The Journal of Explosives Engineering - November/December 2024 - 36

Figure 7. Block Test 2 Experimental Analysis.
Table 4. Block Test 2 Final Calculations.
mass occur so rapidly that data collection has been insignificant.
By extrapolating the timing data, a unique timeline, figure
7, was developed to create a visual depiction of the processes.
Timings from the Synergy DAQ were integrated with
data from the seismographs to develop the remainder of the
timings presented in table 4. The collection of pressurization
timings within the block provided a realistic means to further
understand the blast mechanics and rate of expansion within
a mass.
Utilizing this unilateral theory, it can be suggested that the
air overpressure origin does not coincide with the air pressure
pulse itself. The timing shows that even in scaled models that
the correlation between face movement and the arrival of the
AOP at the face are so inherently apart that the origin can only
likely rise from one mechanism. Due to blast geometries and
abnormalities within the structure it is nearly impossible to infer
an exact timing correlation between the gases exiting and
the calculated AOP arrival at the face. However, due to the
small window of time in which this phenomenon appears it is
reasonable to be able to utilize this information for designing
lower AOP's during the blasting process.
The collected data falls in line with relevant research to
date substantiating the validity of the block model and further
warranting that the movement of the face does not give rise
to the origin of air overpressures. The pressurization timing of
the gas release pulse exiting the face and the AOP arrival at
the face happen so coincidentally that a direction for future
research has been established.
Conclusion and Future Work
At this juncture it can be assumed that the movement of
the face occurs so far beyond the arrival of the AOP that it
is not truly the origin of the air overpressure. Utilizing different
materials to mimic different geologies will be critical to
gathering enough data to assess the theory behind the gas
November/December 2024
release pulse. The other potential origin of air overpressure
where the shockwave impacts the face will need additional
evaluation to fully compare to the data collected from this
continued research. Additional work will be conducted utilizing
the same methodology presented to validate the model
further, followed by a more robust design to finally identify
the actual origin of air overpressures.
Acknowledgements
I would like to thank Dr. Catherine Johnson and Dr. William
Birch for providing the basis of this phenomenon and
guiding me to successfully complete the test. This has been a
long outstanding project for them in which we hope to further
clarify the mechanisms at play with the origins of air overpressure.
I would also like to thank Gracie James and Francis
Schott, students at Missouri Science and Technology, for their
technical field support to build and conduct the testing.
References
Birch, W.J, Bermingham L., Farnfield R., Hosein S. & Johnson
C. (2013, February). Investigation to determine the origin of air
overpressure from quarry blasting. Proceedings of the thirty ninth
annual conference on explosives and blasting techniques, Dallas,
Texas, USA.
Birch, W. J. and White, T. (2011, February). Full Scale Investigation
into the Prediction of Air Overpressure from Quarry Blasting.
Thematic Research Priority: Impact Mitigation and Management,
The University of Leeds, Leeds, UK.
Oriard, L. (2005). Explosives Engineering, Construction Vibrations,
and Geotechnology. International Society of Explosives Engineers.
Stiehr, J. F. (Ed.). (2011). ISEE: Blasters Handbook 18th Edition.
International Society of Explosives Engineers.
Siskind, D. E, Stachura, V. J, Stagg, M. S, Kopp, J. W. (1980).
Structure Response and Damage Produced by Airblast from Surface
Mining. USBM Report of Investigations 8485.
The Journal of Explosives Engineering
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