Ground Control Downloadable Mining Publications

Sixty years of rockbursting in the Coeur d'Alene district has taught painful lessons and led to a number of practical advances in controlling rockburst hazards. This paper summarizes those lessons, concentrating on practical measures that have been successfully adopted to reduce hazards. (PDF, 409 KB, 2002-02)

Stability analyses of fractured and faulted rock masses require delineation of the position, extent, and orientation of geologic discontinuities. Recommendations are made for increasing the accuracy and precision of locations of microseismic events detected under similar field conditions. (PDF, 4026 KB, 1992)

Evaluation of the "Advance and Relieve" mining method is described to determine effectiveness for conditions where high horizontal stresses caused long running roof falls resulting in hazardous conditions and the premature abandonment of panels. "Advance and Relieve" mining involves the removal of a pillar of a portion of a pillar during development, creating a cave along one side of the panel.  (PDF, 5767 KB, 2001)

As part of an on-going study at the Spokane Research Laboratory, several new methods for monitoring slope instabilities are being investigated. This paper describes the potential adaption of systems such as interferometric synthetic aperture radar, imaging spectroscopy, and time-domain reflectometry, to slope monitoring and design. (PDF, 654 KB, 1998)

A U.S. Bureau of Mines investigation of longwall panel layouts to maximize coal recovery and minimize interactive problems in multiple-seam operations. (PDF, 992 KB, 1992)

This paper summarises the results of a research project whose goal was to provide the Australian coal industry with a rib support design methodology and software tool that could be utilised by suitably qualified colliery staff. (PDF, 286 KB, 2005)

A case study is presented that relates statistical descriptions of joint sets to the distribution of local wedge failures along the crest of a catch bench at the Yellowstone Talc Mine. (PDF, 575 KB, 2004-05)

The objective of this is paper is to review the current state of knowledge and practice in highwall mining. (PDF, 1182 KB, 2005)
                                            

NIOSH completed a major study to identify the location and likely severity of multiple seam interactions (undermining and overmining). More than 300 multiple seam case histories were assembled into the largest data base of multiple seam case histories ever collected. These data were analyzed with the multivariate statistical technique of logistic regression, LaM2D to estimate the multiple seam stresses, ALPS and ARMPS to determine pillar stability factors, and the CMRR to measure roof quality. The study resulted in the development of a computer program, called Analysis of Multiple Seam Stability (AMSS), which can help mine planners to evaluate each potential interaction and take steps to reduce the risk of ground control failure.  (PDF, 658 KB, 2007)

As underground stone mining expands to deeper cover situations, and more efficient mining methods are utilized, effective stone pillar design methods become more important. Seventy-two stone-mine pillar designs were examined or factors effecting stability and results are presented. (PDF, 1315 KB, 1999-12)

Some of the issues discussed in this article include highwall stability, reasons for early pull out of highwall miner holes, and geotechnical engineering and planning factors and operating practices to improve highwall stability and minimize the risk of a trapped highwall miner. (PDF, 335 KB, 2004-08)

A state-of-the-art, three-dimensional, full waveform, microseismic system was used to analyze the rock failure around a deep bump-prone longwall panel. Analysis of the recorded events is discussed. (PDF, 442 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. (PDF, 140 KB, 2001-08)

A study was conducted to determine the causes of slope failure and highwall/spoilbank failure and included: a review of accident statistics; a review of mining laws pertaining to surface mining; a literature review; and mine visits. The study emphasized surface mines in West Virginia, Ohio and Pennsylvania. (PDF, 248 KB, 2000-08)

A seismic monitoring system located at NIOSH's Lake Lynn Experimental Mine has monitored experimental gas and dust based explosions and impact tests. The results suggest a large explosion that's not restricted can generate potentially the same magnitude as a small explosion that is restricted. (PDF, 959 KB, 2008)

To provide a better understanding of the mechanics of strata deformation, the authors have collected and reviewed measurements of convergence and stress in one western U.S. mine and have completed pseudo-three-dimensional, boundary-element modeling for two typical pillar-pulling plans. (PDF, 202 KB, 1998)

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. (PDF, 864 KB, 2002-08)

The objective of this study was to test the capability of ground penetrating radar to determine the extent of grout penetration into the mine roof strata in the 13-G room area of the NIOSH Safety Research Coal Mine. The study showed that GPR technology can be a useful tool for detecting changes in mine roof due to the injection of the grout. (PDF, 1051 KB, 2004-08)

This paper examines the effect of end conditions and load profiles on prop support performance and applies a new analysis methodology based on eccentric loading to determine a factor of safety for load capacity. Recommendations for installation practices that minimize eccentricity and therefore preserve capacity are also provided. (PDF, 304 KB, 2007)

An investigation of the hazards in and around ore passes in hard rock mines. Risk assessment methods, such as fault-tree analysis, have been employed to identify the most probable causes of ore-pass failures, define research priorities and analyze the factors that result in malfunctioning and unsafe ore passes. (PDF, 903 KB, 1997)

The Coal Mine Roof Rating (CMRR) has been widely accepted as a tool for geologic characterization and mine planning. The application of the CMRR to extended cuts (cuts greater that 6 m (20 ft) in length) is discussed. (PDF, 313 KB, 1999-04)

Several remote sensing technologies are being evaluated as tools to assess slope stability and monitor slopes for hazards. An interferometric radar device capable of detecting very small displacements on slopes has been assembled and tested. (PDF, 1440 KB, 2004)

This paper summarizes developments in the application of ground-based radar to slope stability monitoring and presents information on NIOSH-sponsored experiments recently completed. Field tests of a hyperspectral imager were conducted to assess its value for improving geologic maps of potentially unstable alteration zones on mine slopes (McHugh and others, 2001). Computerized monitoring methods using images from digital and video cameras are being assessed for application to mine slope surveillance. (PDF, 7065 KB, 2006-04)

The point estimation method is a computationally efficient approach for estimating the probability of sliding. This method expedites slope stability simulation routines used by NIOSH software to stochastically describe rock slope behavior and assist the engineer in designing catch benches for large rock slopes. Enhanced bench design translates into increased operational efficiency and safer working conditions in open pit mines and quarries. (PDF, 1713 KB, 2004)

Rock drilling parameters including thrust, rotational speed, torque and velocity were examined to determine the ability to identify the strength of the rocks being drilled from the measured parameters. (PDF, 724 KB, 2000)

This paper introduces various warning signs of slope instability so operators are better able to recognize hazards. The most common slope monitoring equipment and practical methods of installation are discussed as well as the limitations of these systems. (PDF, 413 KB, 2001-08)

A methodology to assess the risk for a roof fall is proposed in a preliminary fashion based on engineering judgment acquired from extensive underground stone mine experience and examination of related literature. The proposed method uses an observational technique to identify the risk of roof falls in three categories. (PDF, 201 KB, 2006-03-27)

This paper describes research designed to quantify the behavior of a particular size abutment pillar prone to burst or bump (local terminology). This information reflects the overriding influence of the local geologic characteristics on bursts, provides the field measurements needed to verify concurrent modelling studies, and suggests some basic mechanisms associated with coal pillar bursts. (PDF, 516 KB, 1990-08)

This report presents results of a U.S. Bureau of Mines study of longwall gob material. The objective of this work was to determine material stiffness properties of the gob for use in numerical models or rock mass response to longwall mining. (PDF, 5208 KB, 1993)

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. (PDF, 141 KB, 2003)

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. (PDF, 1971 KB, 2000)

The San Juan Mine and the National Institute for Occupational Safety and Health conducted a study to measure how development mining affected bolt loads. (PDF, 600 KB, 2004)

The Bureau of Mines developed a computerized method to calculate vertical stress exerted on surfaces at depth that includes the effect or topography. The limitation of the method is that stresses cannot be accurately determined near an outcrop. (PDF, 4167 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. (PDF, 4632 KB, 1992)

NIOSH, RAG Pennsylvania and Strata Control Technologies of Australia collaborated in an intensive study of ground behavior, reinforcement performance, and stress redistribution at the Emerald Mine in Southwestern Pennsylvania. The study site was a longwall tailgate subjected to a severe horizontal stress concentration. A computer simulation of the field site was conducted using FLAC-2D. Comparison between actual field measurements and the simulation showed that the model was able to capture the most significant aspects of the roof and support system behavior. The model also showed that supplementing the normal roof bolt support pattern with cable bolts would allow the entry to survive a further 20-25% increase in the applied horizontal stress. (PDF, 1254 KB, 2007)

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. (PDF, 3413 KB, 2001-07)

This paper presents the results of a case study conducted in a two-entry gateroad in a coal mine where excessive roof deformation and bolt loading resulted in failure of many roof supports. (PDF, 803 KB, 1998)

This paper examines catastrophic failures of evaporite mines (including salt, potash and trona) that show that violent failure does, in fact, occur and attempts to identify common factors and characterize the mechanism of failure. (PDF, 772 KB, 2008)

This report presents a Bureau of Mines study to identify the causes of self-heating events beneath the floor of a deep underground coal mine. The combined results led to the conclusion that pyrite oxidation was the prime cause of the heatings. (PDF, 4994 KB, 1992)

This study used microseismic emissions to help identify three local rock failure processes. It was also shown that analysis of microseismic emissions can aid in assessing the degree of instability associated with these local rock failure processes. (PDF, 312 KB, 2005)

This paper reviews 11 prevention control techniques for coal mine bursts. (PDF, 468 KB, 2008)
                                                                              

Describes the procedures and thought processes used by coal mine geologists when determining various mineability and reserve extraction feasibility issues. The paper also address underground geologic hazard mapping and prediction techniques. (PDF, 152 KB, 2006)

Research on techniques that will reduce the hazards in the mining workplace associated with coal bumps. (PDF, 301 KB, 2000)
                                                

This paper presents several case studies in which a mechanics-based boundary-element program is used to back-calculate the surface subsidence associated with various panels at several northern Appalachian coal mines. (PDF, 448 KB, 1999)

Ground conditions at 10 Australian longwall mines and two room-and-pillar mines are compared with an extensive data base from U.S. mines. The comparisons include the Coal Mine Roof Rating, roof support installed, pillar design, and an in-depth discussion of ground control conditions. (PDF, 507 KB, 1998-08)

