Abstract:
During deep underground mining, the coupled effects of near-and far-field strata on mining-induced ground pressure are complex, while control measures targeting a single stratum are often insufficient. Therefore, coordinated treatment of multiple strata is essential for safe high-intensity extraction and high-production mining. Based on surface hydraulic fracturing for rockburst prevention and seismic mitigation at the Hongqinghe Coal Mine, this study investigates load transfer, overburden movement, stress redistribution, and energy release after multi-level hydraulic fracturing through theoretical analysis, physical experiments, numerical simulations, and field applications. The results show that increasing the degree of fracturing and selecting target strata adjacent to relatively weak rock layers facilitate load transfer. The fracturing degree and adjacent-strata stiffness exhibit a nonlinear coupling relationship and are exponentially correlated with the transferred load, whereas the overburden load shows a positive linear correlation with it. During the early mining stage, hydraulic fracturing weakens lower-level strata and reduces the block size generated by strata breakage. During the later stage, the development of a complex fracture network promotes the breakage of higher-level strata, thereby suppressing large-scale overburden collapse and the formation of high-level masonry-beam structures. After fracturing, overburden fractures preferentially propagate along induced fracture paths, increasing the total number of caving events by more than 50% and the fracture number by 2.6 times. Successive breakage of lower- and higher-level strata effectively mitigates stress and energy concentrations at the working face, with the maximum stress and strain energy decreasing by more than 20% and 60%, respectively. Moreover, multi-level fracturing combined with mining disturbance enhances fracture-network connectivity, promotes coordinated overburden movement, and reduces the likelihood of large-scale strata collapse and mining-induced seismic events. However, the effectiveness of hydraulic fracturing gradually diminishes as overburden movement becomes fully developed, indicating the need for additional control measures during later mining stages. These findings provide a scientific basis and engineering reference for surface multi-level hydraulic fracturing in rockburst prevention and seismic mitigation in deep coal mines.