If the maxim in building is measure twice, cut once, then the underground mining equivalent would be to measure production hole deviation and analyze before blasting. Underground mining is challenging and the environment unforgiving of mistakes that often carry cost and safety implications.
Imdex commercial manager underground survey applications Mike Ayris has been promoting the importance of surveying blastholes since he founded Downhole Surveys in 1989. For him, the process is not drill and blast; it’s drill, measure, analyze, and blast.
Imdex is developing a new system for the job: Imdex Bolt, a production hole survey tool for underground applications measuring blasthole deviation using a north seeking gyro. Boltis in the commercial prototype phase and has been installed at four sites with two trials underway.
Recent design changes have reduced the weight, making it easier to deploy overhead, thereby solving one of the key challenges of working in an underground environment – and from ground level.
The original Bolt had a depth limitation of about 20 metres, but the new version is accurate at a depth of 30 metres. Knowing accurately the deviation avoids the most common problem: stope hang up or bridging. Surveying and measuring the deviation is one way to avoid this.
Engineers typically designed blast holes to have a maximum deviation of 3%, but experience shows that few holes fall within that specification, with some deviating by as much as 17%.
“With Bolt we are trying to create a system that is on every underground mining operation so that blast holes are routinely measured.
“It’s not just drilling, filling the hole with explosives and hoping for the best. Now it’s drilling, surveying, reviewing and analysing the data, and making adjustments to the pattern based on that information before firing,” said Ayris.
For further information visit www.ImdexLimited.com.
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