Abstract:
Maintaining an appropriate width for coal pillars is essential for the stability of the working face and the effective and safe extraction of coal. The optimal width for coal pillars in specific sections is determined based on geological conditions and the operational context along gob-side entry driving in a thick coal seam, using limit equilibrium theory. This calculation serves as a basis for further investigation with FLAC
3D numerical simulation software, which analyzes the internal stress in coal pillars, the degree of plastic deformation, and the deformation of the roadway surrounding rock at various pillar widths (5 m, 7 m, 9 m, 11 m) along the gob-side entry driving. The study identifies the most suitable width for coal pillars is these sections. Despite the coal pillars being of reasonable size, high stress levels and significant roadway surrounding rock deformation persist, prompting the proposal of a scientifically effective support method using long rods/short cable bolts + shotcrete. The results show that a coal pillar width of 7 m reduces stress concentration within the pillars compared to widths of 9 m and 11 m. This reduction in stress results in less plastic damage, giving the coal pillar a strong load-bearing capacity and causing only minor deformation to the roadway surrounding rock. Conversely, reducing the coal pillar width to 5 m decreases stress concentration but significantly increases plastic damage and roadway surrounding rock deformation, adversely affecting both the load-bearing capacity of the coal pillar and the safety of the roadway. Thus, maintaining a coal pillar width of 7 m in these sections is considered most rational, closely matching the 7.8 m predicted by limit equilibrium theory. Implementing the long rods/short cable bolts + shotcrete support strategy significantly reduces the deformation of the roadway roof by 70%, and the deformation of the coal pillar rib and the solid coal rib by 58% and 51%, respectively. This innovative support scheme proves to be both effective and scientifically sound, effectively controlling the deformation of the roadway surrounding rock. This research provides theoretical guidance for establishing reasonable coal pillar widths under similar geological conditions and offers a scientifically valid support strategy for managing deformation of the roadway surrounding rock.