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Groundfall accidents have been the leading cause of fatalities in the underground coal mining industry for many years. Statistics from the Mine Safety and Health Administration (MSHA) indicate that approximately one-quarter of the victims of these fatal accidents were in an area where no devices had been installed to support the mine's roof. Mine operators rely primarily on threats of disciplinary action and classroom safety lectures to discourage miners from going under unsupported roof. However, several other options may also be worth pursuing: Eliminate sources of motivation for going under unsupported roof by changes in equipment, work procedures and policies. Eliminate the precursors of going under unsupported roof via incentives or feedback. Increase fear of the harm that roof falls can cause. Conduct behavioral modeling to show supervisors how to interact with miners who they find under unsupported roof. Have high level managers communicate their commitment to the goal of keeping people away from unsupported roof. Use disciplinary actions. This article summarizes the opinions of 268 coal miners and 29 first-line supervisors concerning why people go under unsupported roof and how to prevent this behavior. The interviews were conducted at six mine sites during 1989 and 1990. For additional information on this topic contact: Robert Peters Pittsburgh Research Laboratory 412-386-6895 RPeters@cdc.gov

Background

Going under unsupported roof is a very dangerous activity. It directly contributes to many fatalities and severe injuries in the underground coal mining industry. According to MSHA's accident statistics, in most years, roof fall accidents continue to be the leading cause of fatalities in underground coal mines. During the 5 year period 1997-2001, 51 coal miners were killed by falls of roof and rib, and over 2,300 were injured. Fortunately, the number of coal miners killed each year by groundfalls has been declining since we interviewed miners about going under unsupported roof in 1990. At the time of that study, about half of the miners who were killed by roof falls were in an area of unsupported roof. Not only has the number of deaths caused by roof falls declined since 1990, the proportion of these victims who were under unsupported roof at the time of the roof fall has also declined--from approximately one-half to one-quarter. Nevertheless, it is important to keep in mind that the factors contributing to this type of fatality are still present, and that miners and mine operators should continue to be very diligent in their efforts to prevent people from going under unsupported roof.

Groundfalls have been a major threat to miners' safety ever since mining began. Most miners are told repeatedly that it is very dangerous to go under unsupported roof and know that mine safety regulations prohibit this behavior. Nevertheless, accident investigations and data from interviews with coal miners suggest that there are individuals in the coal mining work force who, in certain circumstances, do not hesitate to go under unsupported roof.

Some of the reasons for going under unsupported roof are directly related to the task being performed. However, there are other factors:

• the miner's perception of the company's policy concerning going under unsupported roof and how it is enforced,
• the attitudes and behavior of the employee's supervisor and coworkers,
• the employees' own attitudes and expectations regarding the risks and benefits of doing things under unsupported roof. 

Interview data were also collected on these other factors. The complete findings from interviews with 297 miners can be found in Bureau of Mines IC Report No. 9300 (4). The focus of this paper is limited primarily to miners' views about what types of activities are likely to be performed under unsupported roof, and what types of actions might help to prevent miners from performing these tasks under unsupported roof.

How the Information Was Collected

A sample of miners and section supervisors was asked to respond to a variety of questions concerning going under unsupported roof in one-on-one interviews. All interviews were conducted in private, usually at the dinner hole near the miner's worksite. Employees were interviewed only if their job required them to work near face areas of the mine on a daily basis. All participants were assured that their responses would be held in confidence and were told that their participation was completely voluntary.

Data were collected from February 1989 to March 1990. A total of 297 employees from six underground coal mines participated in the study. The table below shows the mine, the number of miners interviewed, the number of underground employees, the location, the rate of lost-time injuries per 200,000 hours of exposure, the seam height, and whether or not miners were represented by a union. All mines were using the room-and-pillar method of extraction, remotely operated continuous miners, and roof bolters equipped with automated temporary roof supports.

¹Per 200,000 employee-hours of exposure.

Note that the results of this study are not representative of the entire industry. The sample of mines that participated in the study was small, and it was not randomly selected. Several mining companies who were invited to participate in the study were unwilling to do so.

Reasons For Going Under Unsupported Roof

Miners were asked three sets of questions concerning why people sometimes go under unsupported roof. In the first set of questions miners were asked to describe an incident in which they have recently observed a coworker doing something under unsupported roof. The second set of questions asked miners to describe the most recent instance in which they unintentionally went under unsupported roof. The third set of questions asked miners to identify tasks that are likely to be performed under unsupported roof by people who perform their type of job (e.g., roof bolters).

Observations Concerning Coworkers

One way to determine what might cause miners to go under unsupported roof is to ask them to describe a recent incident in which they observed a coworker doing something under unsupported roof. Miners were asked several questions concerning such incidents. They were first asked, 

Have you ever seen someone go under unsupported roof?

