A misfire in blasting is defined in engineering and mining literature as the complete or partial failure of an explosive charge to detonate as planned during a blasting sequence. Misfires in surface and underground mining blast operations have resulted in serious injuries and fatalities among mine workers and other exposed personnel (Abdulkadir et al., 2022). Given that explosives are highly energetic and sensitive chemical compounds, a thorough understanding of misfire causes, as well as appropriate control and prevention measures, is essential to ensure safe storage, handling, and industrial application (Abdulkadir et al., 2022). In mining, a misfire is often treated as a mistake. In reality, it’s data. Let’s explore the lessons that we can learn from misfires.
The meaning of a misfire
In the world of blasting and explosives, a misfire is exactly what it sounds like, but with much higher stakes: it is the failure of an explosive charge to fire or detonate at the intended time. Think of it as a “sleeping giant.” The fuse was lit or the signal was sent, but the rock didn’t move and now you have live, unstable explosives buried in a debris pile or a borehole. Misfires can happen for multiple reasons.
The causes of misfires
To understand why a misfire happens, you have to look at the “firing chain”—the sequence of events that must go perfectly from the moment the blaster pushes the button to the moment the rock breaks. If any link in that chain snaps, you get a misfire. The main causes of misfires are:
Physical interruptions (cut-offs)
This is one of the most common reasons for misfires in larger-scale blasting activities. This phenomenon is a result of geological conditions or the delay sequence functioning unfavorably. The blasting of the initial holes triggers a movement of the rocks. Excessive movement, caused by poorly designed delay sequence systems, often leads to damage to the lead wires or shock tubes for adjacent holes. In some instances, the fly rocks resulting from the explosions of the initial holes may destroy the surface wires of the unpopped holes.
Environmental & site conditions
Explosives are tough but are not indestructible. In a “wet” borehole, if not highly resistant to water (for example, some ANFO mixtures), this energy can become “deadened,” or the chemical composition ruined, so that there is no detonation. Also, if boreholes are too close together, the shockwave from a given “near” hole can compress the explosive in the next too tightly so that it gets “too dense” to explode and effectively becomes a solid plug.
Human error (setup issues)
Blasting needs surgical precision in a messy environment. In the case of the electric blaster, a simple loose wire or a ground leak caused by electricity leaking into damp soil will stop the detonator from collecting enough voltage. The primer must be correctly seated in the explosive. Should the detonator not correctly seat in the primer, or if the primer is not seated to the correct depth, the explosive will not detonate. In the case of a non-electric blaster that relies on a shock tube, a kinked or tightly knotted wire will stop the chemical flickering down the wire.
Product failure
Modern manufacturing, while very reliable, can produce “duds”; i.e., the explosives and detonators can have an expiration date or they can degrade the chemicals they contain. Eventually, the chemicals can change their composition, especially if exposed to humidity or high heat. Once in a while, the detonator may not have the necessary delay mechanism or Bridge Wire which does not get hot enough.
The lessons hidden by misfires
A misfire is more than just a technical failure; in the blasting industry, it is considered a diagnostic tool. When a blast doesn’t go as planned, the “frozen” evidence left in the ground tells a story about what is happening beneath the surface that you otherwise wouldn’t see.
The “geology lesson” (unexpected weakness)
A misfire can show that the rock isn’t as hard as it was made to sound on surveys. If a hole was cut off because of ground movement, it will let you know that there was a weak layer of rock or a fault line that you didn’t plan for when blasting. The misfire could have gone through a natural cavern, or a ‘vug,’ and therefore not had enough power to unleash the rest of the blast sequence. Your geological map? Time to adjust the burden and spacing of your next shot.
The “timing lesson” (the race against physics)
Blasts take place in milliseconds. A misfire caused by a cut off is an indication that the initiation sequence is not synchronized correctly with the rock movement. Should the ground movement be fast enough to snap the shock tube prior to the signal transmittal, then your delay timing is too slow. The rock is “faster” than your fuse. You have to make the delay time between the holes shorter so that the signal will be able to outrun the ground movement.
The “product-environment fit”
Very rarely, the misfire will demonstrate that the choice of explosive was an optimistic one. For instance, should the blaster prefer as inexpensive an explosive as possible, say ANFO, which hates water, and get a misfire, the moral of the story is that the borehole wasn’t as dry as they thought. Possibly artesian water, high pressure, is down the bottom, desensitizing the charge. Stop scrimping on the cost of the explosive; it’s the expensive water-resistant emulsions that are needed.
The “culture lesson” (human factors)
This is the most bitter pill to swallow: misfires mask a failure in crew discipline. Uncovering a misfire due to a loose wire or a poorly tied knot raises a red flag that the crew is rushing or tired. When the same type of misfire happens over and over again, it indicates that your team doesn’t really understand the “why” behind the wiring patterns; they’re simply working off a checklist. Safety culture is beginning to erode. Slow it down, or someone gets hurt during muck-out.
Closing remarks
After a misfire, you have to carry out analysis in order to identify its origin. Also look at document conditions and if possible, adjust your design or procedures. Finally share the lessons across teams to reinforce the learning culture. Safety improves when learning replaces blame and performance improves when feedback is respected. In mining, progress doesn’t come from perfect blasts but it comes from listening to the imperfect ones.
References
Abdulkadir, S., Taiwo, B., Moshen, J., Akinsode, A., & Oluwasanmi, E. (2022). Blasting Misfire: A Review of Causes, Economic Effect, Control and Handling Techniques. International Journal of Energy Research, 3, 967–972.
