International Experience with Airblasts and its Relevance to Underground 

Stone Mines

Christopher Mark and Gregory Rumbaugh

Mine Safety and Health Administration

ABSTRACT

Recent pillar collapses have caused five large airblasts in underground U.S. limestone mines. One of these 

events injured three miners, but all of them put many other miners at risk. To better understand the hazards, 

Mine Safety and Health Administration (MSHA) conducted a comprehensive review of the international 

literature on airblasts. More than 40 airblast cases have been documented, in a wide variety of minerals. 

Experience shows that miners that are in the direct path of the air as it moves towards the mine exits are at 

the greatest risk. The paper describes a risk management methodology that can be used to evaluate the level 

of hazard throughout the mine and aid in the selection of controls to reduce the risk. The paper concludes 

with a detailed case history of an actual pillar collapse and airblast.

INTRODUCTION

On April 29, 2015, three limestone miners were waiting in front of the portal for their shift to start. Suddenly 

they were engulfed in a powerful airblast caused by the collapse of 35 pillars underground (Esterhuizen et al., 

2019). The outrushing air severely injured all three miners, two of whom had to be life-flighted to a nearby 

hospital.

Five years later, a crew of miners at a Tennessee limestone operation heard a series of crashing sounds that 

emanated from an abandoned area containing more than 40 benched pillars. They evacuated the mine and

were waiting outside the mine office when they felt the ground shake. Within seconds they watched as 

enormous clouds of dust, driven by hurricane force winds, rolled out of the nearby portals (Figure 1). Less 

dramatic airblasts were also associated with three pillar collapses at two other Pennsylvania limestone mines 

in 2020 and 2021 (Rumbaugh et al., 2022).

Airblast has been a hazard in underground mining for nearly two centuries (McPherson 1980). During the 

past 50 years, airblasts have been documented in at least 40 mines around the world (see Table 1), and

undoubtedly many others were not described in the literature. Airblasts have occurred in a variety of

minerals, although coal seems to be the most common. 

Each of the airblasts described above were caused by the collapse of an entire array of pillars. In other mines, 

airblasts have been caused by large caving events during longwall mining, pillar recovery, block caving, or 

similar types of operations.

AIRBLASTS IN UNDERGROUND STONE MINES

Before 2015 pillar collapses were highly unusual events in stone mines. Esterhuizen et al. (2011) did not find 

even one example of a area-wide pillar failure in their studies of historic pillar performance at 34 limestone 

mines. They did identify two pillar collapses in abandoned mines, but neither was well documented. They 

also observed a handful of individual pillars that had failed without triggering area-wide collapses.

Phillipson (2013) described a pillar collapse and airblast that occurred at a marble quarry in Georgia. At this 

mine, employees on the surface felt vibrations that they thought were from a shot being fired underground. 

Later they found that a portable toilet inside the mine and a tag-in board outside the portal had been knocked 

over by an apparent airblast. Further investigation revealed that 19 pillars had had collapsed in a benched 

area that had been abandoned in the early 1990s (Figure 2). There were no injuries, and damage to 

underground infrastructure was minimal.

Two major pillar failures have been documented in mines extracting lead-zinc ore hosted in dolomite. The 

failure at the Magmont Mine began with the failure of four centrally located pillars and spread over six
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months to include approximately 25 pillars, before culminating in the sudden collapse ninety pillars over an 

area of approximately 400 feet by 600 feet (Dismuke et al. 1994). The final failure caused a significant

airblast but caused no injuries. A 1972 failure at the Bautsch Mine, near Galena, IL, apparently progressed 

over several months, punctuated by larger incidents (Touseull and Rich 1980). Airblast is not mentioned. At 

this mine, the irregularly shaped pillars were 93 feet high and 32 feet wide, with unsupported spans 

exceeding 75 feet

PILLAR COLLAPSES IN OTHER NON-COAL MINES

One of the most extensive pillar collapses in the history of mining was in 1995 at the Solvay Chemicals trona 

mine (Swanson and Boler 1996; Goodspeed and Skinner 1995). The collapse generated a magnitude 5.3 

seismic event and involved an area measuring 0.75 square miles. The associated airblast blew out 

approximately 200 stoppings and reversed the air flow in the intake shaft for 17 minutes. Dense clouds of 

dust and high concentrations of gases were liberated. 

