ABSTRACT

The main objective of occupational health and safety research is 

to minimize or eliminate the events that may cause fatal or nonfatal injuries to human workers. A commonly used technique is to 

devise an “incident prevention plan”, which is more often the

product of thorough investigations of past reported incident events. 

Incident documentation and methodical reporting and systematic 

and thorough data collection, often help identify the root cause of 

the incident – in other words, the etiology of the incident. These 

retrospective analyses of the incidents can efficiently identify the 

future steps to take to achieve the objective of minimizing

occurrence of “events of interest”.

This paper introduces a novel technique – “Taxonomic

Analysis”, which identifies the root causes of an event (an incident 

in this case) and can provide future direction for corrective

measures to reduce the probability of occurrence of the event. A 

taxonomic analysis involves systematic and organization of data 

based on observation, description, and classification. This paper 

utilizes the rock fall related incident narratives, available with the 

Mine Safety and Health Administration (MSHA) database (1984-

1999), for a taxonomic analysis.

The study found that 67.6% of groundfall incidents occurred in 

supported areas with the remainder (32.4%) in unsupported areas. 

Some form of rock mass failure appears to cause about 50% of 

groundfall incidents, although in 39.7% of the overall groundfall 

incidents or two-thirds of those involving rock mass failure, the 

exact nature of the rock mass failure could not be determined from 

the narratives. Human activities factors such as scaling or barring 

down, drilling or bolting, and setting timbers or cribbing accounted 

for another 34.5% of the groundfall incidents. Finally, support 

system failures made up the remaining 15.5%. Results from this 

taxonomic analysis may suggest focus areas toward which

preventive measures and future research activities could

concentrate.

INTRODUCTION

Groundfalls are a major source of fatal and non-fatal injuries in 

underground mines in the U.S. Coal mines, compared to metal or 

non-metal mines, are more prone to groundfall-type incidents due 

to the nature of the rock mass involved and fundamental

differences in mining practices. According to MSHA statistics 

during the 10-year period 1986 – 1995, groundfall was responsible 

for the largest proportion (31.7%) of fatal incidents in the coal 

mining industry and about 50% of fatal incidents in underground 

coal mining. Recent statistics show that the trend continues in the 

new millennium. Though new developments in ground control 

techniques helped to improve the ground stability problem in 

underground mines, it remains a substantial source of human 

fatalities (1).

This study broadly classifies groundfalls in underground mines 

into two categories:

a. induced or intentional, meaning rock falls are purposefully 

caused by the mining method such as caving rock behind a 

longwall face, collapsing roof in a retreat room-and-pillar mine 

or caving rock in a block-caving hardrock mine.

b. unplanned or unintentional, meaning any rock fall in mine 

workings where humans could be present.

The groundfalls of interest are the “so called” unintentional 

falls. Incidents due to unintentional groundfalls involve fatal or 

non-fatal injuries to a miner or a group of miners resulting from 

direct impacts of dislodged rock from the surfaces of mine

openings. Groundfalls in underground mines take place in

innumerable geologic and operational situations. In practice, the 

rock mass surrounding mine openings can collapse in different 

forms even though primary and secondary support systems

reinforce it.

A groundfall originates from two locations that have the

potential to endanger miners:

a. collapse or bursting of roof rock layers

b. spalling, slabbing or bursting of rock from the sides/ribs of 

openings

Occurrence of a ground-fall-related incident requires

fulfillment of three conditions:

a. The groundfall itself (ground element domain).

b. Some deficiency in the support system (support element

domain).

1Dr. Biswas has joined U of Maryland and VA Coop Studies after study was 

completed.

ROOT CAUSES OF GROUNDFALL RELATED INCIDENTS IN U.S. MINING INDUSTRY

Kousick Biswas1, Biostatistician

Dept. of Epidemiology & Prevention Medicine

School of Medicine, University of Maryland at Baltimore

and

VA Cooperative Studies, Perry Point, Maryland USA

R. Karl Zipf, Jr., Mining Engineer

National Institute for Occupational Safety and Health

Pittsburgh Research Laboratory

Pittsburgh, Pennsylvania USA
c. The presence of a miner or a group of miners (human factor 

element domain).

