Guides

Best Practices to Mitigate Injuries and Fatalities from Rock Falls (PDF, 1971 KB, 2000)
This paper presents an overview of the most significant ground control hazards facing today's mineworkers, as well as best practices to reduce these risks.

A User's Guide for the Bplane, Bstepp, and Bwedge Computer Programs (PDF, 2108 KB, 2007-03)
This user's guide covers the operation of a suite of three computer programs - Bplane, Bstepp, and Bwedge. These programs can be used to evaluate the potential for plane shear, step-path, and wedge failures along the crest of a slope bench. The theoretical basis, application, and operation of these programs are described.

Hazards

Numerical Model Calibration for Simulating Coal Pillars, Gob and Overburden Response (PDF, 738 KB, 2010)
The paper provides a basic set of input data and a modeling approach that can be used for numerical modeling investigations of various coal mine designs using the FLAC3D software package.

Pillar Strength in Underground Stone Mines in the United States (PDF, 419 KB, 2011)
Stone mines in the Eastern and Midwestern United States make use of the room-and-pillar method of mining to extract relatively flat-laying sedimentary formations. A survey of pillar performance was carried out to identify potential modes of instability.

Diseases, injuries & disorders

Current trends in Reducing Ground Fall Accidents in US Coal Mines (PDF, 1796 KB, 2011)
Ground falls (roof and rib) have historically been responsible for nearly 50% of all fatalities in bituminous underground coal mines. In recent years, the number of some annual ground fall fatalities has approached zero, indicating that significant progress has been made.

Measurement & analysis

Comparative Analysis of Moisture Sensitivity Index Tests for Coal Mine Roof (PDF, 217 KB, 2009)
This paper describes the work NIOSH has completed in evaluating three moisture-sensitivity index tests on roof rocks from 23 U.S. coal mines.

Effects of Specimen Age on the Uniaxial Compressive Strength and Moisture Content of Weak Coal Measure Rocks (PDF, 764 KB, 2008)
This paper presents the results of a NIOSH study to evaluate UCS changes occurring in a broad range of weak coal measure rocks over a one-year time span.

An Evaluation of Microseismic Activity Associated with Major Roof Falls in a Limestone Mine: a Case Study (PDF, 253 KB, 2007)
Roof falls are often preceded by a period of elevated microseismic activity, but not all periods of elevated activity result in a roof fall, nor do all roof falls occur after some amount of elevated activity. The objective of this study is to review periods of elevated microseismic activity and determine whether fracture activity rate can be used to anticipate the initiation of roof falls. The results show that limited success would have been achieved by the microseismic system as a roof fall alarm trigger. However, the trigger would have been successful at warning of the onset of elevated activity, allowing mine employees to respond appropriately.

Failure Characteristics of Roof Falls at an Underground Stone Mine in Southwestern Pennsylvania (PDF, 617 KB, 2001-08)
The location and time of 2,007 microseismic emissions from a limestone mine in southwestern Pennsylvania were compared with the development of mine faces and the characteristics of the mine layout. Based on analyses of these results, the occurrence of roof failure zones appears to be associated with certain characteristics of the mine plan.

Methods for Determining Roof Fall Risk in Underground Mines (PDF, 322 KB, 2007-11)
This paper discusses a method to determine the roof fall risk using a qualitative risk analysis technique.

Technology News 540 - Field-Expedient Shotcrete Adhesion Test System (PDF, 509 KB, 2011-06)
To develop a practical method of measuring shotcrete adhesion strength in underground mines.

Time Dependent Roof Deterioration at a Central Ohio Coal Mine (PDF, 1296 KB, 2009)
This paper describes a NIOSH field study to evaluate (1) the long-term stability and (2) the seasonal affects on mine entries with highly moisture-sensitive roof rock and presents the results from the field study, and the key issues determined from the study.

Case studies

Stability Mapping to Examine Ground Failure Risk: A Field Study at a Limestone Mine (PDF, 801 KB, 2009)
This paper presents a description of geologic settings, mining conditions, rockmass characterization with geotechnical risk assessment, analysis, mapping, and control techniques used at an underground stone mine in Central Pennsylvania.

Engineering controls

Design of Primary Roof Support Systems in U.S. Coal Mines Based on the Analysis of Roof Fall Rates (PDF, 588 KB, 2001-06)
A study is described where information was collected at 37 coal mine on roof falls, and other geotechnical, mining, geologic and roof bolting factors. A statistical analysis was conducted on the data with the roof fall rate being the outcome variable.

Early Strength Performance of Modern Weak Rock Mass Shotcrete Mixes (PDF, 762 KB, 2011)
A field-expedient test method and portable on site test equipment have been developed to measure shotcrete strength in the first six hours after application.

Evaluating Techniques for Monitoring Rock Falls and Slope Stability (PDF, 3017 KB, 2002)
Several remote-sensing technologies are being evaluated as tools to monitor slopes for hazards and to assess slope stability.

