GPS technology improves rig performance

Advances in technology are helping to deliver both improved hole straightness and BLAST detonations for better fragmentation

No matter how carefully the load and haul functions and crushing and screening processes have been designed, if the feed stock does not match the design, any efficiencies are lost. Improvements in drilling techniques and blasting technology are helping to deliver benefits that mean the actual blast matches the design more closely than ever before.

Reduced flyrock and better breaking are just two of the benefits to quarry operators of these advances but the biggest gains must be in terms of reduced costs and vibration. Better blasting is helping to minimise the amount of explosives needed and adding productivity throughout the production by achieving the optimum fragmentation.

Technology

One of the biggest advances in terms of drilling technology has been the addition of GPS capabilities to rigs. Use of modern laser scanning techniques means that the blast design is more bespoke than ever before, but this calls for precise blast hole drilling and this is what GPS has added to the process.

GPS technology ensures that not only is the hole collared in the correct location without the need for positions to be surveyed and marked, the bore is more straight and true to the planned azimuth than was previously possible.

Introduction of new software that can plan blasts in real time also remove the problems associated with not being able to drill holes in the planned positions. Such software can recalculate the ideal hole length and orientation required to deliver the blast outcome needed based on a slightly offline hole position from the original design.

According to Germany-based 1932 Geo-Konzept, systems like its Quarry 6 software, which is used by 385 Atlas Copco's GPS-enabled SmartRigs, makes it very easy to keep accurate records of blasting. "It is very easy to get answers to questions such as the distance to the vibration monitors or nearest buildings," explained Geo-Konzept's Johannes Kutschera. "Of course it also makes it easy to continuously update mine maps. Last but not least saving data this way offers precise accounting for quarries." The company has recently extended its software offering with the launch of QuarryDetonator which can be used to model overlaps and connections before blasting. The system also allows users to closely monitor the cost of the blast and look at the impact of changing the design on not just the blast results but also the financial implications.

While advances in positioning and alignment are helping to improve hole straightness, Atlas Copco has said that selecting the right tool for the application is still important. To emphasise this message, the company points to its recent work with the drilling and blasting contractor working in 1934 Norsk Stein's Jelsa Quarry in Norway. Bertelsen & Garpestad is helping Norsk Stein to ramp up production from 6million tonnes per year to 10million tonnes and was looking to improve its operation to aid this.

Atlas Copco suggested the company use the Secoroc Coprod top hammer drilling system and B&G trialled a ROC L7 40 CR drill rig, fitted with the system and a COP 4050HE-CR rock drill.

The system was used to drill 165mm diameter holes 15 to 18m long with a 5.6 by 4.2m spacing into the ganodiorite, which has a high volume of quartz making it an abrasive material. B&G has said that it has been impressed with the result in terms of both straightness and also drill rate.

Environmental advances

Silenced rigs launched in the last few years have significantly reduced the noise associated with drilling. While these were intended for use on construction sites, some quarries with close neighbours have also found the systems to be useful.

The next issue that rig designs need to tackle more effectively is that of dust - something 460 Sandvik is doing with its new DI550 DTH rig. The company has said that the rig's new efficient dust collector has a non-stop cleaning system to restrict the amount of dust emissions into the environment. The dust collector also improves filter lifetime, reducing the need for maintenance.

Vibration is a major issue concerning quarry operators when it comes to blasting and trying to minimise the impact on neighbours around the quarry is an important task.

"Detailed quarry design is needed to ensure vibration is within specified guidelines but wider adoption of electronic detonators is also helping to optimise the timing to minimise the vibration and improve the quality of the blast," said 1939 GWP blasting engineer Emily Vallance.

"Electronic detonators came on the market a few years ago - they are expensive but more and more companies are now using them and seeing the benefits." In addition to providing consultancy services to the quarry sector, GWP also has a cooperation with 1749 Leeds University which has been running for many years but has now been formalised as a separate company called 1937 BlastLog, which specialises in vibration monitoring and predicting.

The cooperation started off as a PhD study to optimise use of electronic detonators at 725 Lafarge's Whitwell Quarry in the UK. "There is a railway line next to the site and previously Lafarge could only blast up to 80m form the railway line," explained Vallance. "But the greater control that could be demonstrated with electronic detonators enabled this boundary to be dropped to 40m, allowing the quarry to access more reserves." According to Vallance, quarry operators need to be more proactive on monitoring. "Some are good at planning blasts and are well under vibration limits by design but others fall below more by luck than prediction and are not using data for modelling," she said. "This is all okay while they are below the limits but if something happens and they exceed them, then they do not have the knowledge to understand why or prevent it happening again."