The significance of structural coal in regional coal and gas outbursts in southern Sichuan Coalfield

The prediction of coal and gas outburst zones in structurally complex coalfields remains a critical concern globally. Focusing on the southern Sichuan Coalfield, this study systematically analyzes geological factors governing gas accumulation, develops a quantitative model linking structural coal evolution to outburst susceptibility, establishes standardized logging interpretation criteria for structural coal, and completes regional outburst hazard assessment. This work offers practical methodological references for outburst prediction in structurally disturbed coal-bearing areas.The study results indicate that gas outbursts in the southern Sichuan Coalfield are highly severe, with gas content showing a positive correlation with burial depth. Structural controls are pivotal to outburst distribution: gentle-dipping fold limbs and blind fault zones act as high-susceptibility hotspots. structural coal properties exhibit robust statistical correlations with outburst risk: coal firmness coefficient f and composite outburst index K scale with the proportion of structural coal thickness, while outburst intensity follows an exponential growth trend with single-layer structural coal thickness. Zones with single-layer structural coal exceeding 1.1 m are prone to catastrophic outbursts.Using the JGS-6 integrated digital logging system, regional structural coal thickness ranges from 0.19 to 1.72 m, with single-layer structural coal accounting for 10–50% of the total coal seam thickness. The predicted f and K values show minimal deviations from field measurements, and modeled outburst intensities match observed event magnitudes. Spatial zoning identifies the Daxueshan and Baijiao areas as extreme outburst-prone zones, with maximum predicted outburst intensity reaching 8840.06t. Large-scale outbursts are concentrated in the Guanwen and Shiping areas, while the remaining coalfield is dominated by small-scale outburst risk. This study provides data-driven zoning references for targeted gas outburst prevention and control in the southern Sichuan Coalfield.