Study on reasonable position of mining roadway under repeated mining overburden structure in shallow buried close distance coal seam: A case study

In order to determine the reasonable position of the mining roadway in the first mining face of 3-2-2 coal seam under repeated mining of shallow-buried close-distance coal seam group in Shigetai Coal Mine of Inner Mongolia Mining Area, a method for determining the fracture structure of overlying strata in close-distance coal seam group was proposed, and the corresponding fracture structure model of overlying strata under repeated mining was obtained. Based on the overburden fracture structure model, the stress calculation model and numerical model of the residual coal pillar in the 3-2-1 goaf are established, and the stress distribution characteristics of the coal pillar and the propagation law of the floor are analyzed. It is concluded that with the increase of the vertical distance between the floor and the coal pillar, the overall distribution characteristics of the floor abutment pressure gradually change from ‘M’ type to inverted ‘U’ type and finally to inverted ‘V’ type. It is determined that the reasonable position of the mining roadway in 3-2-2 coal seam is below the edge of the residual coal pillar in 3-2-1 goaf, and the corresponding first mining face should be arranged below the residual coal pillar. Through on-site monitoring and borehole peeping, it is concluded that after the application of the roadway, the maximum displacement of the roof and floor is 47.8 cm, and the fracture development of the surrounding rock is within 3 m, and the application effect is good.