Study On Mining Pressure Characteristics And Control Technology Of Fully Mechanized Mining Face In Thick And Hard Sandstone Roof

With the advancement of the working surface,due to its unique physical and mechanical properties,the thick and hard sandstone roof cannot be collapsed in time.Resulting in a stress concentration zone behind the work surface,and the impact dynamic pressure generated by the sudden breaking of the thick and hard roof triggers a series of disaster accidents seriously affect the normal recovery of the working face.This paper takes the 1611 A working face of Zhangjibei Mine as the research object,and adopts theoretical analysis,physical experiment simulation,numerical simulation and engineering practice to study the breaking mechanism,slump deformation characteristics and roof weakening control of thick sandstone roof.The research has a certain guiding role for the safe recovery of working surfaces in similar working conditions.Firstly,the mechanical model of the thick and hard sandstone roof is established.The top plate is regarded as the cantilever beam for mechanical analysis.The period of the thick hard roof is obtained.The pressure step is proportional to the thickness of the roof,and the thickness of the roof is related to the thickness.The caving span of the roof increases as its thickness increases.In the similar simulation test,after the hard top plate is weakened,the roof of the goaf is degraded in time with the advancement of the working face.the initial caving span of the main roof is 35 cm,the periodic caving span is 20~25cm,and the problem of largearea suspended roof in goaf is effectively controlled.Face on both ends of the overlying strata caving form characterized by layered type caving,the strata caving presents a symmetric distribution,and presents the oblique type caving working face end surrounding rock,strata on the working plane after "stable instability-stability",the process of maximum subsidence is 5.92 cm,surrounding rock strata subsidence decreases down from the lower strata to high strata.The numerical simulation results show that with the recovery of the working face,the peak value of the supporting pressure of the working face gradually increases,and the peak point is about 40 m in front of the working face.Before and after the weakening of the roof,the vertical stress of the surrounding rock first increases to the limit value and then reduces the stress.The lowest point is then increased to the peak value of the leading support pressure and then reduced.Finally,the vertical stress of the surrounding rock tends to be stable.From the low rock formation to the high rock formation,the vertical stress variation of the surrounding rock decreases.Through deep hole pre-splitting blasting and mine pressure observation on the thick and hard sandstone roof of 1611 A working face,the bearing surface of the working face and the macroscopic mining pressure appear(the pressure step,the peak distribution of the bearing force,the coal wall gang,the roadway)The top and bottom plates and the two sets of deformations,etc.are further improved and controlled,so as to optimize the implementation scheme and technical parameters of the deep-hole pre-split blasting of the thick and hard sandstone roof,which ensures the safe recovery of the working face and provides a certain guiding significance of the thick hard roof.Figure:[40];table:[8];reference :[58];...