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By M. MacLaughlin, J. Whyatt

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. The fracture sets and bench width were mapped by teams of geological engineering students from Montana Tech under the direction of Dr. Mary MacLaughlin. The students analyzed the fracture data, conducted physical property tests, and used a beta version of a NIOSH program “Bwedge” to predict the distribution of surviving bench widths. In the course of this analysis the students developed evidence of software performance issues that, unfortunately, frustrated their analysis. These have now been addressed and a full analysis completed. The analysis confirms the validity of the student mapping program and provides insight into the effects of blasting and excavation practices on the bench. It also provides a tool for exploring the pattern of bench crest failure that would result from variations in both bench geometry and blasting practices.

This study presents a reservoir modeling approach to investigate the relative effects of different coalbed parameters on the migration of methane into development entries. A base coalbed reservoir model of a three-entry development section, where grids were dynamically controlled to simulate the advance of mining at a constant section advance rate, was created and calibrated for a Pittsburgh Coalbed mine in the Southwestern Pennsylvania section of the Northern Appalachian Basin. The values of coalbed parameters were varied to evaluate their effects on predicted methane emissions for various development distances. The results of these parametric simulations were then used to derive linear expressions relating these parameters to methane emissions into the workings. These models were analyzed to assess their significance and adequacy for predictive purposes. This work shows that coupling reservoir simulations with linear modeling yield a technique that can be applicable to different coalbeds. The reservoir parameters used by the linear models (coalbed thickness, pressure, sorption time constant, Langmuir parameters, permeability) can be determined by running relatively simple laboratory tests, such as adsorption equilibrium and permeability determination, on coal samples obtained either from the mining operation or from the exploratory boreholes drilled ahead of mining.

Jan 1, 2008

By Suresh K. Bhatt, Gary L. Mowrey, Timothy R. Rehak, David K. Ingram

Coal and nonmetal mining used about 4.3 billion pounds of explosives and blasting agents during 2001 in the United States. A major part of this consumption was related to surface mining. Mine Safety and Health Administration accident data indicate that flyrock and lack of blast area security were the primary causes of blasting-related injuries in surface mining. Fatal injuries due to lack of blast area security were primarily caused by failure to clear blast area or inadequate access control to the blast area. At a coal mine, a neighbor walked into the blast area and was fatally injured. The blaster could not see the victim entering the blast area from the firing station. In another case, a passenger in a vehicle was fatally injured by flyrock because highway traffic was not monitored during the blast. In another example, a dozer operator entered a blast area due to lack of access control. Several fatalities resulted from using inadequate or no blasting shelter. A crane operator was fatally injured while standing in the open about 120 ft from the blast site. In another instance, a helper, standing about 150 ft away from the edge of a blast, was fatally injured by flyrock. In a limestone mine an equipment operator was fatally injured while guarding access roads in a pickup truck. This paper briefly describes six representative fatalities due to flyrock and lack of blast area security in coal and nonmetal mines. Several mines were visited to collect information relative to working practices aimed at mitigating blasting hazards. Salient information obtained through these visits is presented.

By W. K. Overbey

Knowledge of fracture systems in oil or gas reservoirs is essential to the efficiency of both primary and secondary production operations. A relationship was established between structural features of the surface and both natural and induced fractures in oil and gas reservoirs, thus providing a method of predicting the direction of rock fracture prior to field development and well completion. Correlations between the surface features and under-ground fractures resulted from analysis of joint strike measurements, bottom-hole impression packer surveys, photographs of hydraulically fractured wells, fracture data from oriented cores, in situ strain measurements from formation outcrops, and lineament analyses from aerial photographs. The mean orientation of surface fractures, lineaments, and stress field directions ranged from N 53° E to N 73° E, compared with an average orientation of N 63° E for the hydraulically induced fractures. Tectonic stress field was shown to influence the direction of hydraulically induced fractures. This report presents the details and application of techniques to obtain the orientation of the principal horizontal compressive stress field component and thus the direction of induced fractures.

Jan 1, 1971

Provide mine personnel with a convenient means of determining the optimum installation geometry of roof trusses in bedded roof. Background Mine operators frequently ask the following questions concerning roof truss installations: 1. Where should the bearing plates or brackets be placed or where should the inclined holes be started? 2. At what angle should the holes for the inclined chords or angle holts be drilled? 3. What tension should be put into the inclined chords so as to achieve the most effective results for the effort and expense? Truss hardware manufacturers have responded to these questions with answers based on what seems to work best. While designs based on past experience are frequently reliable, there was a need for a rational approach that could accommodate a variety of conditions. The Bureau has developed a procedure that enables mine operators to optimize roof truss installations in bedded roof.

Jan 1, 1989

By Fred N. Kissell, J. E. Matta, J. C. LaScola

The methane gas emitted from coal samples collected from the conveyor belts dumping into silos was measured by the Bureau of Mines. Approximately 50 pct of the total gas desorbed into a sealed can within 1 week was released during the first 24 hours. No simple correlation between the gassiness of the coal stored and the methane concentration in the silo open space above the coal was found. This was probably because the gassier coals were stored in open-top silos, which were better ventilated. Although the methane concentration in the open space above the coal pile was less than 1 pct for all 34 silos investigated, a methane measurement in the coal pile showed that high methane concentrations can exist. The methane released in the pile appears to accumulate and not liberate freely into the open space above the coal pile. Probably this gas is released during reclaiming operations, but further research is required to substantiate this claim.

