Open Cut Vibration Management  

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Technology for Advanced Vibration Management, When there's a lot on the line

When you’re blasting close to sensitive infrastructure, you rely on sophisticated technology to predict and manage your vibrations. At Orica, we use our Global R&D and technical capability to find solutions to the blasting challenges previously thought impossible. You can see the results in our blast design and execution, supported by our Electronic Blasting Systems, technical measurement and advanced vibration management software. It’s all backed by the technical service and support you need. That’s the power of partnership.

Managing Vibration Levels to Meet Production

Author: Ben Duncan, Blasting Technician, Orica Mining Services

Coal & Allied’s Hunter Valley Operations engaged Orica Mining Services to conduct an Advanced Vibration Management (AVM™) project in their Riverview pit where a high tension tower, which supplies electricity to a major city is within 40 metres of mining and blasting activities. Hunter Valley Operations has carried out vibration related blasting in other areas of the mine generally at distances in excess of 300m. The goal of the AVM™ project is to maintain an efficient mining process whilst controlling vibration to agreed levels.

Coal & Allied in conjunction with Orica Mining Services Technical Services representatives completed a comparison of the available scenarios with the outcome being that if they were able to blast the complete bench height, they would effectively halve the required amount of blasts and the associated closures of a major road. Maintaining the efficiency of the mining fleet due to blasting in this fashion was projected to save 10% of total mining costs.

To deliver the technical solution required, Orica Mining Services utilised a seed wave superposition model generated from ten single blastholes. This model was designed to predict the expected vibration produced by each blast. The use of the i-kon™ Electronic Blasting System ensured the accuracy of the blast and bulk products from the Flexigel™ range enabled Orica Mining Services to limit the maximum instantaneous charge (MIC), whilst maintaining effective energy distribution.   Rock samples were also collected and modelled proprietary mechanistic blasting models ELFEN/MBM, CPeX and SoH for damage based on the assumed MIC to ensure fragmentation would be acceptable for the design blast pattern. Figure 1 shows a typical output from the Orica Mining Services MBM model.

Orica Mining Services Technical Services designed the blast pattern using SHOTPlus-i™ blast design software and modelled the vibration levels and probability of exceeding the limit for each design.   Figure 2 shows the design of blast 2.

Harnessing the flexibility and accuracy of i-kon™ electronic detonators allowed a blast design, not possible with non-electric initiating systems, firing two to four explosive decks with up to 3 seconds delay between decks.

Flexigel™ bulk explosive was ideally suited to the geology and blast design, allowing a 0.8 density product to be loaded in each blasthole deck to give an effective column distribution whilst controlling MIC.

Hunter Valley Operations Shotfirers, Mick Main and Dave Bennett were trained in the use of the i-kon™ Electronic Blasting System and mentored on bench by Orica Mining Services Technical Services whilst conducting the blasts. This training will allow Mick and Dave to be recognised as certified i-kon™ users for future application of electronic detonators at Hunter Valley Operations.

A total of 4 blasts have been fired successfully by Hunter Valley Operations and Orica Mining Services as the first stage of the project. Vibration levels for each blast have been below the agreed vibration limit for the high tension tower of 50mm/s.

Blast 1 was a calibration blast to verify the parameters for the seed wave superposition vibration model. It consisted of 322 blastholes, loaded with 38 tonnes of ANFO and 323 i-kon™ detonators in a single explosive deck. The distance to the high tension tower was 160m. The vibration result was 20.15mm/s.

Figure 1: MBM fragmentation modelling

Figure 2: SHOTPlus-i™ software showing blast 2 design

Figure 3: Firing Blast 2 adjacent to the high tension tower
 

Figure 4: Hunter Valley Operations Drill and Blast Engineer Ernie Martin pictured with Orica Mining Services Blasting Technician, Ben Duncan.

Blast 4 was fired in two blasts due to inclement weather. A combined total of 200 blastholes were loaded with 27 tonnes of Flexigel™ 80 with 4 decks per blasthole and 547 i-kon™ detonators. The distance to the high tension tower was 39m with Blast A producing 9.6mm/s and Blast B producing 25.6mm/s

Excavation of the first bench is now complete. Blasting will continue throughout 2010 as the mining sequence returns to the area to excavate each bench.

Orica wishes to thank Ernie Martin, Drill and Blast engineer and Mick Main and Dave Bennett, Shotfirers from Hunter Valley Operations for the opportunity to assist them with this project and look forward to its continued success.