An investigation of an underground pillar at a mine in Lead, SD. Using the results, researchers hypothesize that pillar rocks have the ability to withstand stress an order of magnitude greater than they currently sustain. (PDF, 524 KB, 1999)

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. (PDF, 428 KB, 2008)

A computer analysis of bench stability was developed to account for multiple occurrences of potential slope-failure modes in discontinuous rock masses. Bench-scale plane shears and tetrahedral wedges are simulated and stochastically analyzed to estimate the probability of retaining specified catch-bench widths. (PDF, 625 KB, 2000)

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. (PDF, 1100 KB, 2004)

Roof Monitoring Safety Systems (RMSSs) were installed in 13 underground limestone mines in six states. This paper analyzes the data obtained at three of the mines and also provides an overview of the system, data, analysis and applications relevant to the RMSS. (PDF, 1000 KB, 2003-08)

A design technique is presented which provides stone miners with a method for making stability assessments. The consequences of widening rooms, changing geology and horizontal stresses, and different rock bolts on roof beam failure are discussed. (PDF, 836 KB, 1998-08)

To study bump mechanisms, conditions in the vicinity of a deep longwall mining face in bump-prone strata were monitored using three discrete systems. Results from the three systems are correlated in an effort to increase understanding of mining-induced stress redistribution and bump potential. (PDF, 1090 KB, 2001)

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. (PDF, 591 KB, 2008)

A NIOSH study of the time-dependent response of rock stressed along weakness planes with the objective to improve mine safety by reducing the number of roof falls that cause injuries and fatalities to miners. (PDF, 119 KB, 2000)

The National Institute for Occupational Safety and Health is investigating various remote sensing technologies as possible tools to detect, monitor, and mitigate hazardous situations in surface mines that could lead to catastrophic slope failure. Promising technologies include a field-portable spectro-polarimetric imager and a stationary interferometric radar device. (PDF, 2162 KB, 2000)

As part of a research program to reduce injuries and fatalities in the U.S. mining workforce, NIOSH is investigating the potential use of noncontact vibration measurements to identify hazardous ground fall conditions. (PDF, 447 KB, 2004)

A study is described with the objective of evaluating the various methods and strategies by which panels, production pillars and barrier pillars are developed and extracted under deep cover, and to develop appropriate design guidelines. (PDF, 655 KB, 2002)

As part of an investigation aimed at improving the health and safety and competitiveness of the mining industry, the U.S. Bureau of Mines evaluated the application of common offset radar profiling, using a 250-MHz ground-penetrating radar (GPR) system, for the detection of fractures in igneous rock (PDF, 16185 KB, 1992)

The U.S. Mine Safety and Health Administration (MSHA) has identified ore pass hazards as s significant safety problem in underground metal mines in the United States. Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health are investigating these hazards and developing methods to improve safety during transport of ore and waste. (PDF, 677 KB, 1998)

The Spokane Research Laboratory (SRL) of the National Institute for Occupational Safety and Health (NIOSH) and Thiessen Team USA, Spokane, WA, have developed a pull claw that can be attached to any accessible friction bolt ring to test the performance (i.e., load-carrying capacity) of bolts without the use of a pull collar. This would allow true random testing of friction bolts, which need to be evaluated to determine if they are still providing an adequate level of support months or years after installation. Such support is critical to maintaining safe working conditions for underground miners. (PDF, 553 KB, 2004-03)

The purpose of this paper is to set goals for the future generations of longwall shields. (PDF, 877 KB, 2001)
                                                              

One focus of ground control research at NIOSH is to incorporate data on weak rock masses into existing design relationships, with an emphasis on updating the span design curve for manned entries and the overbreak curve for longhole entries. Both curves were originally developed at the University of British Columbia, Vancouver, BC. The original database has been augmented by information from mines throughout the United States, Canada, Australia, and Europe. The common factor in all of these mines is the presence of a weak back and/or walls. In most cases, the ore zone is the weakest rock unit and must be stabilized so that the mineral-bearing rock can be extracted safety. The current NIOSH research attempts to provide rock mechanics tools to assist a mine operator in making economic decisions that will also ensure a safe working environment. This paper documents the Nevada database with a special emphasis on Nevada underground gold mines. (PDF, 396 KB, 2005)

This paper discusses a design methodology for standing secondary tailgate supports. The methodology uses the performance characteristics generated in the NIOSH Mine Roof Simulator (MRS) to match the stiffness and load characteristics of various supports to the measured ground reaction behavior. (PDF, 666 KB, 1999)

Methods are described to limit "cascading pillar failure", which occurs when one pillar in a mine layout fails, transferring its load to neighboring pillars, which causes them to fail, and so forth. Design approaches are illustrated with practical examples for coal mining at shallow depth. (PDF, 624 KB, 1997)

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. (PDF, 588 KB, 2001-06)

A calibrated three-dimensional finite element model, developed in conjunction with an underground test area, provided the critical components and design principals for a comprehensive parametric study. (PDF, 329 KB, 2004-02)

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. (PDF, 386 KB, 2005)

Slope stability accidents are one of the leading causes of fatalities at U.S. surface mining operations. The National Institute for Occupational Safety and Health is conducting research to reduce the fatalities associated with slope failures. This paper discusses some of this research and presents potential new technologies for slope monitoring and design. (PDF, 329 KB, 2002-08)

This paper describes a case study where a surface-based microseismic system, using triaxial geophones in boreholes drilled from the surface, was deployed at a large limestone mine. (PDF, 945 KB, 2008)

As part of safety and stability studies at three underground mines in the United States, researchers installed earth pressure cells and embedment strain gauges in cemented rockfill to measure stress and strain changes as mining progressed and the rockfill was loaded. Data from these instruments were used to calculate the in situ modulus of the rockfill for two of the mines. A three-dimensional numerical model of a cemented rockfill cap was validated with data from extensometers anchored in the mine roof and sill; this model was then used to estimate deformation modulus at the third mine because the earth pressure cells and embedment strain gauges recorded negligible changes. (PDF, 757 KB, 2003-09)

Researchers are investigating the physical properties of cable bolts by replacing the conventional king wire with a modified king wire on which strain gauges have been installed. (PDF, 621 KB, 2000-04)

Researchers from private industry and NIOSH have studied mechanisms of violent failure and have identified individual factors that contribute to coal bumps. In an attempt to develop tools for assessing coal bump potential, the authors initiated a comprehensive study using information from 25 case studies undertaken in U.S. mines. (PDF, 331 KB, 1997)

An automated PC-network-based seismic data acquisition and processing system has been developed by NIOSH for use in mine safety studies. Several systems have been constructed and deployed in the field for testing and application. These systems are now being applied in studies designed to reduce hazards associated with roof falls, rock bursts, coal bumps, and mine collapse. (PDF, 264 KB, 2001-12)

This paper presents the results of a study into the ground response around tailgate entries using numerical models. The ground response is shown to be significantly affected by the strength of the immediate roof as well as the main roof. The importance of yield capacity of standing support is demonstrated. Gob height and compaction are found to affect the amount of convergence in the tailgate. The potential exists to develop site-specific tailgate design curves by combining model results with field observations. (PDF, 587 KB, 2006-06)

A new protocol based on rigid arch loading of the structure is proposed to determine the true transverse load capacity of block stoppings. The rigid arch tests have shown that the load capability is dependent on the physical properties of the block and geometric properties of the wall, not the sealant. (PDF, 338 KB, 2006-06)

A system was developed to monitor rock and coal stresses during mining of an entire longwall panel. The system was designed to generate data in near real time to evaluate rock behavior in roof strata and the onset of hazardous conditions as overburden stress was redistributed over working entries during gob formation. Computer simulations and in-mine evaluations were used to optimize instrument placement. A prototype packer assembly was designed and tested for installing sensitive instruments in a mine roof. This paper provides background information on the stress monitoring concept and focuses on the development of instrument placement techniques and the prototype packer assembly. (PDF, 654 KB, 2001-07)

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. (PDF, 462 KB, 2002-08)

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. (PDF, 520 KB, 2008-01)

Various methods of monitoring slip movements on bedding planes, as well as examination of rock burst damage in stopes, suggests that rock bursts in the Lucky Friday Miner are closely associated with these movements. (PDF, 929 KB, 1999-06)

A large Pittsburgh seam longwall mine had begun to develop in a different direction from its original portal area to access additional reserves. A large area of the mine would be abandoned and sealed, but continued use of the original mine portal area required that the water accumulating in the abandoned mine would eventually need to be pumped to the surface. Several pumping and sump options were investigated to handle the quantity and quality of the anticipated discharge water. (PDF, 764 KB, 2001)

The process of drilling and bolting the roof is currently one of the most dangerous jobs in underground mining, resulting in about 1,000 accidents with injuries each year in the United States. Researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health are studying the use of a drill monitoring system to estimate the strength of successive layers of rock and assess the integrity of a mine roof so that roof drill operators can be warned when a weak layer is being drilled. (PDF, 2025 KB, 2002-07)

The centerpiece of this project is development of a Dynamic Failure Control Program to monitor evolution of dynamic failure hazards with changing geologic conditions to assure that control and protective measures are appropriately deployed. (PDF, 301 KB, 2008)

Standing crib supports have been applied in underground mining programs to resist large roof movements and sustain high-loads. The parameter that has not been examined and is not well understood is the effect that a crib or other types of standing support has on the primary and secondary bolting systems. Utilizing a combination of field measurements and 3-dimensional finite element modeling techniques, the relationship between system stiffness and the subsequent performance of the installed bolting system is evaluated. (PDF, 248 KB, 2003-08)

Underground limestone mines typically use the room-and-pillar method of mining in the generally flat-lying limestone formations. In some cases the dip may exceed 5° which can result in unique roof instability problems. Stability may be further exacerbated by the presence of horizontal tectonic stresses. Field studies and numerical model analyses are combined to assess the effect of the dip in various stress conditions. (PDF, 1007 KB, 2005)

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. (PDF, 318 KB, 2001)

Researchers are investigating the causes and mechanisms of roof failure in underground mines. It is expected that a better understanding of these causes and mechanisms will lead to better layout and support designs that will help prevent accidents and fatalities associated with fall of ground. (PDF, 1531 KB, 2004)

This U.S. Bureau of Mines paper discusses the importance of an interface slip mechanism between the coalbed and the surrounding strata in controlling the extent and pattern of stresses and deformations in a coal pillar. (PDF, 531 KB, 1990)

