Study On Mechanism Of Intense Strata Behaviors Along The Empty Side Of Fully Mechanized Coal Face With Super Great Mining Height In Shallow Buried Coal Seam

During the mining process of coal face 52303 with the mining height of 7m of Daliuta Coal Mine in Shendong Mining Area, intense strata behaviors occur in air return way and tail area along the empty side, which brings serious influence on safety and high effective product. By the comprehensive application of field measurement,theoretical analysis and numerical simulation,the paper makes further research in mechanism of intense strata behaviors, influence factor and prevention countermeasures along the empty side.Through contrastive analysis of intensity index of various strata behaviors in three different mining areas,strata behavior law in coal face and air return way ranging from No.130 to No.151 support near the tail was found to be significantly different in different mining areas.According to rock mass ultimate balance theory,section coal pillar in the two sides of the gob lost stability when the buried depth reaches 250 m, which caused the concentrated stress imposed on section coal pillar to transfer to the front goaf-side coal pillar area and ahead integrated coal of working face,exacerbated the extension of width of plastic area,and then resulted in the intense strata behavior occurrence in the tail and air return way of working face 52303.By means of the FLAC3 d numerical simulation, influence law of three factors,that is,burial depth of coal seam,mining height of coal face and width of section coal pillar,on intense strata behavior occurrence was grasped. When burial depth reached to 250 m or mining height 7m,section coal pillar will get close to the plastic instability state,which is bound to cause intense strata behavior along the empty side of coal face. When width of section coal pillar added to 25 m.Based on the effect of rotational motion of arc triangle block and width of coal pillar,various prevention countermeasures has been put forward such as adding the width of section coal pillar,grouting reinforcing the section coal pillar ahead of working face,blasting the coal face roof to reduce the overlying load of coal pillar and so on, which could provide further guidance of the safety mining of nearby working face 52302.