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 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.

The objective of this work is to study the relationship of the deformation-strength characteristics of the fastening system with its displacement value. The tendencies of influence are divided into two groups. The multivariate computational experiments have been performed in the conditions of coal-face works. It is shown the influence of geomechanical conditions of the mine working maintenance on the fastening system operating mode change when choosing its rational deformation-strength characteristics. On the basis of the performed studies, it was concluded that it is necessary to adjust the fastening elements of each specific support setting scheme. This is necessary to provide recommendations for the maintenance schemes optimization of reusable extraction workings.

Purpose.Development of a comprehensive methodology for assessing the state of mine workings based on the analysis of their contour displacement patterns when solving the problem of minimizing the risks during the closure of coal mines in Ukraine. Methods. Based on an integrated analysis of international and domestic trends when assessing the consequences of mine closure, the main provisions of using the method of instrumental mine observations have been substantiated. When solving the problem, the approaches of regulatory documents are taken into account to identify the geomechanical situation according to two conditions: the structure and strength properties of the lithotypes in the adjacent coal-bearing stratum and the peculiarities of the rheological processes manifestation during the development of its displacements. Findings. The geomechanical, technological and hydrogeological factors have been distinguished that are required to take into account when closing the coal mines. Fundamental methodological provisions have been substantiated for the most reliable assessment of the mine workings state, taking into account the long period of their operation. A criterion for making a decision on the decommissioning of mine workings or their further maintenance is presented. Originality.A series of generalizing dependences of the mine working contour displacement development has been obtained, which can be divided into four main groups according to the criteria of the structural and strength properties of lithotypes in the adjacent mass, as well as the type of their rheological manifestations: decaying and persistent deformation creep. For each group, using the methods of correlation-dispersive analysis, empirical formulas have been determined for calculating the convergence of the roof and bottom of mine workings, as well as their sides, depending on the geomechanical criterion H/R of the maintenance conditions and the duration t of this period. Practical implications.The obtained correlation ratios make it possible to predict the residual section of mine working at any time of its maintenance. They are a geomechanical component of its operational state assessment. The result of this research is the development of a new methodology for assessing the mine working state according to the patterns for predicting its contour displacement.