Overviews

Empirical Design of Span Openings in Weak Rock based upon Support Type Employed (PDF, 115 KB, 2008)
This paper presents a focus of ground control research presently being conducted by the Rock Mechanics Group in the DBC Mining Department in incorporating weak rock masses (RMR₇₆ <50) into existing empirical design relationships. This work attempts to provide rock mechanic tools that will enable a mine operator to make economic decisions that will also ensure a safe working environment.

Pumpable Roof Supports: An Evolution in Longwall Roof Support Technology (PDF, 1284 KB, 2008)
This report examines the development of modern pumpable roof support technology and provides a full description of the performance capabilities of each of the support products now on the market.

History

Twenty-four Conferences; More than One-hundred and Seventy Papers; Understanding Roof Bolt Selection and Design Still Remains Priceless (PDF, 613 KB, 2006)
This retrospective paper discusses changes in bolt types and usage over the past 24 years, pointing out some of the biggest myths and hailing the most significant advances.

Software

AHSM - Analysis of Horizontal Stress Effects in Mining
AHSEM contains two modules to improve mine layouts for control of horizontal stress. For development, the user specifies the orientations of the entries, the crosscuts, and the maximum horizontal stress.

ARBS - Analysis of Roof Bolt Systems
ARBS is a software toll for selecting roof bolts for primary support in underground coal mines.

STOP - Support Technology Optimization Program
STOP is a software tool that provides mine operators with a simple and practical tool to make engineering decisions regarding the selection and placement strategy of these various standing roof support technologies. This program includes a complete data base of the support characteristics and loading profiles obtained through safety performance testing of these supports at the NIOSH Safety Structures Testing Laboratory.

CMRR - Coal Mine Roof Rating
The Coal Mine Roof Rating is a roof classification system that was first introduced to the mining community in 1994. The CMRR is a rock mass classification system which calculates the inherent strength of coal mine roof. It can be used in the design of gateroads, roof bolt selection, extended-cut decisions, and numerical modeling.

Guides

TGRSS - Troubleshooting Guide for Roof Support Systems
This guide provides a logical sequence to resolving the most common problems encountered with roof supports.

Models

Field Observations and Numerical Studies of Horizontal Stress Effects on Roof Stability in U.S. Limestone Mines (PDF, 974 KB, 2008)
This paper describes a modeling approach that can be used as a tool to evaluate potential roof failure and optimize the stability of room and pillar layouts.

Measurement & analysis

Analysis of Roof Bolt Systems (PDF, 140 KB, 2001-08)
A statistical study was conducted of roof bolt performance at a number of mines throughout the U.S. Analysis of the results led to guidelines that can be used to make preliminary estimates of the required bolt length, capacity, and pattern to improve roof stability for more difficult conditions.

Anchorage Pull Testing for Fully Grouted Roof Bolts (PDF, 864 KB, 2002-08)
Despite its potential importance, there is no widely accepted anchorage test for fully grouted roof bolts. Recent studies using short encapsulation pull tests are described.

Bolt Load Changes During Initial Face Advance and Cross-Cut Breakthrough (PDF, 600 KB, 2004)
The San Juan Mine and the National Institute for Occupational Safety and Health conducted a study to measure how development mining affected bolt loads.

Canopy and Base Load Distribution on a Longwall Shield (PDF, 4632 KB, 1992)
Roof and floor contact pressure provided by the interaction of a shield with the surrounding strata are examined. Controlled forces were applied to an 800-ton two-leg shield using a mine roof simulator.

Case Studies of Cable Bolts Using Instrumented King Wires (PDF, 3413 KB, 2001-07)
Instrumented cable bolts were used in conjunction with existing ground control to monitor rock mass loads at various field sites. Axial and shear loads were determined by strain gauges as these loads were transferred to instrumented cable bolts. Cable bolt performance, quality of grout, and installation techniques were also assessed. By monitoring load on and discplacement of the rock mass, more effective ground support can be selected and installed, which will lead to safer working conditions for miners.

Comparison of the Transverse Load Capacities of Various Block Ventilation Stoppings under Arch Loading Conditions (PDF, 428 KB, 2008)
NIOSH has been conducting research to develop a new testing protocol for rating mine ventilation stoppings. This paper compares the transverse load capabilities of several block materials and wall dimensions commonly used in stopping constructions based upon simulated three-hinge, rigid-arch loading tests of half-wall constructions in the NIOSH Mine Roof Simulator.

