Study on Stress Distribution Laws of Coal Pillar of Fully-Mechanized Top Coal Caving Face in Complicated Ultra Thick Seam

In order to know the coal-pillarOs stress distribution and the roadway0s deformation law of No.3-5 seam fully mechanized top coal caving faces, model GYW25 borehole stress sensors and model KJ216-F2 intrinsically safe type monitoring stations were embedded into two surveyed areas which were selected in tailentr y of the fully mechanized top coal caving face based on an investigation of the coal-pillarDs stress behavior condition. Dynamic monitoring data of the coal-pillarOs stre ss and the roadway0s deformation showed that the pillar Os stress fluctuation was acute, and the peak data located in an area which was 25 m away from 8210 mining face and 13 m away to 8208 face. In the case of a 38-meter-wide coalpillar, the roof to bottom cumulative convergence of an area within the range of 100 m in front of 8208 mining face was 1 000 ~ 1 400 mm, value between two sides was 600 ~ 1 000 mm, which indicated that the coal-pillar with a width of 38 m was safe and reasonab le under the condition of relative construction between mining and driving. And further analysis of the position of the stress distribution peak suggested that the width of the coal-pillar could be compressed to a range of 30 m to 35 m.