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.  (PDF, 764 KB, 2008)

Observations of pillar conditions in limestone mines showed that the presence of weak bands in the limestone can result in pillar damage at stresses that are lower than one would otherwise expect. The objective of this NIOSH study was to investigate the mechanism of failure caused by the presence of weak bands by using a series of numerical models based on realistic physical properties. (PDF, 1398 KB, 2007)

The U.S. Department of Energy Pittsburgh Research Center, has developed and field tested a spatial, spectral sensor for measuring the thickness of mineral deposits. (PDF, 30 KB, 1996)

This paper discusses a) the results of a ground-based hyperspectral imaging tool used to map the geology of an open-pit mine highwall; and b) interferometric synthetic aperture radar and how it can be used in a variety of geotechnical situations. It is hopeful that these new developments will lead to better geotechnical monitoring and design in slope stability and other important areas of rock mechanics. (PDF, 468 KB, 2001)

A major focus of ground control research presently being conducted by the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) is to incorporate weak rock masses (such as are associated with operations in the Carlin Trend in Nevada) into existing design relationships. The original database that led to most of the empirical design relationships presently employed in hard-rock mining was derived from fair-to-good-quality rock. In this study, the relationship between weak rock quality and opening design (non-entry/entry methods) is being investigated. The common factor in all mines is a weak back or wall. This work attempts to provide tools that will enable a mine operator to make economic decisions that will also ensure a safe working environment. (PDF, 334 KB, 2005)

A major focus of ground control research is to incorporate weak rock masses (such as are associated with operations in the Carlin Trend in Nevada) into existing design relationships. The original database that led to most of the empirical design relationships presently employed in hard-rock mining was derived from fair-to-good-quality rock. In this study, the relationship between weak rock quality and opening design (nonentry/entry methods) is being investigated. The common factor in all mines is a weak back or wall. This work attempts to provide tools that will enable a mine operator to make economic decisions that will also ensure a safe working environment. (PDF, 401 KB, 2003)

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. (PDF, 115 KB, 2008)

The goal of this project was to design and evaluate devices that can be installed with traditional primary or secondary roof supports, and that are easy to handle/install under temporary or previously supported roof. (PDF, 5119 KB, 2001)

Researchers at the U. S. Bureau of Mines conducted investigations to evaluate the potential for ground watercontamination by mine waste used as backfill. Samples of cemented waste backfill and water discharging fromdrillholes and seeps were collected to use in chemical analyses and laboratory tests to determine the physical andchemical factors that control release of heavy metals to ground water. (PDF, 351 KB, 1996)

Researchers at the U.S. Bureau of Mines investigated the use of close-range photogrammetry and subsequent stereo digitizing to obtain data from rock fracture roughness profiles. (PDF, 3830 KB, 1993)

Several remote-sensing technologies are being evaluated as tools to monitor slopes for hazards and to assess slope stability. (PDF, 3017 KB, 2002)
                          

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. (PDF, 664 KB, 2001)

Whereas many researchers and mine engineers have conducted tests on cable bolts using various grouts, water:cement ratios, and physical modifications of the cable to determine the load-carrying characteristics of a bolt, few studies have been conducted on cable bolts fitted with internal instruments. Researchers at the Spokane Research Laboratory (SRL) of the National Institute for Occupational Safety and Health in Spokane, WA, are investigating the physical properties of cable bolts by replacing the conventional king wire with a modified king wire on which strain gauges have been installed. (PDF, 615 KB, 2004-04)

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. (PDF, 253 KB, 2007)

Studies conducted have identified a number of "risk factors" that can be used to evaluate pillar extraction plans: cut sequence; final stump; timber or mobile roof supports; roof bolting; intersection span; depth of cover; roof quality; and age or workings. This paper discusses each of the risk factors in turn, presents the relevant accident statistics, and shows how the risk factors can be combined to estimate the overall hazard. (PDF, 636 KB, 2002-08)

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. (PDF, 373 KB, 2004)

To help evaluate the usefulness of the natural gamma radiation (NGR) technique for the coal interface detection (CID) project, the U.S. Bureau of Mines (USBM) collected data from various mining companies conducting underground and surface operations in 15 major and 110 minor coal seams in the United States (1).2 This work was done in support of the USBM goal to improve the method of recovering coal from the nation's mines in a safe and economical manner. (PDF, 2527 KB, 1995)

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. (PDF, 608 KB, 2007)

Numerical modeling is used to evaluate the degree the pillar strength is increased with a rectangular pillar over a square pillar. (PDF, 164 KB, 2007)

The conclusion drawn from this study was that standing supports do not have sufficient capacity to control main roof or floor loading or prevent the resulting convergence of the tailgate entry. (PDF, 255 KB, 2005)

This paper investigates some of the issues affecting pillar strength at low width-to-height ratios in hard, brittle rock. The investigation includes an evaluation of empirical pillar strength data presented in the literature and observations of pillar performance in underground limestone mines in the Eastern United States, supplemented by numerical modeling in which failure processes and sensitivity of slender pillars to variations in rock mass properties are evaluated. The results showed that the strength of slender pillars is more variable than that of wider pillars. (PDF, 1206 KB, 2006-01)

Investigates some of the issues affecting pillar strength at low width-to-height ratios in hard, brittle rock. The investigation includes an evaluation of empirical pillar strength data presented in the literature and observations of pillar performance in underground limestone mines in the Eastern United States, supplemented by numerical modeling in which failure processes and sensitivity of slender pillars to variations in rock mass properties are evaluated. (PDF, 677 KB, 2006)

A new protocol based on arching has been developed to determine the true transverse load capacity of stoppings. (PDF, 7182 KB, 2005)
                                        

This paper discusses progress in the science of coal pillar design over the past 25 years and some of the current research needs. (PDF, 664 KB, 2006)
                      

This report examines shield design and operation practices and their consequences for the utilization of high-capacity shield support systems. An optimization goal is to minimize support loading by selecting an active shield setting force that is compatible with strata behavior and shield loading characteristics. (PDF, 1569 KB, 1992)

A close look at the Loyalhanna Limestone of southwestern Pennsylvania reveals a complex structural environment.  Geologic and engineering analyses were performed using gas well and core logs, outcrop examinations, underground observations, and mine maps. Many of the structural conditions cause ground control problems at local quarries. (PDF, 2678 KB, 2002)

NIOSH is conducting research aimed at helping mine planners prevent hazardous conditions due to multiple-seam interactions. More than 300 case histories have been collected from underground mines mainly in central Appalachia. This paper focuses on several of the more challenging situations that have been encountered, including: room-and-pillar development 20 ft beneath full-extraction workings at a depth of 1,000 ft of cover; pillar recovery 45 ft above full-extraction workings at 900 ft of cover; near-simultaneous room-and-pillar mining with pillar recovery with 40 ft of interburden and 1,500-2,000 ft of cover; and longwall mining directly beneath main entries in overlying seams. (PDF, 629 KB, 2006)

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. (PDF, 523 KB, 1998-08)

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. (PDF, 617 KB, 2001)

This research seeks to provide design guidelines that enable mine planning engineers to correctly assess the safety risk of an adverse multiple seam mining interaction based on mine geometry factors, mine layout factors and site specific geologic conditions. (PDF, 425 KB, 2005)

This paper looks at the feasibility of using noncontact laser-based vibration measurements to detect roof fall hazards with the ultimate vision of improving, expanding and automating procedures for mine roof inspection. (PDF, 369 KB, 2002)

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. (PDF, 847 KB, 2001-08)

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. (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. (PDF, 1109 KB, 2008-06)

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. (PDF, 334 KB, 2003)

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. (PDF, 594 KB, 2003-08)

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 to monitor rock mass loads at various field sites. (PDF, 960 KB, 2000)

The results of field tests conducted by the Bureau of Mines on elastic bolt behavior showed that the anchorage length of grouted bolts installed in shale was slightly longer than the anchorage length determined in laboratory tests conducted in concrete blocks. (PDF, 895 KB, 1991)

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. (PDF, 665 KB, 2006)

This paper summarizes the results obtained from a field-scale test and shows that mapping voids within a coal pile is possible. (PDF, 822 KB, 2002-07)
                        

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. (PDF, 603 KB, 2008)

Researchers have conducted a large number of experiments on cable bolts to determine their load characteristics for different grout types, grout ratios, and cable configurations (Garford bulb, buttons, birdcage, nut cage, etc.) (PDF, 686 KB, 2002-04)

Monitoring technology and techniques can provide a means to warn of hazardous roof fall conditions. Measuring roof deflection is the most common method of detecting roof instabilities. (PDF, 195 KB, 2005)

In the past few decades, a considerable amount of effort was directed at accurately determining the coal/pillar strength to use for safely designing coal mines. This paper addresses the deficit of pillar loading research by exploring the accuracy of the empirical abutment load calculations using insight provided by an elastic overburden model, a laminated overburden model and field obserbvations. (PDF, 588 KB, 2000)

This report describes the geologic origin, association, and potential danger from the most common hazards. Discussions of weak rock include drawrock, rider coals, head coal, stackrock, and stream valley effects. (PDF, 3940 KB, 2003-10)

Geology is an integral part of roof control, mine design, and production operations. Yet, the importance of geology, coal/rock as an engineering construction material and its properties and behavior within the planned mine areas, in overall mine production operations has not been fully appreciated. Understanding the nature of roof geology could explain why roof control plans sometimes fail. (PDF, 708 KB, 2001-12)

Bowie Resources maintains one of the most pro-active ground control programs in the U.S. mining industry today. Its guiding philosophy is that everyone in the organization, from the miners at the face all the way through the top management, are involved in ground control. This paper will describe the program in detail, discussing the involvement of roof bolters, section foremen, surveyors, technical staff, and production managers. It will also show how the program has contributed to the mine planning process. (PDF, 457 KB, 2006)

When the Washington National Cathedral showed signs of continuing differential settlement in the early 1990's, the US Bureau of Mines was asked for assistance in monitoring the movements of the massive towers and walls. The paper discusses the major findings of the study, implications for the future of the Cathedral, and conclusions regarding the use of geotechnical monitoring at major national monuments. (PDF, 286 KB, 2001-07)

