Barabash M. Intensification of mining operations while simultaneous development of coal seams, taking into account the inter-layer softening areas

New regularities of the development anomalies of rock pressure and the areas of rock disintegration while combined and downward coal seams mining for the conditions of slightly metamorphized coal-bearing strata, as well as new-onset tendencies of the influence of the basic geomechanical factors on the degree of the interlayer stability and the probability of dangerous zones occurrence during panel extraction through underlying seam, are defended. These results were obtained on the basis of the creation of a complex methodology for carrying out multivariate computational experiments, the novelty of which is the consistent reflection of structural transformations of the interlayer in the process of working out the seams. An analysis of the data array of SSS calculations made it possible to establish for the first time the phenomenon of activation of the growth in the sizes of the zones of the anomalies of the rock pressure and their connection with the main geomechanical factors in the process of underlying seam mining. It is proved that, under other equal conditions, the influence of only the type of structure, thickness and occurrence coordinates of different-strength lithotypes on the height of the interlayer can lead to a loss of its stability. In addition to those mentioned above, the depth of development and the strength characteristics of the lithotypes composing the interlayer are also attributed to the most influential geomechanical parameters. The criteria and algorithm for determining the boundaries of the areas of interlayer rock disintegration are substantiated; the ambiguity of the relationship between their size and the main geomechanical factors has been revealed. The "stochastic" influence of the thickness and coordinates of the location of the hardesest rock - sandstone, is superimposed on fairly stable trends in the influence of the depth of development, the interlayer thickness and the strength characteristics of its lithotypes. This ambiguity didn't allow us to directly establish correlation relationships between the parameters, in return for which families of graphical dependencies were constructed that provide an operative determination of the height (depth) of the disturbances in the roof of the underlying and floor of the overlying strata. The most dangerous zones (along the length and width of the extraction panel) have been identified from the point of view of the loss of stability of interlayer. The developed criteria and the algorithm for integrated stability assessment formed the basis for a new method for predicting dangerous zones, which makes it possible to quickly identify problem areas and preliminary to develop measures for safe and high-performance of combined seams development in downward order. The adequacy and reliability of the predictive assessment of the interlayer stability are confirmed by mining industrial observations which were carried out in accordance with the original methodology in the 914 longwall face and the 914 conveyor drift "Zakhidno-Donbaska" mine PJSC "DTEK Pavlohradvuhillia".