Study of massif stress-strain state while mining the series of flat strata

Purpose.To determine the effect of rock overworking and underworking on massif stress-strain state while extracting the series of flat coal seams. Methods. Mining, geological and technical conditions; current approaches to solution of the related problems were theoretically analysed on the basis of the developed calculation algorithm with the help of the boundary element method. We calculated maximum coefficients of stress concentration in the roof and floor of the working seam in the zones affected by pillars and contiguous seams. Findings. Boundaries for areas of increased rock pressure in the roof and floor of the extracted seam at mining enterprise “Lvivvuhillia” were determined. Values of maximum coefficients of stress concentration were derived. The load acting on the section of powered support was calculated considering the weight of rocks located in the area of boundary stress state in the roof above the longwall face. It was stated that during stope workings in areas affected by contiguous seams' selvage, the period of longwall face exposure from under the selvage of the low seam is the most hazardous in terms of rock pressure manifestation. Originality. Analysis of stress-strain state of stratified heterogeneous massif around the stope was conducted considering overworking and underworking. Actual values of the force and geometrical parameters of the powered support were derived; rational velocity of stope advance in the given mining and geological conditions was determined. Practical implications. The results of the study allowed to obtain the data necessary to choose the type of standing support and estimate rational force parameters for the powered support during its operation in the areas of high and low rock pressure as well as to determine the velocity of longwall face advance and permissible distance between stopes of contiguous seams for the mines of Lviv-Volyn basin.