To devise and implement a “groundfall incident prevention 

plan”, it is very important that each groundfall related incident 

involving a human fatality or injuries receive a thorough

investigation in order to understand the exact contributions of the 

three conditions mentioned above. Investigating the patterns and 

the root causes of groundfall related incidents, i.e., the etiology of 

the incident (fatal or nonfatal), is essential for improving risk 

management plans and establishing key focus areas for future

control.

This pap er introduces a novel technique – “Taxonomic

Analysis”, which identifies root causes of an event (an incident in 

this case) and in turn can provide future direction of corrective 

measures to reduce the probability of occurrence of the event. A 

taxonomic analysis involves systematic and scientific organization 

of data based on observation, description, and classification. This 

paper utilizes the rock fall related incident narratives, available 

from the MSHA database (1984-1999), to pinpoint focus areas in 

which preventive measures and future research activities could 

concentrate.

METHODOLOGY

MacCollum (2) addresses the need for detailed analysis of

quality historical data:

Serious injury or death that occurs repeatedly from

similar circumstances should be considered epidemic. These 

occurrences should be examined to identify hazards so that 

appropriate hazard prevention measures can be initiated in 

the same diligent manner that the medical profession

examines a disease or infection to develop a vaccine or 

antibiotic for its prevention or control.

The main objective of this study was to gain sufficient insight 

into the etiology of the groundfall incidents in underground mines. 

The first step was to access the MSHA database and develop 

understanding of the patterns of etiology of groundfall incidents. 

The MSHA database, available on the MSHA website, were

reviewed for all groundfall related incidents (1984 – 1999). These 

data include industry-wide incident data related to fall of ground 

with detailed narrations of the actual incidents for coal, metal, nonmetal, stone, sand and gravel mines.

Available information on groundfall incidents was organized 

using the principles of taxonomic analysis. Taxonomy is defined as 

observation, description, and classification of data into hierarchical 

groups according to common patterns and individual differences 

(3). Triggers of groundfall incidents is the basis for the taxonomic 

scheme, and the taxonomic scheme attempts to utilize taxons

(classification parameters) in layers such that a combination of a 

group of taxons in successive layers paints a broad picture of the 

actual cause of the incident. The objective then became to create a 

system containing mutually exclusive categories sufficient for the 

classification of any eventuality.

A data set was generated for each year (from 1984-1999) of 

MSHA’s aforementioned database. These sets contained all

incidents from MSHA’s accident/injury classifications (06)

involving fall of face, rib, pillar, side, or highwall (from in place) 

and (07) involving fall of roof, back or brow (from in place). In 

addition, the sets included many incidents from accident/injury 

classification (05) involving falling, rolling or sliding rock and 

certain groundfall incidents from the (17) and (12) classifications 

involving machinery and powered haulage. The sets included the 

entire degree of injury range from fatality to days-lost injuries to 

non-days-lost injuries. Both operator and contractor injuries were 

included in the data sets.

After examining representative narratives of incidents within 

the data set, a taxonomic scheme containing five layers ranging 

from the broadest classifications (first level) to the most specific 

classifications (fifth level) was created. The first taxon layer 

merely identifies the incident as a rockfall incident. The second 

layer indicates whether the incident occurred in a supported or 

unsupported area. A supported area is one where the designed and 

approved support system was installed fully according to plan, and 

an unsupported area includes those areas with no support or

temporary supports including an automated temporary roof support 

(ATRS). The third taxon layer indicates whether the mining area 

was active or inactive. Active areas are those where mining

activities are occurring, and miners are likely present. Inactive 

areas include accessible but not abandoned workings where miners 

are not normally present such as secondary escapeways or bleeder 

entries. The fourth layer classifies the failure initiation as either 1) 

rock mass failure, 2) support system failure or 3) human activitiesrelated failure. Finally, the fifth layer further categorizes the failure 

initiation mechanism or activity (trigger) occurring at the time of 

the groundfall.

