The width of coal pillars affects how rocks around gateways deform and fracture in fully mechanized top-coal caving mining. Different pillar widths lead to varied deformation and fracture patterns. Narrow pillars cause integrated deformation and fracture, while wider pillars support high pressure but lose more coal. The type of fracture near gateways is mainly cutting, while pillars experience a mix of cutting and pulling. The ideal pillar width prevents collapse, leakage, and self-ignition, but overly wide pillars may lack stability.