lower pack if the longwall longwall face advance is 1.9 up to 4.8 m/day. Both physical and geometrical parameters of the reference pressure have been defined as well as the parameters of lower sandstone pack in the process of the main roof subsidence. Impact of the extra pressure forces on the immediate roof rocks has been analyzed at the moment of critical lowerings of the immediate roof rocks. In this context, standard loading from the overlying formation in addition to tangential stresses in the roof result in rock failure due to vertical cracks above a longwall face. Practical implications. The engineering methods have been developed making it possible to identify impact parameters of a longwall face advance on the geomechanical situation in the neighbourhood of a mining site. In future, it will help forecast changes in the reference pressure around a longwall face while preventing emergency settlement of the powered support.

Substantiating the rock mass control parameters based on the geomechanical model of the Severny Katpar deposit, Kazakhstan

Purpose. The research purpose is to develop a geomechanical model for ensuring the safety of mining operations by determining the optimal slope angles and probabilistic assessment of the stability of the open-pit walls. Methods. Three-dimensional geomechanical models for surface mining of deposits have been developed based on calculations of the stability factor (safety factor SF) of the open-pit walls in the Rocscience program to determine the rock mass stress-strain state at the end of mining using the finite element method. The geological wireframe model (GWM) has been built on the basis of the available geological sections, horizon plans and the results of the engineering-geological surveys using the Surpac geoinformation system. Findings. Strength reduction factor (SRF) has been determined taking into account the physical-mechanical properties of rocks that constitute the near-wall mass. An assessment of the stability of walls according to the selected geological sections is given, taking into account the projected contour of the Severny Katpar open-pit walls. The calculation of the projected contour stability of the open-pit walls by several different methods has revealed that the open-pit walls are generally stable. The open-pit parameters at the end of mining have been determined. Originality. For the first time, it has been determined that in the Southern and South-Western area of the Severny Katpar open-pit wall in the horizons +700…+400, there is a decrease in SF from 1.18 to 1.41 due to the predominant occurrence of siltstones and tectonic disturbances of the walls. Practical implications. The mathematical calculation results of the stability of the projected contour walls in the Severny Katpar open pit have been generalized. In addition, a geological and structural wire-frame model of the deposit has been developed, which makes it possible to ensure the safety of mining operations in the open pit.

Justification of the stress-strain state’s parameters of the mine workings contours depending on the influencing factors

The complication of mining and geological conditions is associated with the involvement in the development of areas and entire deposits with complex tectonics, an increase in the depth of development, the manifestation of dangerous dynamic effects of rock pressure, which necessitates the improvement of methods, systems, methods and means of supporting mine workings, as well as improving the quality of materials used for support. Mining and geological factors affecting the use of mining support include: the depth of occurrence, which determines the magnitude of the vertical and horizontal components of the rock pressure; layer thickness, developed deposit; bed angle; properties of the host rocks, structure and physical and mechanical properties of rocks and minerals. The paper presents the conduction of the analytical modelling of the rock mass stress-strain state around the active mine workings using the ANSYS software with the assessment of the influence of its cross-section shape and the angle of the coal seam fall on the value of the maximum stresses arising in the rock mass when the workings are supported with the anchoring support depending on the thickness of the easily collapsible rock layer at different lengths of anchoring.

Stress-strain state index of the Imex quarry rock mass, Bioko Island, Equatorial Guinea

Purpose. The purpose of this research is to determine the index of the rock mass stress-strain state in the Imex quarry, Bioko Island, Equatorial Guinea. Methods. To determine the number of required samples by the method of stratified random sampling, the t-Student principle is used. The physical-mechanical properties of rocks have been determined by tests and methods of saturation, pycnometry, hydrostatic weighing, axial loads and clock-type indicators. The classification of the degree of weathering has been carried out to assess its impact on the physical-mechanical properties of rocks and rock mass on the basis of direct observation in different areas of the studied rock mass. To determine the rock mass stress-strain state, the Hoek-Brown failure criterion is used, including laboratory tests to determine the models, dimensions and shapes of ruptures. Findings. Significant changes in rocks, high values of stress and weathering, which generate distributions of new forces in the rock mass and originate instability and large deformations, as well as a high porosity index, average values of compressive strength and a high value of elasticity modulus, have been revealed. Significant differences in the degree of weathering in the prevailing zones, from insignificant values of weathering in the northern areas to moderate values of weathering in the south, have been confirmed. Originality. Information is presented on the physical-mechanical properties, the degree of weathering and the stress-strain state index of the rock mass in the Imex quarry, Bioko Island, Equatorial Guinea. Practical implications. Knowledge about the rock quality, management and implementation of technological processes during operation can be used as a useful material for the construction industry.

