Abstract: Blast hole pre-split orientation(BHPO) is proposed based on the analysis of rock blasting mechanism and pre-engineering experiments. It's a kind of new type pre-split blast model which combines the advantages from large hole size deep hole pre-split blast in the open pit and normal pre-split blast. It's the new improved technology of pre-split blast at present. The BHPO method is based on modern mechanics which could do better on slope protection.

Key words: Blast hole orientation, BHPO, Blasting fracture mechanics, Blasting stress