Because backfill has occasionally collapsed into an active working area, posing a hazard to miners, engineers installed instruments in a cemented, backfilled, stope-ramp intersection at Hecla's Lucky Friday Mine to measure stress and strain changes in the backfill and reinforcing members during undercut mining. Based on this study, use of trusses was discontinued, and an alternative support system of wood beams and posts was installed. The purpose was to measure stress and strain changes in the backfill and reinforcing members during undercut mining. (PDF, 5487 KB, 2001-07)

Highly stressed rock in stopes continues to be a primary safety risk for miners in underground mines because this condition can result in failures of ground that lead to both injuries and death. Personnel from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health studied two methods for identifying stress in rock. (PDF, 5799 KB, 2004-03)

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. (PDF, 848 KB, 1997)

This paper explores the relationships between deep-seated and shallow in situ stresses in several of the world´s coalfields, using a data base of more than 350 stress measurements from underground coal mines. (PDF, 452 KB, 2008)

Highwall stability remains a major concern during highwall mining. Geologic structure (hillseams) and pillar stability are the two major factors affecting highwall stability. (PDF, 199 KB, 2005)

This paper discusses the two most significant highwall ground control hazards; rock falls from the highwall and equipment entrapment underground. (PDF, 508 KB, 2007-09)

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.  (PDF, 1641 KB, 2001)

The guidelines in this report are to be used as a tool to identify areas or conditions that could impact the long-term stability of an underground fluid retention system and to give direction in addressing these situations. (PDF, 508 KB, 2008-06)

This study of the Chestnut Ridge Anticline found that high levels of horizontal stress are to be expected in this very stiff rock formation and that local geologic and topographic structures are capable of altering the magnitude and possibly the orientation of the horizontal stress field. (PDF, 358 KB, 2002-11)

Horizontal stresses are caused by global plate-tectonic forces. During 1995 alone they were largely responsible for the closing of two longwall mines in the U.S. This paper presents six case histories of mines that encountered roof falls or difficult ground conditions at the headgate caused by horizontal-stress concentrations. (PDF, 1365 KB, 1998-01)

This work identified the most important variables contributing to coal bumps. These are (1) mechanical properties of strata, including local yield characteristics of a mine roof and floor, (2) gate pillar factors of safety, (3) roof beam thickness, joint spacing, and stiffness characteristics, which influence released energy, (4) stress gradients associated with the approach of mining to areas of higher stress concentrations, and (5) the mining method. By combining the strength of both analytical and statistical methods, new capabilities were developed for predicting coal bump potential and for building confidence intervals on expected damage. (PDF, 68 KB, 1999)

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. (PDF, 730 KB, 2004)

NIOSH conducted wet/dry immersion cycling of clay-rich rocks. The wet/dry immersion cycling test used provides an accurate, quick and inexpensive method for estimating the moisture sensitivity of mudrocks. With this information mine operators can begin to anticipate hazardous ground and prepare appropriate roof support. (PDF, 850 KB, 2006)

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. (PDF, 482 KB, 2008)

This paper describes an intelligent drilling system that can complement scoping and core analysis to provide a more complete picture of roof strata and is capable of seeing features or conditions that are not always obvious in more traditional methods. (PDF, 714 KB, 2007)

Cable bolts are gaining increased popularity in U.S. coal mines. Factors involved with this are discussed including the switch to resin anchorage. (PDF, 1794 KB, 1998-03)

The U.S. Bureau of Mines conducted an overcore stress measurement on the 5300 level of the Lucky Friday Mine, Mullan, ID, to investigate the stress regime around an experimental stope in a rock-burst-prone mine. The result indicated a stress field with unexpected magnitude and orientation. (PDF, 302 KB, 1995)

U.S. Bureau of Mines researchers reviewed an in situ stress estimate developed from measurements of overcore strain taken at test sites on the 7300 and 7500 levels of the Star Mine near Mullan, ID. Although the field measurements of overcoring strain were found to be useful, significant deficiencies were found in the stress estimation procedure. (PDF, 355 KB, 1995)

Researchers at the U.S. Bureau of Mines collected and analyzed overcore measurements and other indicators of in situ stress characteristics at the Lucky Friday Mine, Mullan, ID. An analysis of these data revealed that significant local variations in in situ stress are present in this mine and that these variations existed prior to mining. High stresses were found to be associated with the most competent strata and a locked section of a fault. (PDF, 1594 KB, 1995)

Using hollow inclusion stress cells, researchers obtained two in situ stress measurements from the face of two footwall lateral drifts at the Stillwater Mine near Nye, MT. (PDF, 457 KB, 2003)

In situ stresses are important input data for the design of safe, stable stope layouts and extraction sequences. In situ stresses were measured at the Homestake Mine, Lead, SD, using overcoring on hollow inclusion cells and borehole deformation gauges. (PDF, 2480 KB, 1993)

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. (PDF, 1794 KB, 1998-03)

The investigation reported here is an initial study of the stability of the first of the proposed chambers at the Homestake Mine in Lead, SD. (PDF, 206 KB, 2002-07)

This paper describes a seismic monitoring network that has recently been installed in the North Fork Valley coal mining region of western Colorado as part of a NIOSH mine safety technology transfer project with two longwall coal mine operators. (PDF, 619 KB, 2007)

Unusual circumstances may require that a longwall retreat into or through a previously driven room; there have been a number of spectacular failures which exposed miners to serious roof fall hazards. To help determine what factors contribute to such failures, NIOSH compiled a comprehensive international database of 130 case histories. (PDF, 663 KB, 1998)

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. (PDF, 3504 KB, 2002)

Rock masses in deep-level mines are subject to high stresses, which can result in unexpected failure of rock into mined-out openings. Personnel from two research centers of the former U.S. Bureau of Mines, Spokane and Twin Cities, investigated a rock burst that occurred in May of 1994 in a rock mass between the 4400 and 4600 levels of the Sunshine Mine, Kellogg, ID. (PDF, 336 KB, 1997)

Field studies were conducted to record electromagnetic (EM) emissions at the Galena Mine, Wallace, Idaho. The goal of the research was to determine if EM emissions were valid precursors to imminent ground failure. (PDF, 275 KB, 2004-08)

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. (PDF, 364 KB, 2005)

The roof in underground limestone mines in Northern Appalachia can be subject to high horizontal stresses in spite of the shallow depth of the workings. A case study is presented in which failure at the pillar-roof contact was observed where the dip of the workings was 7 deg. in a high horizontal stress field. The high horizontal stresses at this site are an important contributing factor to the observed failures. (PDF, 366 KB, 2004-08)

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. (PDF, 2262 KB, 2002)

This U.S. Bureau of Mines report summarizes a study of large-scale strata response to longwall mining at a western U.S. coal mine. This study utilized surface and subsurface measurements, geologic mapping, in situ stress measurements, and pressure cell readings to characterize strata behavior. (PDF, 1429 KB, 1992)

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.  (PDF, 707 KB, 2001)

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. (PDF, 805 KB, 2006)

The objective of this study was to determine whether a qualitative but coherent redistribution of velocity, indicating change in location of induced stress, could be imaged as mining occurred in known locations by using a local earthquake tomography software code. (PDF, 267 KB, 2008)

The purpose of this paper is to evaluate the preliminary findings of a long-term underground study of various types of surface support liners, and to examine installation practices that are critical for an effective liner material application. (PDF, 566 KB, 2003-08)

This report describes an investigation into the removal of gate road chain pillars in conjunction with longwall retreat mining. The objective was to determine, through evaluation of the loads imposed on the gate road pillars and supplemental support elements in the entries, how the pillars, supplemental support, and entries were affected by the longwall abutment pressure. The findings are the result of information collected from instrumentation and observation at the mine. (PDF, 1244 KB, 1993-01)

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. (PDF, 705 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. (PDF, 1217 KB, 2007)

The primary objective of the paper will be to discuss strata mechanics and ways in which the support and strata interaction can be evaluated to provide an optimized secondary support design, particularly standing support systems, for longwall tailgates. (PDF, 566 KB, 2003)

The document is instructional material for a 7-minute video that shows how well roof screen keeps loose rock from falling in difficult roof conditions. (PDF, 1575 KB, 2005-03)

More that 700 microseismic emissions were collected from two underground limestone mine roof fall areas in southwestern Pennsylvania. Microseismic events were located and magnitudes determined using the moment magnitude technique. The amount of new fracture surface length was calculated based on the stored strain energy within the rock prior to fracture. A significant amount of microseismic activity was observed as much as two days before the first signs of failure in the roof fall areas. Additionally, results from this analysis reveal much about the behavior of strata prone to failure and allows for the construction of hazard maps based on microseismic emissions. (PDF, 855 KB, 2004-08)

Material properties affecting slope stability were measured in a large 50-year-old, partially consolidated rock dump located in an active open-pit mine. Field tests included single-ring infiltration and density. (PDF, 3455 KB, 1999-12)

A case study of a rock burst was conducted as part of a project to reduce rock burst hazards being undertaken by the Spokane Research Laboratory (SRL) of the National Institute for Occupational Safety and Health (NIOSH). (PDF, 278 KB, 2002-07)

Assuring ground control safety in many mining and tunneling projects depends, at least in part, on an understanding of in situ stress conditions that will be encountered. (PDF, 194 KB, 2001-07)

A method to assist in the evaluation and selection of roof bolts using in situ measurements of roof bolt loading has been developed by researchers of the Spokane Research Center, National Institute for Occupational Safety and Health. (PDF, 452 KB, 1997)

Methane can be a significant hazard in coal mine longwalling operations and extensive methane mitigation techniques are employed by coal mine operators. Reservoir modeling techniques are used to better understand the liberation and migration of methane from the surrounding rocks towards the mine ventilation system. The caved rock behind the advancing longwall face, known as the gob, can contain high void ratios, providing high permeability flow paths to the methane. The gob is progressively compacted by the weight of the overburden, resulting in a reduction in the void ratio and associated permeability. Estimating the permeability distribution within the gob poses challenges due to its complexity. The authors have developed a new methodology to determine both horizontal and vertical variations in the permeability of the gob. The resulting three-dimensional permeability distribution in the gob is then transferred to a reservoir model. The paper demonstrates the application of the method and shows that reasonable results are obtained when compared to empirical experience and measurements. (PDF, 1146 KB, 2007)

This paper discusses a method to determine the roof fall risk using a qualitative risk analysis technique. (PDF, 322 KB, 2007-11)
                                             

