Disaster-causing mechanism of multiple key strata linked fracturing and the synergistic evolution law of stress field

Aiming at the unclear linkage mechanism of dynamic disasters induced by superimposed multi-layer hard strata, this study seeks to reveal the synergistic evolution law of the fracture chain of multiple key strata and the stress field, thereby providing theoretical support for source prevention and control of dynamic disasters in deep mines. Taking the 30210 working face of Muduchaideng Coal Mine as the engineering background, a mechanical model of linked fracturing of multiple key strata was established. Combined with on-site microseismic monitoring and in-situ stress measurement data, the correlation among the fracture horizon and time sequence of overlying strata and the stress fluctuation in the mining space was comparatively analyzed. The study found that overlying strata fracturing exhibits a time sequence characteristic from bottom to top and from near to far. Based on the equivalent breaking span and stress transfer criterion, the third siltstone layer is identified as the main controlling key stratum, whose fracture energy release rate reaches up to 38.7%, serving as the dominant source of dynamic load release. The fracture of the main key stratum triggers the stress field to undergo a three-stage evolution of "static concentration - linked transfer - reconstruction equilibrium," causing the vertical stress at monitoring points to surge to 50 MPa and inducing a horizontal impact dynamic load of 51.6 MPa in the gob-side roadway. Statistical analysis confirms a significant correlation between main key stratum fracturing and roadway deformation (correlation coefficient 0.4～0.5), indicating that the fracturing of the main controlling stratum is the fundamental driving force for the "stepwise" cumulative damage of the roadway. This study can serve as a basis for early warning of dynamic disasters under similar conditions.