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. Substantiation of the mechanism of loading the preparatory mine working support to optimize its deformation-strength characteristics based on the calculation of the stress-strain state of the "massif -support" system. Improving the cost effective technologies for fastening and maintaining the preparatory mine workings.Methods. The analysis of the elements interaction modes of the "massif -support" system has been performed by the two-parameter diagram for optimizing the deformation-strength characteristics of the rock massif and the preparatory mine workings support using the research results of the stress-strain state of a system by means of finite element method. A comparison has been made of computational experiment with mine instrumental observations.Findings. The geomechanical model of the computational experiment on the choice of operation modes of the fastening system, as well as the methodology of the approach to optimize the process of interaction between the massif and the support have been substantiated. The analysis of search patterns for the rational deformation-strength characteristics of the fastening system in the preparatory mine working, taking into account the influence of the main geomechanics factors on this process, has been developed and performed.Originality. The patterns have been established of the geomechanics factors influence on the choice of rational operation modes of the load-bearing elements of the fastening system and the support in general based on research of the stress-strain state of the "massif -support" system. The optimization principles of interaction based on the analysis of a two-parameter interaction diagram have been substantiated.Practical implications. The wide perspective has been substantiated for strengthening the soft rocks in reusable preparatory mine workings with combined roof-bolting systems, which makes possible to realise the resource-saving conditions of maintenance. The calculations have been made with account of the optimization criteria for interaction of massif and support.
Purpose. Analysis of the current state and prospects of Ukraine coal industry development until 2020.Methods. Complex analysis of data regarding mine productivity, coal reserves, mine funds as well as coal consumption and electricity generation has been presented in the paper. The studies of statistics related to geological and extraction thickness in longwall faces are discussed.Findings. The current state of Ukraine coal mining industry and prospects of its development for the period until 2020 are considered. The analysis of Ukraine mine fund conditions is carried out. Statistical data of gross coal production at state-maintained and private mines are given. The reasons for low profitability and coal production decline in the country are considered. Results of the research into ash content of extracted coal, formation and accumulation of mine waste are interpreted. The main promising trends of efficient energy resources use and reduction of environmental impact on coal-mining regions are emphasized.Originality. According to the analysis of the current state of coal industry, several options of its further development are formulated. Practical implications.The presented results can be used to evaluate the investment attractiveness of Ukraine coal mining enterprises.
Purpose. The investigation of the stress-strain state (SSS) of a parting under the joint and downward mining of coal seams.Methods. The studies have been carried out on the basis of a computational experiment by means of the finite elements method, mining observations of rock pressure manifestations and their comparative analysis. Findings.A research methodology has been developed of the parting rocks state under the joint and downward mining of coal seams.Originality. The patterns of the stress-strain state change of the parting rocks have been determined in the process of joint mining of two coal seams by the descending order.Practical implications. The conducted researches will make possible to improve stability of mine workings and their repeated use.
The aim of the forecasting effort is to identify troublesome zones of stability loss by a parting lengthwise of the extraction panel under the joint and downward mining of coal seams. Analyses have been carried out of active stress component curves for a 3-D model computational experiment compared with the strength characteristic of each lithotype of a parting. An algorithm has been developed for the stability assessment of a parting lengthwise along the extraction panel. The relationship patterns have been estimated between the sizes of the parting rocks discontinuity zones and the main geomechanical parameters. A scientifically grounded basis has been created for the detection of the parting rock weak zones lengthwise along the extraction panel for the calculation of the mounting and security systems of the development works. A complex of underground instrumental observations was made, which was used to set up a correspondence of patterns to indicate the variation in rock pressure manifestation intensity and the tendencies for changes in the parting structure. All of this confirms the adequacy of the techniques for parting state forecasting, which is recommended for use in the engineering documentation for the joint and downward mining of coal seams.
Purpose. The purpose is to develop the calculation methods for minimizing the load on the fastening system of the preparatory mine working in difficult mining and geological conditions of its maintenance. Methods. By analysing the multivariate computational experiments on the study of the stress-strain state of the load-bearing elements of the ‘massif – support’ system in the preparatory mine workings by means of the finite-element method, as well as mine observations and measurements of displacement in the coal-overlaying rock formation. Findings. An algorithm has been developed for searching the rational modes of the fastening system resistance and methods for minimizing the load on the support of the preparatory mine working, maintained in very complex mining and geological conditions. Originality.The methodical principles have been developed of minimizing the load on the fastening system of the preparatory mine working, which are based on the use of a combination of stress-strain state studies of the ‘massif – support’ system by means of the finite element method and provisions of normative documents for calculating the dimensions of the dome of natural equilibrium of the mine working roof rocks. Practical implications. The operation modes optimisation of the load-bearing elements interaction of the mine working fastening system reduces the material and labour costs during its construction and increases its stability during operation. Keywords: analysis, calculation, optimization, support, preparatory mine working, stope works, roof rocks, collapse
The degree of influence has been determined of diversified deformation-strength characteristics of load-bearing elements in the fastening system of the preparatory mine workings, while maintaining them in a laminal massif of soft rocks. The analysis has been performed of multivariate computational experiments of the stress-strain state of the load-bearing elements of the fastening system in the preparatory mine workings from the position of the mutual influence of their deformation-strength characteristics and the support loading as a whole. An analysis is represented of the mutual influence of the operation modes of the mine working support elements between themselves and the fastening system as a whole; it has been studied the stress-strain state of the mine working fastening system with a central hydraulic prop stay, as well as a significant increase in reliability of the support performance has been analysed and determined. The tendency has been substantiated of minimizing the load on the mine working fastening system – increasing the coherence of the diversified operation modes of fastening elements by enhancing preferentially the yielding property of the rigid element. The application has been substantiated of the central yielding prop stays of the strengthening support of a frame in case of intensive rock pressure manifestation in the zone of the stope works active influence.
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