Study On Dynamic Disaster Prevention Under Fully-mechanized Mining Face Of The Residual Pillar Of Steeply Inclined Coal Seam

Sinkiang is the 14 th national planned and constructed 100-million-ton large coal base of a high starting point,high standard and high benefit.It is also the main energy base of "the Belt and Road Initiatives" economic zone planning and construction.The steeply inclined extremely-thick coal seam of the Urumqi mining managed by Shen-hua Xinjiang Energy CO.,LTD.accounts for 30% of the world's deeply inclined coal resources.The existing condition of the coal resources is quite complex(45°~87°),safe mining is extremely hard,and dynamic disasters occur frequently.The B3-6 coal seam of Jiangou coal mine belongs to the steeply inclined extremely-thick coal seam(87°),and the horizontal sublevel caving mining method is used.The +495horizontal B3-6 working face works through the residual pillar of length·width·height(120m·50m·108m).The working face forms a complex spatial structure under the action of mining(the working face clamps between roof,floor and the overlying coal pillar and the surrounding rock induces dynamic disasters easily under the action of static and dynamic load).Through theoretical analysis,the three main points for the residual-pillar-induced dynamic disasters are as follows.A.the pillar clamps between the roof and floor and makes the horizontal stress concentrated and thus leads to great shear stress increase,making the coal pillar prone to shear failure.B.the residual coal pillar makes the internal stress of the rock pillar between B3-6 coal seam and B1-2 coal seams increase,and the internal stress of coal pillar positively correlates with rock pillars gravity G,horizontal stress q0 and high coal pillar section h0.C.affected by the mining of the working face,the internal concentration stress of the coal pillar and the abutment stress of the working face overlaps,leading to great stress increase in front of the working face at the dangerous scope of the residual coal pillar.Byanalyzing the internal stress difference of coal pillars when not affected by the mining and affected by the mining using FLAC3 D,it can be concluded that the top stress of the working face varies obviously at 60~120m distance to the pillar,0~60m distance to the pillar and-60~0m distance to the pillar and they are separately the smooth stress zone(60~120m),the stress transition zone(0~60m)and the stress superposition zone(-60~0m).The stress concentrates significantly at stress transition zone and stress superposition zone and dynamic disasters are easily induced.The working face's safe and efficient across through of the dangerous zone of the residual coal pillar can be achieved by arranging fan-shaped blasting hole in the cross-hole,arranging high phase advance blasting hole in +495 B3 roadway,arranging normal pre-splitting water injection and blast holes in advance and arranging rock column precracking water injection and blasting holes and top deep hole pre-split blasting holes to sufficiently release pressure of the dangerous zone of the coal pillar.This study has guiding significance for safe and efficient mining through overlying residual pillar of steeply inclined extremely-thick coal seam working face and rock pillars stability control.