Space structures and scales of mined-out area are dynamic changed with high-sublevel fully mechanized caving in steep and thick coal seam. In weakening and disturbance of segment pre-blasting, the degree of coal damage and crack would be increased, and the complexity of physical-geometric structure and spatiotemporal evolution of mined-out area would be intensified. Firstly, the complexity of geological environment and mining technologies, balsting parameters and technologies optimization, and blasting effect of B1+2 steep coal seam of Weihuliang coal mine were analyzed comprehensively. Then, the pre-splitting blasting was applied successfully in 52m sublevel top-coal caving and weak the coal effectively. Finally, the blasting effect was detected in broken zone with RSM-SY5 acoustic detector and YS(B) borehole optic camera, and the front and behind support forces were monitored before and after blasting. The results showed that blasting effect was obviously, and which provided technological reference for the subsequent safe mining of 102m and 18m sublevel top-coal caving.
In top-coal caving, the weakening and accessibility of top coal directly determine its fully-breaking and caving safety and efficiency (Xie 1999, Shi 2006, Kang 2004, Chen 2002). The mined-out area caused by high-sublevel fully-mechanized caving in steep and thick coal seam is a spatial structure with dynamic sizes (or dimensions). In weakening and disturbance of segment pre-blasting, the degree of coal damage and crack would be increased, and the complexity of physical-geometric structure and spatio-temporal evolution of mined-out area would be intensified. In the high-sublevel caving workface of +579E2EB1+2 steep seam (from 64° to 69°), there are some coal pillars with different heights, respectively 52 m, 102m and 18 m, along the trend direction of the B1+2 coal seam. In 52m sublevel top-coal caving, large-scaled dynamic collapse occurred several times, and some harmful gases were squeezed into workface and injured people.