Abstract:
The fracture movement and structural instability of hard roof strata in large-mining-height faces are fundamental triggers for rock burst occurrences in mining panels. Elucidating the correlation between the fracturing of roof strata and mining-induced seismic events is therefore of significant importance for the scientific prevention and control of rock burst. The high-energy seismic events and rock burst manifestations at the Yingpanhao Coal Mine, operated by a subsidiary of Yankuang Energy Group in Ordos City, are investigated with the 2215 gob-side face employed as a case study. Focusing on the concentration of large-energy events ahead of the working face and along the gob-side edge, the research integrates theoretical analysis, numerical simulation, and field measurement. By applying an elastoplastic plate structure ultimate load analysis method, the fracture characteristics of roof strata and the geometric dimensions of plastic hinged blocks under conditions of a large-mining-height gob-side face were determined. A Fish program was developed to simulate the evolution of dissipated energy during strata fracturing, enabling the characterization of the distribution and dynamic evolution of dissipated energy in roof strata as the face advances. The main fracture trace distribution and the structural morphology of broken blocks in the roof strata of large-mining-height faces are identified, thereby revealing the structural configuration of roof fracturing. Through this, the mechanism behind the concentration of high-energy events in the front abutment pressure zone and the gob-side area is elucidated. The findings indicate that: The ultimate load-bearing capacity of the roof strata decreases exponentially with increasing face advance distance until the initial and periodic fracturing intervals are reached. Moreover, the roof in the large-mining-height gob-side face exhibits eccentric fracture characteristics, with the main fracture location shifting toward the gob-side edge and the rear of the goaled area. An overhanging structure is formed in the roof strata above the front abutment and the gob-side area. The interaction of successive fracture traces results in the formation of an approximately “L”-shaped roof block, whose rupture and movement are identified as the primary cause of high-energy microseismic events in these zones. In thick and hard multi-layer strata, the implementation of high-density advanced destressing boreholes during the mining cycle of the two gate roads effectively disrupts the combined structural effect and holistic movement behavior of multi-layered “L”-shaped roof blocks. This measure has proven effective in reducing the occurrence of high-energy microseismic events in large-mining-height faces with hard roof strata at the Yingpanhao Mine, which provide valuable references for safe extraction of high-quality coal resources under similar geological and mining conditions.