Dynamic response of bolting support roadway under blast loading to pressure relief
Blasting is an effective approach to pressure relief in coal mine roadway with rock burst tendency. To investigate the effect of blast impact on bolting support system and surrounding rock, dynamic response of bolting support roadway was numerically studied using FLAC3D. Firstly, the excavation and the bolting support of roadway were conducted to achieve the static equilibrium and then, with the built-in dynamic mode, blasting to pressure relief in the drill hole was performed in dynamics. The evolution of rock bolt axial force, grout shear stress and deformation of coal roadway were analyzed with regard to the time. The results show that, in the process of blasting impact, (1) the axial force of the first free bolt length (in the near end of roadway) increased by 6.54% in maximum; the shear stress of grout changed 43.6% in maximum. Hence, the near end of rock bolt and the bolt grout are weak points which may firstly fail under blast loading; (2) With the same distance to blasting position, the axial force of rock bolt is affected by its installation angle inclined to the blast borehole; and (3) the peak value of the axial force due to blasting impact can be reduced by adopting millisecond delay blasting approach. The maximum increment of axial force is reduced from 3.94% to 2.86% while using millisecond delay blast method. However, the influence of different delay time interval on the maximum increment of axial force is not significant. This study provides effective technical guidance for coal roadway support with rock burst potential in Qianqiu coal mine, China.