Having the right tools for the job conserves time, reduces inefficiencies, and limits waste – which, in the mining, quarrying, construction, and manufacturing industries could translate into millions in annual savings for your business.
By contrast, using the wrong explosives and not adapting correctly to changing circumstances could mean decreased blast efficiency, resulting in secondary blasting and the use of additional, expensive resources to get the job done.
However, knowing which explosive is best suited for each operation can be difficult, and will vary according to the desired results.
Mining Energy Acuity (MEA) is a leading expert in explosives selection and a prime candidate to guide you through the selection process, ensuring optimal results and maintaining safety standards across a diverse range of operational contexts.
Here’s a quick overview of five key factors you need to consider before selecting the right explosive for the job at hand:
1. Velocity of detonation (VOD)
The velocity at which the shockwave moves through the explosive is crucial for determining the fragmentation of the material and the cast distance.
With fragmentation as the primary goal, the aim should be to achieve a VOD at or near the sonic velocity of the rock. Velocity refers to the speed at which stress waves spread through a material.
When detonation closely matches this threshold, it maximises the efficiency of the energy transfer to the surrounding rock mass. The result is more effective fragmentation of the rock.
In scenarios where cast takes precedence over fragmentation, such as blast casting operations or when producing very large fragments for riprap or slabbing, you should rather aim to use explosives with a VOD notably lower than the rock's sonic velocity.
This reduction in VOD could then help to minimise the degree of fracturing, and instead displace larger pieces of rock.
2. Timing
Correct timing ensures good fragmentation and the proper cast of the blasted material.
Sequential firing with appropriate inter-spacing timing – which refers to the delay between the detonation of the blast holes – and a sufficient burning front will reduce the chances of any cut-offs occurring.
The inter-burden timing will also determine the cast. There must be sufficient time for the material of the first row to move before the next row moves.[JH1]
3. Gas or pressure release
The gas released during detonation directly affects the heaving effect of an explosive, otherwise known as the cast. When an explosive is ignited, it quickly turns its chemical energy into kinetic energy, generating high-pressure gases that expand rapidly and violently. This expansion exerts a substantial force on surrounding material, causing it to move, break apart, or shift.
Releasing more gas in an explosion causes more material to move or be displaced, which is advantageous in operations that need to shift large amounts of earth. For instance, in open-pit mining, quarrying, or construction projects, explosives with a high gas release can successfully lift and displace large sections of overburden or rock. This makes it easier to excavate and transport the materials.
4. Water resistance
The water resistance of an explosive refers to its ability to maintain its efficacy and stability when exposed to water.
In dry conditions, water resistance is not a significant concern, as there’s no moisture that could potentially degrade the explosive’s performance. So, for situations where there will only be short-term exposure to low levels of water, such as where the time between the loading of the explosive and detonation is relatively short, an explosive with a ‘good’ water resistance rating is generally adequate, as there isn’t enough time for significant water infiltration.
However, for prolonged exposure, explosives with a higher resistance level, such as ‘very good’ or ‘excellent’ are needed.
Water gels and emulsions are renowned for their superior water resistance. These formulations are designed to withstand prolonged exposure to water without major degradation. Additionally, higher-density explosives tend to offer fair to excellent water resistance because their compact structure limits water penetration.
5. Fume class and oxygen balance
Explosives are categorised by the amount of fumes they produce when detonated. This classification system is particularly important when assessing the safety and environmental impact of explosive usage. Explosives that produce smaller amounts of fumes are typically regarded more favourably, as the reduced emissions lower the risks associated with inhalation hazards and environmental pollution.
The amount of fumes released is determined by the oxygen balance of the explosive. If the oxygen balance is negative, the explosive will release a large amount of fumes due to insufficient oxygen. A positive oxygen balance is more advantageous for areas where toxic fumes are a concern.
Notably, in confined spaces such as tunnels, underground mines, or building interiors, limited ventilation can lead to the rapid accumulation of fumes, posing severe health risks to personnel working near the blast site. In these situations, selecting explosives with lower fume ratings helps safeguard workers and minimises the risk of respiratory issues or toxic exposure.
When detonation occurs in open areas, such as on outdoor construction sites, fumes disperse more easily and are less of a concern.
By partnering with Mining Energy Acuity, you can gain access to expert, tailored explosives solutions that will optimise your blasting operations. We can advise on the right explosives to suit your needs, and assist with procurement, logistics, storage, and compliance for maximum convenience and efficiency.
[JH1]Please double-check whether these explanations are correct. I couldn’t confirm these terms online. We must thus refer to the client’s expertise on this.
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