Abstract：When tunnel face of mining meets gas-bearing fault,sediment interface in rock pillar will be damaged by gas. Based on flow-solid theory and cohesive unit of T-P damage evolution standards,numerical simulation of a large scale gas outburst accident in the slant of track 21 of Daping coal mine in Western Henan was conducted by secondary development of ABAQUS. The results showed that the two sediment interface in rock pillar were first damaged because of the combined effect of gas pressure in fault zone and secondary stress caused by tunnel excavation. As the tunnel was excavated to fault zone,the erosion of gas turned to be strengthen and the damage of sediment interface increased sharply and extended to the tunnel face,but the damage effect of different levels were not the same. When the distance between excavation surface and fault zone were19,17,15 m,the upper level produced corresponding damage cracks which were 6. 2,9. 7,13. 4 m at length,while the cracks in lower level were shorter and the length of them were 4. 1,4. 6,4. 8 m. At the same time,the gas penetration dramatically extended and high pore pressure zone with a value of 3. 5 MPa began to appear at the place 1 ~ 2 m away before excavation surface. The calculation results indicated that the upper level was easily damaged which it had a strong interface difference and the crack surface after damage. When the cracks are eventually through the rock pillars between tunnel face and fault plate,namely the length of cracks reaches the safe thickness of rock pillars,the gas will break through the impedance of rock and produce impact pressure.

Keyword：sediment interface;damage softening;gas penetrate expansion;advance outburst;safe thickness of rock pillar;