Smooth blasting is generally used to excavate rock anchor beam at the underground power station

its aim is to better quality and smaller crushed region. However

the blasting of the main hole damages the smooth layer to a certain extent to reduce the mechanical parameters of rock mass. The more powder is charged each hole and rock mass is over excavation or generate lots of cracks without considering this effect of damage. The 2D dimension elastic-plastic model of rock mass is adopted and the smooth blasting procedures with and without this damage are simulated in the dynamic finite program. According to the results of comparison of maximum effective stresses of different distance of 2 kinds of models

when the effect of this damage is considered

the interval of holes and the burden can be widened under the same condition. The model considering damage is proved by in-site blasting experiment well.