Study on distribution characteristics of collapse zone, fissure zone and curved subsidence zone and layered settlement of overburden on 8.8 m super-large mining height coal mining face

Affected by mining activities,collapse zone, fissure zone and curved subsidence zone(“three zones”)will be formed in the roof cover rock.The observation and research of “three zones” in gob are very important for coal mine safety production, but at present the observation and research of “three zones” of overburden at home and abroad are mostly limited to medium and small mining height working faces, and the research on full-height and large-height mining working faces is still limited. In response to this problem, the first 8.8 m ultra-large mining height No.12401 face in Shangwan coal mine was taken as the research object, and comprehensive analysis of the overburden rock in the gob of the ultra-large mining face was carried out by means of drilling, in-hole video camera and geophysical logging. The distribution characteristics of the “three zones” and the development height of the “three zones” were determined. At the same time, this study also continuously monitored the subsidence of overburden rock on the No.12401 mining face by installing the monitoring equipment of stratified subsidence in the borehole before mining, and comprehensively analyzed the characteristics and laws of stratified subsidence in the gob of this area.The research results show that the height of the collapse zone of the No.12401 working face is 33.20～33.25 m, and the mining ratio is 3.91; the height of the water-conducting fracture zone is 118.08～132.83 m, and the fracture mining ratio is 13.91～15.65; the distance between the continuous deformation zone and the surface is 39.17～48.92 m. The research also found that the overburden of working face experienced two rapid settlements from subsidence to stability. The maximum subsidence of layered settlement of overlying rock relative to the surface is 1.618 m, the final subsidence of the surface was 4.706 m and the subsidence coefficient was 0.5. As the area of gob increases, the overburden movement in this area is mainly controlled by the lower and upper two key layers.