Blasting rock can be an expensive and – if done incorrectly – a dangerous business.
It isn’t something that you do unless you have to. In mining, for the most part, you have to.
Blasting is a key element of the mining cycle and getting it right is critical to project optimisation.
So why do we blast?
It seems an obvious question. We need to blast rock so we can dig it up. But the blasting process has a much greater impact on the mine cycle than simply breaking up rock.
The objective of mining is to remove material from the ground so it can be processed, treated, milled, shipped and eventually sold in an economic way. The more cost efficient and productive the process, the more viable and profitable the mine.
While it’s possible for some material to be freedug, the type of rock found in most mines in the world can’t be simply dug up. There are also technologies such as road headers or surface miners which negate the need for blasting. But for the most part, blasting is an essential element of the mining cycle. Get it wrong, and all the steps that follow cannot be optimised.
What happens if blasting isn’t performed properly?
Incompetent personnel, poor blast design and technique, using the wrong explosives and unsuitable equipment will be detrimental to a project, leading to:
- Poor productivity: Without proper or sufficient blasting, digging will be slower and Ground Engaging Tools (GET) will cost more. Milling and crushing will be slower and more expensive. In fact, there is a genuine argument to increase the horsepower (powder factor) in a blast to reduce downstream mining and milling costs and the overall project costs.
- Loss of dilution control and ore: All mines require very careful planning and processes to ensure that the ore and waste can be dug separately.
Miners don’t want ore on the waste dump any more than they want waste in their ore stockpile.
Bad blasting results in a loss of control over where the ore is which negatively impacts on mine economics.
- Increased safety risk: Personnel must be highly skilled and trained, and committed to safety best practice.
Modern blasting is actually an extremely safe business. It has developed that way out of necessity and by learning from mistakes. Modern explosives are inherently safe and are in fact quite difficult to detonate unless they are used in the right combination. Modern blasting procedures and the level of training required to become a shot firer mean that, if used properly, explosives will only detonate when they are supposed to!
What are the safety risks if things go wrong?
- Poor design and technique: If blasts aren’t designed and loaded properly, flyrock can result. It can damage people and equipment.
In some circumstances blasting needs to take place very close to infrastructure such as railways and buildings or houses. Even if flyrock is contained, much care needs to be taken to ensure that the vibrations from the blast do not damage the infrastructure.Careful blast design is also required to ensure noise is contained. Excessive noise can result in complaints from locals.
- Wrong explosives: If the wrong type of explosive is used then fuming can result. If fumes travel from a blast area to an area containing people then serious health issues can occur.
How can the blasting process be controlled to deliver optimal safety and economic outcomes?
- Planning – get the blast design right: What are the objectives? What are the restrictions? What approach, explosives and equipment will deliver the best outcome? These questions need to be addressed to determine good blast design.
- Drilling – holes must be accurate: The best planning will count for nothing if the holes aren’t in the right place, or they aren’t to the right depth. Drilling must be accurate. The holes have to stand up for enough time to allow you to load them with explosives (which can sometimes take weeks) and the drilling equipment needs to be productive. Drilling three perfect holes a day won’t cut it when your mine production requires one hundred holes a day.
- Loading – use the correct technique: The best blast design has been achieved and all holes have been drilled perfectly; each hole must then be loaded correctly taking into account any new factors such as water inflows. Each hole should have the right delayed detonator and all the holes must be hooked up in the right sequence. This all requires highly skilled and meticulously trained personnel.
- Blasting – safety first: The planning process, drilling and loading of a blast pattern can take several weeks to carry out. The whole blasting process can take a matter of minutes – but it is the most critical. The blasting area must be secured properly, all personnel must be out of the blast area and factors such as wind and weather need to be taken into account to make sure nearby residents aren’t affected.
Blasting is integral to the success of a mining project. Investing in quality personnel, safety and training systems, technology and equipment will ensure the greatest return.