Computer Simulation of Ground Behaviour and Rock Bolt Interaction at Emerald Mine (PDF, 1100 KB, 2004)
A collaborative project was conducted to investigate ground behavior, reinforcement performance, and stress redistribution in a coal mine entry subjected to a severe horizontal stress concentration. This paper focuses on the computer simulation that was undertaken to provide more insight into the roof behavior and rock bolt interaction during mining.

Correlation of Sonic Travel Time to the Uniaxial Compressive Strength of U.S. Coal Measure Rocks (PDF, 591 KB, 2008)
This paper describes research conducted by NIOSH aimed at developing a correlation between sonic travel time logging of exploration boreholes and estimates of coal mine roof rock strength.

Design Spans: Underhand Cut-and-Fill Mining (PDF, 386 KB, 2005)
The underhand method under consolidated fill ensures a high recovery under an engineered back that is comprised of cemented rock fill and/or cemented paste fill. This method of mining is generally necessary either due to a weak rock mass comprising the immediate back and/or high induced back stresses. A major concern in the design of sill mats is the loading and strengths associated with the overlying sill mat. This paper reviews past practice coupled with present observations and measurements from over ten mines throughout North America related to mining under consolidated fills.

Effects of Bolt Spacing, Bolt Length, and Roof Span on Bolt Loading in a Trona Mine (PDF, 318 KB, 2001)
NIOSH researchers installed 39 instrumented, fully grouted bolts at six test sites in a trona mine retreat panel to study mine roof stability for the improvement of workplace safety.

Effects of Specimen Age on the Uniaxial Compressive Strength 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.

Evaluation of Support and Ground Response as Longwall Face Advances into and Widens Pre-Driven Recovery Room (PDF, 608 KB, 2007)
A cooperative study was conducted to evaluate the effectiveness of (partially) pre-driven longwall recovery rooms supported with pumpable roof supports. This paper evaluates the load transfer mechanics associated with the advancement of the longwall face into the pre-driven recovery room and the widening of the room to recover the longwall shields.

Factors Influencing Intersection Stability in U.S. Coal Mines (PDF, 523 KB, 1998-08)
NIOSH is using the experience of U.S. coal mines to determine the factors which influence intersection instability and provide guidelines for the safe excavation and support of intersections. By using the roof fall rate as the outcome variable, correlations between roof geology, intersection span, and roof support have been established.

Field Performance Testing of Fully Grouted Roof Bolts (PDF, 334 KB, 2003)
This paper reports on an extensive series of short-encapsulation pull tests that were conducted in the NIOSH Mine Safety Research Laboratory and operating mines in WV and PA.

Field Test with Strain-Gauged Friction Bolts at the Gold Hunter Mine, Mullan, Idaho, USA (PDF, 594 KB, 2003-08)
To measure the loading behavior of friction bolts, NIOSH researchers installed strain gauges on the interior of friction bolts and developed a battery-powered miniature data acquisition system (MIDAS) that fits inside the hollow portion of the friction bolt.

Field Verification of the Roof Fall Risk Index: a Method to Assess Strata Conditions (PDF, 665 KB, 2006)
The Roof Fall Risk Index helps the underground stone mine operator to assess defects the mine strata and rate the relative roof fall risk these defects pose. This paper examines how the defect information is collected using two field verification sites and proposes methods to analyze the RFRI data.

A First Step in Developing Roof Support Design Criteria Based on Ground Reaction Data for Pittsburgh Seam Longwall Tailgate Support (PDF, 603 KB, 2008)
In this NIOSH study to optimize standing roof support design, ground response curves were developed for longwall tailgate conditions from numerical models of Pittsburgh Coal Seam geology.

Impact of Deformable Materials and Convergence on the Transverse Load Capacity of Mine Ventilation Stoppings (PDF, 482 KB, 2008)
This paper presents the results of a NIOSH parametric study that quantifies the impact of various deformable materials in block stopping construction under transverse load conditions.

Investigation of Fully Grouted Roof Bolts Installed Under In Situ Conditions (PDF, 364 KB, 2005)
This paper describes the results of three studies: 1) A series of 24 pull tests of bolts installed fully grouted and overcored to leave 12 inches of grouted bolt. The tests compared the pull-out performance of offset-head roof bolts with that of standard 5/8-inch bolts; 2) A second series of 24 tests that compared the pull-out loads obtained by bolts installed with 1 ft of resin (a Short Encapsulation Pull Test or SEPT) to that of fully grouted bolts overcored to leave only 12 inches of grouted bolt, and; 3) An investigation into the pressures generated during the installation of fully grouted resin bolts.

