Mechanism of stress relief by deep-hole blasting in floor drainage roadways and its effectiveness evaluation

To address the Rockburst prevention challenges caused by the limitations of roof blasting in deep coal mines, the stress relief mechanism of floor strata was investigated through numerical simulations based on 195 field practices of cross-layer blasting in floor drainage roadways. Three real-time evaluation indices, namely the scalar seismic moment B_m, stress drop B_d and apparent stress B_a per unit charge, were proposed, and a four-level discriminant standard was established. Results show that the scheme effectively intercepts the horizontal stress transmission path by inducing rock mass damage in the floor. Under high tectonic stress conditions, the average vertical and horizontal stresses in key strata decrease by 29.38 and 12.30%, respectively. Simultaneously, the blasting induces the transfer of high-stress concentration zones into the deep surrounding rock, with the maximum offsets of vertical and horizontal stress peaks reaching 5.0 m and 6.0 m, respectively, achieving stress field reconstruction in both intensity and spatial distribution. Cross-validation with seismic wave computed tomography inversion confirms that B_m and B_d indices are highly sensitive in identifying ineffective stress relief events. Field engineering applications significantly reduce the frequency of high-energy microseismic events and stabilize seismic activity, validating the effectiveness of the evaluation system and providing a scientific basis for the quantitative assessment of deep dynamic disasters.