Fifty-five miners were underground at Solvay Chemicals at the time of the event. Most of them apparently 

reported the same observations: they felt the ground roll (with mostly vertical motion), then a moment later 

they heard the noise and felt the airblast. Five miners working in the 1S–13W Panel directly adjacent to the 

collapse (Figure 3) experienced “severe upward and downward movements as the floor heaved violently and 

rib and roof material fell on top of and around them.” Accounts of the event do not indicate that any injuries 

were directly associated with the airblast, though one miner who was trapped underground for nearly two

days succumbed to ammonia and carbon dioxide poisoning.

A second major pillar collapse occurred just five years later at the same Solvay Chemicals mine (MSHA 2000; 

Board et al. 2007). The pillar collapse encompassed an area approximately 1,800 feet by up to 5,200 feet and 

generated a magnitude 4.3 seismic event. One miner was injured when he was “showered with rocks.” This 

area of the mine was a "Controlled Closure" experimental area, designed to allow the roof to subside in a 

controlled manner to eliminate the potential of massive pillar collapse. 

Zipf and Mark (1996) list four other historical incidents of pillar collapses in U.S. non-coal mines. The damage 

from the airblast in each instance was either minor or unknown. 

More recently, a massive pillar collapse occurred at the Mosaic Potash Carlsbad Mine in Eddy County, New 

Mexico. The collapse measured approximately 1,700 feet by 3,000 feet and generated an airblast that 

knocked three miners off their feet in an adjacent section. The event registered 2.4 on nearby seismic 

systems. Another event, at the Troy Mine in Montana, began with the failure of about 12 pillars in a 750- by 

750-foot area. It eventually spread until it caused the entire mine to be abandoned. Fortunately no miners 

were injured. 

AIRBLASTS ASSOCIATED WITH PILLAR COLLAPSE IN COAL MINES

The Crandall Canyon Mine disaster was the largest coal pillar collapse in recent times. It involved hundreds 

of pillars over an area of approximately 2,500 by 1,000 feet, and it generated a magnitude 3.9 seismic event. 

The resulting airblast destroyed or damaged stoppings for an additional 1,500 feet. Several miners were 

travelling in the mine at the time of the pillar collapse and they experienced the airblast differently,

depending on their proximity to its source (Gates et al. 2008). The two miners nearest the pillar collapse area

were driving separate trucks, and the force of the airblast slid one truck sideways and pelted the other with 

dust and pieces of foam sealant from destroyed ventilation controls. A mile outby another miner felt a large 

gust of air that peppered him with small rocks and injured his eardrum. Another mile outby two miners were 

working just inside the portals, and they did not notice anything.

The largest coal mine pillar collapse in history occurred at the Coalbrook Mine in South Africa in 1960. An 

area greater than 1.2 square miles collapsed, trapping 438 miners whose bodies were never recovered. Other 

miners who were working in the vicinity of the pillar collapse “became aware of increasing thunder-like 

noises from Section 10 and increasing methane emissions. They withdrew but before they could reach a safe

place, were overtaken by a hurricane of dust laden air accompanied by crashing like thunder. The gale swept 

through the mine for 10 minutes with great force and then at diminished force for a further 45 minutes. Men 
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were blown over, and a general exodus from the mine ensued” (van der Merwe 2006). Seismic records show 

that the pillar collapse occurred over a period of 5 minutes.

Numerous other pillar collapses have occurred in South African coal mines, including at least 23 since 

Coalbrook (van der Merwe 2006). Despite an extensive literature on the pillar design aspects of those 

incidents, there is very little mention of the airblast hazard. However, van der Merwe (2006) notes that the 

average age of the post-Coalbrook collapsed pillars was 21 years, which implies that most of these failures 

occurred in long-abandoned areas.

Mark et al. (1997) describe 13 pillar collapse cases that occurred in the U.S. during the 1980s and 1990s. All 

happened suddenly and without significant warning, and most resulted in airblasts that damaged the 

ventilation systems. Figure 4 shows the map of a typical failure involving pillars that had been split on 

retreat. Other failures occurred in areas where floor coal had been mined on retreat, or where pillars were 

developed on very small centers. The effects of some of airblasts generated by these events are detailed 

below:

• Three weeks after second mining was completed in a panel, an area measuring approximately 450 by 

500 feet and containing 107 fenders (remnant split pillars) collapsed. The airblast knocked miners 

to the floor on a nearby section. One miner was bounced off a steel rail and required 26 stitches to 

his head. 

