LAUSR

Reasonable coal pillar size is a necessary condition for high strength and safe mining of coal face with double roadway arrangement. On the basis of the lack of theory of coal pillar retention between alleys and taking coal pillars between alleys as engineering background, this paper analyzes the mechanical behavior of coal pillar bearing arranged in double roadways, calculates the width of plastic zone of coal pillar according to SMP criterion, and determines the minimum theoretical size of coal pillar between alleys with elastic core width of 0 m is 13.5 m. FLAC 3D software was used to simulate the coal pillars of 13.5 m, 17 m and 20 m, respectively, to obtain the distribution characteristics of surrounding rock stress and plastic zone during the primary and secondary disturbances of coal pillars between roadway. It can be concluded that with the increase of the width of the coal pillar, the peak stress in the coal pillar decreases, the plastic zone around the roadway shrinks and the bearing capacity of the coal pillar increases. It is found that the elastic core of 13.5 m coal pillar is 5 m and 9 m respectively, and the increase of coal pillar width leads to the broadening of elastic core. Considering the above coal seam are weak aquifer, have an old goaf water, and adjacent rocks of coal seam has obvious degradation under the influence of water features, adverse to the mining working face, especially on floor stability, lastly, between the pillars of 20 m field test, to effectively control deformation of coal pillar, proves the rationality of the design coal pillar between roadway.