Abstract: A close distance coal seams in a coal mine is selected as a case. Deviatoric stress distribution under coal abandon pillars #8 is simulated with FLAC3D. Research results are as follows: (1) Deviatoric stress field in floor distributes as diffusion, the farther the distance is, the wider the range spreads; it transfers from border to floor in 45o direction; (2) When the width of pillar is narrow, the deviatoric stress influence depth at midline and border is shallow; with the width increasing; deviatoric stress at floor varies obviously and the influence depth is deeper; when the coal pillar width is wide enough, middle part is as stress of primary rock; (3) In the same horizontal plane, deviatoric stresses are distributed as saddle shape, with pillar width increasing, the pillar midline and border increase at first and then decrease; and the position of deviatoric stress peak at coal pillar border has little change; (4) as to a certain coal pillar width, deviatoric stress peak at border decreases in vertical direction and its tendency is slower; meanwhile, the peak is far away from coal pillar quickly and its tendency gets faster. Through vertical stress, horizontal stress and shear stress analytical solution, a floor deviatoric stress analytic formula is derived; the analytic solution is consistent with the simulated result. In this case, track roadway 9205 has a 20 m distance from coal pillar border (inboard-type); return airway 9205 is located in coal pillar border; transportation roadway 9205 is located in coal pillar midline, track roadway 9205 maintenance effect is the best of them, which proves that the inboard-type layout roadway with an enough distance from coal pillar bears a little deviatoric stress. Macrostress field is more suitable to the roadway surrounding rock self-stabilization.

Key words: coal pillar, floor, uniform load, deviatoric stress