This Bureau of Mines report describes photo-lineaments obtained from stereoscopic examination of vertical aerial photographs and by the ronchi grating study of aerial photoindex sheets. The photo- lineaments are compared with the trends of oriented fracture systems procured by measuring the compass direction of joints in bedrock. The relative reliability of the methods is shown, and the results are presented in graphical, tabular, and written form. The three methods give similar findings and verify the work of previous authors. The ronchi grid method is a useful guide, but it cannot be substituted for the two more painstaking methods. (PDF, 4240 KB, 1977)

A deep longwall coal mine was instrumented with a three-dimensional microseismic system in order to help determine the exact strata mechanics associated with the rock failure, redistribution of stress and the associated gob formation from the longwall. Analysis showed a close correlation between the seismic activity and advance rate, and that the majority of the recorded seismic activity occurs in the immediate area of the advancing longwall face. (PDF, 4797 KB, 2002)

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. (PDF, 3983 KB, 2001)

A hydrologic-subsidence investigation was performed to evaluate the effects of longwall mining on the local ground water regime through field monitoring and numerical modeling. A combined finite element model of the deformation of overlying strata, and it's influence on ground water flow was used to define the change in local and regional water budgets. (PDF, 308 KB, 1995)

This paper describes a seismic network installed in western Colorado in the vicinity of three underground coal mines, its features for user access to data, and then gives two examples of seismic events resulting in some damage to mine workings. (PDF, 1082 KB, 2008)

MULSIM/NL is a U.S. Bureau of Mines boundary-element-method program for calculating stresses and displacements in coal mines or thin, tabular metalliferous veins. This manual gives detailed operating instructions for MULSIM/NL and illustrates its use with several practical examples. (PDF, 4395 KB, 1992)

The program described in this U.S. Bureau of Mines report is part of the MULSIM/NL package, which features the actual BEM program described herein, as well as a preprocessor program called MULPRE/NL and a plotting postprocessor program called MULPLT/NL. (PDF, 3556 KB, 1992)

Relatively few longwall mines in the U.S. operate under multiple seam conditions where the two seams are less than 200 ft apart. This paper describes the experience of six that do. These operations are located in PA, WV and UT, and include examples of both undermining and overmining. Some operate above or beneath their own workings, others are in historic mining districts and must contend with abandoned mines that are decades old. (PDF, 658 KB, 2007)

The most significant findings of this investigation was that the size of the remnant upper seam structure can influence the extent of the multiple seam interaction. More specifically, this study suggests that smaller critically loaded upper seam pillars are more likely to cause lower seam ground control problems than are wider pillars. The LaModel program was used to examine this supposition and the results verified this premise. (PDF, 3415 KB, 2005)

The Clean Air Act of 1992 required lower sulfur dioxide emissions, increasing demand for low-sulfur coal. Some of the the low-sulfur coalbeds in the Appalachian Coal Region occur at depths ranging from 500 to 2,000 feet. Historically, coal in this region has been mined without consideration for the influence on other adjacent coalbeds. As a consequence of this practice, environmentally acceptable compliance coal may be more difficult to mine because of ground control problems associated with multiple-seam mining. Developing design technology or models to safely mine coal above or below an existing mine provides an economic and employment opportunity and a domestic source for U.S. energy requirements. (PDF, 1502 KB, 1998-09)

In some U.S. coalfields, particularly in central Appalachia and the West, the majority of today's mines are operating above and/or beneath previously mined seams. The effects of multiple-seam interactions can include roof falls, rib spalling, and floor heave, which can seriously disrupt mining operations and threaten the safety of miners. Accurate prediction of which interactions are likely to be higher-risk allows mine planners to prepare for them or avoid them. For the past several years, NIOSH has been conducting research to develop better techniques for predicting the location and severity of multiple-seam interactions. This paper presents the background to that study. (PDF, 8193 KB, 2007-05)

Multiple-seam interactions are a major ground control hazard in many U.S. underground coal mines. The two most common types are: Undermining and Overmining. The goal of the study described in this paper is to help identify the location and likely severity of these interactions. Mine planners can use this information to adjust the ground support, pillar design, or mine layout to minimize the hazard. NIOSH relied mainly on an empirical approach. Empirical methods in ground control start with the concept that real-world mining experience, in the form of case histories, can provide valuable insight into the performance of very complex rock mechanics systems. (PDF, 9281 KB, 2007-05)

The Harris No. 1 Mine in Boone County, WV, has been longwalling the Eagle Coalbed for over 30 years. Harris has experienced numerous interactions associated with the extensive room-and-pillar and longwall mining operations that have been conducted in the overlying No. 2 Gas Coalbed. The problems have included roof falls, excessive rib sloughage, and gate road and bleeder entry closure. A detailed evaluation of the multiple-seam experiences at Harris No. 1 Mine was done as part of NIOSH's nationwide multiple-seam mining case history database. (PDF, 9281 KB, 2007-05)

The process of drilling and bolting the roof is currently one of the most dangerous jobs in underground mining, resulting in about 1,000 accidents with injuries each year in the United States. To increase the safety of underground miners, researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health are applying neural network technology to the classification of mine roof strata in terms of relative strength. (PDF, 319 KB, 1999)

The Coal Mine Roof Rating (CMRR) has been incorporated into many aspects of mine planning, including longwall pillar design, roof support selection, feasibility studies, and extended cut evaluation. This paper presents recent improvements and application of the CMRR. (PDF, 1358 KB, 2002)

This paper presents an overview of recent innovations in support technology for hard rock mining. (PDF, 987 KB, 2007)
                                                      

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. (PDF, 530 KB, 2003-08)

The Coeur d'Alene Mining District of northern Idaho is remarkable for its number of large ore bodies and for the amount of its historical production of lead, zinc and silver. Since veins were first discovered in 1884, more than 127 Mt (140 million st) of ore have been produced from narrow, high-grade veins. Mining continues at the Lucky Friday, Galena and Sunshine mines. (PDF, 12576 KB, 1998-01)

A package of bench design programs is being publicly released by the National Institute for Occupational Safety and Health (NIOSH). These programs are designed to provide a probabilistic estimate of the likelihood that various widths of catch bench will be retained. The capabilities and application of this software are demonstrated through a case example. (PDF, 179 KB, 2005)

Longwall shields provide essential ground control in longwall mining, yet a high percentage of shields are operating at less than peak capacity and many at well below the rated support capacity due to defective hydraulic cylinders or malfunctions in other hydraulic components. NIOSH developed a computer program that is designed to analyze leg pressure data and identify shields that are not performing to rated specifications. (PDF, 224 KB, 2002)

In underground coal mines, concrete block stoppings are widely used to control mine ventilation. A combination of numerical simulations and large scale physical tests were employed to develop a scientific understanding of stopping performance. The product of this study is a numerical model that can be used to evaluate the performance of stopping materials and different wall geometries in a controlled environment. (PDF, 204 KB, 2004)

This paper reviews design methodology in the placement and analysis of sill mats with reference to site observation coupled with on going numerical and analytically derived solutions. (PDF, 307 KB, 2006)

A three-step method is presented to determine nonlinear stress-strain curves for boundary-element programs used in many mining applications. The method requires a suite of laboratory-scale strength tests at various confining pressures. (PDF, 810 KB, 2003-08)

A method is presented for creating realistic numerical models for practical coal mine ground control. The method includes procedures to collect the necessary mechanical input parameters from a geologic core log, to set up a model, and to interpret calculation results. This procedure enables realistic comparison of the effectiveness of alternative rock support systems. (PDF, 457 KB, 2006-06)

A survey of roof and pillar conditions in underground limestone mines in the United States has revealed that bench mining of the floor between pillars can cause instability in the pillars at the perimeter of the benched area. The paper describes a study that was carried out using numerical models to assess the effects of bench mining on pillar load and stability. (PDF, 204 KB, 2007)

One of the most difficult, longstanding engineering problems associated with coal mining is the catastrophic failure of cog mine structures known as bumps. For more than 70 years, researchers and practitioners have assembled a wealth of technical information on coal bumps in an attempt to understand and control them. However, many technical issues raised long ago are still being debated today. This paper examines past experiences and recognizes achievements in the realm of coal bumps. U.S. Bureau of Mines (USBM) researchers collected and analyzed 172 coal bump incident reports and compiled the pertinent statistics into a database.  (PDF, 2946 KB, 1995)

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). (PDF, 395 KB, 2000-08)

This presents a review of past and present Unites States mining practices for optimum design to minimize coal bumps. (PDF, 813 KB, 1992)
                                   

NIOSH researchers have identified a pattern of fracture zone development that suggests an explanation for fracture formation around rectangular openings in underground mines.  Two computer modeling codes were used to model different aspects of this pattern. (PDF, 905 KB, 2004)

NIOSH has been actively gathering ground control information in the Illinois Basin in an effort to understand and control difficult mining conditions and has documented best practices for screen installation which has resulted in safe, efficient operations.  (PDF, 615 KB, 2008)

A study on the mechanics of strata behavior determined through extensive field measurements. Practical techniques for assessing roof behavior were developed along with a prototype remote controlled roof support system. (PDF, 1330 KB, 1999)

NIOSH has developed an entire toolbox of computer programs that have been effectively transferred to the mining community. (PDF, 1067 KB, 2001)
                             

This paper provides an overview of the support design and application philosophy in the United States. (PDF, 1210 KB, 2005)
                                                 

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. (PDF, 1421 KB, 1998-08)

The primary goal of this project was to obtain detailed data on the interaction between the mine roof and the support elements for use in modeling studies.  The study site was a longwall tailgate subjected to high horizontal stress. (PDF, 267 KB, 2004-02)

The U.S. Bureau of Mines is field testing and refining a "user friendly" computer program called Analysis of Retreat Mining Pillar Stability (ARMPS) to estimate abutment pressures developed during pillaring. The goal is to provide miner safety and an efficient recovery of reserves through design of sufficiently sized production pillars that will prevent pillar squeezes, excessive pillar spalling, severe floor heave, roof falls, and pillar bumps.  (PDF, 8693 KB, 1994)

This paper examines current design practices for stone mines and discusses issues for safe mine layouts so that a rational first approach towards balancing the demands for increased production can be weighed against increased risk to worker safety from rib instabilities and pillar failures. (PDF, 859 KB, 1999-01)

