Laserfiche WebLink
Mr. Larry Petrino <br /> August 15, 1988 <br /> Page Three <br /> Smooth-Wall Blasting at the Final Wall <br /> In the current practice, a smooth-wall approach is implemented by reducing the spacing to <br /> 3 ft centers at the final row with every other hole charged. This increases the actual spacing by <br /> 20 percent and reduces the powder factor by 20 percent. However, the burden remains the same. <br /> We do not see any practical benefit to drilling the extra holes and then leaving them empty. <br /> A more conventional smooth-wall approach could be implemented to include: <br /> • reduce the burden and spacing on the final row; <br /> • reduce the charge density; and <br /> • introduce a significant delay on the final row. <br /> The charge density is generally reduced by putting a smaller diameter plastic or cardboard <br /> tube in the hole. For example, a one inch diameter charge is recommended for a 3.5 in. hole <br /> using standard dynamite. This is difficult to achieve using ANFO in a small hole. However, one <br /> of our clients (Asamera Minerals (U.S.), Inc.) uses ANFO mixed with styrafoam beads <br /> (manufactured by Dupont) to achieve the reduced density in similar size bench holes used in <br /> their underground operation. <br /> I look forward to discussing the potential for implementing these modifications in the <br /> current practice. Please contact me if you have any questions. <br /> Sincerely ours, <br /> CA <br /> Carl E. rechtel <br /> Senior ssociate <br /> CEB/klg <br /> cc: Mike Fouts, Sunnyside <br />