In the practice of gas control engineering in coal mine,pre-split blasting is one of the effective measures to improve the permeability of low-permeability coal seams,and its effect depends on the generation and expansion of blast cracks.In order to research the generation and expansion characteristics of pre-split blasting cracks in low permeability coal seams,the blasting process is regarded as a plane strain problem.Then the numerical model for pre-split blasting is constructed based on the HJC model,the HIGH_EXPLOSIVE_BURN material model,the JWL equation of state,and meshing with hexahedral elements.Furthermore,the LS-DYNA software is used to solve the numerical model so that to analyze the generation and development process of the crushed and fractured zone areas around the blasting hole.In addition,the characteristics of cracks and stress changes in the coal body around the blasting hole are also worth discussion.Finally,reasonable suggestions are given for the selection of pre-split blasting parameters in coal seams.The research shows that when No.2 rock emulsion explosive with a diameter of 94 mm is charged into a blast hole with a diameter of 120 mm,the crushed area around the blast hole is 1.43m 1.25 m,and the radius of the fractured zone is about 3.4 m with the length of the main crack within 2.0~2.62 m.The connection direction between the blasting hole and the control hole is mainly affected by the compressive stress,while the tangential direction is mainly affected by tensile and compressive stresses.And the left and right sides of the control hole are also significantly affected by tension and compression.The stress waves generated by successively initiated blasting holes are superimposed on the stress field in the fractured area,which has a certain influence on the generation and development of the cracks.The reasonable layout of the pre-split blasting holes in the coal seam should be comprehensively considered with the attenuation effect of the coal seam on blasting stress waves,the reflection effect of the uncharged hole wall on the blasting stress waves and the superposition of blasting stress waves.