The rock damage induced by blasting excavation is an important influence factor to rock stability. Blasting damage characteristics of the diversion tunnel in Jinping cascade II hydropower station were studied by numerical analysis and field testing. The results of numerical analysis show that the in-situ stress redistribution caused by diversion tunnel excavation is the main reason for rock damage

the coupling effect of blasting load and in-situ stress redistribution increased the rock damage zone about 1.2 meters; if the dynamic damage effects of transient unloading of excavation load is taken into account

the rock damage zone would increase by 1.9 meters compared with only considering in-situ stress redistribution; the average damage zone depth is about twice times than the damage zone induced by in-situ stress redistribution. Field test results verify the numerical analysis results well. It is shown that the blasting excavation can increase the rock damage zone significantly. In the process of Jinping cascade II hydropower diversion tunnel excavation

the damage effects of blasting load and transient unloading of excavation load should not be ignored