At this time, a formal scientific basis does not yet exist for the 

taxonomy schema utilized, although engineering reasons exist for 

the proposed method. The second taxon layer recognizes the

fundamental difference in risk and behavior between supported and 

unsupported ground. The third layer considers exposure. Active 

areas are where miners are expected to perform most of their 

normal duties, whereas, inactive areas expose very limited numbers 

of miners to any groundfall hazards. The fourth layer considers 

broad causes of groundfalls as either something geologic related (a 

rock mass failure), something engineering related (a support system 

failure) or something induced by what the person was doing

(drilling, bolting, mucking, scaling, etc.). Finally, the fifth layer 

considers specific triggers of groundfalls.

To justify this approach, consider classification of animal

species. Early classification schemes used physiological factors 

such as shape, bone structure and organ development to group 

animals into various genera and families. An underlying scientific 

basis for these classifications did not arise until development of 

evolution theory. While a firm scientific basis for ground-falltrigger classification is desirable, an initial attempt based on

experience may lead toward that end.

Each groundfall narrative in the data sets was read and

classified by the taxonomic schema. Groundfalls within the sets, 

which did not cause injuries or did not take place in an

underground operation, were not included. Narratives from 13,277 

groundfall related incidents in a 16-year period (1984-99) in the 

U.S. underground mines were classified successfully with the

schema. The actual number of groundfall incidents extracted from 

the accident/injury classifications was much greater though by 

about several thousand. Only those groundfall incidents that 

included sufficient information for classification by this schema 

(13,277 in all) were considered.
Incident reports, which included data on the volume of rock fall, 

were noted and classified as small (less than 0.25 ft3), medium 

(between 0.25 and 1 ft3) or large (equal to or greater than 1 ft3). 

Falls from which a volume could be assumed were also included in 

this classification. For example, it is reasonable to assume that a 

groundfall that buries a victim to the waist consists of a volume of 

material greater than 1 ft3. No correlation was made between the 

triggers of the injury causing incidents and the size of the ensuing 

falls. 

The ages of those injured by groundfalls were also noted. The 

ages of the individuals were classified as under 20, 20 to 29, 30 to 

39, 40 to 49, 50 to 59, and over 60. No correlation was made 

between the triggers of the injury causing incidents and the ages of 

the individuals involved. 

RESULTS AND DISCUSSION

Figure 1 illustrates the year-to-year number of groundfall

incidents. A downward-moving trend in the number of injuries 

from groundfalls exists from 1984 to 1999. Between 1991 and 

1999, the number of injuries from groundfalls decreased by 42%. 

While this decrease seems dramatic, the number of man-hours 

worked in the same period also declined by 31% making the 

apparent decline in incident rate less impressive. The number of 

man-hours worked in underground coal operations, which 

accounted for 87% of all underground lost time injuries during the 

period 1991 to 1999, declined by 35% (4), indicating that the

frequency of injuries from groundfalls did not decrease

dramatically from 1991 to 1999.

Figures 2a and b show the five-layer taxon tree. Again, the first 

taxon layer merely represents the broad classification of rock fall 

incidents. The second layer of the classification is composed of 

two taxons, incidents in a supported area and incidents in an 

unsupported area. The third layer has two taxons, incidents in an 

active mining area and incidents in an inactive mining area. In 

layer four, there are four taxons and subsequently, in layer 5, there 

can be up to six taxons. A particular branch in this taxon tree maps 

to the root cause “inadequate number or inappropriate spacing of 

supports” and accounts for 11.9% of the total incidents classified. 

This layer five taxon belongs to the layer four taxon “incidents 

caused by rockfall initiated by support failure” that accounts for 

15.5% of the total incidents classified. This layer in turn belongs to 

the layer three taxon “incidents in active mining area” that includes 

67.6% of the incident database, and in turn belongs to the layer two 

taxon “incidents in a supported area” which also contains 67.6% of 

the incidents analyzed. Depending on the clarity and completeness 

of the narrations of the incidents recorded, these taxons can be 

phrased more precisely and more layers can be formed to pin point 

the root cause of a particular incident and the ultimate utilization of 

taxonomic analysis can be realized. 

