Abstract:

Tunnels located in limestone area in Yunnan province are subject to serious corrosions. In the excavation of these tunnels, problems, such as serious overbreak, multiple secondary blastings, serious dust after blasting and poor air quality in tunnel, may occur. Therefore, hydraulic blasting, which includes the injection of some water into the blast holes and stemming the blast holes with special materials, is adopted in the excavation of Laogeshan tunnel located in limestone in Yunnan province. During the tunnel excavation, the parameters of the hydraulic smooth blasting are optimized. In the end, optimum blasting effect has been achieved, the content of dust has been minimized, the air quality in the tunnel has been improved and the excavation rate has been enhanced. Compared to the conventional blasting methods, the hydraulic blasting method described has obvious advantages. 

Key words: tunnel in limestone, Laogeshan tunnel, hydraulic blasting, drilling and blasting design, charging structure, effect analysis