OCR

TOQUEPALA PROJECT JOB EXPERIENCE Prilled ammonium nitrate, fertilizer grade, is extensively used by SPCC as primary explosive in Toquepala mine stripping operations and pit development. It was also used for the milk of blasting work performeed by SPCC in the required concentration area excavation. Ammonium nitrate was first tested for use on Railroad blasting in June, 1957. Tests proved so satisfactory that there after and until facility completion it was substituted almost entirely for gelatin dynamite and bag powder in such work. In drill holes from 2 l/2" to 5 3/8" diameter, consistently good results were obtained, equal to those obtained with 40% dynamite. As a general rule, ammonium nitrate was not used in holes ranging 1" to 2 3/ " diameter unless dynamite was in short supply. Job experience indicated that such, sized holes, when using ammonium nitrate, required a greatly reduced spacing pattern to obtain desired fragmentation. Tight ground was also a firm requisite, although in the stratified formation, satisfactory results were obtained with deck loading, using the ammonium nitrate in the harder strats. Dynamite primers, 6% to 9% of the ammonium nitrate by weight, were used to detonate charge. Approximately the came weight ratio, explosive to round volume, was used for ammonium nitrate a for 40% gelatin dynamite. Diesel fuel in the proportion of 1 l/2 gallon to 100 pounds of ammonium nitrate was added, mixing being accomplished at the blast site just prior to charging drill holes. The extremely dry and arid climate of the general project area was of definite advantage in the economical use of ammonium nitrate. The material is extremely hydroscopic and will cake beyond usability if not carefully protected against moisture. The most practical specification for purchase and shipment is in the 50 lb. airtight poly-ethelyne bags as a protection against moisture damage and for case of transport and handling in rough and remote country.