Large deformation failure mechanism of surrounding rock for gateroad under dynamic pressure in deep coal mine

In terms of the large deformation unstable failure and its control problem of deep dynamic pressure in gateroad,the mechanical model of circular roadway under dynamic pressure environment in deep mine was estab- lished. Also,the implicit boundary equation of plastic zone around deep dynamic pressure gateroad was deduced. Based on this,the morphology evolution rules of plastic zone in deep dynamic pressure roadway was deeply analyzed. Then the mechanical conditions for the formation of the class I and class II butterfly-shaped plastic zone were illustrated,and the definitions of malignant expansion of the plastic zone and its criticality were made. Finally,the failure mechanism of deep dynamic pressure gateroad was revealed. The results indicate that it is easier for surrounding rock to produce the butterfly-shaped plastic zone under dynamic pressure effect in mining than the normal conditions,and the develop- ment size of butterfly leaf,plastic damaged zone are greater. With the increase of dynamic pressure influence,the re- gional stress field of gateroad becomes extraordinary high stress field and the plastic failure of roof,floor and ribs ex- pand to deep rock mass,which leads to the more serious deformation and formation of malignant expansion of plastic zone. Eventually that cause a large deformation failure of surrounding rock. For the gateroad design and supporting un- der deep dynamic pressure,how to avoid or reduce the impact of dynamic pressure,improve surrounding rock stress environment and decrease the failure depth of butterfly leaf must be all considered adequately,which are beneficial to the maintenance of gateroad.