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Drilling and Blasting Technology Innovations

Drilling and Blasting Technology Innovations

Gary Cavanough, Research Program Leader for Drilling – Deep Exploration Technologies Cooperative Research Centre / Commonwealth Scientific and Industrial Research Organisation(CSIRO), spoke to AMR about their latest drilling and blasting projects.

Can you talk about research that CSIRO is undertaking regarding blasting technologies?

CSIRO with funding from the Australian Coal Industry Research Program (ACARP) has been working with a group of researchers (including Dr Alastair Torrance, Principal Consultant with Kilmorie Consulting; and, Dr Italo Onederra, Principal Advanced Blasting Engineer with CRC Mining) on a range of blasting technologies. Recently we undertook a research project to examine the way in which low-density explosives work. As part of that project we developed novel detonation temperature and pressure transducers. That project was completed, and we now have this instrumentation in place for ongoing research.

What are the implications of these low-density explosive projects for industry?

One impact regarding low-density explosions is that these products tend not to generate post-blast fumes. Fume generation is a current HSE and environmental problem for the coal industry, so the use of low-density explosives will contribute to better performance in these areas. Another desirable characteristic of low-density explosives is that they have slower reaction rates, which means that explosives operators can take advantage of the heave energy available to improve overall ‘throw’. There are some fundamental energy models based on explosive formulations that have been derived over the years that describe how explosives perform, Unfortunately these models do not accurately predict the behaviour of low-density explosives, and the models indicate that these explosives will fail to perform adequately; however our research, backed up by field observations has found that these explosives actually do work effectively. No-one to date has been able to characterise this phenomenon of why low-density explosions work, when the empirically-derived model that has been developed over years suggests otherwise. The work we have done using our newly-developed instrumentation indicates that low-density explosions detonate at a significantly higher temperature than conventional explosions; and higher temperature means higher gas pressures. Our work to date suggests that the higher-temperature/gas-pressure finding explains why low-density explosions work.

What is the cost effectiveness of low-density explosives compared to conventional explosives?

Low-density explosives are more cost effective because less explosive is required to load each metre of a blast hole. Essentially low-density explosive are conventional explosives mixed with inert materials, such as polystyrene beads. Low-density explosives have both open-cut and underground applications.

Can you talk about CSIRO’s research that is centred on post-blast fumes?

As discussed, the coal industry is experiencing problems with post-blast fumes. Post-blast fumes are a health risk. There are large exclusion zones placed around blasts in case fumes occur which affects mine operation. The generation of post-blast fumes is not completely understood, however it is believed to be caused by an inefficient detonation reaction due to confinement effects in soft-rock and product stability in wet conditions; this has been noticeable in Queensland where recent heavy wet-weather events have led to an increase in fumes. We are conducting a project at present to understand the main mechanisms that cause fumes. This involves developing a risk matrix to assist the decision-making process towards reducing fumes. What we have done is to go back to the base explosives and setup test methods to characterise the chemical composition of different explosive formulas. We have commissioned the necessary equipment at a site in Central Queensland, and have also set up a laboratory at CSIRO where the mining industry -can send raw materials for testing. We can look at ammonium nitrate, fuel and water contents, etc. If this facility proves successful we will replicate it in the Hunter Valley.

We are also intensively taking blast measurements in the field. We are measuring reaction rate, detonation temperature and pressure transducers at the blast sites. We also have a test program for mixing explosives at different moisture contents and evaluating their energy through an underwater explosive test. At the end of 2012 we aim to have a matrix that determines the likelihood of post-blast fume production under certain conditions. The major outcome that we intend to produce for the industry is to be able to take samples of their explosive products and raw materials, conduct independent tests in a laboratory, and ensure that the quality is good, and that there are not situations that will create fumes when products are used in specific ground conditions.

Are there any other significant blasting projects currently being worked on?

Another instrument that we have developed is an in-hole density measurement device. When explosives reach a specific density, they don’t detonate. We have developed an instrument that is placed in the hole and tells the operator the density of the explosives in the hole. We think this will be very useful for the industry because there is a feeling that one of the main problems at the moment is a lack of understanding of the true density of an explosive down the hole. If it is too high it can lead to a detonation failure.  

On drilling, what research is currently being undertaken at Deep Exploration Technologies Cooperative Research Centre (DET CRC)?

There is a drilling program through the Deep Exploration Technologies CRC that builds on existing and ongoing CSIRO research programs. We currently have a percussive drilling research rig set up at CSIRO in Brisbane. This is an important research topic because effectively top-hole percussive drilling is the cheapest and most effective form of drilling, however it typically can only drill quite short holes due to efficiency losses, and also the drill-bits become blunt quite quickly. Our research has managed to extend the reach of top-hole percussion drilling by developing a drill-steering method, a drill-optimisation method. We are also working on methods to reduce the wear rates, and reduce the efficiency losses; the improvements are being realised by various sophisticated control methods. We are approximately half way to what we would like to achieve with these drill optimisations. Ultimately once completed we will be able to drill longer holes (up to 70-100 metres) with top-hole hammer drills, which will reduce costs across the board. At the moment long holes can only be drilled using down-the-hole hammer drills, which are a lot less efficient, slower, and a lot more expensive. The financial benefits are quite significant.

Gary Cavanough

Gary Cavanough has Bachelor and Master’s Degrees in Physics and a PhD in Mining Engineering. He has  over 34 years’ work experience comprising eight years in biomedical engineering, six years in R&D in mining/mineral processing, 13 years as an engineer in heavy industry (mining, steel and power generation) and 10 years at CSIRO  on drilling and blasting research. Gary has numerous publications and patents in drilling. He is currently the Drilling Research Program Leader DET CRC and also leads projects in blasting and low density explosives. Gary is a member of the AusImm, IEAust, IEEE and a Registered Professional Engineer in Queensland.

 

 

 

 

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