Investigation of the Jacking Force Capability of Tunnel Liners (PDF, 2262 KB, 2002)
Steel liner plates, which are bolted together to form a shell, are commonly used to provide temporary protective linings in the tunneling industry to ensure the stability of the tunnel and safety of the workers until more permanent ground reinforcement can be installed. This report summarizes the full-scale test results, examines design parameters that impact the jacking force capability, and develops new mathematical models to improve the prediction of design loads.

Load and Deflection Response of Ventilation Stoppings to Longwall Abutment Loading: A Case Study (PDF, 707 KB, 2001)
Few studies have specifically measured and documented the large-scale loading behavior and durability of ventilation stoppings to mining induced movements, particularly from longwalls. This paper presents the investigations of underground measurements that have been conducted to determine the loading response of stoppings constructed from lightweight aggregate concrete masonry units.

Load Capacity and Stiffness Characteristics of Screen Materials Used for Surface Control in Underground Coal Mines (PDF, 805 KB, 2006)
NIOSH conducted an evaluation of screen materials commonly used in U.S. coal mines to determine their support characteristics and identify the parameters that could affect their performance with respect to controlling the fall of rock from the roof surface.

New Tools for Roof Support Evaluation and Design (PDF, 530 KB, 2003-08)
This paper describes the capabilities of two instruments developed by NIOSH for identifying and monitoring ground control hazards. The miniature data acquisition system (MIDAS) has the potential to make the use of geotechnical instruments in underground mines more feasible. The "rock strain strip" (ROSS), in conjunction with MIDAS, can measure rock movement more accurately.

Performance and Safety Considerations of Hydraulic Support Systems (PDF, 1421 KB, 1998-08)
This paper examines the basic operating principles of state-of-the-art hydraulic cylinders and discusses relative issues pertaining to: setting loads; support stiffness; yielding behavior; errors in assessing support loading; and hydraulic failure mechanisms and how to detect them.

Pumpable Roof Supports: Developing Design Criteria by Measurement of the Ground Reaction Curve (PDF, 710 KB, 2003)
Pumpable roof supports provide an alternative longwall tailgate roof support and have grown in usage during the past few years. Despite the success of these supports, questions remain regarding critical design issues for optimizing the use of this support technology.

A Retrospective Assessment of Longwall Roof Support with a Focus on Challenging Accepted Roof Support Concepts and Design Premises (PDF, 718 KB, 2006)
This paper explores the history of longwall shield design over the past 25 years. It also addresses questions such as whether two-legged designs are better than four-legged shields and whether setting pressures should be set as high as possible.

Rock Mass Behavior and Support Response in a Longwall Panel Pre-Driven Recovery Room (PDF, 903 KB, 2008)
Some surprising results were revealed in this study designed and implemented by NIOSH to evaluate the effectiveness of pre-driven longwall recovery rooms supported with pumpable concrete roof supports.

Short-Encapsulation Pull Tests for Roof Bolt Evaluation at an Operating Coal Mine (PDF, 175 KB, 2003-08)
This paper presents information that shows that short-encapsulation pull tests can provide the information necessary to improve ground control in variable roof conditions.

Time-Lapse Tomography of a Longwall Panel: A Comparison of Location Schemes (PDF, 437 KB, 2007)
This paper describes a project in which three-dimensional time-lapse velocity tomograms were generated to image stress redistribution around a longwall panel to produce a better understanding of the mechanisms that lead to ground failure.

Using Major Hazard Risk Assessment to Appraise and Manage Escapeway Instability Issues: A Case Study (PDF, 462 KB, 2007)
A Major Hazard Risk Assessment (MHRA) is a structured process that identifies the characteristics of major hazards, assesses and ranks the risk they present, and evaluates engineering and administrative controls to mitigate them. This paper provides a case study example as to how the MHRA approach might be used to mitigate the risk of roof instability and fire hazards in US underground mines.

Case studies

Diagnosing and Controlling Moisture-Sensitive Roof Rock in Coal Mines (PDF, 520 KB, 2008-01)
In a recent study, NIOSH has used a wet/dry cycling test to determine the moisture sensitivity of over 800 specimens of roof rock from 25 U.S. coal mines. Three case studies are presented in which the moisture-sensitivity index is correlated to roof conditions underground, and can be used to indicate long term deterioration.

Engineering controls

Coal Mine Burst Prevention Controls (PDF, 468 KB, 2008)
This paper reviews 11 prevention control techniques for coal mine bursts.

Design Considerations for the Next Generation of Longwall Shields (PDF, 877 KB, 2001)
The purpose of this paper is to set goals for the future generations of longwall shields.

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.

Developments in Sealant Support Systems for Ground Control (PDF, 462 KB, 2002-08)
During the past few years, NIOSH has been evaluating developments in sealant support systems from a ground control perspective. This paper briefly reviews the current state-of-the-art technology in shotcrete and membrane developments, evaluates the preliminary findings of a long-term underground study of various types of sealant materials, and examines installation practices that are critical for an effective sealant material.

