Research On Overbufden Rock Activity In Fully Mechanized Face Of Large Mining Height Under The Goaf Of Close Distance Coal Seams

Lower coal seam will be affect by the advanced support pressure, postharvest decompression and recompaction of gob in the downward mining of close distance coal seams.It will be no longer complete and will be different from single coal seam mining.The thesis Study the overlying strata movement and mine pressure behavior of downward mining of close distance coal seams by similar material simulation, theoretical analysis and field monitoring.First of all, seting up similar material model and measuring point locating according to rock physical and mechanic parameter, and then finish excavating simulation of 903 face and 1103 face.In the process of the excavation using the digital image correlation method record point displacement data.And clustering analysis the measuring point displacement data and obtained caving zone, fractured zone and bend subsidence zone.Analysis to pressure rule, it is concluded that coal seam mining under the first weighting interval less than on coal seam, the periodic weighting interval on average less than coal seam, rock fracture line in front of working face. Analysis of abscission layer development, it is concluded that abscission rate tun out to be double hump shaped, the upper coal seam is bigger than the lower coal seam in peak point and abscission rate diminish in goaf.The vertical abscission rate curve has two peak valley double hump shape, key strata in the trough area on the right side of the peak point.Through to the analysis of the laws of pressure and strata movement, put forward the close distance coal seam mining the lower coal seam "inside the block-medium-pressure arch-masonry beam-external pressure arch" strata structure model. Analysis of the influence of parts for mine pressure appear.Rock fracture at the delamination growth model is set up, the influence factors of abscission layer thickness are analyzed.Finally combining with the field monitoring,1103 face 9 coal mined-out area under the first weighting interval average 48.2 m, periodic weighting interval average 18.6m, and similar material simulation conclusion.