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 n 7 b 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 n 7 b 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.

The formation of the stress-strain state of rocks in the several phase gasification processes was considered. Proceeding from the well-known principles of thermodynamics and phase formation of the multi-type rockmass under the influence of the temperature field, a geomechanical model of a two-layer artificially-formed shell formed during the gasification process by the method of variation feeding of the blowing mixture to the body of the gas generator was developed. The Neumann principle is used for the magnitude determination of the maximum stress vector, which involves the definition of the axial tensor of mechanical deformations through the anisotropy of the thermal expansion (the polar tensor of the second rank). This makes the possibility to create the base for a package of information programs creation. Such programs give the possibility to simplify the study of the rockmass deformation characteristics and to evaluate the stresses in a thermally changing environment. Researches are carried out by creating the final element system with the adaptation to the specific mining-geological conditions. These approaches are checked both for working out the coal reserves and for utilization of the mining waste products. Results of this investigation were included to the Roman Dychkovskyi thesis of the scientific degree of the Doctor of the Technique Sciences “Scientific Principles of Technologies Combination for Coal Mining in Weakly Metamorphoses Rockmass”. They contain the researches, which were conducted within the project GP – 489, financed by Ministry of Education and Science of Ukraine.

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The method of investment attraction evaluation for the implementation of mining equipment was substantiated. Discounted financial results were taking into account. Pros and cons of chosen method were analyzed. The practical results of the method for definite technical and technology conditions at the SC "Lvivvuhillia" were presented. Values of investment attractiveness taking account monthly costs were determined. The methodology which was worked out by UNIDO were used for conditions of mining equipment implementation for coal reserves exploration of extraction area of mine taking into account cash flow values at the different periods of project realization. It was definite that chosen methodology gave possibility to estimate projects investment attractiveness and could be used for similar projects at the other mining enterprises.

Purpose. Underground coal gasification, as a complex and technically difficult process, should be supported in many aspects by computer simulations or analytical calculations of rock mass behavior. However, little is known about the formation of stratification cavities in the roof rocks during coal seam gasification. To research the formation of stratification cavities and rocks deformations by mine pressure with the methods of calculation based on hypotheses or statistical information, a number of hypotheses are used. The main purpose is to examine the rock mass behavior and formation of stratification cavities during gasification of a thick coal seam.Methods. Analytical calculations were used as the research method for the work presented. The mathematical model of the stress-strain state of rock mass based on the theory of elasticity, resiliency, and maximum equilibrium, was developed and used in this paper.Findings. Critical analysis of geomechanical models of coal gasification together with their mathematical formulation was the result of considerations presented in this paper. Equations were derived for substantiating parameters of stratification cavities above the goaf of the underground gasifier. Subsequently, the volumes of stratification cavities depending on the length of gasification channel were calculated. The results have significant influence on gasifiers development and the final efficiency of gasification process.Originality. The research results were obtained from analytical calculations of rock mass behavior during thick coal seams gasification. The authors implemented a mathematical model based on the method suggested by professor A. Savostianov which was used in carrying out the calculations. Practical implications.The present study provides a starting point for further research and analytical calculations of rock mass behavior. The data and conclusions outlined in this paper may be useful in preliminary optimization and analysis of coal seams gasification. They can also be a point of reference for more advanced geomechanical simulations.