Abstract: Blasting excavation of tunnel would give rise to damage of surrounding rock inevitably. In this article, the damage evolution of surrounding rock during blasting excavation is simulated in LD-DYNA, a 3-D dynamic finite element software. The influence of jointed surface and excavation procedures on damage evolution are analyzed in emphasis. The headrace tunnel of Yuwa Hydropower Plant is selected for case study. Results show that during blasting excavation process, the damage perpendicular to joint surface is weakened, while the damage parallel to joint surface is exacerbated. Blasting excavation procedures, excavation footage and single dosage contribute to rock damage obviously, which however, could be weakened effectively if measures of layered excavation, footage decrease and single dosage control are taken. The research achievements are of guiding significance for reducing over-excavation and ensuring stability.

Key words: headrace tunnel, blasting excavation, damage of surrounding rock, jointed rock mass, excavation sequence