Fully mechanized caving faces in close-distance coal seams involve extensive extraction spaces and high mining intensity.The extraction of roadways in lower coal seams is affected by stress concentration and support challenges resulting from the mining of upper seams.Hence,determining the optimal roadway position is crucial for effective support control in these settings.This study focused on the No.2 coal seam and the No.1-1 sub-seam at Xilutian Coal Mine.It evaluated both the stress reduction zone in the floor caused by upper seam extraction and the limit equilibrium zone during lower seam extraction,concluding that the optimal roadway position should be more than 22.79 meters away from the solid coal pillar.Theoretical calculations were used to analyze the stress distribution pattern in the floor following upper seam extraction,as well as the deformation and failure characteristics of the surrounding rock at various internal offsets.The results revealed:①A pronounced difference between maximum and minimum stresses occurred closer to the floor of the mine-out area.②With increasing internal offset,the surrounding rock stress and stress concentration coefficient initially decreased sharply,then increased slowly,and eventually stabilized,with relatively low values observed within the 20-25 meters internal offset range.③The plastic zone of the surrounding rock decreased and then increased,with minimal damage to the roadway rock observed at internal offsets of 20 and 25 meters.④Roadway deformation decreased as the internal offset increased,and surrounding rock displacement stabilized when the internal offset reached 25 meters.⑤The optimal internal offset for the roadway was determined to be 20-25 meters.Engineering applications confirmed that a 24-meter internal offset maintained both rock looseness and deformation within controllable limits,further validating this internal offset.
关键词
近距离煤层/综放工作面/巷道布置/围岩破坏/内错距/底板应力
Key words
close distance coal seam/fully mechanized caving face/roadway layout/surrounding rock damage/internal offset/floor stress
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