Frequently Asked Questions About Nxburst™

What is Nxburst™?

The technology is based on a non-detonating propellant compound enclosed in a cartridge, which reacts very quickly when ignited to produce high volumes of harmless gas, mainly consisting of nitrogen, carbon dioxide and steam. When the cartridge is sealed in a drill hole, the high pressure gas generated by the ignition of the propellant enters into the micro-fractures created from the percussive drilling process and into the natural fractures and planes of weakness of the rock, expanding the fractures and propagating cracks towards the nearest free face of the rock. The number of cracks propagated is related to the maximum pressure and peak pressure rate achieved by the expanding gasses within the drill hole. The gas pressure, within the drill hole and propagated cracks, then causes the fractured rocks to heave apart, producing a shearing of the rock often called splitting.

What is Nxburst™ used for?

The Nxburst™ rock breaking technology was developed to solve problems associated with specialist excavations and rock breaking in sensitive conditions. The collateral damage associated with excavations using explosives in poor rock conditions or in blast sensitive areas often creates a larger problem than the original explosive solution set out to address. Problems of blast damage in highly jointed rock and collateral damage to sensitive installations and infrastructure have persisted in the industry for many years due mainly to the absence of credible alternative methods to address such situations. Nxburst™ offers the industry a solution, which allows a controlled approach to excavation in these difficult situations without the vestiges of damage associated with traditional methods of rock breaking using explosives.

The Nxburst™ rock breaking method, developed by NXCO Mining Technologies, has recently been applied to several applications in a wide variety of rock conditions. The Nxburst™ technology allows a tailored rock breaking (“TRB”) approach whereby energy can be applied more efficiently to break and dislodge the rock in a controlled fashion, which can be optimally adapted to suit the rock breaking requirements of any particular situation in all types of rock conditions.

What are the advantages of using Nxburst™?

(1) Nxburst™ is environmentally sensitive

minimal fly rock (< 10m)

minimal vibration

lower noise and overpressure levels than conventional explosives

negligible noxious gasses

(2) Only localised clearance of personnel is required with Nxburst™

(3) Nxburst™ cartridges are safer to transport, store and use than conventional explosives.

How does Nxburst™ rock breaking differ from rock breaking using conventional explosives?

The major difference between Nxburst™ and explosives can be summarised as follows:

Explosives can explode in their packaged state whereas Nxburst™ cartridges do not explode in their packaged state.

Explosives are designed to detonate whereas Nxburst™ cartridges are designed to deflagrate

Explosives produce a destructive shock wave giving rise to high vibration-levels, which damage the surrounding rock mass whereas Nxburst™ cartridges produce a controllable pressure wave with low vibration levels.

The rock breaking event produced by explosives is a largely uncontrolled, violent event producing large amounts of fly rock, noxious gases and dust whereas the deflagration of a Nxburst™ cartridge confined in a drill-hole is a controlled event which produces minimal fly rock, low concentrations of noxious gases and negligible amounts of dust.

Rock breaking using Nxburst™ cartridges can be carried out continuously with re-entry periods measured in seconds whereas explosive blasting using conventional explosives requires the mine to be evacuated for up to 4 hours after each blast.

Is Nxburst™ an explosive?

The Nxburst™ cartridge is classified as a 1.4S product under the United Nations hazardous substances classification, in the same category as small arms ammunition. This classification is given to products that do not explode when ignited in their original packaged state and as such the classification defines Nxburst™ as a non-detonating product for transport and storage purposes.

What are the transport and storage requirements for Nxburst™?

The Nxburst™ cartridge is classified according to the United Nations Classification of Hazardous Substances as a Division 1.4S hazardous substance. The UN classification system is used by most countries of the world to classify hazardous products according to the danger that each of the products poses whilst in storage and transport. The 1.4S classification that applies to Nxburst™ cartridges is the same classification as that applied to small arms ammunition. The Nxburst™ cartridge was tested by a UN accredited testing agency and subsequently classified under UN1.4S as a “Cartridge Power Device”.

The UN 1.4S classification is defined as follows:

“Articles and substances that present no significant hazard.”

Does Nxburst™ detonate?

What applications are Nxburst™ used for?

Nxburst™ are used in a wide variety of rock breaking applications, which include the following:

Secondary breaking (i.e. breaking of oversize rocks) in surface mines, quarries and underground.
Civil excavation and demolition on environmentally sensitive sites.
Slipping or stripping of underground tunnels & excavations
Shaft sinking
Mass rock breaking
Underwater demolition

What is involved in the drilling and breaking cycle?

Nxburst™ application is simple, however in the modern world today, accurate planning, method statement and risk assessment is part of the process. The operating team must be properly trained and certificated, led with discipline and experience, adequately clothed and protected by regulation PPE and follow due safe process and procedures.

What is air blast over pressure?

Air blast overpressure (pressure above atmosphere) is caused by vibrations or compressional waves transmitted through air, produced by the rapid expansion of explosive gasses and the rapid movement of the rock, resulting in the sudden displacement of the air surrounding the blast.

Overpressure levels produced by Nxburst™ cartridges are low when compared to conventional explosives and of a shorter duration and much less damaging frequency. This gives our cartridges a major advantage over explosives in environmentally sensitive areas.

What is a safe level for noise?

A well stemmed Nxburst™ cartridge in granite will generally produce a noise level in the range of 80 to 85 dBL at 50 metres from the hole. Well within the safe level of 128dB specified by the US Bureau of Mines. Noise level can be attenuated by the use of conveyor belting, other matting or ground cover to cover the holes being fired.

What kind of vibrations does Nxburst™ produce?

Ground borne vibrations from blasting can cause damage to buildings and infrastructure which are in the vicinity of the blast. The degree of vibration-induced damage caused by the blasting is dependent on the magnitude, frequency and duration of the vibration. The vibration signature produced by the combination of high frequency, low duration and low magnitude vibration waves enables Nxburst to be used in close proximity to vibration sensitive sites where conventional blasting is prohibited or impractical

Hazard of flyrock?

Flyrock hazard is controllable if using the appropriate amount of cartridges and charge weight for an application. Nxburst™ cartridge produces an optimal pressurization of the hole for a given burden and type of rock. By controlling the characteristics of the pressure pulse, the velocity and distance traveled by dislodged rock can be limited. Controlled gas release from the Nxburst cartridge, at a relatively low pressure, results in a minimal quantity of low velocity flyrock, which is generally contained within 10 meters of the rock breaking event.

Can I use this on concrete?

Yes. It is advantageous to use Nxburst™ on reinforced concrete because it can remove the concrete cleanly from the reinforcing. This is because the gas pressurizes the space between the steel and the concrete forcing it to crack and dislodge.