Study On The Mechanism Of Rib Spalling In Working Face With Steeply Dipping Coal Seam And Large Mining Height Under The Coal Gangue Interbedded Roof

Steeply dipping coal seam refers to the coal seam with an inclination angle of 35°?55°,which is recognized as a hard coal seam at home and abroad.Especially when the thickness of the coal seam is large and the roof is a coal gangue interbedded roof,rib spalling and roof caving in front of the shelf occur frequently,and the safe and efficient mining of the working face is extremely difficult.Taking the 25213 working face of the 2130 coal mine as the engineering background,Comprehensive use of theoretical analysis,physical similarity simulation,numerical calculation,and field test research methods,the strength characteristics of the coal gangue interbedded roof,the deformation and failure laws of the surrounding rock of the coal gangue interbedded roof with steeply dipping coal seam and large mining height,and the load and deformation characteristics of the coal wall in working face under non-uniform filling conditions in the goaf are analyzed,and disclose the mechanism of rib spalling in coal face with steeply dipping coal seam and large mining height of coal gangue interbedded roof.Research shows:The roof of coal gangue interbedded is a composite roof of soft coal and hard gangue.The strength of coal in the gangue layer has a great influence on its overall strength.As the thickness of the coal line increases,the overall strength of the coal gangue interbedded roof decreases and the space for crack development is larger;the gangue layer enhances the strength and stability of the coal gangue interbedded roof to a certain extent.In the process of face mining,the breakage and migration of coal gangue interbedded roof have obvious characteristics of time sequence and imbalance,the tendency to stack gangue along the working face has non-uniform filling characteristics.Compared with the general roof working face,the coal gangue interbedded roof is prone to leaking in front of the shelf,the working resistance of the support is reduced,the peak bearing pressure peak and the influence range are farther from the coal wall,but the cracks in the top area of the coal wall are well developed.Under the influence of non-uniform filling in the mined-out area,the vertical stress and displacement distribution of the coal wall has the characteristics of "largest in the middle,second in the upper part and smallest in the lower part".The coal wall plastic damage range in the upper and middle areas of the working face is wide,mainly shear failure.The lower the strength of the coal gangue interbedded roof composite structure,the lower the vertical stress and displacement of the coal wall.Compared with the general roof,the vertical stress and deformation and failure tendency of the coal wall are weakened.The zoning characteristics of coal wall loading in coal gangue interbedded roof working face are:the middle and upper areas are higher than the lower areas.The loading and deformation of coal walls along the vertical direction are asymmetric,and the most vulnerable position is the middle and upper areas of the working face the top of the coal wall.The criterion for determining the coal wall instability strength is given,and the main factors affecting the stability of the coal wall are obtained.This paper analyzes the causes of rib spalling in coal gangue interbedded roof with steeply dipping coal seam and large mining height,and puts forward comprehensive prevention and control measures for coal gangue slabs,such as coal gangue interbedded roof caving prevention and control measures,coal wall pre-reinforcement technology,etc.The application shows that the problems of rib spalling and roof caving in the working face are alleviated.Research can provide a theoretical basis for safe and efficient mining of working face under similar conditions.