In this study, data available for a range of U.S. bursts were considered in an effort to evaluate both common and distinctive features of coal mine bursts. (PDF, 1195 KB, 1995)

A survey of pillar conditions was carried out at 21 operating limestone mines that use the room-and-pillar method. Nine cases of pillar instability were recorded. It is concluded that pillar instability is most likely to be caused by unfavorable geological structures in pillars with width to height ratios of less than 1.5. Stress related instability such as rib spalling becomes more prevalent when the average pillar stress approaches approximately 20 MPa. (PDF, 1137 KB, 2006)

This paper presents a pillar design methodology that was developed from a study of pillar performance in operating stone mines and concludes with guidelines for applying a developed equation and selecting appropriate input parameters. (PDF, 690 KB, 2008)

A significant risk factor in assessing and modeling potential catastrophic slope movement in open-pit mines is the presence of argillic alteration in host rocks. High-resolution hyperspectral imagery operating in the visible to shortwave infrared can be a useful tool for identifying and mapping potentially dangerous argillic zones. (PDF, 267 KB, 1999-03)

This presents details of a research program initiated in Maxwell Hill, WV to determine whether subsurface ground movements associated with the abandoned mines could be responsible for the seismic activity experienced at the surface. (PDF, 264 KB, 1990-08)

Mines with exceptionally low-strength roof are much more likely to struggle with roof falls that other mines. This paper focuses on two mines, one operating in the Upper Freeport seam and the other in the Herrin No. 6 seam. Detailed statistical analysis was conducted to determine which support combinations have proven to be most effective. (PDF, 184 KB, 2004)

To help mitigate the potential for falls of ground injuries to underground stone miners, NIOSH developed the Roof Monitoring Safety System (RMSS) to aid in monitoring dangerous levels of roof beam deflection. If enough site-specific information is collected and placed on highly visible maps, individual mining operations could establish general guidelines for responding to specific roof beam deflection occurrences. This would help in implementing a pro-active, comprehensive roof control plan for reducing falls of ground injuries. (PDF, 2506 KB, 1999)

Rock mass classification is widely used throughout the underground mining industry-in both coal and hard-rock mines. It is used in all stages of the mining process, from site characterization to production operations. The goal of the International Workshop on Rock Mass Classification in Underground Mining was to provide a forum for leading practitioners of rock mass classification to come together and share their methods and experiences with the technique. The proceedings of the workshop contain 16 invited papers from 9 countries, reflecting the international depth and breadth of current practice. Applications in both hard-rock and coal mining are well represented. (PDF, 10425 KB, 2007-05)

A collection of 15 papers from leading ground control specialists in the United States, Canada, Australia, the United Kingdom, and the Republic of South Africa. The papers address the entire range of issues associated with coal pillars and have a decidedly practical flavor. Topics include numerical modeling, empirical design formulas based on case histories, field measurements, and postfailure mechanics. (PDF, 3559 KB, 1998-06)

Papers presented at a U.S. Bureau of Mines technology transfer seminar describe the causes of violent material failure in U.S. mines, measurement techniques for monitoring events that result in violent failure, and mitigation techniques for controlling failure. Among the topics included are specific factors contributing to violent failure, new monitoring and analysis techniques, geotomographic methods that provide new capabilities for the study of material failure and stress changes over large areas, and seismic methods for determining source locations, calculating energy release, and determining source mechanisms.  (PDF, 24298 KB, 1995-05)

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. (PDF, 18284 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) (PDF, 52 KB, 2000-10)

Multiple-seam interactions are a major ground control hazard in many U.S. underground coal mines. In some U.S. coalfields, particularly in central Appalachia and the West, the majority of today's mines are operating above and/or beneath previously mined seams. For the past several years, the National Institute for Occupational Safety and Health has been conducting research to develop better techniques for predicting the location and severity of multiple-seam interactions. These Proceedings also contain previously published papers that cover facets of multiple-seam mining research as well as three papers that describe the extensive multiple-seam experience of the Harris Mine, examples of extreme multiple-seam mining from the central Appalachian coalfields, and longwall mine experiences in Pennsylvania, West Virginia, and Utah. The final paper reports on a numerical modeling study that provided some insight into the mechanics of multiple-seam mining. (PDF, 9281 KB, 2007-05)

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. (PDF, 5087 KB, 1997-03)

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. (PDF, 710 KB, 2003)

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. (PDF, 1284 KB, 2008)

In addition to developing various types of cool-interface detection systems, the US Bureau of Mines is actively involved in developing a coal rib-thickness monitoring system for highwall mining applications. One particular system to detect the coal-air boundaries of coal ribs. (PDF, 468 KB, 1995-01)

This study tested whether ground penetrating radar (GPR) could be used to resolve adjacent mine workings. Results indicate that it may be possible to utilize GPR for initial underground mine studies followed by directional drilling to accurately delineate the extent and position of adjacent abandoned mine workings. (PDF, 1691 KB, 2003)

Since the end of 2000, there have been 28 ground fall fatalities in U.S. coal mines. Of these, 10 occurred during pillar recovery operations. Although pillar recovery has been associated with about one-third of recent ground fall fatalities, it accounts for only about 10% of U.S. underground coal production. Statistically, a coal miner engaged in pillar recovery is several times more likely to be killed in a ground fall than a miner on an advancing section of a longwall. This article describes the most significant risk factors associated with pillar recovery and prescribes control techniques that, taken together, can reduce the overall risk to miners. (PDF, 4007 KB, 2005-12)

Pillar recovery has been associated with nearly one third of roof fall fatalities in underground coal mines during the past decade. This paper discusses design methods and technologies that have been transferred to the mining community and implemented. (PDF, 1948 KB, 2003-12)

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. (PDF, 674 KB, 2008-10)

For the first time in an underground stone mine, the relationship between roof movement and microseismic emissions was examined in conjunction with two distinct roof fall areas. As roof monitoring increases in acceptance and monitoring technology advances, the goal of providing reliable roof fall detection systems to enhance the safety of underground mine workers moves closer to reality. (PDF, 397 KB, 2004)

NIOSH and the Stillwater Mining Company worked cooperatively with the Montana Bureau of Mines and Geology to develop a system that would collect seismic data at the Stillwater and East Boulder mines. The purpose was to obtain baseline information on the magnitude and location of mining-induced seismicity to determine if the mines needed multi-channel in-mine monitoring systems. Rapid access to seismic data allows personnel at the Stillwater Mine, Spokane Research Laboratory, and Earthquake Studies Office to evaluate seismic events quickly and respond in ways that may improve the safety of mine personnel underground. Installation of the system also broadened earthquake coverage to south-central Montana, a region previously not covered by the seismograph network. (PDF, 551 KB, 2003-09)

Room-and-pillar retreat mining has been growing in popularity because of productive new technology, including remote control continuous miners, extended cuts, and mobile roof supports. Pillar retreat mines can achieve the same high recovery as longwalls, with lower capital costs and greater flexibility. Unfortunately, between 1990 and 1995, nearly 30 percent of all roof and rib fatalities occurred on retreat mining sections. Also, millions of tons of minable coal are left in place each year because of pillar squeezes, floor heave, pillar line roof falls, and pillar bumps. Traditional pillar design methods are of little help due to the complex mining geometrics and abutment pressures that are present during pillar extraction. This article describes the Analysis of Retreat Mining Pillar Stability (ARMPS) software program, which was developed to ensure that pillars are of adequate size for all anticipated loading conditions. (PDF, 1014 KB, 1998)

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. (PDF, 718 KB, 2006)

Reviews the mechanics of rib failure and the relationship of coal mine geology and pillar constraint to rib instability. Strategies for choosing an effective method of rib support are considered and various rib support methods are discussed. (PDF, 3617 KB, 1992)

A comprehensive survey of mine seismicity a rock bursting during development of two sublevels at the Lucky Friday Mine, Mullan, ID, was conducted to better define rock failure mechanisms and sources of ground control hazards. Survey data included rock burst damage reports, seismic event locations and magnitudes and, for the most energetic events, first- motion information. (PDF, 905 KB, 1998)

Outlines the concepts used to correlate rock failure with microseismic events and presents examples of microseismic monitoring together with associated computer modeling of the rock failure from several mine sites. (PDF, 9567 KB, 2001-07)

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. (PDF, 903 KB, 2008)

Researchers monitored rock mass response to mining of an experimental underhand longwall stope in Hecla Mining Company's Lucky Friday Mine, Mullan, Idaho. This is part 1 of 3. (PDF, 5188 KB, 1992-01)

Researchers monitored rock mass response to mining of an experimental underhand longwall stope in Hecla Mining Company's Lucky Friday Mine, Mullan, Idaho. This is part 2 of 3. (PDF, 859 KB, 1992-01)

The advance-and-relieve method benefits from lateral destressing associated with mining in laminated rocks and a high horizontal stress regime. This stress control method is based on measurements showing that occurrence of rock failure in the roof and floor of an entry results in redistribution of stresses in adjacent entries. Numerical modeling proved useful in studying the basic mechanics of lateral relief while investigating the sensitivity of results to different geologic and mining parameters using controlled experiments. (PDF, 1696 KB, 2003-08)

A U.S. Bureau of Mines case study of pillar recovery in high-grade ore near the Ross shaft at the Homestake Mine, Lead, SD, has demonstrated the usefulness of the finite-element method for evaluating shaft pillar mining plans and shaft stability. This report focuses on mine measurements and calibration of the two-dimensional computer model and is the second in a series of three Reports of Investigations describing the Ross shaft study. (PDF, 694 KB, 1995)

A U.S. Bureau of Mines case study of pillar recovery in high-grade ore near the Ross shaft at the Homestake Mine, Lead, SD, has demonstrated the usefulness of the finite-element method for evaluating shaft pillar mining plans and shaft stability. In this study, borehole extensometers and other instruments were installed to provide data for model verification and to monitor shaft displacement. (PDF, 354 KB, 1996)

Various methods of monitoring slip movements on bedding planes, as well as examination of rock burst damage in stopes, suggest that many rock bursts in the Lucky Friday Mine are closely associated with these movements. Slip displacements along bedding simultaneously reduce the physical dimensions of stopes and increase compressive stress along stope margins. Such changes, in turn, contribute directly to sudden failures of rock and cemented sandfill surrounding stopes (PDF, 674 KB, 1999)

