Abstract：With numerical simulation method，the distribution law of coal pillar support pressure in the floor was studied. The result shows that stress distribution of floor under coal pillar has obvious heterogeneous characteristic in that the highest stress concentration lies under coal pillar and concentration degree decreases quickly away from coal pillar. The reason that roadways were easy to transform and fail under heterogeneous load was analyzed. Under the heterogeneous load，the roadway support structure is subjected to emergent partial overload and produces local failure and will lose its stability. It is pointed out that the influence of the heterogeneity of stress distribution on the bottom plate under the coal pillar should be considered when laying the roadway of ultra-close lower-seams besides avoiding the coal pillar abutment stress concentration area. The heterogeneous degree can be measured by the rates of stress variation. In-situ observation confirmed the method，which indicates that the proposed methods are feasible to the study of reasonable position of the roadway for ultra-close lower-seams. The results have references to the layout of roadway with similar conditions.