• An airblast resulted from the collapse of fenders in a panel that was being retreated. A roof bolter 

operator said that he and his coworkers were knocked to the floor, and 103 stoppings were 

destroyed.

• When 94 pillars that had been developed on small-centers collapsed, the airblast blew out 37 

stoppings as far away as 800 feet from the collapse area. The airblast threw 30-lb cinder blocks 500 

feet. Fortunately, the pillar collapse occurred on an idle shift and no one was in the mine.

• At a mine in Utah, floor was being recovered in a thick coal seam, resulting in remnant pillars that 

were 40 feet wide by 18 feet high. A worked-out area measuring 500 by 1,600 feet collapsed while

the section was being actively mined. The force of the airblast hurled three miners for distances of 

40–100 feet, causing one severe head laceration. The airblast also blew a two-ton shop car through a 

permanent stopping, caused extensive damage to ventilation controls, and scattered concrete blocks 

from for distances up to 100 feet. It also stalled the main mine fan and temporarily reversed the 

airflow in the mine. 

Galvin (1996) presented a database of 13 Australian coal mine pillar failure case histories. At least four 

occurred suddenly and caused “major windblasts.” Sharma and Fowler (2004) mention the “violent” pillar 

failure at the Muswellbrook No. 2 Colliery that resulted “one of the most severe windblasts in underground 

coal mines.” No fatalities occurred in any of these events.

AIRBLASTS ASSOCIATED WITH CAVING

The Northparkes block caving operation in New South Wales (NSW), Australia, suffered four fatalities in 1999 

when an enormous plug of ore and overburden caved at once (see Figure 5). At the time of the collapse, the 

caveback (the crown) extended from the surface down approximately 650 feet. Below the crown the 

maximum air gap height was around 500 feet, and the caved ore column (muck pile) height varied from 270 

to 500 feet above the extraction level (Ross and As 2005). When the crown caved all at once, approximately 

13 million tons of material collapsed into the air gap and rapidly displaced 4 million cubic yards of air. 

The destruction and damage caused by the massive air-blast was confined to the direct flow path of the air

(Ross and As 2005). Extensive damage was caused to decline services, ground support, ventilation

barricades, light vehicles, and hoisting shaft cabling. The most severe damage occurred in the 1 Level heading 

that directly accessed the air gap below the crown. The collapse propelled such a powerful airblast through 1 

Level that a large pump weighing 5 tons was transported over 600 feet and rotated through 180 degrees from 

its original position. The airblast killed all four miners that were in this heading.
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The airblast did not appear to affect areas outside its direct flow path, even immediately adjacent areas. On 1 

Level empty plastic bottles and 5-gallon fluid containers were completely undisturbed in a crosscut only 160 

feet from the main entry point of the blast. Both the undercut and extraction levels were undamaged, and 57 

miners were safely evacuated later in the day (Ross and As, 2005).

Two other airblasts in block caving operations in Chile and the Philippines are discussed by Fowler and 

Hebblewhite (2003). The same authors also describe crown pillar failure at the Epoch Mine in Zimbabwe that 

resulted in a major airblast.

Violent caving events have also disrupted several Australian longwall coal mines, particularly ones located in 

the Newcastle coalfield of NSW. The roof there often consists of massive 100-feet thick conglomerate directly 

above the coal seam. In addition, the two-entry longwall gate systems employed at Australian mines limit the 

number of flow paths that are available to an airblast. During the late 1990s, the Moonee Colliery suffered a 

series of airblasts which caused numerous injuries and resulted in the mine’s temporary closure. Moonee

only reopened when hydraulic fracturing proved capable of delivering “caving on demand” (Hayes, 2000). 

Fowler and Hebblewhite (2003) also list five NSW mines, some longwalls and some room and pillar, where 

“skeletal injuries [caused by airblasts] have included broken necks, ribs, arms and legs, and severe facial 

trauma, while internal injuries have resulted in the surgical removal of a lung and spleen.” It is not clear 

whether all of these were due to goaf falls, or whether some may have resulted from pillar collapses. In South 

Africa, eight miners were injured over one four-year period by airblasts associated with roof caving behind 

the longwall at the New Denmark colliery (Makusha and Minney, 2005).