Ideas to Reduce Roof Fall Injuries (HTM, 1997)
A range of ideas to deal with reducing roof fall injuries from miners, mining safety professionals, and NIOSH research.

Personal Bolter Screen: Surface Control to Protect Underground Workers in Coal Mines (PDF, 297 KB, 2003-08)
The Personal Bolter Screen is simply standard wire mesh, produced in approximately 5-ft square sheets. The small sheets provide much of the same protection as traditional 13-16 ft wide wire mesh, but are much easier to handle, store, and install. The results of the trials conducted underground have been extremely positive.

Potential of Roof Screening to Reduce Workers´ Compensation Cost (PDF, 837 KB, 2010)
Each year more than 400 coal miners are injured (fatally and nonfatally) by rock falling from between or around roof supports. Many of these injuries can be prevented by the installation of roof screen. However, many coal mines are reluctant to use roof screen because of the added cost. The goal of this study was to determine the potential savings in workers´ compensation (WC) premiums that can be achieved due to a reduction in rock fall injuries after roof screening.

Reduced Workers´ Compensation Costs With Roof Screening (PDF, 679 KB, 2012)
In this paper, the potential savings in WC premiums that could be achieved due to a reduction in rock fall injuries after roof screening in Pennsylvania´s underground coal mines were quantified. Hypothetical mines (representing two mine sizes: 67 and 150 employees) were constructed with realistic estimates of injuries and WC premiums.

Roof Screening for Underground Coal Mines: Recent Developments (PDF, 1421 KB, 2007)
This paper describes some successful techniques and machine modifications that were evaluated for ergonomic considerations and are being used in productive mines to assist with roof screen installation.

Roof Screening for Underground Coal Mines: Recent Developments (PDF, 247 KB, 2008-06)
This paper discusses roof screen and its potential to prevent hundreds of injuries caused by the fall of small rocks between permanent roof supports.

Technology News 541 - Field-Use Early-Strength Shotcrete Test System (PDF, 752 KB, 2011-06)
To develop a practical method of measuring shotcrete early strength onsite in the first six hours after application using a partial beam test standard, ASTM C 1 16-90.

Technology News 542 - Field Use Round Determinate Panel Test System (PDF, 747 KB, 2011-06)
To develop a portable field-use testing system for conducting ASTM-1550-05 round determinate panel tests. The test system can be used at the mine site to obtain shotcrete toughness strengths that are required for determining the support requirements for mine openings, minimizing falls of ground, and reducing mine roof-fall incidents.

Administrative controls

How to Prevent People from Going Under Unsupported Roof (HTM, 2002)
Ground fall accidents have been the leading cause of fatalities in the underground coal mining industry for many years. Statistics from 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.

Technique to Assess Hazards in Underground Stone Mines: the Roof Fall Risk Index (RFRI) (PDF, 2535 KB, 2007)
A roof-fall hazard-assessment technique was developed based on engineering judgment acquired from extensive underground stone mine experience and on examination of the related literature. This technique utilizes observational processes to determine roof fall likelihood. Case-study scenarios offer a realistic picture of model implementation.

Equipment

Roof Hazard Alert Devices (HTM, 2001-06)
Miners have been known to unknowingly venture beyond the last row of roof bolts in underground coal mines. To help discourage miners from going under unsupported mine roof, NIOSH researchers have developed two flashing light roof hazard alert devices that direct a miners attention to a written message, warning the miner to avoid the hazard beyond the device.

Training exercises

Roof Fall Entrapment: Eyewitness Account by Dave Garry
Dave, a miner helper, tells about witnessing a roof fall that covered a continuous mining machine. He discusses efforts that were made inby supports to rescue the trapped, but unharmed operator and recognizes that danger could have been minimized by installing temporary supports before continuing rescue.

Roof Fall Entrapment: Eyewitness Account by Dave Murone
Dave tells about the experience of having to recover the body of a friend who was killed by a roof fall. The individual who was killed was inby supports at the time of the accident. Dave speculates on why his friend was under unsupported top and discusses the effect that witnessing this accident had on him.

Roof Fall Entrapment: Eyewitness Account by Larry Strayer
This video consists of an interview with a miner who tells about a fall that occurred while he and another miner were attempting to bar down top just inby the last row of supports.

Videos

Make it Safer with Roof Screen
Using extensive underground footage, this7-minute video shows how well screens keep loose rock from falling in difficult roof conditions. Techniques for installing screens for both outside-controlled and walk-through roof bolting machines are shown. The video also provides safe handling tips, best practices, and information about machine technology that can greatly improve material handling.

Rock Falls - Preventing Rock Fall Injuries in Underground Mines
This video teaches the importance of proper roof scaling in underground mining to avoid injury and improve work conditions.