Research on Fracture Characteristics of Key Strata and Prevention of Mining-Induced Seismic Disasters in Kilometer-Deep Coal Mining

Understanding the fracture characteristics of overlying key strata in goaf during coal mining and the mechanisms by which they induce seismic disasters is crucial for seismic disaster prevention and control. Using a mining-induced seismic event in the 0901 working face of the Daqiang Coal Mine as the research context, this paper conducts bottom unloading experiments on rock beams under dual-sided loading with varying rock beam thicknesses and unloading spans. These experiments simulate the dynamic phenomenon of key stratum rock beam fracture induced by sudden subsidence of lower strata during mining. Experimental results indicate that, after bottom unloading, rock beams generally exhibit a tensile–shear composite failure mode. As rock beam thickness increases, the proportion of shear cracks rises and the dynamic surface failure characterized by rock debris ejection intensifies; as the unloading span increases, the proportion of tensile cracks increases and the arched fracture zone disappears. During fracturing, rock beams commonly experience 2–4 stress reduction episodes, with the first stress drop having the largest amplitude and occurring prior to the peak energy release, serving as a precursor for identifying high-energy events. The cumulative AE count, peak energy, and cumulative energy all increase approximately linearly with increasing rock beam thickness and unloading span. Based on the full-cycle failure mechanism of seismic impact on roadways, this study proposes a seismic disaster control mechanism and strategies based on the "dual compensation theory." Field applications demonstrate that the "dual compensation theory" and its associated control techniques effectively reduce the frequency and energy level of seismic events while significantly improving roadway stability during retreating operations. • The unloading experiment at the bottom of the rock beam reveals the influence of key strata thickness and unloading span on the fracture characteristics. • Acoustic emission monitoring shows that the stress reduction phenomenon is a precursor of energy dissipation, which provides a basis for early warning of mine earthquakes. • The proposed “double compensation theory” can effectively control the mine earthquake disaster by compensating the excavation stress and mining space.