Stability of small coal pillar for 223102 working face of Hanjiawan Coal Mine

With the continuous increase of mining depth and the increase of coal demand, in order to realize the safe and efficient mining of coal mines, the stability of coal pillars in the lower 3⁻¹ coal seam section of Hanjiawan Coal Mine under the influence of overlying 2⁻² coal seam mining is studied. The 223102 working face of 3⁻¹ coal seam in Hanjiawan Coal Mine is taken as the research object, and the stability of section coal pillar under superposition condition is systematically discussed by means of theoretical analysis, numerical simulation and field monitoring. The results show that the maximum vertical range of coal pillar floor stress in the working face is 43.1 m, the maximum horizontal influential distance is 21.3 m, and the average stress transfer angle is about 29.9°. The theoretical derivation further shows that the vertical stress can reach 1.47 times of the original ground stress at a depth of about 43 m below the remaining coal pillars in the upper coal seam. The monitoring results of the on-site return airway show that the maximum convergence of the two sides is 25 mm, and the overall deformation is obvious, while the roof and floor are hard due to the sandstone lithology, and the maximum convergence is 15 mm. The coal pillar of the underlying 3⁻¹ coal seam section is generally stable, and it can still meet the requirements of safe production under the existing support conditions.