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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.

The analysis of sudden outbursts of coal and gas in coal mines is presented in the article. Phase transitions of gas to gashydrate state are investigated in the laboratory. Thermobaric parameters of phase transitions of mine methane are established. The new hypothesis is described of sudden outbursts of gas that is based on a gashydrate condition of methane in mines at depths (near 1000 m and more) and their explosion-like failure – Percy Bridgman’s effect.

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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.