Study on evolution law of bearing stress of coal pillar in steeply inclined coal seam section of mountain topography

Abstract The stability of section coal pillar in steeply inclined coal seam under mountain landform is beneficial to the stability of surface and mountain. Based on the engineering background of N2821 working face in Fengchun coal mine, the force model of the steeply inclined coal pillar under the mountain and the three-dimensional numerical model of the landform characteristics of the mountain are established; the necessary conditions and reasonable size calculation of the steeply inclined coal pillar under the mountain are analyzed; the bearing stress evolution law of the steeply inclined coal pillar under the mountain is studied. The research shows that when the dip angle of coal seam is greater than the arctangent value of the sum of friction coefficients of upper and lower surfaces of coal pillar, the coal pillar has sliding instability ; the reasonable coal pillar size of N2821 working face is 12 m. After working face mining, due to the short size of coal pillar, there is no obvious elastic core area ; with the advancement of the working face, the coal pillar in the middle of the goaf is most affected by the stress superposition, and the shear stress of the coal and rock mass gradually increases and concentrates on the coal pillar ; although the coal pillar is plastically damaged by mining, it still has good supporting capacity. The field monitoring data analysis is consistent with the simulation conclusion, and the coal pillar size is reasonable. The research results have certain reference and reference significance for coal pillar retention under similar conditions.