Research on the law overburden movement and failure under the influence of double period coal seam mining

Taking the Tongxin coal mine as a case study,the law of overburden movement and failure caused by double period coal seam( DPCS) mining is analyzed by using of key strata( KS) theory,the physical detection and numeric simulation technology. The results show that:( 1) When workface advances to 193 m,the height of overburden fractured zone( OFZ) has a maximum of 174. 7 m;( 2) The height of OFZ caused by 3- 5#seam mining which is obtained by physical detection is about 180 m,the ratio of height of OFZ and mining thickness is 11. 7 ~12. 0 by theoretical calculation and field test;( 3) The floor damage caused by Jurassic coal mining and lack of soft interlayer provide further conditions to connectivity of double period coal goaf;( 4) Jurassic coal mining influences the variation of advanced support pressure of Permo-Carboniferous coal seam. When Permo-Carboniferous coal seam coal workface is located at the bottom of Jurassic coal pillar,the advanced support pressure is increased by 12. 4% than those without goaf.( 5) These results reveal the interactional relationship of DPCS mining,which provides a scientific basis to take security measures to weaken mutual influence of mining.