The U.S. has limited published experience with airblasts on longwall faces. At the Kopperston Mine in 1989, 

the longwall had advanced 180 feet from the set-up room without a cave when approximately half of the 500-

feet-wide face fell at once. One worker was killed and four suffered minor injuries (Bowman 1989). More 

recently, one miner was propelled 80 feet and very severely injured by an airblast caused by an initial caving 

event at the Bull Mountain longwall mine in Montana (Federal Mine Safety and Health Review Commission, 

2015).

Chinese experience with airblasts in gob areas of room and pillar mines was described by Song and Xu 

(1992). The most severe problems occurred in the Datong coalfields where the roof is a thick conglomerate, 

like that in the Newcastle coalfields of NSW. In the four examples described, the sudden caving involved

areas ranging from 70 to 400 thousand square feet. Two of the events resulted in fatalities (including one 

devastating airblast that resulted in 14 deaths and 19 injuries (McPherson et al. 1995), and all four damaged 

ventilation and equipment. Song and Xu (19920 state that two mitigation techniques have been employed,

one being induced caving and the other “leakage roadways” that allow the impacted air to flow quickly to the 

surface.

No discussion of the airblast hazard would be complete without mentioning its association with explosions in 

coal mines. At least six explosions or fires in coal mines have been associated with large caving events, one 

each at the Endeavor and Moura No. 4 collieries in Australia (Fowler and Hebblewhite, 2003) and two each at 

the Willow Creek and Buchanan mines in the U.S. (Brune, 2013). 

AIRBLAST MECHANICS

The NSW Department of Primary Industries (NSW DPI) (2006) defines an airblast as “a rapid displacement of 

large quantities of air, often under pressure, in a constrained underground environment caused by a fall of 

ground or other material. It is often characterized by significant overpressures and air velocities which can 

result in fatal injuries to persons and cause severe damage to equipment and infrastructure. The extent of the 

consequences of such an airblast depends on the amount of air that is compressed and the rate of that 

compression.” 

Researchers at the University of New South Wales (UNSW) made the most extensive measurements of 

airblasts underground more than a decade ago (Sharma and Fowler 2004). The measurements were 
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primarily conducted at Moonee Colliery, and they show that a “wind blast” (the Australian coal mining term 

for airblast) comprises a rapid rise in absolute pressure to a maximum (positive compression phase), 

followed by a similarly rapid fall to below ambient atmospheric pressure (expansion phase ‘suck back’). At 

around the same time, although not necessarily in phase with the overpressure, the wind velocity also rises 

rapidly to a maximum and then exhibits a sudden reversal into the ‘suck back’ phase. Each event usually lasts 

for a few seconds. Sharma and Fowler (2004) also make the following observations:

• The overpressure pulse in a single heading attenuates with distance as it propagates outby. The 

attenuation is predominantly related to air viscosity, although other factors, such as flow through 

crosscuts (spreading) contribute.

• The rate of propagation of the airblast typically equals the speed of sound.

• There appears to be an upper bound to peak overpressure with increasing goaf/fall area.

• Wind blasts with peak wind velocities greater than 45 mph are hazardous because they can result in 

injuries to mine personnel according to Fowler and Torabi (1997).

• Hurricane level wind speeds have been measured in mine roadways but not exceeding Mach 1

values.

• Empirical scaling laws for wind blasts, based on explosive equivalency, could not be well defined due 

to the unpredictability and the variability associated with the roof fall, the caving mechanism in the 

goaf, and the geotechnical properties of the coal measures involved in the caving process.

The measurements also show a clear relationship between larger areas of caving ground and higher 

overpressures and wind velocities. In addition, NSW DPI (2006) state that “the potential energy, and 

therefore the magnitude of the consequence of an airblast, increases proportionally with the height of the 

void.”

