(1. Chongqing Energy Investment Group，Chongqing 401121，China；2. Science and Technology Co.，Ltd.，Chongqing Energy Investment Group，Chongqing 400060，China；3. State Key Laboratory of Coal Mine Disaster Dynamics and Control，Chongqing University，Chongqing 400030，China)
Abstract：To resolve the problems of low gas draining rate in soft coal seam with low permeability，a new technology of improving seam permeability by pre-splitting blasting on floor rock is proposed. The process of increasing permeability is divided into two stages：firstly forms penetrative cranny area in the interaction of blasting stress wave and detonation gas；secondly forms releasing pressure area by coal-rock caving at the top of the blast cavity. Dynamic variation of blasting stress wave of different drilling intervals was researched by numerical simulation；and it is found that the influence sphere of the pre-splitting blasting is divided into smash area and penetrative cranny area. The smash area is 6 times of the diameter of blast hole；and the tensile wave caused by large diameter pores reflection plays the major role to connect fissures. The optimal space of forming unicom fissures and keeping same high destruction scope with the control hole is 0.9 meter，which is applied to gas pre-drainage engineering in a bottom road of a Chongqing coal mine. The application result shows that the gas drainage flow is 2.8 times of the original，and the gas drainage efficiency is improved by 3.75 times of the original. Besides，it is obvious that the much better results was achieved 20–30 days after blasting.
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2013, Vol. 32 
