Stress distribution and energy-driven rock burst hazard assessment of coal pillars in gob-side entries

Ensuring roadway stability is fundamental to coal mine safety, with the retention of a reasonable coal pillar width being a key factor in maintaining roadway integrity. This study establishes a mechanical model of roof structure and coal pillar load-bearing based on engineering practice, and derives a theoretical formula for stress distribution varying with coal pillar width. Research indicates that the vertical stress distribution in the coal pillar transitions from a single-peak to a double-peak pattern as the width increases. Coal pillars without an elastic core exhibit limited bearing capacity at smaller widths, with stress peaks and plastic zone ranges expanding as the width increases. In contrast, coal pillars with an elastic core demonstrate significantly enhanced bearing capacity, where the elastic core range expands markedly with increasing width, and the stress peak stabilizes. Based on the stress characteristics of elastic-core coal pillars, a corresponding loading–unloading constitutive model was further developed. Based on this model, an energy-based rock burst hazard index K was proposed, where K < 1 indicates the pillar is in a stable state with no risk of rock burst. Ultimately, a method for determining the optimal width of coal pillars was established.