ABSTRACT The accurate determination of early‐warning indicators for critical impact stress in deep soft coal seams is a key scientific challenge for rockburst prevention in kilometer‐deep mines. Based on the engineering context of the Hongyang No. 3 Mine, this study systematically investigates the evolution mechanism of relative stress in soft coal seams and establishes a set of targeted early‐warning indicators. Through theoretical derivation based on damage mechanics, laboratory experiments comparing the loading response of soft and hard coal specimens, and FLAC³ᴰ numerical simulations replicating roadway excavation under various overburden conditions, the relationship between absolute stress and relative stress is quantitatively established. The results reveal that: (1) The low elastic modulus and rapid damage evolution of soft coal directly amplify the stress gauge response, with the stress change rate being linearly and negatively correlated with the damage evolution rate. (2) Under identical loading conditions, the increment in monitored stress values for soft coal is approximately 3.1 MPa per 10 MPa of load, nearly double that of hard coal (nearly double the 1.6 MPa per 10 MPa observed for hard coal). (3) By back‐analyzing a historical rockburst event, the absolute critical stresses are determined to be 60.5 MPa (shallow boreholes) and 70.3 MPa (deep boreholes). Based on a linear conversion factor of approximately 2.34 between absolute and relative stress changes, the relative stress warning thresholds are set at 18 MPa (shallow) and 20 MPa (deep), with a unified daily stress change rate threshold of 3 MPa/d. Field validation on the 702 working face confirms that exceeding these thresholds correlates strongly with the occurrence of high‐energy microseismic events. This study provides a quantitative theoretical basis for optimizing rockburst early‐warning systems in deep soft coal seams, offering practical reference values with significant engineering implications for safe mining under similar geological conditions.
Yin et al. (2026) studied this question.