Law of strata behaviors in shallow contiguous coal seams mining under oblique district coal pillars
In order to explore the law of strata behaviors in shallow contiguous coal seams mining under oblique district coal pillars and guarantee the safe and efficient mining,we analyzed the mining stress evolution characteristics when mining along different oblique angles,i.e.11°,30°,45°,60° and 75°,based on field measurement and numerical calculation.The research results show that:in terms of on-site measurement,when the oblique angle is 11°,weighting position in the mining face moves with the superposition area of the coal wall and the oblique coal pillars;the pressure is large on the middle part,medium on the tail,and small on the head of the mining face.The stress concentration is the most prominent when the mining face tail passes under the coal pillars.When the middle part of the mining face intersects at oblique angles with the coal pillars,as the oblique angle increases,the advance stress of coal wall changes,which shows a wide and gentle unimodal distribution within 30° oblique angle;and shows double peaks at the middle and tail of the mining face between 45°～75°,and the tail peak is higher.When the oblique angle decreases,the peak of the maximum advance stress on tail of the mining face rises and gets closer to the tail;and when the oblique angle exceeds 45°,another stress peak appears in the middle of the mining face,showing double peaks.The research can provide a reference for mining at similar working faces crossing oblique coal pillars.
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