The taxonomic analysis of groundfall incidents in U.S. mines 

from 1984 to 1999 portrays a very clear picture regarding the 

etiology or root cause determinations of these incidents. The taxon 

tree shown in figures 2a and b is presented next as a “layered bar 

chart” in figure 3 to illustrate better the relative importance of each 

taxon category in terms of percent of total incidents.

Moving down the taxonomic layers shown in figure 3 provides 

potentially useful insights into groundfall incidents. The layer 2 

taxon indicates that 67.6% of groundfall incidents occur in a

supported area with the remaining 32.4% occurring in unsupported 

NUMBER OF GROUNDFALL INJURIES PER YEAR

0

200

400

600

800

1000

1200

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Year

Number of groundfall injuries

Figure 1. Annual distribution of the number of groundfall injuries (1984 to 1999).
areas. The two-thirds of all groundfall incidents that occur in a 

supported area suggest continuing need for improvements in

support systems; however, other strategies could also prove

effective such as improved hazard recognition training. The onethird of groundfall incidents that occur in unsupported areas may 

suggest a need for improved temporary supports or better training 

in support installation. The layer 3 taxon does not provide any new 

significant information on groundfall incidents. Fully 99.9% of all 

such incidents occurred in active mining areas. Evidently, very few 

miners are exposed to additional groundfall risks that may be

present in inactive mining areas.

Figure 2A. Distribution of injury causing ground fall incidents by trigger (continued in Figure 2B).

Rockfall Accidents

1984-1999

Accidents cause

by a Rockfall in a

Supported Area

(67.59%)

Accidents caused

by a Rockfall in an

Unsupported Area

(32.41%)

Accidents Occuring in

an Active Mining Area/

Transport Conduit

(67.58%)

Accidents Occuring in

an Inactive Area of the

Mine (.008%)

Accidents Caused by

Rockfall Initiated by

Rockmass Failure

(43.54%)

Accidents Caused by

Rockfall Initiated by

Support Failure (15.52%)

Accidents Caused by

Rockfall Initiated by Direct

Human Action (8.46%)

Accidents Caused by

Rockfall Initiated by

Seismic Activity (.07%)

Result of Drilling or

Bolting (.836%)

Result of Mucking

(.941%)

Result of Barring

Down (.429%)

Result of

Operating a Miner

(6.251%)

Result of Fall

Between Sheilds

(3.450%)

Result of

Inadequate

Maintenance of

Supports (.128%)

Result of

Inadequate Bolt

Length (.045%)

Inadequate Number of

Inappropriate Spacing

of Supports (11.893%)

Result of

Excessive Span

(.008%)

Result of

Rockburst

(1.235%)

Result of Sliding

Plane (.015%)

Result of Bedding

Plane Sparation

(.030%)

Result of Other

Weakness

(34.533%)

Result of Spontaneous

Rib-Roll/Sluff-Off

(7.720%)

Result of

Earthquake

(.038%)

Result of Blasting

or Failure not in

Immediate Area

(.030%)

Accidents Caused by

Rockfall Initiated by

Rockmass Failure

(.008%)

Accidents Caused by

Rockfall Initiated by

Support Failure (0.00%)

Accidents Caused by

Rockfall Initiated by

Seismic Activity (0.00%)

Result of

Inadequate

Maintenance of

Supports (0.00%)

Result of

Inadequate Bolt

Length (0.00%)

Inadequate Number

or Improper Spacing

of Supports (0.00%)

Result of

Excessive Span

(0.00%)

Result of

Rockburst (.008%)

Result of Sliding

Plane (0.00%)

Result of Bedding

Plane Sparation

(0.00%)

Result of Other

Weakness (0.00%)

Result of Spontaneous

Rib-Roll/Sluff-Off

(0.00%)

Result of

Earthquake

(0.00%)

Result of Blasting

or Failure not in

Immediate Area

(0.00%)

Continued in Table 1b
Figure 2B.- Distribution of injury causing ground fall incidents by trigger (continuation of figure 2A).

