Abstract: The detonating delay time of millisecond blasting is an important parameter during shaft excavation by one-step deep-hole blasting. If detonating delay time and detonating sequences are reasonable, the millisecond blasting technology has many advantages. The foregoing blasting can create free face and compensating space for the following blasting to achieve the purpose of layered and segmented blasting. Also, the vibration damage of the surrounding rock can be reduced by decreasing detonated explosive charges in every turn. Based on deep-hole millisecond blasting theory, calculation methods of the detonating delay time of presplitting blasting, cut blasting, the same segmentation auxiliary holes blasting and the adjacent segmentation auxiliary holes blasting of shaft excavation by one-step deep-hole blasting are studied. In addition, six kinds of detonating sequences are put forward, such as bottom-up presplitting blasting, up and down before the middle smooth blasting, etc. The one-step deep-hole blasting technique is seen to meet the requirements in the Huaheng coal mine which proves that this research is applicable to other similar projects.

Key words: shaft excavation by one-step, millisecond blasting, detonating delay time, detonating sequences