Replacement of Dynamite with ANFO in Tunneling

In resent years, dDrilling and blasting is the most applicable methods of excavation of underground structures. In tunnel blasting, the pattern design and the selection of type of explosive used, play a crucial role in achieving the desired results. In Iran, the common explosive used in tunnel blasting is dynamite, which is very expensive compare to ANFO. In this research, an investigation was carried out to substitute dynamite as a relatively expensive explosive but with high specific energy with ANFO as a relatively cheap explosive with low specific energy. Tests were carried out in Abasaleh Almahdi tunnel, a road tunnel, connecting Eghlid city to Yasooj city, Iran. At the first stage of the research, the existing pattern was modified (two tests) to improve the results obtained. HCF (Half-Cast Factor), Over Break (OB), Advance Rate (AR) and Specific Cost Factor (SCF) were used to do the quantitative assessment. In the second stage of the research, based upon the modification carried out, substitution of dynamite with ANFO was studied by 10 designed blast tests designed and the best dynamite-ANFO substitution option was suggested. The results obtained showed that by substituting dynamite with ANFO, as well as an AR of 95%, an OB of less than 5%, a HCF of more than 20% and a reduction in explosive costs up to 32% can be achieved.