Evaluation of Instrumented Cable and Rebar Bolts as Ground Support at a Trona Mine (PDF, 664 KB, 2001)
Instrumented cable bolts developed at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health were used in conjunction with existing ground control systems to monitor rock mass loads at Tg Soda Ash's trona mine in Granger, WY.

Evaluation of Polyurethane Injection for Beltway Roof Stabilization in a West Virginia Coal Mine (PDF, 373 KB, 2004)
Polyurethane injection is a proven method of rock stabilization in even the weakest, most broken ground. Optimization of the injection design by pre-injection video diagnostics can greatly contribute to the successful and efficient roof stabilization.

Field Evaluation of Mobile Roof Support Technologies (PDF, 847 KB, 2001-08)
This study presents a historic overview of the role of mobile roof support (MRS) technologies in improving stability and worker safety and presents the results of recent field evaluations of the MRS load rate monitoring device and other remote deformation-monitoring techniques.

Geotechnical Factors Influencing Violent Failure in U.S. Mines (PDF, 848 KB, 1997)
Sudden, violent failures of rock around mine openings influence access, ventilation, and safety in both hard-rock and coal mines. To develop predictive tools for assessing the potential for violent failure, the authors initiated a comprehensive study using multiple linear regression and numerical modeling analyses of geological and mining conditions at 25 sites.

Ground Control Issues for Safety Professionals (PDF, 1641 KB, 2001)
Falls of ground continue to be one of the most serious causes of injury to U.S. miners. This goal of this chapter is to provide guidance to safety professionals tasked with preventing ground fall injuries. This chapter combines an analysis of the Mine Safety and Health Administration's (MSHA) accident and injury data with a survey of industry "best practices" to safeguard miners from ground falls.

Hydraulic Prestressing Units: An Innovation in Roof Support Technology (PDF, 730 KB, 2004)
A new generation of hydraulic mine support prestressing devices has been developed. This paper examines the performance capabilities of these inflatable prestressing units and the impact they have on the performance of various support systems, including an evaluation of the overall stiffness of the support system and the load control during yielding of the prestressing unit.

In Focus - Cable Bolts: A 'New Support' (http://holmessafety.org/1998/MAR98.pdf) (PDF, 1794 KB, 1998-03)
Cable bolts are gaining increased popularity in U.S. coal mines. Factors involved with this are discussed including the switch to resin anchorage.

In the Field - Cribs Versus Cables (http://holmessafety.org/1998/MAR98.pdf) (PDF, 1794 KB, 1998-03)
A full-scale test of a cable bolted cribless tailgate was conducted on an eastern United States longwall. Cable bolts proved more than adequate to provide a stable cribless tailgate.

The Introduction of Roof Bolting to U.S. Underground Coal Mines (1948-1960): A Cautionary Tale (PDF, 3504 KB, 2002)
Perhaps the most significant development in coal mine ground control during the last century was the introduction of roof bolting during the late 1940's and 1950's. From an engineering standpoint, roof bolts are inherently more effective than the wood timbers they replaced. The story of how roof bolting was implemented by the mining industry, but took so long to live up to its promise, is a fascinating example of the interaction between economics, technology, regulation, and science. It still has important lessons for today.

Longwall Shield and Standing Gateroad Support Designs - Is Bigger Better? (PDF, 705 KB, 2007)
Roof support systems, longwall shields in particular, have persistently grown in size and capacity for the past 25 years. Why is this? Is it a good thing or is it unnecessary? What are the consequences of this bigger-the-better design philosophy? Does high capacity ensure failures will not occur? There are fundamental aspects of support design and ground control that we still do not understand or recognize when designing a support system. This paper provides an interesting evaluation of these issues and proposes a different approach to support design that attempts to match the support performance characteristics to the ground behavior.

Longwall Shield Recovery Using Mobile Roof Supports (PDF, 1217 KB, 2007)
This paper addresses both the safety and the operational issues associated with mobile roof support (MRS) usage during shield recovery. It also discusses new developments, including the use of the inherently safer battery powered MRS's, which have been recently certified by MSHA.

Mistakes, Misconceptions, and Key Points Regarding Secondary Roof Support Systems (PDF, 3983 KB, 2001)
This paper discusses misconceptions about how roof supports perform and factors that impact their performance. The paper is limited to a discussion of secondary roof support systems and powered roof supports such as longwall shields.

