Determination of Blasthole Parameters Based on Field Results (TECHNICAL NOTE).

Correct selection of coefficients for blasthole parameters in Ghalat limestone mine in Shahr-e-kord of Iran has resulted is designing and performing 20 blasting operations. After each blast, fragmented rocks larger than one square meter, called oversize, are estimated and prepared for secondary blasting. Next blasthole pattern were designed based on previous blasting results. The results of these field operations studies have shown that the best ratio between spacing (S) and burden (B) in Ghalat limestone mine is 1.25. The ratio of cut height (H), subdrilling (J) and length of stemming (T) to burden are: 4, 0.5 and 1 (H/B=4,J/B=0.5,T/B=1). Field results of these relations have shown that more than 90 percentage of fragmented rocks have sizes less than one square meter and the cost of production is reduced by 18.9 percentage.