Roof and rib conditions were observed and assessed in 33 underground stone mines. Hazard assessment indicated that the ground failures that occurred under moderate to substantial overburden were caused by stress concentrations and geologic structures. Selection of the mining horizon and mine-layout decisions tremendously influence ground stability. (PDF, 410 KB, 1998)

Recent studies by researchers from the National Institute for Occupational Safety and Health indicate that shear loading contributes significantly to failure of bolts used for rock reinforcement in coal mine roofs. Laboratory tests on 17 bolts were conducted to study the behavior of roof bolts subjected to shear loading over a range of axial bolt loads. (PDF, 699 KB, 1999)

The Roof Monitoring Safety System (RMSS) is described, compared to other roof-monitoring technology, and described in context with proactive ground control plans for stone mines. (PDF, 944 KB, 2000-11)

This paper outlines the evolution of the Roof Monitoring Safety System (RMSS) and how it can be used in a comprehensive proactive ground control safety program. A case history is described where the RMSS was used in an evaluation of the effectiveness of a mechanical impact sealing machine at an operating limestone mine. (PDF, 5765 KB, 2000)

The Roof Monitoring Safety System (RMSS) provides a first step in roof behavior awareness. By understanding and measuring roof movement in an underground mine, the potential for injuries or fatalities to mine workers from fall of ground can be lessened. Also, officials at an underground mine with a history of data on roof movement are better prepared to make a decision on remedial actions if falls of ground become a problem. The RMSS provides a safer, simple, and inexpensive means for measuring roof movement. (PDF, 1014 KB, 1998-11)

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. (PDF, 1421 KB, 2007)

This paper discusses roof screen and its potential to prevent hundreds of injuries caused by the fall of small rocks between permanent roof supports. (PDF, 247 KB, 2008-06)

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. (PDF, 514 KB, 2002)

This paper presents the results of a study of roof conditions in 34 limestone mines in the Eastern and Midwestern U.S. (PDF, 700 KB, 2007)
                                 

This paper utilized the rock fall related incident narratives from the MSHA database for a taxonomic analysis, which identifies the root causes of an event and can provide future direction for corrective measures to reduce the probability of occurrence of the event. (PDF, 620 KB, 2003-08)

At an underground stone mine in Pennsylvania, a modified stress-control mine layout is reducing the hazardous conditions associated with excessive horizontal stresses. Findings to date show that the stress control layout provides more stable conditions, resulting in a safer environment for the mine workers. (PDF, 3459 KB, 2003-04)

NIOSH has developed an automated PC-based seismic event (induced earthquake) monitoring system for use in mine ground control studies. This paper describes the system's design philosophy, hardware and software components, examples of installations, and a few observational results. (PDF, 1539 KB, 2002-02)

The U.S. Bureau of Mines conducted research at the Galena Mine, Wallace, ID, with the aim of mitigating the effects of rock bursting. A digital seismic array and an array of borehole pressure cells had been installed near the site of a stope undergoing mining and periodic distressing. (PDF, 1611 KB, 1993)

Two examples of an echelon mining-induced fractures seen in hard-rock mines provided a basis for inferring that fracture zones and bedding plane sap rations immediately surrounding mine openings are promoted by oblique shear into the openings. (PDF, 5625 KB, 2002)

The authors hypothesize that excavation-induced extension fractures are caused by elastic shearing displacement that in turn causes tension oblique to a propagating shear zone. (PDF, 396 KB, 2003)

This study reviewed 31 technical papers which contain analysis of shear strengths for clay and sands with varying mixtures of rock particles. These technical papers, published over the last 40 years, are comprised of field case studies, laboratory investigations, and theoretical analysis. Evaluation of this body of knowledge has shown that the shear strength gradually increases with increasing percentages of floating particles in unsaturated clays. (PDF, 2209 KB, 2000)

This paper presents information that shows that short-encapsulation pull tests can provide the information necessary to improve ground control in variable roof conditions. (PDF, 175 KB, 2003-08)

A prototype portable hyperspectral imager was field tested at an open-pit mine as part of an investigation of remote sensing technologies for use in detecting and monitoring conditions in surface mines that could lead to catastrophic slope failure. (PDF, 1865 KB, 2001)

Two of the major ground control safety issues confronting underground mine operations today are shaft pillar stability and the failure of rock around active mine openings. The purpose of this paper is to demonstrate one technique developed at the Spokane Research Center that allows the user to create a finite-element model of a two-dimensional section of an underground mine in a relatively straightforward manner. (PDF, 611 KB, 1997)

The risk of major pillar falls can often be reduced by leaving final stumps that are large enough to protect the intersection, but small enough that they do not inhibit the caving of the gob. Analyses were conducted to assess the effect of seam height and depth of cover on the potential variation in the size of remnant stumps. (PDF, 127 KB, 2001-08)

Rock mechanics testing is central to a geotechnical exploration program and typically, average uniaxial compressive strength (UCS) is the measure used to quantify a particular roof unit at a given corehole. Issues are that the average UCS may differ between coreholes but not be statistically significant; and whether or not widely spaced coreholes can identify valid spatial trends in rock strength. The paper describes NIOSH's extensive investigation of these issues. (PDF, 290 KB, 2004)

Displacement and stress changes in cemented backfill and ore pillars at the Buick Mine, near Boss, MO, were monitored by engineers from the U.S. Bureau of Mines and The Doe Run Co., St Louis, MO. Objectives of this research were to evaluate the effect of backfill on mine stability, observe backfill conditions during pillar removal, and calibrate a numeric model to be used to design other areas of the mine. (PDF, 745 KB, 1995)

In cooperation with Cyprus Twentymile Coal Co., researchers from the National Institute for Occupational Safety and Health (NIOSH), Spokane Research Laboratory, conducted a study at the Foidel Creek Mine, an underground coal mine near Oak Creek, CO, to evaluate the stability of underground working conditions as a longwall advanced through a series of backfilled cross-panel entries. (PDF, 919 KB, 1998-08)

This paper discusses roof monitoring, the roof movement, the large roof fall, propagation of the roof failures, and the recent support measures undertaken to stabilize the escapeway over a portion of the older limestone mine workings at the NIOSH Lake Lynn Laboratory, a mining health and safety research facility. (PDF, 243 KB, 2003)

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

This article compares the performance characteristics of various support systems, including wood cribs, can supports, cluster props and pumpable supports. (PDF, 1973 KB, 2006-02)

Recently, powerful design methods have emerged from analysis of large data bases of real-world pillar successes and failures. In the process, our understanding of pillar mechanics has been greatly enriched. (PDF, 502 KB, 1999)

Researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) are developing numerical modeling tools to forecast time-dependent deformation around coal mine entries. (PDF, 481 KB, 1998)

An experiment is described in which hollow inclusion cells were used to measure stress in a jointed rock mass during drift development at the Stillwater Mine, Nye, MT, USA. (PDF, 855 KB, 1999)

The goal of the research described here is to develop a stress monitoring system that will provide immediate information to mine managers for making daily safety decisions as areas of poor ground are mined through. (PDF, 1943 KB, 2002)

This paper summarizes case studies where unusual circumstances required that a longwall retreat into or through previously driven rooms. Two types of roof failure are identified and discussed. (PDF, 1525 KB, 2001-01)

Historically, the surface subsidence over underground coal mines has been predicted using empirical profile or influence functions which have little or no connection to the actual mechanics of the subsidence. This paper presents a case study where a mechanics-based, boundary-element program is used to calculate the surface subsidence associated with several panels of a Northern Appalachian longwall coal mine. (PDF, 1285 KB, 1998)

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. (PDF, 2535 KB, 2007)

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. (PDF, 67 KB, 1994-04)

The underground stope leaching mining system involves applying leach solutions to mineralized rock that has been fragmented by blasting ore in place, or by backfilling empty stopes. (PDF, 182 KB, 1994-05)

Room-and-pillar operators are provided with practical information and guidelines concerning multiple-seam mine design to reduce ground problems associated with the interaction of adjacent workings. (PDF, 66 KB, 1994-11)

The objective of this work is to develop a comprehensive, practical method for designing longwall gate entries that considers coal pillar size, mine roof quality, and artificial support in an easy-to-use computer program. (PDF, 71 KB, 1995-02)

The new permissible-type, intrinsically safe design modules described here represent an engineering intervention strategy toward improving miners' ability to recognize and avoid the hazardous zone of unsupported mine roof. (PDF, 97 KB, 1997-05)

The analysis of Retreat Mining Pillar Stability (ARMPS) computer program was developed in 1995 and has been widely accepted by the mining community. A Windows version of ARMPS is now available. It features simplified data input, graphics, and an expanded online "HELP" facility. (PDF, 91 KB, 1997-07)

A method is described for allowing operators to predict methane emissions from panels with increased face width. (PDF, 30 KB, 1997-11)
                                       

The use of seismic tomography to identify geologic hazards in underground mines is discussed. (PDF, 39 KB, 1997-11)
                                                          

With the increasing cost of wood and greater dependency on wood cribs for support in applications such as longwall tailgate and bleeder entries, more efficient use of wood crib supports is required. (PDF, 155 KB, 1997-11)

Recent ore pass failures have underlined the lack of ore pass design methods and standards available to both MSHA and mine engineers. (PDF, 1155 KB, 1998-02)

The Roof Monitoring Safety System (RMSS) provides a safer, simple, and inexpensive means for measuring roof movement; its use in underground stone mines is described. (PDF, 53 KB, 1998)

Development of methods and tools to assist in the evaluation and selection of rock supports could reduce the number of unplanned rock falls significantly. (PDF, 1158 KB, 1998-11)

The Roof Monitoring Safety System (RMSS) introduced in late 1997 has been modified to improve durability and simplify the measurement of roof or rib movement. (PDF, 483 KB, 2000-06)

This video, entitled "Ground Support...It's Important, or Miner Mike Saves the Day," presents information on why ground supports work and how to install them properly. (PDF, 533 KB, 2000-07)

Scaling, the removal of loose rock from the roofs and walls of a mine by manual or mechanized means, may be necessary during any stage of mining. Manual scaling is very labor intensive, and mechanical methods can be too powerful and actually produce a less stable roof. (PDF, 1106 KB, 2001-01)