Rock mass management to ensure safe deposit development based on comprehensive research within the framework of the geomechanical model development

Purpose. To create and study a three-dimensional geomechanical model in order to determine the parameters of the open-pit walls and benches, ensuring safe and economically feasible mining, as well as predicting unstable zones within the open pit. Methods. A comprehensive methodological approach is used, including a systematic analysis of scientific, normative and methodological literature; analyzing the results of previously performed studies on the object; engineering-geological surveys in the near-edge rock mass of the Kurzhunkul’ deposit; laboratory testing of rock strength properties; determining the rock mass rating according to the MRMR classification; kinematic analysis of bench faces; calculating the stability of the Kurzhunkul’ deposit final boundary using the limit equilibrium method; numerical modeling of the rock mass stress-strain state at the Kurzhunkul’ deposit using the finite element method. Findings. The paper represents the results of data collection and analysis for the development of a geomechanical model of an operating iron-ore open pit in the Republic of Kazakhstan. Comprehensive geomechanical studies to substantiate the optimal parameters of the Kurzhunkul’ deposit walls and benches on the limiting contour, as well as calculations to determine the degree of the open-pit walls and benches stability have been performed. Based on the results of studying the geological-structural configuration of the deposit, as well the mathematical modeling data of stability and acting stresses, subsequently entered into a unified digital database, weakened zones have been identified. Originality. For the first time, the geomechanical model has been created for the conditions of the Kurzhunkul’ deposit, which makes it possible to combine in one database all the parameters that affect the safety of mining operations. The model takes into account structural disturbances of the rock mass that have an adverse impact on stability. Practical implications. The developed model gives a visual representation of the rock mass state at various sites of the deposit, simplifies the selection of design sections for stability calculations, facilitates the choice of optimal technical solutions and analysis, especially for complex geological structures with multiple geotechnical or geological units with different texturing and inclination.

Substantiation of mining-technical and environmental safety of underground mining of complex-structure ore deposits

Purpose. Substantiation of mining-technical and environmental safety of underground mining of complex-structure ore deposits based on the study of a rock mass stress-strain state (SSS), as well as determining the safe parameters of stopes for specific mining-geological conditions and patterns of rock pressure propagation in various environments. Methods. To assess the improvement of mining-technical and environmental safety of mining operations, the research includes theoretical generalizations with the use of mathematical statistics, physical and mathematical modeling, performing calculations, as well as technical and economic feasibility, laboratory and full-scale experimental studies, industrial tests in mine conditions and on the earth's surface in the zone of blasting influence, based on the standard and new methods. Findings. A functional interrelation between the rock mass SSS value and the number of impulses (destruction sounds) per minute, characterizing its structural (а) and strength (b) properties, is proposed, which is described by a curvilinear dependence of the type y = axb and allows to quickly determine the stable parameters of stopes. Assessment and prediction are made for various forms of rock pressure manifestation, based on the stress concentration coefficient within 0.91 Kv 0.70, taking into account the conditions of the elastic behavior of rocks. The value of = 0.0002-0.0003 is taken as permissible relative deformation, which ensures both mining-technical and environmental safety, as well as the rock mass stability during repeated blasting operations. Originality. A classification of the rock mass SSS has been developed depending on the direction of the maximum stresses relative to the mine working location, the level of the rock mass stress state and the mechanism of rock pressure manifestation (η), as well as the category of rock-bump hazard. In particular, the rock mass with the values in the range oof 0.12 < η ≤0.2; 0.2 < η ≤ 0.3; 0.3 < η ≤ 0.5 and η > 0.5 are classified as non-rock-bump hazardous and belong to III, II, and I hazard categories, respectively. Practical implications. To substantiate the safe parameters of stopes based on the results of multi-year research into underground mining of complex-structure deposits, depending on the rock mass properties, a graphical-analytic method (nomographic charts and calculation formulas) is recommended. These parameters are determined for highly fractured, medium fractured and weakly fractured rock mass with its horizontal outcropping to the surface. Using this method, the Instruction on the Geomechanical Substantiation of the Safe Mining of the Reserves at the Skhidnyi Hirnycho-Zbahachuvalnyi Kombinat, DP (SE VostGOK), Ukraine, has been developed.