Accidents

Occuring in an

Active Mining

Area/Transport

Conduit (32.40%)

Accidents

Occuring in an

Inactive Area of

the Mine (.008%)

Accidents Caused by

Rockfall Initiated by

Rockmass Failure

(6.39%)

Accidents Caused by

Rockfall Initiated by

Direct Human Contact

(26.01%)

Accidents Caused by

Rockfall Initiated by

Seismic Activity (0.00%)

Result of

Earthquake

(0.00%)

Result of Blasting or

Failure not in

Immediate Area

(0.00%)

Result of Drilling or

Bolting (7.554%)

Result of Mucking

(.746%)

Result of Barring

Down (9.151%)

Result of

Operating a Miner

(3.886%)

Result of Setting

Timbers or

Cribbing (4.670%)

Result of

Excessive Span

(.008%)

Result of

Rockburst (.889%)

Result of Sliding

Plane (0.00%)

Result of Bedding

Plane Sparation

(0.00%)

Result of Other

Weakness

(5.182%)

Result of Spontaneous

Rib-Roll/Sluff-Off

(.316%)

Accidents Caused by

Rockfall Initiated by

Rockmass Failure

(.008%)

Accidents Caused by

Rockfall Initiated by

Seismic Activity (0.00%)

Result of

Earthquake

(0.00%)

Result of Blasting or

Failure not in

Immediate Area

(0.00%)

Result of

Excessive Span

(0.00%)

Result of

Rockburst (.008%)

Result of Sliding

Plane (0.00%)

Result of Bedding

Plane Sparation

(0.00%)

Result of Other

Weakness (0.00%)

Result of Spontaneous

Rib-Roll/Sluff-Off

(0.00%)

From Accidents Caused by

Rockfall in an Unsupported Area
The layer 4 taxon indicates that some form of rock mass 

failure accounted for 49.9% of groundfall incidents, some kind of 

support system failure caused 15.5% of the incidents and human 

activity factors initiated the remaining 34.5%. Thus, engineering 

controls to prevent groundfalls, i.e., support systems, seem to 

have relatively few failures. Efforts to detect anomalies in the 

rock mass or to improve human activities connected with support 

installation may be avenues for reducing groundfall incidents 

with more potential for impact.

Figure 3.– Relative importance of the etiology or root cause of groundfall injuries.
Table 1 summarizes the relative importance of level-5 taxons 

of groundfall incidents from figure 3.

Table 1. Ranking of level 5 taxons of groundfall incidents for 

each level 4 taxon.

Rock Mass 

Failure

Support System 

Failure

Human Activity 

Factors

Type % Type % Type %

Other 

weakness

39.7 Inadequate 

or improper 

spacing

11.9 Operating 

a miner

10.1

Rib-roll or 

slough-off

8.0 Fall 

between 

shields

3.5 Scaling 

down

9.6

Rockburst 2.1 Inadequate 

maintenance

0.1 Drilling 

or bolting

8.4

Joint 

planes or 

bedding 

planes

<0.1 Inadequate 

bolt length

<0.1 Setting 

timbers or 

cribbing

4.7

Excessive 

span

<0.1 Mucking 1.7

TOTAL 50.0 TOTAL 15.5 TOTAL 34.5

Unfortunately, the analysis shows that the taxon “other

weakness” under rock mass failure, which is defined as “falls that 

are not described by other categories; incidents in

supported/unsupported areas which have no listed cause and from 

whose description no cause can be inferred”, has the highest 

overall percentage (39.7%). In other words, the brief narratives 

did not provide enough information to identify clearly the root 

cause of almost 40% of groundfall incidents considered by this 

taxonomic scheme. This high percentage category may reflect 

inadequacies in the taxonomic scheme utilized, lack of sufficient 

detail in the incident narratives or some other deficiency. 

However, the etiology of over 60% of the 13,277 groundfall 

incidents considered is identified.

