Reasonable width of coal pillar in fully mechanized caving mining face of extra-thick coal seam–A case study

To address the issue of resource wastage caused by the extraction of thick coal seams with large coal pillars, this study is based on the 1st Panel of the 110 Working Face at the Suancigou Coal Mine. It employs methods such as on-site measurement, physical similarity model experiments, theoretical analysis, and numerical simulation to investigate the reasonable width of coal pillars under the disturbance of comprehensive mechanized mining in thick coal seams. The study reveals the damage and deformation evolution patterns of the coal pillars, calculates the critical width of the coal pillars based on limit equilibrium theory and strength theory, and simulates the distribution characteristics of stress and damage failure zones in the coal pillars. The results indicate that a 45 m coal pillar still possesses substantial load-bearing capacity after multiple mining activities, suggesting the possibility of reducing its width to enhance coal recovery rates. The calculations show that the minimum width of the coal pillar should not be less than 26.18 m. Simulations demonstrate that when the width of the coal pillar is 30 m, the coal recovery rate is relatively high and meets safety production requirements. The findings of this research are significant for improving coal recovery rates in the Suancigou Coal Mine and similar mining conditions.