IDENTIFICATION OF WAVE DEFORMATION PROCESSES OF LANDSLIDES IN THE NORTHWESTERN BLACK SEA USING THE INSTRUMENTAL OBSERVATION DATA

Problem Statement and Purpose. At present, considering the conditions of slopes equilibrium, only the stresses caused by gravity, hydrodynamic and seismic effects are most often taken into account. As for tectonic stresses, their effect on landslide slopes has hardly been studied. At the same time, landslides and deformations ofslopes in a wide spatio-temporal range (with the frequency from several months to several dozens of years and the levels of massifs tectonic discreteness from first tensof meters to first kilometres) is also recorded in fact. Empirical data indicate that wave mechanism caused by rotational regime of the Earth can be one of the possible mechanisms explaining the high-frequency quasi-cyclic spatio-temporal variability of the rock mass stress-strain state. Purpose of the work has been to identify wave deformation processes in the Earth’s upper crust according to the data of instrumentalobservation of landslide slopes and relatively long line facilities deformation regime. In this work, we also intend to substantiate the thesis that wave exotectogenesis isone of the factors reducing the overall stability of landslide slopes. Data&Methods. The data of instrumental observations of structural components deformation in the underground drainage facilities of the landslide prevention works on Odesa coast that have accumulated during 50 years of operation, as well as the results of geodetic monitoring of landslide slope and the crest of plateau on the right bank of the Malyi Adzhalyk Liman within the territory of the Port Plant (ammonium plant) in 2000–2019 have been used to study the dynamics of deformation wave processes in the Earth’s upper crust. Statistical and cartographic analyses of the data sets mentioned above were carried out according to traditional methods using the Statistica, Matlab and Surfer software packages. Results. It has been found that modern dynamics of landslide slopes is significantly influenced by the periodic change of the stress-strainstate of rocks in space and time. The authors interpret the empirically revealed alternating in space zones of compression and extension, which cause the dynamics of vertical and horizontal reference benchmarks displacements in the inter-annual regime of marks displacement on the right bank of the Malyi Adzhalyk Liman and in the tunnels of Odesa coast as thereflection of wave geodynamics with periodic change of the stress-strainstate of rocks in space and time. Hierarchical layering of the tectonosphere in depth (the presence of layers with different elastic properties), tectonic discreteness and blockiness of rock massifs determine the spatial framework of the dynamically complex structure of the deformation field. Multiple cycles of compression-extensionof rocks lead to decrease in the rocks strength, accumulation of plastic deformations and activation of landslide displacements even on the coastal areas where anti-landslide measures have been implemented. To prepare design models correctly, it is important to take into account both the landslide formation mechanism and the factors that reduce the overall stability of the slope. The latter include the quasiperiodic variability of the rock mass stress-strain state controlled by rotational dynamics via wave mechanism.

Опыт применения CAE Fidesys при разработке численных геомеханических моделей Ждановского месторождения

The Zhdanovskoe copper-nickel sulfide ores deposit is located in the north-west of the Murmansk region and is a mineral raw material source for JSC «Kola MMC». The main mining method used is sublevel caving. In some areas, due to the complex shape of the ore bodies, the open stoping mining method is used which requires determining stable parameters of stopes and pillars. It is necessary to study the stress-strain state of the deposit to ensure safe mining conditions. One of the possible solutions is the modeling of the stress-strain state of rock mass using the finite element method, for example, CAE Fidesys, which is FEMbased software. The use of CAE Fidesys for solving geomechanics tasks allows creating models of individual excavation units to determine the stability of stopes and pillars, and large-scale models that include several ore bodies and areas of the host rock mass. The article considers solutions of both types of geomechanic tasks using CAE Fidesys for conditions of the Zhdanovskoe deposit.

