Study on Stability of Upper and Lower Double-seam Pillar in Staggered Mining out of Close-distance Coal Seam
The stacking of upper and lower coal pillars in close range coal seams and the stability of the double coal pillars are related to the success of coal pillar retention.Through theoretical calculation,the calculation formulas of the load and the reasonable width of the upper narrow and lower wide double-level coal pillar are derived respectively.It is concluded that the influencing factors of the stability of the upper narrow and lower wide double-level coal pillar are as follows:with the increase of the width ratio of the lower and upper coal pillar,the load of the lower coal pillar decreases gradually,while the width ratio of the lower and upper coal pillar is constant,with the increase of the width of the goaf,the load of the lower pillar increases with the increase of the width of the goaf,the load of the lower coal pillar increases with the increase of the thickness ratio of the lower and upper coal pillars,the load of the lower coal pillar increases with the increase of the thickness ratio of the lower and upper coal pillars,and the load of the lower coal pillar increases with the increase of the thickness ratio of the upper and upper coal pillars,the load of lower coal pillar decreases with the increase of width ratio of lower coal pillar and upper coal pillar.
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