An announcement of the availability of the proceedings of the Second International Workshop on Coal Pillar Mechanics and Design. Included are 15 papers from leading ground control specialists in the United States, Canada, Australia, the United Kingdom, and the Republic of South Africa. The papers address the entire range of issues associated with coal pillars and have a decidedly practical flavor. (PDF, 230 KB, 2001-08)

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

The AHSEM computer program contains two modules to improve mine layouts for control of horizontal stress. ARBS is designed to help with selecting the proper roof bolt system from the great variety of available bolt types and patterns. (PDF, 174 KB, 2003-04)

The Coal Mine Roof Rating (CMRR) is a roof classification system. It was first introduced to the mining community in 1994. It has now been written to a userfriendly version that can be run on any PC with a Windows operating system. (PDF, 278 KB, 2003-04)

Investigators collaborated to develop a new training module that would address the hazards of working around highwalls. Such a module would be applicable to surface mines and road construction sites, both of which require personnel to work under and on top of steep and often unstable slopes. (PDF, 163 KB, 2004-08)

Most rock fall injuries can be prevented by installing roof screen during the bolting cycle. This video and accompanying instruction booklet explain techniques for roof screen installation and use of the personal bolter screen. The video also provides safe handling tips, best practices, and information about machine technology that can greatly improve material handling. (PDF, 726 KB, 2005-03)

The use of highwall mining systems has increased substantially in open-pit coal mines. It is used where overburden depth exceeds economical recovery. Highwall stability remains the major safety concern during highwall mining. The Mine Safety and Health Administration requires highwall mining operators to follow ground control plans that specify the pillar sizes necessary to prevent a pillar collapse that would threaten highwall stability. NIOSH has developed the Analysis of Retreat Mining Pillar Stability-Highwall Mining (ARMPS-HWM) computer program to assist mine planners with pillar design. Based on extensive research into instances of highwall mining pillar instability and pillar collapses in underground mines, ARMPS-HWM uses the Mark-Bieniawski formula to estimate the strength of long strip pillars. The suggested design procedure addresses the following issues: (1) the number of holes between barrier pillars, (2) the size of the individual web pillars, (3) the size of the barrier pillars, and (4) the stability factor of the overall design. The program is simple to install and easy to use. It contains extensive "Help" files that provide more background on the research upon which design formulas are based. The Help files also contain suggestions for highwall mining through old auger holes and for close-proximity, multiple-split highwall mining. (PDF, 89 KB, 2006-03)

The NIOSH suite of coal mine ground control software addresses nearly every aspect of coal mine ground control planning, including geologic characterization, mine layout, pillar design, and support selection. Mine planners who use the software have access to the knowledge gained during years of NIOSH research--packaged in a simple, easy-to-use format. Several of these software packages have recently been updated and improved. These include Analysis of Roof Bolt Systems (ARBS), the Support Technology Optimization Program (STOP), the Coal Mine Roof Rating (CMRR), and the Analysis of Horizontal Stress in Mining (AHSM). (PDF, 632 KB, 2006-04)

Describes the Roof Fall Risk Index (RFRI), a method of systematically characterizing the risk of roof falls in underground limestone mines. (PDF, 300 KB, 2006-10)

NIOSH has released a new report entitled "Roof Bolting Machine Operators Skills Training for a Walk-Thru Roof Bolter: Trainer's Guide" (IC 9489). It is designed to help safety trainers develop structured training for new operators of walk-thru bolting machines. (PDF, 1129 KB, 2007-06)

Rock mass classification is widely used throughout the underground mining industry - in both coal and hard-rock mines. The technique has been successful because it 1. Uses simple measurements to rate rock mass strength. 2. Helps mine planners to make the best use of geologic information in mine design. 3. Makes it possible to compare ground control experiences between mines, even when the geologic conditions are very different. The International Workshop on Rock Mass Classification in Underground Mining provided a forum for leading practitioners of rock mass classification from around the world to come together and share their methods and experiences with the technique. (PDF, 88 KB, 2007-07)

Research by NIOSH on multiple-seam mining has resulted in two new ground control products. The first is IC 9495 which is a proceedings document containing a variety of papers that summarize recent knowledge about multiple-seam mining. The second is the Analysis of Multiple-Seam Stability (AMSS) software package which is a simple user-friendly computer program to help mine planners. This document briefly describes each product. (PDF, 224 KB, 2007-11)

Determining backfill stress is an important part of evaluating mine safety, whether personnel are working in proximity to backfill or in other areas of the mine where backfill is an integral part of regional support. To assist in determining stress in backfill more accurately, researchers used temperature readings recorded by thermistors to correct for the influence of temperature on stress data. These thermistors were positioned in the stems of earth pressure cells installed in backfill. (PDF, 8304 KB, 2006)

In an effort aimed at monitoring mining-induced stress changes that may influence ground failure, the U.S. Bureau of Mines conducted a series of active 3-D seismic tomographic surveys at the Homestake (Lead, South Dakota) and Lucky Friday (Mullen, Idaho) mines. (PDF, 1435 KB, 1997-01)

Researchers conducted tests to evaluate the tensile strength, fiber count, and adhesion of shotcrete applied to panels at the Chief Joseph Mine, a research and training facility operated by Montana Tech. The goal is to reduce the need to install multiple supports at the advancing face by creating a safer mining system that limits the time miners are exposed to unprotected roof. (PDF, 175 KB, 2005)

Recent NIOSH research focused on a longwall coal mine in Utah with overburden greater than 750 m containing several massive sandstone units. The primary field instrumentation at the site was three-dimensional, full waveform, autonomous microseismic arrays placed underground and on the surface in order to surround the active multipanel longwall district. Overall 13,000 seismic events were detected and located with on-site processing during the five months the panel was being mined, including a magnitude 4.2 event. (PDF, 171 KB, 2001-07)

This paper describes the three-dimensional velocity tomograms that were generated to image the stress redistribution around an underground coal longwall panel to produce a better understanding of the mechanisms that lead to ground failure, especially rockbursts. (PDF, 2086 KB, 2008-06)

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. (PDF, 437 KB, 2007)

Three alternative design approaches to decreasing the risk of large-scale catastrophic collapses are described: the containment approach, the prevention approach, and the full-extraction approach. Until good data on the post-failure behavior of pillars become available, the containment and full-extraction options are the safest. The limitations in our ability to evaluate both the stability of old workings and the long-term performance of room-and-pillar mines are described. (PDF, 866 KB, 2001)

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. (PDF, 613 KB, 2006)

This paper describes a project involving modeling rock masses with varying Rock Mass Rating (RMR) values to determine the degree of instability that develops around an underground opening as a function of RMR. (PDF, 333 KB, 2004)

Details of the operational aspects of the backfilling and mining cycles at each of three mines in the western US are presented in this paper, accompanied by a summary of the mechanical properties of the backfill and its in-situ geomechanical behavior.  (PDF, 420 KB, 2007)

A unique circumstance created by monitoring a pre-driven longwall recovery room permitted measuring the stresses of a coal pillar throughout its entire life cycle in less than a week. The complete transformation, or life cycle, took place in less than 12 hours. Roof to floor closure measurements, combined with the timing of the pillar behavior, provides a detailed look at the uncontrollable convergence of underground mine openings. (PDF, 1166 KB, 2007)

The Support Technology Optimization Program (STOP) was updated to Version 2.3. This paper describes the additional features: including uncontrolled convergence into the design requirements for standing roof supports; the addition of design procedures for cable bolts as an alternative secondary roof support; and the addition of new standing roof support technologies. (PDF, 2336 KB, 2001)

An experiment is described in which instrumented rock bolts were used to measure strain in the rock mass during drift development at the Stillwater Mine, Nye, Montana, USA. (PDF, 272 KB, 1999)

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. (PDF, 2108 KB, 2007-03)

Ground penetrating radar (GPR) has been investigated by NIOSH for its potential to determine roof hazards in underground mines. GPR surveys were conducted at four field sites with accompanying ground truth to determine the value of GPR for roof hazard detection. Differences in data quality are discussed, as well as suggestions for collecting improved data. (PDF, 3302 KB, 1996)

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. (PDF, 462 KB, 2007)

NIOSH is conducting research to develop mine design algorithms that will result in safer multiple seam mines. This paper presents an overview of multiple seam issues in the central Appalachian coalfields.  (PDF, 546 KB, 2003)

The Coal Mine Roof Rating (CMRR) has been developed to quantify the defects in the rock mass and compile a strength value which can be used for engineering design. The CMRR has been applied to a number of ground stability problems, including chain pillar design, roof bolt selection, hazard assessment, intersection design, and numerical modeling. The CMRR procedure and some of these applications are described in this paper. (PDF, 1209 KB, 2001)

Point load testing is used to determine rock strength indexes in geotechnical practice. A study was conducted where more than 10,000 individual test results, from 908 distinct rock units, were used. This allowed for intact rock strength data to be made available through point load testing for numerical geotechnical analysis and empirical rock mass classification systems such as the Coal Mine Roof Rating.  (PDF, 482 KB, 2000)

The practical application of the "advance and relieve" method is discussed, where a pillar is removed on one side of the panel as it is being advanced, creating a cave. A trial of the method was conducted for a room and pillar coal operation that was experiencing roof cutters and long running roof falls caused by high horizontal stresses. (PDF, 2100 KB, 2000)

This paper describes a study where the variations of the magnitude of the horizon stresses in sedimentary deposits in the eastern and Midwestern U.S. are examined with respect to two factors, the elastic modulus of the rock and the site depth. (PDF, 436 KB, 2003)

A surveillance system using low-cost video cameras and computer software from the security industry was tested for effectiveness in monitoring mine slopes and providing real-time warning of rock falls. (PDF, 1085 KB, 2004)

Presents the results of NIOSH research to identify state-of-the-art bulkhead designs, including design criteria, leakage monitoring systems, and emergency warning systems. (PDF, 315 KB, 2006)

This paper will review current and historic work practices used internationally to minimize the hazard to miners from mining in conditions which could produce a bump. (PDF, 204 KB, 2008)

Workers in underground stone mines have a high fatality rate caused by falls of ground from the mine roof or rib. NIOSH recommendations to reduce ground fall injuries and deaths address baskets, mechanical scalers, mechanical bolters, drill steel changing, personal protective equipment, and training. (PDF, 1255 KB, 2003-11)