Instability mechanism and control of surrounding rock in composite roof working face under concentrated load
The downward mining method of multiple coal seams layer by layer,when the distance between the coal seams is relatively close or the roof of the lower coal seam is a composite roof,the concentrated load of the residual coal pillars in the upper coal seam will have a significant impact on the control of the roof of the lower coal seam working face.Through theoretical analysis,numerical simula-tion,on-site testing and verification,the characteristics of mine pressure manifestation in the composite roof working face under concen-trated load were obtained.It was believed that there was a phenomenon of large and small periodic pressure in the working face below the goaf,while the pressure in the area below the coal pillar was generally low,and the pressure characteristics were unclear.Further a-nalysis suggested that the core of controlling the surrounding rock of loose composite roof was to control the early separation and deform-ation of the roof,and the given deformation pressure of the support on this type of direct roof should be much greater than its intact state.A method for determining the supporting strength of composite roof working face under concentrated load and shallow hole grouting technology for surrounding rock control in the stress affected area of coal pillars were proposed,providing a basis for controlling the sur-rounding rock of composite roof working face under concentrated load.
concentrated loadcomposite roofsurrounding rock controlrib spalling and roof fallsupporting strength
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