The Saffir-Simpson Hurricane Wind Scale may be helpful in evaluating the potential consequences of an 

airblast, though it was primarily developed to estimate property damage. While even a Category 1 hurricane 

produces life-threatening winds in excess of 74 mph, hurricanes rated Category 3 and higher are known as 

major hurricanes. Major hurricanes, with wind speeds above 111 mph can cause devastating to catastrophic 

wind damage and significant loss of life simply due to the strength of their winds. A Category 5 hurricane is 

defined as one with winds greater than 157 mph (NOAA 2022).

McPherson (1995) and Lin (1997) developed mathematical predictions of airblast pressures using a “leaky 

piston” model. Their focus was on the potential temperatures generated by such an event rather than air 

velocities. Logan and Tyler (2004) developed a wind gust model specifically for the Ridgeway block caving 

mine. This model predicts air inrush velocities resulting from a massive cave back failure as a function of (1) 

the expansion void, (2) muck pile thickness, (3) permeability of the broken rock pile, (4) nature of collapse, 

(5) number of exit paths, and (6) measurement error. The model is very site-specific.

MANAGING THE AIRBLAST RISK

The worldwide experience with airblasts clearly indicates that air velocity is the main hazard. As Logan and 

Tyler (2004) put it: “High air pressures are converted to wind gusts when they find an escape pathway to 

areas of lower pressure (e.g., surface). High wind gusts become hazardous when the paths of rapid air flow 

coincide with working location of people and/or infrastructure.”

On the other hand, without wind, the pressure pulse by itself does not appear to pose a significant hazard. 

Based on their extensive research, Fowler and Hebblewhite (2003) concluded that “amongst the published 

reports of personal injuries occasioned during wind blasts in coal mines, there are no instances of eardrum 

rupture.* As the threshold of such injuries is usually taken to be a rapid increase in pressure of 5 psi it is 

considered that wind blast overpressures at the working place are unlikely to have significantly exceeded this 

value.”

* Fowler and Hebblewhite completed their work prior to the 2007 Crandall Canyon disaster, where one miner 

apparently did suffer a ruptured eardrum as described earlier.
6

According to the NSW DPI (2006), if there is a potential source for an airblast, then foremost consideration 

should be given to the pathways of least resistance through the mine that an airblast may follow to vent to the 

atmosphere. Considerations include: 

• the number, location, and size of openings,

• the path of least resistance should an airblast occur,

• any concentrated effect along its pathway,

• access to a void (source of airblast), and

• potential connections to the surface

NSW DPI (2006) continues by saying that the next step is to identify zones where a potential airblast could 

affect personnel and/or infrastructure. This should include determining the air velocities and secondary 

effects (debris becoming airborne) in potential pathways the vicinity of persons or infrastructure. Steps can 

then be taken to minimize the exposure of persons in the highest risk zones.

Strategies suggested by NSW DPI (2006) to reduce the potential airblast velocities in headings where the 

exposure of personnel cannot be eliminated include:

• Deliberately planned zones of high resistance in airways to help dissipate an airblast’s energy. These 

could include a series of broken rock piles placed in the heading. However, these must be 

constructed so that loose rock will not become airborne and travel with an airblast through the mine,

• Planning separate pathways of least resistance, where persons would not be located, which would 

take most of the airblast flow,

• Layouts that incorporate as many entries as are possible on all sides of a potential collapse area to 

dissipate the velocity/pressure effects of a windblast, and

• Leaving blasted or fallen material in the mined-out area to reduce the height of the void to cushion or 

dissipate the energy from an airblast, should it occur.

NSW DPI (2006) also recommends that planning for a potential airblast should also address:

• Effects on the surface (a surface exclusion zone could be considered),

• The ingress and egress headings, and the effects on egress from the mine should they be blocked 

after an airblast has occurred, and

• Effects on ventilation fans and all other infrastructure.

NSW DPI (2006) discusses “safe havens” where personnel could go if an airblast appeared imminent. 

Experience indicates that if persons go into a nearby dead-end crosscut or heading they would be protected 

because they would not be in the pathway of the high-velocity air. But a “safe haven,” or a mine evacuation 

strategy for that matter, is only useful if there is sufficient warning. A seismic monitoring system or an array 

of convergence monitoring stations could conceivably provide sufficient warning, but those approaches are

unproven at this time. Without remote monitoring there is often little warning of a pillar collapse, 

particularly if it occurs in an inaccessible, abandoned area of the mine.

