Wide-space effect. The typical drilling pattern has a spacing/burden ratio of 1.25, which has proved to give good rock fragmentation in multiple row blasting. In the 70s, tests were carried out in Sweden with widespace hole blasting with S/B ratios greater than 1.25. The results of the tests showed improved fragmentation up to an S/B ratio of 8. The burden and spacing must be normal in the first row, otherwise the burden will be too small increasing the risk of flyrock.
Typical drilling pattern
Wide-space drilling pattern
By changing the firing pattern instead of the drilling pattern the same wide-space effect is accomplished. This is easy with NONEL UNIDET and its combination of connection units with different delay times. 21
Published on Oct 26, 2008