Study on Upper Liberated Seam Mining to Pressure Releasing Function of Low Seam

Based on the geological conditions and mining parameters of the coal mining face in No.12 mining block of Jining No.3 Mine,a similar simulation in the la b was conducted on the mining process of the coal mining face in the uper liberated seam.In combination with the site measured results, the pressure releasing function of the uper liberated seam mining to the low seam was analyzed.The study results showed that after the liberated seam mined,selling and deformation occurred in the I oW seam and rock strata and the integrality of the low seam was destroyed. Great number of the elastic energy were released and the seam stress of the liberated seam were released.The max stress released rate was 19.2% and a good pressure releasing effect was well played.The calculation of the site results showed that the pressur e releasing angle along the coal mining face strike was 77° and the inclined pressure releasing angle was 79°.