NSW DPI (2007) states that, for coal mines, “The most severe consequence of windblast is a gas and/or coal 

dust explosion. For such an explosion to develop, fuel and an ignition source are needed, both of which can be 

provided by a windblast.” This concern does not apply to stone operations.

CASE HISTORY

In July of 2021, a massive pillar collapse occurred at a limestone mine in central Pennsylvania. The pillar 

dimensions and other details of the collapse event are discussed by Rumbaugh et al (2022). There were no 

eyewitnesses to either the collapse or the airblast because all of the miners that were underground were 

working in inby areas when the collapse occurred.
7

Two weeks after the collapse Technical Support conducted an underground investigation to determine the 

extent and degree of airblast damage underground. We found that the airblast traveled west towards the 

mine openings, causing the most severe damage along east-west corridors (Figure 6). Severe damage to 

ventilation curtains was observed around the perimeter of the collapse area. The heaviest damage was 

observed near area (A), close to the collapse, where a piece of communication equipment weighing over 100 

pounds was blown over, and signs posted in the area were found several hundred feet outby. 

Moving outby along the travelways, the most severe damage was a toppled chain link fence. However, other 

sensitive features in this area, including signs and mirrors, did not appear damaged from the airblast. 

Similarly, older ventilation curtains were blown down while newer curtains appeared to be largely 

unaffected. The evidence suggests that the force of the blast was largely dissipated by the time it reached (B).

In the portal area (C), ventilation curtains were blown down and a sign was bent. However, other signs, 

cones, and curtains in the area were undisturbed. This suggests that the primary exit path of the airblast may 

have been through the ventilation adits (D). The portal area was apparently protected from damage by its 

distance from the pillar collapse and the availability of multiple openings for the air to exit the mine.

Located north of the portals, three other ventilation adits were serviced by a fan (E). A ventilation curtain 

installed above the fan was blown down, but there were no other signs of damage in the area.

The detonator and explosive magazines (F) were largely shielded from the airblast by solid pillar. A cone was 

overturned in this area, but otherwise sensitive signs and equipment appeared undamaged.

Despite numerous signs, cones, and other equipment that might have been damaged, no evidence of the 

airblast was found in the belt transfer area (G). A large strip barrier pillar apparently provided protection 

from the impact of the airblast.

Overall, this example conformed to experience with airblasts. The greatest air velocities, and thus the highest 

risk, were located near the source of the event. As the air moved through an array of pathways towards 

several different exits, the air velocity evidently reduced. Locations that were protected by pillars, and thus 

outside the direct air pathway, were hardly affected at all.

IMPLICATIONS FOR UNDERGROUND STONE MINES

The initial energy released by a pillar collapse depends on the volume of rock that collapses, the distance it 

falls, and how rapidly the event takes place. The areal extents (plan view) of most of the potential collapses in 

stone mines are not so large, relative to other pillar collapses that have occurred. On the other hand, the 

potential fall height is greater only in block caving operations. Pillar collapses in stone mines generally 

happen so rapidly that they generate a large seismic event. It is clear that pillar collapses in stone mines can 

release very large amounts of energy.

Where does this energy go? Perhaps the most significant finding is that, unless it is associated with high 

velocity wind, the pressure pulse resulting from an airblast poses relatively little direct hazard. Therefore, 

miners inby a pillar collapse (working at the faces for example) would likely not be directly affected. (Indirect 

effects, such as disruption of ventilation, or blockage of egress, are still possible, however.) On the other 

hand, those miners located in the direct path of the air as it made its way to the portals could be at high risk. 

The magnitude of the risk seems to be directly related to the velocity of the air.

Explicit, quantitative prediction of those air velocities seems to be an extremely complex undertaking. 

However, it is possible to estimate the qualitative risk posed by the airblast. The process involves:

• Identifying the likely flow paths of the air leading to the portals,

• Evaluating the number, location, and size of the openings in each flow path, and

• Considering the likely dissipation of energy as the air travels through the mine.
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Based on these considerations, it should be possible to identify those locations where personnel would be at 

highest risk. Risk mitigation can include reducing the potential air velocity or redirecting its flow (using 

techniques such as barriers, seals, or pressure relief pathways), or removing personnel to safer locations.

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11

TABLE 1.—Worldwide Airblast Incidents, 1960-Present.