New Support Concepts for Hard Rock Mining Applications (PDF, 987 KB, 2007)
This paper presents an overview of recent innovations in support technology for hard rock mining.

Optimizing Secondary Roof Support with the NIOSH Support Technology Optimization Program (STOP) (PDF, 395 KB, 2000-08)
The decade of the 90's brought an unprecedented increase in the development of innovative technologies to provide more effective and easier to install roof support in underground mines. To facilitate the application of these technologies to improve mine safety, NIOSH developed the Support Technology Optimization Program (STOP).

Overview of Ground Control Research for Underground Coal Mines in the United States (PDF, 1067 KB, 2001)
NIOSH has developed an entire toolbox of computer programs that have been effectively transferred to the mining community.

An Overview of Standing Roof Support Practices and Developments in the United States (PDF, 1210 KB, 2005)
This paper provides an overview of the support design and application philosophy in the United States.

Proceedings: New Technology for Coal Mine Roof Support (PDF, 18284 KB, 2000-10)
The papers in these proceedings were presented at open industry briefings conducted by NIOSH on New Technology for Coal Mine Roof Support. The proceedings provide information on several important new technologies, including: guidelines for selection roof bolt length, pattern, and capacity that were derived from statistical analysis of the roof fall experience at 37 underground mines; a new design method for longwall tailgates supports; and a technique for measuring loads developed within cable bolts.

Proceedings: New Technology for Coal Mine Roof Support: Errata Sheet (PDF, 52 KB, 2000-10)
Errata sheet for the publication Proceedings: New Technology for Coal Mine Roof Support (Pittsburgh, PA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2000-151, Information Circular 9453, 2000 Oct; :1-280)

Proceedings: New Technology for Ground Control in Retreat Mining (PDF, 5087 KB, 1997-03)
This proceedings volume contains papers presented at technology transfer seminars sponsored by the National Institute for Occupational Safety and Health (NIOSH) on New Technology for Ground Control in Retreat Mining.

Reinforcing Coal Mine Roof with Polyurethane Injection: 4 Case Studies (PDF, 674 KB, 2008-10)
This paper gives the results of 4 case studies that have recently been completed by NIOSH concerning the interaction between polyurethane (PUR) and coal mine roof in order to determine the mechanism of reinforcement, in both highly fractured rock and unfractured rock.

Standing Support Alternatives in Western Longwalls (PDF, 1007 KB, 2005)
Western mines have had limited choices for standing support. This paper compares the performance characteristics of various support systems.

Standing Support Alternatives in Western United States Longwalls (PDF, 1973 KB, 2006-02)
This article compares the performance characteristics of various support systems, including wood cribs, can supports, cluster props and pumpable supports.

Technology News 433 - Resin-Grouted Cables for Enhanced Coal Mine Roof Support (PDF, 67 KB, 1994-04)
This article describes the development of an easy-to-use, reliable, resin-grouted cable support system capable of being installed as primary and secondary roof support in coal mines.

Technology News 493 - Proceedings: New Technology for Coal Mine Roof Support (PDF, 251 KB, 2001-08)
An announcement for Information Circular 9453 - Proceedings: New Technology for Coal Mine Roof Support.

Administrative controls

Best Practices and Bolting Machine Innovations for Roof Screening (PDF, 141 KB, 2003)
Injury data are presented that show a dramatic reduction in roof skin injuries when screening is used. Five case studies in which roof screen was used are presented along with the associated costs of materials, impact on bolting advance rates, and potential ergonomic risks. The effects of roof screening on skin control and safety are also included. Finally, this paper provides information about best practices and features of roof bolting machines that affect production and safety.

Roof Screening: Best Practices and Roof Bolting Machines (PDF, 514 KB, 2002)
Roof screening has been found to be very effective in controlling the fall of small rocks from the immediate roof surface. Data is presented from two mines that show a dramatic reduction in roof skin injuries when screening is used. Much of this success is due to innovations in roof bolting machines.

Training packages

Roof Bolting Machine Operators Skills Training for a Walk-Thru Roof Bolter: Trainer's Guide (PDF, 1271 KB, 2006-08)
This trainer's guide is designed as a reference manual. The purpose is to offer information and examples to skills trainers to assist them in structuring training for new operators of Walk-Thru roof bolting machines. Trainers can use this manual as a resource for helping trainees learn, understand, and apply knowledge and skills.

Videos

Miner Mike Saves the Day! or Ground Support... It's Important!
Miner Mike Saves The Day exudes both humor and wisdom. Filmed in 6 different underground locations, the video teaches the necessity and use of ground supports. The video uses actual hard rock miners to teach the videos protagonists (Jeff and Jason) the importance of ground supports underground.

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.