The most common known rock mass failure is the rib-roll or 

slough-off, that accounts for 8% of the incidents classified. The 

substantial number of incidents in this class may indicate an 

ongoing need for improved ribfall control practices.

Rockbursts remain an important class of rock mass failure 

with 2.1% of total groundfall incidents. While this percentage of 

rock mass failures is small, rockbursts or bumps occur in very 

few U.S. mines with relatively few employees. One can show 

that the risk of groundfall-related injury in rockburst- or bump -

prone mines is much higher than the industry-wide average.

The influence of geologic discontinuities such as joint and 

bedding planes did not figure prominently in rock mass failure 

related injuries. Excessive span was also a small number. 

Unfortunately, “other weakness” or cause undetermined remains 

the biggest category under rock mass failure.

Within the class “support system failure”, which account for 

about 15.5% of the groundfall incidents classified, inadequate or 

improper support spacing accounted for 11.9 % of the incidents 

or over two-thirds of the class. This class includes causative 

factors such as inadequate bolt density but may also include lack 

of wire mesh, mats, rib-bolting, shotcrete or other surface “skin” 

control.

The class “human activities factors” accounts for about

35.5% of groundfall incidents and includes those triggered by 

direct human/machine interaction with the rock that occurs while 

operating a continuous miner (10.1%), scaling or barring down 

(9.6%), drilling or bolting (8.4%), setting timbers or cribbing 

(4.7%) or mucking (1.7%). Most of these activities relate to 

ground support installation and may suggest the need for

improved operating procedures that decrease exposure of miners 

to groundfall hazards.

The six top categories of root causes clearly demonstrate 

contributions of ground characteristics, support characteristics 

and human factor domains for a given incident. The rank order 

of these six top major root causes varies somewhat from year to 

year as shown in figure 4.

Figure 5 illustrates the distribution of broken rock volumes 

involved in an injury-incident due to groundfalls. Falls with a 

volume of less than .25 cubic feet were classified as small; those 

greater than or equal to 0.25 but not greater than 1 cubic foot 

were classified as medium sized, and falls greater than 1 cubic 

foot of total volume were classified as large. Rock fall volume 

could be estimated from about 1,570 incident narratives

representing about 12% of the total groundfall incidents reviewed. 

As seems obvious, most of the injuries due to groundfalls 

consisted of volumes of rock greater than one cubic foot. 

However, small- and medium-sized rockfalls (less than 1 cubic 

foot) accounted for about 40% of the groundfall injuries. 

Missing data from the data set probably leads to an underestimate 

of the importance of small- and medium-sized rockfalls as an 

injury source.

Figure 6 displays the age distribution of incident victims; it 

indicates that the proportions of incident victims 40-49 and 50-59 

increased between 1984 and 1999. MSHA data analyzed by the 

National Institute for Occupational Safety and Health (5) show 

that the median age of non-fatally injured miners in the US has 

increased between 1988 and 1997. The rising median age of 

miners correlates to the increase in injuries seen among the 40-49 

and 50-59 age groups. The proportion of victims of groundfall 

related incidents age under age 20 and over age 60 remained 

fairly constant between 1984 and 1999, as did the proportion of 

the injured for whom no age was supplied, but the proportion of 

those injured who were 20-29 and 30-39 decreased.

There is very little doubt that the overall mining workforce is 

aging; for example, the average age of a coal miner was 39 in 

1986, 42 in 1992 (6), and is now near 50 years. These facts, 

according to NIOSH, may contribute to a number of the mining 

injuries which occur each year; they claim that deteriorating 

hearing and eyesight, along with an increase in reaction time may 

become key mine safety issues (6). As we have seen above, 

however, even though the miner population has aged, the 

frequency of injuries (at least those associated with rockfalls) has 

decreased slightly, due to improvements in safety programs, 

geological information, ground support, and equipment. Older 

miners are also likely to have experience, which may help to 

offset many of the factors that contribute to increased injury risk.
YEAR-TO-YEAR DISTRIBUTION OF SEVEN MAJOR CAUSES OF GROUND FALL 

ACCIDENTS

0

5

10

15

20

25

30

35

40

45

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Year

Percent of groundfall accidents

Other weakness

Inadequate

support or

spacing

Operating a

miner

Scaling down

Rib-roll or

slough-off

Drilling or bolting

Timbering or

cribbing

Figure 4.- Year-to-year distribution of seven major causes of ground fall incidents in the U.S. underground mines.