Mineral

(number of 

mines)

Location Date Type of 

Failure

Size of 

Collapse 

Area

Effect on 

Miners

Effect on 

Mine

Reference

Limestone (5) PA, TN 2015 Pillar 

Collapse

500 by 650 

feet

2 severe 

injuries

Rumbaugh 

et al. 2022

Marble GA 2011 Pillar 

Collapse

300*600 feet none Minimal Phillipson 

2013

Dolomite (Pb/Zn 

ore)

MO 1986 Pillar 

Collapse

90 pillars none Dismuke et 

al. 1994

Dolomite MO 1972 Pillar 

Collapse

Touseull and 

Rich 1980

Trona WY 1995 Pillar/Floor 

Collapse

3000*7000 Injuries to 

miners in 

adjacent 

panel

200 

stoppings 

destroyed

McKinney et 

al. 1995; 

Swanson 

and Boler 

1996

Trona WY 2000 Pillar/Floor 

Collapse

1850*5000 Board et al. 

2007

Quartzite (Cu-Ag 

ore)

MT 2013 Pillar 

Collapse

Mine is 

closed

Potash NM 2012 Pillar 

Collapse

1700*3000 

feet

3 miners 

knocked 

down

NSW 

Australia

1996 Block Cave 4 fatalities Minimal, 

except 

access drifts

Ross and As 

2005

Coal WV 1989 Gob Fall 510*150 feet 1 fatality, 4 

injured

Minimal Bowman 

1989

Coal NSW 

Australia

1997–2000 Gob Falls 

(numerous)

60-200 feet * 

300 foot 

longwall face

1 major 

injury

Minimal? Hayes 2000
12

Coal (15) US—

Various

1980–2000 Pillar 

Collapses

150-700

thousand ft2

two minor 

injuries

major to 

minimal

Mark et al. 

1997

Mineral

(number of 

mines)

Location Date Type of 

Failure

Size of 

Collapse 

Area

Effect on 

Miners

Effect on 

Mine

Reference

Coal (4) Datong 

China

1960–1975 Pillar 

Remnant 

Collapses

220-1250

*103 ft2

Two caused 

fatalities

Major Jin and 

Sheng 1992

Non-coal (4) US—

Various

1972–1992 Pillar 

collapse

110-5400 ft2 none noted Minor Zipf and 

Mark 1997

coal NSW 

Australia

1976 Goaf Fall 1 fatality Referenced 

in Sharma 

and Fowler 

2004

coal NSW 

Australia

Pillar 

Collapse

Referenced 

in Sharma 

and Fowler 

2004

Coal (4) NSW 

Australia

various Pillar 

Collapse

not given None noted "major 

windblast"

Galvin 1996

Coal South 

Africa

2000–2004 Goaf Fall 130 feet 

longwall face 

advance

8 injuries in 

separate 

events

minor Makusha 

and Minney 

2005

Coal South 

Africa

1960 Pillar 

collapse

0.75 mile2 438 killed by 

pillar 

collapse, no 

injuries 

reported

Stoppings 

damaged by 

small 

precursors

Van der 

Merwe 2006

Coal (5) NSW 

Australia

1983–1999 Goaf falls (?) All with 

serious 

injures 

Fowler and 

Hebblewhite 

2003
13

FIGURE 1 Airblast exiting an underground limestone mine in Tennessee.
14

FIGURE 2 Map of the collapse area at the Georgia marble quarry (Phillipson 2013). The red pillars apparently failed, and the orange ones 

were taking weight.
15

FIGURE 3 Map of the Solvay mine collapse area (Swanson and Boler 1996). The 1S panels from 1W to 12W all collapsed. 

The crew was in the faces of 13W.
16

FIGURE 4 Map of a pillar collapse at a West Virginia coal mine (Mark et al. 1997). Pillar splitting on retreat left an array of 

slender pillars that suddenly collapsed.
17

FIGURE 5 Schematic of the 1999 caving event at the Northparkes Mine (afeeter Ross and As 2005). The miners who perished 

were in the “1 Level” heading. Note that the “air gap” was approximately 500 feet high at the time of the collapse.
18

FIGURE 6. Map of the airblast case history mine. The airblast damage observed at 

locations A through G is discussed in the text.