Determination of the stress-strain state of rock mass and zone of inelastic deformation around underground mine excavation using modern methods of numerical modelling

The paper reviews methods and trends of numerical modelling of geomechanical processes around underground mine excavations. The most rational method of determining the additional stresses caused by the mine excavations is chosen. Mathematical modelling was performed for excavations of various cross sections and different strength of rocks. The dimensions of the inelastic deformation zone around the mine excavations have been identified. The area of the total fracture zone around the excavation, as well as the area of the roof fracture zone are calculated. The results of the fracture zone modelling are presented both as coordinates and in a graphical form. To simplify application of the modelling results, dependency plots of the obtained parameters were created and analytical dependencies of the fracture zone parameters were identified. The SURFER and KOMPAS software packages were used as the graphic tools to visualize the modelling results

Advancing of the geomechanical forecasting system and substantiation of mining at rockburst hazardous deposits

The paper presents the main approaches and their advancing for the systems of rock mass stress-strain state forecasting during mining of adjacent rockburst hazardous deposits. Such systems based on the original Sigma GT software are used at several Russian mining companies which develop solid rock deposits, prone to brittle fracturing and undergoing the gravitational-tectonic stress-strain state. At that, the mining-induced impact on the rock mass is accompanied by occurrence of dynamic rock pressure. The geomechanical situation forecast systems have been applied directly at mining companies for more than 10 years and have shown their high efficiency. The efficiency is associated primarily with the operative calculation of stress-strain state in case of exacerbations of the geodynamic situation and the potential consideration of various mining options in order to reduce stress concentration and give recommendations for supporting and unloading measures in mine workings. In addition, the Sigma GT software is used in annual and long-term mining planning. Initially, such systems were developed for individual rockburst hazardous mining blocks, and their efficient operation time was limited to a 3-5 year period, that is, the block mining time. Further on, taking into account the needs of companies, the systems began to include a whole deposit or even several deposits. Being applied, the system is constantly developed and advanced and adapted to specific conditions and tasks. The most actual tasks are combination of the results of stress-strain state modeling with seismic monitoring data; creation of a hierarchical system of interconnected multiscale volume models; more complete consideration of structural heterogeneities of the rock mass and development of a recommendation block for safe mining operations, taking into account the geomechanical situation forecast data. The solution of these problems is considered on the example of a section of the Khibiny apatite arc, within which underground and open mining is carried out in the zone of mutual influence.

The numerical modeling of heterogeneities by the finite element method in 3D setting

The paper proposes a variant of the algorithm for 3D numerical simulation of the rock mass stress-strain state in the vicinity of structural heterogeneities by the finite element method. Modeling of the stress-strain state is used, among other things, when analyzing the fractures in the rock mass, which can occur as a breakage or a shear along the weakening planes. The rock massif has a block structure, where the boundaries of various-scale blocks are structural disturbances of different orders. The surface planes of structural heterogeneities usually have complex geometry and spatial orientation, so the most adequate results can be obtained by 3D modeling of the disturbed rock mass. Besides, it is important to take into account the type of the stress-strain state, which can be not only gravitational, but also gravitational-tectonic, including horizontal loading of the rock mass. Accounting these features allows obtaining the most adequate geomechanical model of the studied object. For this purpose, the authors have studied and analyzed the existing approaches to modeling heterogeneities in the rock mass, including using the Goodman contact element, and developed its 3D modification. A mining engineer needs to have a handy tool that allows creating and editing a geomechanical model, taking into account mining plans and related sections. The model navigation, edition of its individual blocks to specify geology and creation of local sub-models make it necessary to use structured meshes of finite elements. Modification of the model with the introduction of contact elements entails the creation of an unstructured mesh, which complicates further manipulations with it. To solve this problem, a special zero element was developed, which allows saving a structured mesh format when implementing a contact element. This zero element, like the contact element, has zero thickness, and its nodes have averaged strength characteristics of adjacent blocks of the undisturbed rock mass. The result of these studies is a tool that allows creating 3D models of the rock mass stress-strain state, taking into account its structural heterogeneities and preserving the regular structure of the finite element mesh.

Stress-strain state of rock mass and lining when constructing underground turbine hall of hydropower plant

Numerical modeling was performed for stress-strain state of the rock mass and lining of underground turbine hall of Rogun hydropower plant. The hall is located in a rock mass at great depths. Numerical modeling was conducted using the method of boundary integral equations based on the model of linearly elastic quasi-isotropic medium. The character and features of forming inelastic deformation zones near the contour of turbine hall cross-section are found. The regularities of distribution of rock mass and lining stress-strain state are determined as well.