Fall Size Distribution

0%

10%

20%

30%

40%

50%

60%

70%

80%

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999

Year

Percent

SMALL

MEDIUM

LARGE

Figure 5.-Distribution of small, medium, and large falls (1984-1999).
CONCLUSION

Groundfalls in underground mines in the U.S. continue to be a 

major cause of fatal or non-fatal injuries among the miners. Over 

the past thirty years, improved ground control, support design and 

safety training for miners have managed to bring down the

occurrences of groundfalls and related incidents, but the problem 

has remained significant. 

This study identifies several areas where improvements might 

decrease the incidence of injury from underground groundfall

incidents. Nearly 15% of injury-causing falls examined in this 

study can be attributed to an improperly supported roof or back; 

ribs rolls and slough off accounted for an additional 8%, and falls 

between longwall shields contributed 3%. These findings may 

indicate that inadequate ground support, an inadequate ground

control plan or inadequate supervision of implementation is a 

significant problem in underground mines in the U.S. Additionally, 

direct human or human-machine interaction with rock triggered 

more than 30% of the falls. It is obviously impossible to prevent 

this type of interaction, but it may be possible to increase

awareness of the risks involved in these types of activities (i.e., 

running a miner, barring down/scaling, drilling/bolting, etc.) and 

improving training for less experienced miners. Improved and 

increased training will become essential in the coming years as 

many experienced miners reach retirement age and those with less 

experienced take their place.

The database that is the basis for these results is not complete. 

For most injury-causing falls, the narratives provided no conclusive 

cause or trigger for the groundfall incident. The overwhelming 

majority of the falls due to rock mass failure (39.7%) were

classified in the “other weakness” taxon since no information about 

the cause was available. Similarly, for most of the years from 1984 

to 1999, 3-5% of the victims’ ages were omitted from the database 

and in no year did more than 15.8% of the descriptions of injurycausing falls include definitive data on the volume of the fall. 

Reducing or eliminating groundfall related injuries will require 

compilation of more complete data.

REFERENCE

1. Anonymous. Don’t Be The Fall Guy: MSHA Preventive

Roof/Rib Outreach Program, OT44, 2000.

2. MacCollum, D.V. Crane Hazards and Their Prevention. 

Washington DC: American Society of Safety Engineers, 1993.

3. Shepherd, G.W., Kahler, R.J., and Cross, J. Crane Fatalities –

A Taxonomic Analysis. Safety Science 36, 2000, pp. 83–93.

4. National Institute for Occupational Safety and Health. 

Number of Employee Hours Reported by Mine Operators (Op) 

and Independent Contractors (IC) by Commodity and Year, 

1991-2000 (Excludes Office Workers). NIOSH Mining

Safety and Health Research; Number of Employee Hours, 

2000, http://www.cdc.gov/niosh/mining/data/graphtab.html.

5. National Institute for Occupational Safety and Health. Median 

Age Of Nonfatally Injured Mine Operator Employees By 

Commodity And Year, 1988-1997. 2000,

http://www.cdc.gov/niosh/mining/data/gt_other.html. 

6. National Institute for Occupational Safety and Health. 

Aging NIOSH Mining Human Factors Design; Human 

Factors Design Recommendations for Underground

Mobile Mining Equipment, 2000,

http://www.cdc.gov/niosh/mining/hfg/default.htm.

AGE DISTRIBUTION OF GROUNDFALL ACCIDENTS

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

50.00%

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 YEAR

PROPORTION

<20 20-29 30-39 40-49 50-59 >60 None

Figure 6. Distribution of ages of those injured in underground ground fall incidents (1984-1999).