Study On Movement Law Of Overlying Strata And Surface Of Fully Mechanized Sublevel Caving Mining In Extremely Thick Coal Seam

In the engineering background of extremely thick coal seam mining of Buliangoucoal mine in Huadian Group, this paper study the movement law of overlying strata andsurface of fully mechanized sublevel caving mining extremely thick coal seam using themethod of field observation, numerical simulation and theoretical analysis.According to the key stratum theory, the formation of the structure of the overlyingstrata on F6201working face in Buliangou coal-mine is analyzed. The height ofbreaking zones and the position of basic roof is determined. The combinatorial main keystratum and secondary key stratum are existed in the overlying strata, between themexisting compound effect, and the broken distance is modified through specificconditions. The breakdown instability form of secondary key stratum and main keystratum between the first and periodical weighting is obtained. With the application ofKJ-216on-line support resistance monitoring system, the distribution characteristic ofworking face resistance is observed, the distribution law of strata behavior, advancedabutment pressure, lateral support pressure and the withdrawing gateway’s stratabehavior regularity of extremely thick coal seam top coal caving face is summarized.Through field observation the characteristic of surface subsidence is grasped in thecondition of seriously mining effected. Furthermore, the relationship between key stratabroken and surface subsidence is analyzed via numerical simulation.Studies suggest that the broken basic roof can’t inform “voussoir beam” structure,but “step voussoir beam” structure in the condition of seriously effected by mining in15m extremely thick coal seam; the first fracture of inferior key stratum will causesliding instability and periodic fracture causes sliding instability. But both first andperiodic fracture of combinatorial main key stratum cause sliding instability, which is amain reason that causes seriously working face strata behavior. The distance betweenadvanced abutment pressure peak position to the coal wall and the distance betweenlateral support pressure peak position to the roadway wall in the extremely thick coalseam fully mechanized caving face is longer than normally working face, but the stressconcentration factor is smaller. The combinatorial main key stratum control theoverlying strata and surface subsidence and the largest surface subsidence is10.07m.Because of the combinatorial main key stratum, the characteristic of key stratum fracture and surface footstep subsidence isn’t synchronous, that lags working face for31m.