Abstract:

Due to the problems of low working efficiency，short cyclic footage，and high excavation cost of per meter roadway in traditional roadway excavation techniques such as air leg rock drill machine drilling and short hole blasting used in underground mines，in order to solve a series of mentioned issues，a new tunnel excavation technique，that is，medium length hole blasting technique of compound barrel straight cutting of equal diameter empty hole in tunnel excavating was well proposed in the present work.Meanwhile，corresponding blasting parameters of the technique were designed.Based on the YT-24 air leg rock drill machine drilling，short hole blasting，DF20-2BD drill jumbo drilling and short hole blasting，DF20-2BD drill jumbo drilling and medium length hole blasting，respectively，the field experiments of the specific mine were carried out under the condition of completing the same length （30 m） tunnel excavation.Some of data indicators were produced by three different methods.Namely，drilling and blasting such as drilling time consuming for each meter，drilling and blasting cost of per meter roadway and average cyclic footage were obtained in the experiments.The results showed that the developed technique can not only reduce the drilling and blasting cost，but also improved the average cyclic footage effectively by adopting DF20-2BD drill jumbo drilling and medium length hole blasting technique，which proved to be an efficiency and economical method of tunnel excavation.

Key words: tunnel excavation, medium length hole blasting, compound barrel straight cutting, blasting parameters, average cyclic footage