Reasonable coal pillar setting and roadway surrounding rock control technology in close-distance coal seam working face

To explore the reasonable width of the coal pillar and surrounding rock control technology of the mining roadway in a close-distance coal seam working face, this paper took the mining of No.10 and No.11 coal seams of the Huipodi coal mine as the engineering background. Through numerical simulation, theoretical analysis, field practice, and other technical means, the evolution of the coal pillar failure, influencing factors, and damage range of floor under different widths were analyzed. The surrounding rock control technology of the mining roadway was studied in depth. Results show that: (1) During the four stages of reserved, section, protective, and isolated coal pillars, the damage scope of the coal pillar gradually increased. The proportion of the elastic core of the coal pillar increased with the increase of the coal pillar width. The mining roadway in this coal seam evolves from asymmetric failure to symmetrical failure. The failure width of the coal pillar is directly proportional to the buried depth and inversely proportional to the coal seam dip angle, cohesion, coal pillar width, internal friction angle, and Poisson’s ratio. (2) With the increase in coal pillar width, the width and depth of the coal pillar floor failure will change. Moreover, the floor failure concentrated on the side of the coal pillar edge, and the damaged floor area under the coal pillar is observed to be small. (3) The maximum principal stress under the floor deflects owing to the concentrated stress of the coal pillar. The larger is the distance between any point of the floor and the centerline of the coal pillar, the smaller is the deflection angle of the maximum principal stress. With the increase in the distance between the roadway and coal pillar edge, the plastic zone of the roadway surrounding rock initially changes from an inclined X-shaped distribution to an inclined 8-shaped distribution, which then changes to an inclined O-shaped distribution and finally to an elliptical distribution. When the distance from the coal pillar is close, the roadway often shows an asymmetric failure, and the support should also take the form of asymmetric support.