Rock pressure control methods based on detected regularities of stress formation in mining structures

Relevance. Subsurface mining at the Gaysky ore mine is intensifying because of the growing need in raw material. It leads to rapid increase in the depth of mining and to problems connected with the stability of mining system constructive elements. The effi ciency of the Gaysky deposit underground development is largely determined by mining system constructive elements stability. Ore cave-in in the chambers of the fi rst and second stages causes the growth of load in the interchamber pillars leading to their collapse, loss of boreholes and development headings. Mining productivity in the chambers of the fi rst, second, etc. stages falls, oversize yield grows, which also impairs the effectiveness of mining. Hanging wall and footwall cave-in in the deposit under consideration may be explained not only by host rock poor stability, but also by the presence of high compressive tectonic stresses, that were determined by the authors. Stress measurements in the rock mass have shown that the east-west stresses have doubled the northsouth stresses and have been 1.5 times as high as the vertical ones. The purpose of the research is to reduce stresses in stopes ore in place when excavating steeply dipping ore bodies using a sublevel stoping method with a hardening backfi ll. Research methodology includes full-scale experimental measurements of the stress state of the rock mass and ore in place at accessible depths and horizons of the deposit. A comprehensive scientifi c research method was used, including the analysis and theoretical generalization of stress distribution regularities in the arrays of the extracted chamber reserves and mathematical modeling of the behavior of the research object; theoretical results were compared with the results of instrumental observations. The analysis of the research results made it possible to establish the stress-strained state behavior in the course of mining. It was revealed that when mining a deposit using sublevel stoping, the most loaded elements are the hanging wall and footwall exposed parts, ceiling, interchamber pillars and bottom. Therefore, it is necessary to take measures to increase ore in place stability in order to guarantee the safety and effi ciency of the mineral extraction technology. Conclusions. Relieve slots method is among the most effective and frequently used active method of rock mass pressure control. The method has come into common use because it is easy to apply. Main labor inputs of a relieve slot creation are only reduced to extra drilling and blasting which do not require additional tunnel driving. The aim of the relieve slot is to create additional free surfaces for deformation, to redistribute rock mass stress-strain state, and remove stress from the protected element of the mining system.

Substantiating the optimal type of mine working fastening based on mathematical modeling of the stress condition of underground structures

Purpose. Predicting the formation of a stress-strain state (SSS) in the rock mass within the boundaries of influence of stope operations on the horizon -480 m in axes 2028 at the 10th Anniversary of Kazakhstans Independence (DNK) Mine. Methodology. An engineering-geological data on the host rocks properties are analyzed based on the international ISRM standard. Numerical modelling of the rock mass stress-strain state and the calculation of the load-bearing capacity of the compound support (roof-bolt+shotcrete+mesh) and arch support used at the mine are 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 rock mass state. Findings. The calculations performed indicate that the support resistance is incommensurably low in comparison with the values of the initial stress field components in the rock mass. In such conditions, it may be more effective to strengthen the mass in the vicinity of mine working than setting more frames or using more massive support profiles. Originality. The paper presents the results of mathematical modeling and calculation of the stress-strain state of the underground supporting aquifer rock mass structures developed for complex mining-and-geological and geomechanical conditions of driving, supporting and operating mine workings on deep horizons of the mines at Donskoy Ore Mining and Processing Plant. Based on the performed research, the preliminary (advanced) strengthening of the border rock mass in the zone of inelastic (destructive) deformations has been substantiated, as a priority method to control the stability of mine workings. Practical value. The research results can be used when creating a geomechanical model of the field and designing stable parameters of mine working support.

Research into rock mass geomechanical situation in the zone of stope operations influence at the 10th Anniversary of Kazakhstan’s Independence mine

Purpose. Predicting the stress-strain state (SSS) of the rock mass in the zone of stope operations influence using the self-caving 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 hydrosta-tic ones σ1 = σ2 = 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. Keywords: stress-strain state, principal stresses, support, mine, ore, rock mass

