Presentation and verification of “cantilever beam-articulated rock beam” composite structure in shallow buried working face

Affected by its special geological occurrence conditions, it is impossible to form complete overburden rock "three zones" in shallow coal seam mining and the bearing structure formed cannot exist stably.After a period of struc-tural instability, the special roof weighting characteristics of shallow-buried deep seam are formed.Based on the special roof breaking and movement characteristics of shallow coal seam, this paper explores the rock breaking movement characteristics and overburden structure form of shallow longwall working face through similarity simulation and dis-crete element simulation, and puts forward the composite rock structure of "cantilever beam-articulated rock beam" in the overburden of shallow working face, in which the articulated rock beam structure is formed by broken main roof rock, and bears the load of itself and weak rock layer under "cantilever beam".Besides, the articulated rock beam is also affected by the cantilever beam fracture subsidence load, and its instability load acts on the support of the working face through the direct roof.The cantilever beam structure is formed by the upper rock strata above main roof, which bears the load of itself and covers the loose layer, and its breaking subsidence step is larger than the "articulated rock beam" instability step.The two-stage rock stratum structure locates in different strata, their formation and instability are different and affect the mining space together.Combining with the measured results of ground pressure and ground subsidence law of typical shallow working face, the composite structure of cantilever beam and articulated rock beam is validated.Through the stress state analysis of the two-stage rock stratum structure of "cantilever beam-articulated rock beam", it is concluded that the sliding and instability of the "articulated rock beam" structure caused by the fracture and subsidence of the "cantilever beam" is the root cause of the roof cutting along the coal wall in the shallow-buried longwall face, and also the main source of roof load affecting the safe mining.Therefore, the control principle of roof cutting disaster in Shallow-buried working face is put forward.