Violence Factor: A New KPI for Assessing Blast Performance
Violence Factor (VF) is the newest KPI in the blasting industry that gives managers and engineers quick insights into a blast performance using simple visual techniques.
Join Dr. Anthony Konya, the lead researcher and developer of Violence Factor, as he explains how violence factor can quickly be calculated and the insights it gives into the performance of a blast.
This lecture will include dozens of example blast videos from around the world in all different blasting environments including construction, quarrying, metal, non-metal, and coal mines to illustrate various types of blast violence and the associated effects on ground vibration, fragmentation, and muckpile heave.
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Q & A
1. Is there a plan to develop (or is this already in the works) to for implementation of violence factor for blasts designs other than for typical bench blasts (i.e. trench blasts, underwater blasts, etc.)?
Violence Factor is an assessment of cratering for surface bench blasts. Situations like trench blasting have to rely on some cratering and vertical movement due to swelling of material and limited directions to break. Underwater blasts have resistance and it is difficult to monitor the vertical uplift during the blast due to vision underwater. In these situations violence factor may help to answer the question to the degree of cratering but the question then becomes to what benefit or design parameter does violence factor answer. There are better KPIs to analyze for these as opposed to violence factor.
2. How do you effectively measure the uplift ? Do you have a specific measurement point or time of measurement? How do you ensure an appropriate measuring scale from the videos?
Typically we use some metric int he video (traffic cone, certain rocks, etc.) and then use one of many video measuring programs or stills that are uploaded into CAD with the reference objects for scaling).
3. Trench blasting, dry wells, sinking cuts -- the top MUST move sufficiently, a violence factor of more than zero must be accepted. Bulking factors of 1.4-1.5 are typical and justified.
Agreed - as discussed Violence Factor is for assessing trench blasting. Other KPIs are more beneficial when viewing other types of blasting, for example a sinking cut we would look at the uniformity of the movement and flyrock that breaks away from the bulk movement. We still have controlled trench and sinking cut blasts versus disconnected and wild blasts with flyrock. Violence Factor is not the KPI for these since cratering is required due to the geometry of the blast.
4. Would you say the violence factor would be an effective tool to evaluate stemming performance?
No, Violence Factor is effectively an assessment of cratering, stemming ejection can be a result of numerous improper design parameters including improper stemming or many design constants that also cause violence. However, stemming can eject and a blast can still be controlled resulting in stemming ejection yet having a low violence factor.
5. Aside from the video of the blast, you could infer a high violence factor based on poor condition of drill benches and irregular bench crest elevations. Do you have a method or procedure for inferring violence factor from existing bench conditions?
We use videos to assess violence factor, which we can correlate to potential backbreak on the shot. We have not analyzed going in reverse - it is important to also remember that blasting is a bayesian statistical process due to geology, so the reverse correlation may not work due to the geologic nonuniformity.
6. What impact foes stemming height and column height have? Does this not impact cratering??
Stemming ejection leads to a loss of confinement and borehole pressure, this can cause cratering due to the increase in confinement or the changing of axisymmetric bending to cantilever bending; however, while there is a positive correlation between the degree of stemming ejection and violence factor the relationship is not predictive. This is partially due to the fact that stemming ejection is not a binary process due to the relationship of the time of ejection and rate of ejection. Research on stemming ejection has shown that these are critically important to the borehole pressure and impulse effects and as such have an effective relationship on the violence factor more than just visually observing the stemming ejection and correlating to violence. The time of stemming ejection and the rate of stemming ejection are significantly more difficult to quantify in practical, real world settings thus they are not reliable and reasonable KPIs to introduce or include. Furthermore, other design parameters can cause stemming ejection even when the stemming height is properly designed - as such other parameters (such as borehole sequencing which was the example given in the presentation) can also cause both stemming ejection and violence; or cause one but not both to occur.
Dr. Anthony Konya
President | Precision Blasting, Academy Blasting TV
Is the President and the owner of Precision Blasting Services, a blast engineering firm that specializes in helping mining and construction clients improve and optimize their drilling and blasting performance. He is also the President and owner of Academy Blasting TV. Developer of the modern presplitting theory and design practices under the precision presplitting applications that's now been accepted by companies all over the world. He has over 100 technical publications in drilling and blasting. He's taught at Colorado School of Mines, in their explosives engineering Department, and at the Missouri University of Science and Technology at Missouri SMT. Dr. Anthony Konya has a bachelor's in mining engineering and a master's and a PhD in explosives engineering.
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