Research on Characterization of Coal Pillar Stability and Mine Pressure Law in Unequal Width Island Coal Face

When a coal mining district enters its final mining stage, the coal resources in boundary areas usually present irregular shapes, and the width of section coal pillars varies with the working-face dimension. Therefore, the stability of section coal pillars under unequal-length working faces is critical for roadway maintenance and working-face mine-pressure control. At present, most international studies on remnant-coal-pillar mining focus on regular-shaped section pillars and mainly concentrate on mine-pressure control, while few investigations concern the high-efficiency mining design for remnant coal pillars. Taking an irregular occurrence area in a Xinjiang mining area as the engineering background, this paper analyzes the geological and mining conditions from the perspective of working-face mining design and establishes a collaborative roof-control model for unequal-length working faces. The distribution law of main roof load under unequal-length working faces is revealed. It is identified that the coal pillar adjacent to the room-and-pillar goaf is the key object for roof mine-pressure prevention and control. A discriminant formula between the ultimate strength and height–width ratio of unequal-width coal pillars is derived. Combined with the load distribution characteristics of the stope, the theoretical reserved width for unequal-width section coal pillars is proposed. Field practice shows that the actual pillar width in situ is basically consistent with the theoretical calculation result. During mining, the maximum dynamic pressure coefficient of the working face is only 1.12, and the maximum roadway surrounding-rock deformation is less than 300 mm, which realizes effective stope mine-pressure control.