ADVANTAGES OF NIEMFE METHOD IN GEOLOGICAL STATE MONITORING WHEN SOLVING APPLIED ENGINEERING PROBLEMS

Problem Statement and Purpose Finding effective methods for monitoring the state of engineering structures and geological conditions in their localization is an extreme­ly urgent issue today. The method of natural impulse electromagnetic field of the Earth (NIEMFE) is widely used for the solution of applied engineering-ecological, geological, geophysical and hydrogeological problems. The purpose of this work is to study the dynamics and the geological environment forecasting in conditions of increasing man-made load and prove the effectiveness of NIEMFE method in solving problems related to the violation of the engineering facilities operating conditions.Data & Methods Data from field observations conducted by employees of the De­partment of Geotechnogenic Safety and Geoinformatics of Ivano-Frankivsk National University of Oil and Gas were used to build the initial models. In particular, measure­ments by the NIEMFE method were performed on the territory of the school in the vil­lage Yunashkiv in the Rohatyn district and on the territory of the university building.Results The efficiency of using the NIEMFE method for solving geological engineer­ing problems is confirmed by the example of two diverse objects. The observations results obtained during the rocks stress-strain state study in the Yunashkiv village school in the Rogatyn district are considered. The NIEMFE method measurements allowed us to establish the stress-strain zones of the study area, which are related to the karst processes development. The analysis of the anomalies distribution and their intensities show that the territory is not stable and one should expect further karst manifestations and earth's surface and building deformation. The monitoring obser­vation results by the NIEMFE method are presented in order to track the dynamics of the change in the the IFNTUOG building state. The reason for the building damage, namely the design on the ancient river bed site, which led to the rocks strength loss due to the suffusion processes and the decomposition of the clay rocks underlying the foundation was identified. The influence of significant rainfall on the stress-strain state change of the studied territory was confirmed. It is proved that the NIEMFE method is a promising method for studying the rock mass stress-strain state in terms of determining the engineering structures stability and providing the deformation pro­cesses forecast.

Ensuring Wall Stability in the Course of Blasting at Open Pits of Kyzyl Kum Region

Involvement of deep deposits in mining predetermined the trend of development of open pit mining towards increasing the depth of open pits. The main limitation imposed on drilling and blasting in the near-contour zone of an open pit is the need to protect the pit walls and engineering structures on the walls from seismic effects of huge blasts. As practice shows, the most effective and proven method of protecting pit walls is the use of blasting by presplitting method, creation of a shielding gap and a shielding layer of blasted rock mass, i.e. pre-splitting of the pit walls, preceding the huge blast. Therefore, the study of stress-strain state of the near-contour rock mass, determination of the parameters of blastholes for edge pre-splitting (preliminary shielding gap formation) in open pits is an urgent task. The analysis of the pit wall design and stress-strain state of rock mass at Kokpatas deposit exploited by Navoi Mining and Metallurgical Combine allowed to determine the model, as well as the method for calculating stress-strain state of the rock mass. When assessing stability of the pit walls, an approach known as the displacement method was used. Applying the boundary integral equations method allowed to develop an algorithm for calculating stresses in the rock mass for the conditions of Kokpatas deposit. A technique has been developed for experimental studies of blasting contour blasthole charges (blasting by pre-splitting method) using models, allowing to study fracturing on volumetric models and wave interaction by the method of high-speed video recording of the blasting process in transparent models, as well as to determine the parameters of stress waves during blasting in samples of real rocks. A method for formation of stable pit wall slopes, an excavator method for bench pre-splitting on ultimate envelope (contour) of a pit, and a method for initiating blasthole charges in the near contour zone of a pit have been developed and implemented in the industry.

Friendly and Resource-Saving Methods of Underground Ore Mining in Disturbed Rock Masses

One of the most problematic aspects in underground ore extraction in mining-disturbed rock masses is backfilling of man-made voids, which affect origination and redistribution of stress-strain state of the rock mass. Their existence in the earth's crust provokes subsidence/collapse of the day surface and also contributes to arising geomechanical and seismic phenomena. The purpose of the study is to substantiate environmental-friendly and resource-saving methods for backfilling of voids in underground ore mining based on revealing the features of rock integrity of the day surface and life-sustaining activity of the population living in the mining-affected area. The main negative consequences of the impact of mining on the environment and humans are high costs for conserving day surface and ensuring life-sustaining activity of the population living in the mining-affected area, as well as removing large areas of land from human activity, etc. Based on the study of a rock mass stress-strain state using geophysical and surveying methods, an environment-friendly method for backfilling of man-made voids in disturbed rock masses is proposed. It enables ensuring the integrity of the day surface and life-sustaining activity of the population living in the mining-affected area (in the vicinity of mines, dumps, sites of backfilling complexes, preconcentration and heap leaching of metals from substandard ores, tailings storage facilities, etc.). Combined geotechnologies are proposed for backfilling of voids during the development of ore deposits by underground block leaching, and scientific and methodological and technical support was provided for drilling and blasting preparation of hard ores and underground leaching of pilot blocks at the Michurinsky deposit of GP VostGOK, Ukraine. The research findings can be used in underground mining of ore deposits of complicated structure.