A Study of the in Hole Processes Involved During the Loading and Stemming of Angled Holes

Little research has been published on stemming blast holes, particularly on what happens during the process of loading and stemming a blasthole. Previous work has concentrated on the performance of the inert material to find the best way to seal the hole and retain the explosive energy, but little has been done to determine what physically occurs during the loading and stemming process. The major problem with stemming studies is that rock is an opaque material, and the actual mechanisms involved during the stemming process cannot be viewed. For this reason, tests were performed using clear tubes to simulate a blast hole with ANFO used as the explosive. The tests incorporated different hole angles, different tube sizes, flow rates for both ANFO and stemming, and four types of stemming. A video camera was used to capture images for each test. It was found that complex interfaces developed between the ANFO and stemming depending upon the hole angle and the flow rate of the stemming. These interfaces varied from steps to streamers of ANFO extending up through the stemming for considerable distances. The recommendations from this work for loading and stemming angled blastholes to avoid problems are the ANFO should be loaded as quickly as possible, then an initial smaller volume of stemming should be loaded slowly, then stemming may continue as desired.Little research has been published on stemming blast holes, particularly on what happens during the process of loading and stemming a blasthole. Previous work has concentrated on the performance of the inert material to find the best way to seal the hole and retain the explosive energy, but little has been done to determine what physically occurs during the loading and stemming process. The major problem with stemming studies is that rock is an opaque material, and the actual mechanisms involved during the stemming process cannot be viewed. For this reason, tests were performed using clear tubes to simulate a blast hole with ANFO used as the explosive. The tests incorporated different hole angles, different tube sizes, flow rates for both ANFO and stemming, and four types of stemming. A video camera was used to capture images for each test. It was found that complex interfaces developed between the ANFO and stemming depending upon the hole angle and the flow rate of the stemming. These interfaces varied from steps to streamers of ANFO extending up through the stemming for considerable distances. The recommendations from this work for loading and stemming angled blastholes to avoid problems are the ANFO should be loaded as quickly as possible, then an initial smaller volume of stemming should be loaded slowly, then stemming may continue as desired