Materiały konferencyjne SEP 2023

Outburst-hazardous coal seams are a natural coal-gas medium or a gasdynamic system "coal- gas" in conditions of great depths. This system, when opened, is transformed into solid and gaseous components [1, 2]. It is theoretically possible to model such a system, but many factors must be taken into account. For example, even before coal sampling, irreversible deformation processes and technogenic transformations of coal matter occur ahead of the roadway face. Coals are most intensively transformed under upridging of beds conditions when changing deformations in the dynamic shift trough (DST), the abutment pressure zone (APZ) and in the bearing pressure zone ahead of the roadway face [2, 3]. Coal in the roadway face, in the zone of maximum bearing pressure (from the face to the depth of the array by 2.5–4.0 m) and in the sample taken, these are three geological objects of different structure. Therefore, the results of laboratory studies of interaction process of coal and gas in comparison with the natural system "coal-gas" have a huge error. Studies of sorption processes, liquid and gas filtration, degassing, etc. make it possible to evaluate the response of an outburst-hazardous array to its dynamic loading. In our studies, coals of especially outburst-hazardous seams of the Central region of the Donetsk basin as coal “K” and “Zh” (Medium volatile bituminous and Hight volatile bituminous A) with an average degree of metamorphism are considered. According to the results of studies [1], they have a globular macromolecules structure of coal matter and, during the transformation of the “coal-gas” system, can generate up to 14 methane molecules [2]. It is almost impossible to study the state, structure and properties of such a system by contact methods. It is optimal to study the reactions of an outburst- hazardous coal massif to hydrodynamic impact (HDI) [4-6]. The goal of this work is to analyze the results of HDI studies and to select scientifically based HDI parameters for modeling the destruction process and initiating self-destruction of an outburst-hazardous coal massif. THE SOLUTION OF THE PROBLEM The HDI mechanism is based on the theory of layer-by-layer destruction of porous media. The essence of the mechanism is as follows. When fluid is supplied to the seam in the filtration mode, its front moves a certain distance into the array depth. The gas located in cavities, cracks, pore channels and other defects is compressed. With a sharp release of pressure in a time that is much less than necessary for the reverse filtration of the liquid, tensile deformations occur at the free surface. When the destruction criteria are met, a layer-by-layer detachment of coal occurs. When studying the hydraulic impact modes (Fig. 1) [7-9] and the parameters of the methods for preventing gasdynamic phenomena (GDP) and degassing of the coal-rock massif using the HDI method [4-5], the coal mining recovery factor was established. It depends on the coal hardness, at f >1.5 it is 1%, and at f <0.9 it reaches 12%. The dependence between the calculated degree of degassing k с of the processing zone and the coal mining recovery factor k rec was established. This made it possible to establish a pattern: the extraction of coal in a volume of more than 7% of its deposits in the formed collector zone does not affect the increase in degassing degree of the coal seam in this zone (Fig. 2). If during the impact the volume of extracted coal exceeds the value of 7%, then this indicates an increase in the zone of effective influence of the borehole. Comparison and analysis of the results of studies obtained with different modes of the HDI showed that not all efficiency criteria always correspond to these modes. For example, when opening outburst-hazardous seams with crosscuts, the criterion for extracting destroyed coal k rec =5-10% is observed in 40% of cases. k rec is 5% to 10% of opening, in other cases k rec =1-4%. In this case, all seams opening cases occur without signs of GDP.