Study on Stable Layer Position in Bidirectional Concave Shaped Roadway Layout System in Thick Coal Seam

In order to research stable layer in bidirectional concave shaped roadway layout system in thick coal-seam, firstly, we find out the factors affecting the stable layer position by theoretical analysis: coal strength and fractures in different layers of coal, thickness and position of relatively stable gangue in coal seam, the coal loss rate, and whether the roadway roof anchor can come into hard and compact rock or not. Secondly, based on the loss rate of triangle coal, we determine the distance from stable layer to coal seam floor by theoretical calculation. The research shows that: the loss rate of triangle coal decreases with the increase of the length of the working face and the decrease of the distance from stable layer to coal seam floor, and we obtain the relation between the loss rate of triangle coal and stable layer position. Finally, we apply simulation analysis to analyze the influence law of the stability of surrounding rock by the stable layer position.