Study on asymmetric deformation and support characteristics of roof in fully mechanized gob-side roadway

The deformation and stress in the roof of gob-side roadway along fully mechanized mining face demonstrates asymmetric distribution characteristics relatives to the central axis, with non-symmetric characteristics along the lead hammer direction. Consequently, here is an urgent need to address the mismatch between the support force of the advance support group and the stress distribution of the roof. Using FLAC^3D with the strength reduction simulation method, this paper analyzes the displacement and stress of the roof under various support strategies. Our findings reveal that under the anchoring support strategy, both displacement and stress exhibit asymmetric distribution characteristics at both ends of central axis of the roof. In comparison, the equal strength coupling support strategy reduces the maximum displacement of the roof by 28.8%, brings the maximum displacement position closer to the central line by 9.2%, and decreases the maximum vertical stress by 25.26%. However, limitations in controlling the asymmetric characteristics of the roof stress are observed, with instances of excessive support in the deep sections of the roadway. Furthermore, the transverse and longitudinal joint non-equal strength coupling support strategy, when compared to the equal strength coupling support, reduces the maximum displacement of the roof by 13.2%, decreases the distance from the maximum position to the central line of the roof by 0.26 m, and leads to gentler deformation along the roadway direction. Additionally, it decreases the average difference between the two ends of the roadway roof by 32.98%, reduces the maximum vertical stress value by 26.8 %, and decreases the average distance from the central line of the roof by 27.4%. These research findings offer valuable insights for effectively controlling complex stress along the roof of an empty roadway.