86% said that they could recall an instance in which they had seen someone go under unsupported roof. Miners were next told, 

Consider the most recent time you saw someone go under unsupported roof. Has it been within the past 6 months?

Of the 225 miners who said that they had seen someone under unsupported roof, 130 (58%) said that the most recent time had been within the past 6 months.

These 130 miners were asked several questions about the most recent incident. The questions and their responses are listed below:

Do you think this person was aware that he/she was under unsupported roof?

Yes	71.5%
No	27.7%
Uncertain	0.8%

Did this person take a look at the roof before he/she went under it?

Yes	59.2%
No	28.5%
Uncertain	12.3%

How far inby the last row of supports did he/she go?

0 to 5 feet	52.3%
6 to 10 feet	30.0%
Over 10 feet	17.7%

How long was he/she there?

A few seconds	54.6%
1 or 2 minutes	22.3%
Under 10 minutes	12.3%
10 to 20 minutes	7.7%
Over 20 minutes	3.1%

These responses suggest that 72% of those who reported recently seeing someone under unsupported roof thought that the incident had been an intentional act. In about half of the incidents that were described, it appears that the people under unsupported roof had tried to be cautious about their behavior. They looked at the roof before going under it, they went less than 10 ft beyond the last row of supports, and they were under unsupported roof for only a few seconds. Of course, miners may behave differently when they realize that someone could be observing them than when no one is present. It could be that miners who go under unsupported roof are less cautious about it when they know no one is around to observe them. Miners were also asked to describe what the person who they observed under unsupported roof was doing. The most frequently mentioned replies were as follows:

• Walking through unbolted crosscuts (17)
• Walking (11)
• Operating a continuous miner (11)
• Hanging or extending ventilation tube (10)
• Retrieving things left laying on the ground (7)
• Marking the roof (5)
• Rock dusting (5)
• Repairing a continuous miner (4)
• Operating a scoop (4)
• Operating a mobile bridge (3)
• Examining a roof fall (3)
• Restoring power to a remote continuous miner (3)
• Carrying supplies (3)
• Operating a roof bolter (3)

Miners were next asked:

Does this person often go under unsupported roof?

Yes	15.4%
No	76.9%
Uncertain	7.7%

Relatively few persons indicated that the person they had most recently observed under unsupported roof was doing it on a frequent basis. (However, at each mine, at least a few miners would mention that, although going under unsupported roof was not common at the mine where they were currently working, it was done rather often at mines where they used to work.) 

If the miner's response to the question above was "No", the miner was asked, "Had anything unusual happened on that day that might have caused this person to go under unsupported roof?" Most were unable to identify any type of unusual event or circumstance. Those who were able to cite something unusual thought that the following events or circumstances may have been at least partially responsible for why the person had gone under unsupported roof:

• There had been a roof fall (5)
• The roof had fallen on the continuous miner (2)
• A rib fall had tripped the circuit breaker on the continuous miner so it could not be operated by remote (1)
• Poor roof conditions had caused us to get behind on production (1)
• The person had only recently been assigned to the job that was being performing (1)
• The continuous miner was broken down and could not be moved (1)
• An unbolted area had been partially rock dusted (1)
• There had been a power outage (1)
• We were working on a Saturday to get caught up on production (1)

Unintentionally Going Beneath Unsupported Roof

Some of those who go beneath unsupported roof may not realize that they have gone beyond the last row of bolts, i.e., their action was unintentional. Miners were asked questions to determine whether this happens very often and to find out what activities are usually being performed when people unintentionally go under unsupported roof. 

Miners were first asked if they had ever unintentionally gone into an area of unsupported roof.

Eighty-two percent of the sample indicated that they could recall such an incident. 

Those who could recall a time that they had unintentionally gone under unsupported roof were asked to estimate how long ago the most recent incident had occurred.

Approximately 60% of those who could recall an instance in which they had unintentionally gone under unsupported roof estimated that the most recent incident had occurred within the past year. About 24% thought that the most recent incident had occurred within the past month.

Miners were next asked:

What were you doing when you realized you were under unsupported roof?

 
The most frequently mentioned replies were:

• Walking (59)
• Hanging or extending ventilation tube (11)
• Operating a scoop (9)
• Repairing a continuous miner or bolter (8)
• Hanging ventilation curtain (8)
• Rock dusting (7)
• Operating a bolter (7)
• Operating a continuous miner (6)
• Carrying supplies (6)
• Setting timbers (5)
• Operating a ram car or shuttle car (4).

Several of those who said that they were walking somewhere when they discovered that they had gone under unsupported roof noted that no warning devices had been posted at the last row of bolts. In a few cases, miners noted that the area they were walking in had been rock dusted, leading them to believe that it was bolted. At one mine, several miners noted that the sliding (telescoping) ventilation tubes would often become jammed, causing miners to have to go to the end of the slider closest to unsupported roof and pull on it to get it to fully extend.

