2
An airblast by definition is a rapid displacement of
large quantities of air, often under pressure, caused by a fall
of ground in a constrained underground environment. This
phenomenon is frequently marked by notable overpressure
and high air velocities, carrying the potential for causing
fatal harm to individuals and substantial damage to equip-
ment and infrastructure. The severity of the outcomes asso-
ciated with an airblast is contingent upon the quantity of
compressed air involved and the speed at which this com-
pression occurs (NSW, 2006). The miners that are in the
high-velocity pathways are at the most risk from an airblast.
Since October 2020, there have been four significant
pillar collapses documented in limestone mines, each
accompanied by a substantial air blast and the subsequent
formation of sizable surface sinkholes (MSHA, 2023). In
2015, a massive pillar collapse resulted in three miners sus-
taining severe injuries due to the forceful air blast (Rock
Products, 2015). It’s noteworthy that all these incidents
transpired in locations where floor mining, or benching,
had significantly heightened the pillars’ height (MSHA,
2023). Furthermore, three out of these occurrences took
place in “legacy” zones, where mining activities had con-
cluded many years ago.
Therefore, further research into the air blasts is criti-
cal at this juncture of time. From a safety point of view,
knowing the velocity of an air blast is critical for assessing
the potential danger it poses to individuals in the vicinity.
High-velocity air blasts can cause injuries, including trau-
matic impacts and the displacement of people and objects.
Understanding the velocity helps in determining safe dis-
tances and designing protective measures. In research and
safety evaluations, knowing the velocity of the blast wave
is essential for characterizing its behavior. This includes
understanding how the blast wave propagates, how it inter-
acts with obstacles, and how it dissipates over distance. This
information is vital for predicting the extent and severity of
blast effects. Calculating the velocity of the air blast helps in
the development of effective mitigation strategies.
2.0 PILLAR COLLAPSE INCIDENT VIDEO
This paper utilizes the pillar collapse from a recent incident.
In 2021, a crew of miners at a Tennessee limestone opera-
tion heard a series of crashing sounds that emanated from
an abandoned area containing more than 40 benched pil-
lars. They evacuated the mine and were waiting outside the
mine office when they felt the ground shake. Within sec-
onds they watched as enormous clouds of dust, driven by
hurricane force winds, rolled out of the nearby portals
(Figure 3).
3.0 METHODOLOGY
The idea behind the methodology to estimate the air blast
velocity is by using an air blast video captured during a
recent pillar collapse incident. This analysis will employ
the optical flow algorithm, a well-established computer
vision technique recognized for its proficiency in tracking
object motion within video sequences (Stanford, 2023). By
implementing this algorithm to process the video data, it
Figure 3. Still frame from the air blast video (MSHA, 2021)
Figure 2. Hour-glass shape of pillars left after benching
An airblast by definition is a rapid displacement of
large quantities of air, often under pressure, caused by a fall
of ground in a constrained underground environment. This
phenomenon is frequently marked by notable overpressure
and high air velocities, carrying the potential for causing
fatal harm to individuals and substantial damage to equip-
ment and infrastructure. The severity of the outcomes asso-
ciated with an airblast is contingent upon the quantity of
compressed air involved and the speed at which this com-
pression occurs (NSW, 2006). The miners that are in the
high-velocity pathways are at the most risk from an airblast.
Since October 2020, there have been four significant
pillar collapses documented in limestone mines, each
accompanied by a substantial air blast and the subsequent
formation of sizable surface sinkholes (MSHA, 2023). In
2015, a massive pillar collapse resulted in three miners sus-
taining severe injuries due to the forceful air blast (Rock
Products, 2015). It’s noteworthy that all these incidents
transpired in locations where floor mining, or benching,
had significantly heightened the pillars’ height (MSHA,
2023). Furthermore, three out of these occurrences took
place in “legacy” zones, where mining activities had con-
cluded many years ago.
Therefore, further research into the air blasts is criti-
cal at this juncture of time. From a safety point of view,
knowing the velocity of an air blast is critical for assessing
the potential danger it poses to individuals in the vicinity.
High-velocity air blasts can cause injuries, including trau-
matic impacts and the displacement of people and objects.
Understanding the velocity helps in determining safe dis-
tances and designing protective measures. In research and
safety evaluations, knowing the velocity of the blast wave
is essential for characterizing its behavior. This includes
understanding how the blast wave propagates, how it inter-
acts with obstacles, and how it dissipates over distance. This
information is vital for predicting the extent and severity of
blast effects. Calculating the velocity of the air blast helps in
the development of effective mitigation strategies.
2.0 PILLAR COLLAPSE INCIDENT VIDEO
This paper utilizes the pillar collapse from a recent incident.
In 2021, a crew of miners at a Tennessee limestone opera-
tion heard a series of crashing sounds that emanated from
an abandoned area containing more than 40 benched pil-
lars. They evacuated the mine and were waiting outside the
mine office when they felt the ground shake. Within sec-
onds they watched as enormous clouds of dust, driven by
hurricane force winds, rolled out of the nearby portals
(Figure 3).
3.0 METHODOLOGY
The idea behind the methodology to estimate the air blast
velocity is by using an air blast video captured during a
recent pillar collapse incident. This analysis will employ
the optical flow algorithm, a well-established computer
vision technique recognized for its proficiency in tracking
object motion within video sequences (Stanford, 2023). By
implementing this algorithm to process the video data, it
Figure 3. Still frame from the air blast video (MSHA, 2021)
Figure 2. Hour-glass shape of pillars left after benching