Control of uniform surface settlement in coal mining: a pillarless coal mining method based on a chainsaw arm machine

Pillarless mining plays a pivotal role in safeguarding and rehabilitating the ecological and geological aspects of mining environments. To improve the safety of hard roof cutting during pillarless mining operations, we have introduced a novel approach known as pillarless mining with roof cutting using a chainsaw arm machine (PM-RC-CAM). Our endeavor begins with a systematic overview of the essential equipment and the coal mining process integral to PM-RC-CAM. Then, a mechanical model for the periodic fracture of hard roofs was established based on the theory of elastic thin-plates. Finally, the three-dimensional periodic fracture characteristics of the hard roof, the differences between this hard roof and a traditional working face, and the evolution of stress in the mining area were analyzed. Under the action of the PM-RC-CAM, the hard roof breaks in a "—" type. This eliminated uneven subsidence of overlying strata and facilitated the ecological restoration of the mine.