The stress distribution law and deformation characteristics of coal around the borehole by the drilling cuttings method

The drilling cuttings method is an important approach for predicting the risk of rockburst mines. The stress distribution law and deformation characteristics of coal around the borehole directly affect the amount of drilling cuttings. The third lower coal seam of Jining No.3 Coal Mine is the research object. The variation laws of stress, displacement and plastic zone of coal under the conditions of a single borehole, 2 boreholes with a spacing of 60 cm, 3 boreholes with a spacing of 40 cm, and 6 boreholes with a spacing of 20 cm are analyzed by the numerical simulation method. The results show that the surrounding coal of boreholes is subjected to compressive stress. The borehole location is in the stress relief zone. The two sides of borehole are in the stress increased zone. The maximum supporting stress is between boreholes is about 1.11 times the original rock stress. When the drilling spacing is 60 cm and 40 cm respectively, there are original rock stress zone and stress increased zone between the boreholes. The range of stress increased zone between the boreholes is 0.20 m and 0.24 m, respectively. The range of original rock stress zone between the boreholes is 0.35 m and 0.12 m, respectively. When the drilling spacing is 20 cm, there is only a stress increased zone between the boreholes. The range of original rock stress zone decreases with the decrease of drilling spacing. The range of stress increased zone increases with the decrease of drilling spacing. The top of the boreholes moves downward while the bottom moves upward. The maximum displacement of coal at the top is approximately 1.30 mm. The maximum displacement of coal at the bottom is approximately 1.10 mm. The displacement at the top is greater than that at the bottom. The research results provide important theoretical support for the prediction and treatment of coal mine rockburst.