In summary, it appears that a significant proportion of people who work at the face unintentionally go under unsupported roof. This suggests that it is very important that warning signs always be posted at the edge of unsupported roof, and that these signs are highly visible.

Job-Specific Reasons

To determine what might cause miners who perform a particular face crew job to go under unsupported roof, each participant was asked to respond to the following open-ended question:

Considering the different tasks involved in doing the [INSERT MINER'S JOB TITLE (e.g., roof bolter's)] job, which ones are most likely to cause them to go under unsupported roof?

The table below lists some of the most frequently cited tasks and indicates the number of people from each job category who mentioned it. For example, the first column of numbers shows the number of continuous miner operators or helpers who mentioned each task listed along the left side of the table as being likely to cause miner operators or helpers to go under unsupported roof.

Preventive Measures

As previously explained, miners were asked to identify tasks that are likely to be performed under unsupported roof by miners who do their type of job. Whenever miners identified such a task they were also asked the following question:

What could be done to make it less likely that [INSERT MINER'S JOB TITLE] would go under unsupported roof while [INSERT TASK CITED]?

This section presents miners' ideas about actions that might be taken to make it less likely that miners would go under unsupported roof to perform various tasks. Some of their ideas may not yet be feasible given the status of current technology and the resources typically available to mine operators.

Recommendations

It appears that mine operators currently rely primarily on threats of disciplinary action and classroom safety lectures to discourage miners from going under unsupported roof. However, several other options may also be worth pursuing. The following is a list of suggested actions for keeping miners away from unsupported roof.

1. Eliminate sources of motivation for going under unsupported roof by means of changes in equipment, work procedures, policies, etc. To accomplish this, it may be helpful to ask miners to identify situations that are likely to tempt people to work under unsupported roof, and to suggest what might be done to prevent these situations from occurring. This input could be obtained through interviews, surveys, or small group discussions. Research suggests that many of the factors influencing miners to go under unsupported roof vary from mine to mine. Therefore, it is important that the operators of each mine perform their own assessment. Remember to revaluate the situation at least every year or two, and whenever new equipment or work procedures are introduced to a face crew.
   
2. Offer incentives for eliminating the precursors of going under unsupported roof. For example, miners may go under unsupported roof unintentionally because warning signs are not posted immediately after a cut of coal has been removed by the continuous miner. In such a situation, a system could be developed for randomly measuring performance on this task and tying rewards to how often the signs are missing at locations where they should have been posted. Do not necessarily offer incentives on a continuous basis. They should be used whenever the target behaviors (or target conditions) appear to become less prevalent.
   
3. Increase fear of the harm that roof falls can cause. Perform this action with all new employees and as a reminder to first-time transgressors.
   
4. Conduct behavioral modeling to show supervisors how to interact with miners who they find under unsupported roof. Perform this action with all new section supervisors, and conduct refresher training every few years.
   
5. Have high level managers communicate their commitment to the goal of keeping people away from unsupported roof. Do this at least annually and whenever someone has been found violating this rule.
   
6. Use disciplinary actions. Threaten formal action with first-time transgressors. Use formal action if a second transgression occurs. If the behavior reappears after one attempt has been made at formal punishment, the person should be quickly eliminated from working near areas of unsupported roof. If the person has other types of useful skills, offer them an inherently safe job, one that is removed from areas of unsupported roof and that is unlikely to tempt the person to perform other types of unsafe acts, e.g., a job in an office or some other safe work area aboveground.

References

1. Peters, R., Fotta, B., and Mallett, L., The Influences of Seam Height on Lost-Time Injury and Fatality Rates at Small Underground Bituminous Coal Mines. Applied Occupational and Environmental Hygiene, 16(11), 2001, pp. 1028-1034.
   
   
2. Peters, R., Strategies for Encouraging Miners to Stay Away from Unsupported Roof and Perform Self-Protective Actions. BuMines IC 9283, 1991, 29 pp.
   
   
3. Peters, R. The Challenge of Enforcing Safety Rules in Remote Hazardous Work Areas. Professional Safety, November 1991, pp. 27-31.
   
   
4. Peters, R., and R. Randolph. Miners' Views About Why People Go Under Unsupported Roof and How To Stop Them. BuMines IC 9300, 1991, 59 pp.
   
   
5. Peters, R., and W. Wiehagen. Human Factors Contributing to Groundfall Accidents in Underground Coal Mines: Workers' Views. BuMines IC 9127, 1987, 24 pp.
   
   
6. Peters, R., Miners' Views About How to Prevent People From Going Under Unsupported Roof. In: Proceedings of Preventing Coal Mine Groundfall Accidents: How to Identify and Respond to Geologic Hazards and Prevent Unsafe Worker Behavior. Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, IC 9332, 1992, pp. 25-31.