bstract：In order to study the hypotonic and rheological particularity of a “three soft”coal seam in west Henan,the deformation characteristics of a Ⅱ1coal seam as gas-generation strata and gas-preservation strata are discussed. In addition,the characteristics of stress and damage of coal fracture are explored under fracturing conditions by using ABAQUS platform. Pore pressure cohesive elements and T-P Damage Evolution criterion were used to describe the approximately linear relationship between the soft coal fracture crack width and an extending distance. The research results show that the soft coal fracture stress and damage evolution have a gradual development process over time under water injection fracturing. When the static injection pressure is 5~ 10 MPa and the injection time is about 1 ~ 2 h,the fracture damage range of soft coal can basically be 80 ~100 m. The hypotonic performance of a “three soft”coal seam will be improved greatly.

Keyword：“three soft”coal seam;directional water injection fracturing;crack damage;gas seepage;coalbed methane extraction;