Jan 1, 1978

By Lon Santis, Scott Deitchman, John A. Decker

This report describes three cases of carbon monoxide (CO) poisoning in a manhole, including one fatality, from CO migrating through soil after nearby use of explosives. A municipal sewer project involved installation of new pipes and manholes. Work of the general construction contractor was interrupted when a subcontractor detonated 265 pounds of nitroglycerin-based explosive 40-60 feet south of the manhole to break up underlying rock. A construction worker who descended into the manhole 45 minutes after the explosion collapsed within minutes, and two co-workers descended into the manhole to rescue him. One rescuer retrieved the unconscious worker, and the other rescuer died in the manhole. All workers had elevated carboxyhemoglobin levels. In the subsequent NIOSH investigation, air monitoring was conducted with real-time instruments, and air samples were collected in Tedlar bags. Laboratory analyses of the bag samples collected near the bottom showed 1905 parts per million (ppm) CO, 19.5% oxygen, and 3% carbon dioxide. Direct reading instruments showed progressively higher concentrations as the sensor was lowered into the manhole. Subsequent chamber tests on sample explosive yielded 27 liters CO per kilogram detonated. Based on this value, the surface blast at the construction site may have produced about 3,250 liters (114.8 cubic feet) CO. The CO in this incident most likely was released from the nearby explosion and migrated through soil and fractured rock into the manhole. The blasting and construction industries should be made aware of this previously unrecognized CO exposure hazard associated with surface blasting. The extent of CO exposure from explosives used in construction is not known, and additional information on the extent of CO exposure must be collected. In addition, confined space entry procedures (including monitoring confined space atmospheres before entry) should be observed; CO monitoring of confined spaces in the presence of blasting can prevent future incidents such as this one.

Oct 30, 1997

To develop and design a bit that will rapidly drill smooth and precise instrumentation holes in soft rock. Approach Use a one-piece bit made by combining a drag bit and a diamond bit. Because a smooth-walled borehole with a precise diameter is needed for borehole pressure cells (BPC) and other borehole instruments, a diamond bit is usually used. However, diamond bit drilling is slow, and the bit will tend to bind when squeezing ground is encountered. On the other hand, the drag bit will cut faster, but the walls of the drill hole will be rough and the diameter will not be as precise. The combination will provide a bit which penetrates as rapidly as a drag bit, but retains the smooth-wall and precise borehole diameter of a diamond bit. How It Works A three-foot-length of EW-size drill rod is centered in a diamond bit by welding it to three equally-positioned spacers at each end of the bit. A drag bit is attached to the EW rod with a standard EW-to-drag bit adapter as shown in the diagram. Three equally-spaced diamond inserts are set to the desired hole size and welded to the diamond bit barrel behind the crown. These inserts increase the smoothness and precision of the hole by cut-ting away any hole closure. Three equally-spaced shims are set approximately 0.020-inch under the overall insert diameter size and welded to the rear of the diamond bit barrel. The combination bit should be used on a diamond drill with either water, mist or air as the coolant.

Jan 1, 1982

Develop methods to detect and repair poorly functioning dust collectors on roof bolters. Approach In conjunction with a research project to reduce silica dust in coal mines, a variety of roof bolting machines operating under different conditions were examined to find out how much these machines were contributing to the silica dust problem. Results The investigation concluded that if the bolting machines' dust collector is properly maintained, very little dust can be measured in the air, even with minimal airflow over the bolter. Poor maintenance, however, frequently results in high dust levels. Three major problem areas were found. These were: (1) filter leaks, which allowed dust to escape, (2) accumulations of dust in the collection system, and (3) low airflow at the bit due to hose, fitting, and relief valve leaks.

Jan 1, 1984

Mining and reclamation procedures that meet the requirements of SMCRA are illustrated on pages 8 and 9 for each of the three major surface coal mining methods -- area mining, contour mining, and mountaintop removal mining. The three methods involve the same basic steps: clearing the land of trees and other vegetation, removing topsoil and overburden, mining the coal, and reclaiming the land. Although all three methods would not usually occur on any single site, the illustration facilitates comparison of mining and reclamation methods and aids basic understanding of the reclamation processes that take place under SMCRA. Area Mining The area mining method is commonly used to mine coal in the flat to moderately rolling terrain found principally in the western and midwestern states. After the overburden is excavated down to a coal seam, the mining area is enlarged horizontally to expose more coal for removal. In the West, where coal seams are commonly 10 to 20 feet thick (and range up to 100 feet thick in the Powder River Basin of Wyoming), the life of some mines maybe more than 50 years. In the Midwest, coal seams are typically 3 to 7 feet thick and 75 to 100 feet below the surface. Because of the large expanse of area mines and their relatively unrestricted sites, enormous equipment is used to remove overburden and reconstruct the land. The area mining operation in the illustration is on land that was formerly used for farming. The drawing shows that the agricultural use is being reestablished immediately following reclamation. Mining is proceeding across the land toward the left side of the site. The initial excavation was made far enough away from the stream along the right edge of the site to prevent damage to the water supply. The coal under most of the site has been removed, and reclamation has been completed on some of the land. For example, some of the cattle in the foreground and those in the feedlot behind the silo are grazing on reclaimed land that has been mined. At the far left of the illustration, topsoil from the unmined area is being removed by scrapers, transported across the area of active mining, and immediately spread on the land on the right, which is being reclaimed. (Reclamation of mined land as soon as practical, as required by the Act, is called contemporaneous reclamation.) A

Jan 1, 1992

By Oscar Lee

"Flotation is generally regarded as a process that is only applicable to metallic minerals. However, its scope is now known to be greater than this, because some of the nonmetallic minerals are floatable, such as graphite, sulphur, and fluorite. Recent observations show that limestone may be added to the list of floatable nonmetallic minerals. Such work is being done on a laboratory scale at the Southern Experiment Station (Tuscaloosa, Ala.) of the Bureau of Mines, Department of Commerce, where experimental magnetic concentration of the low-grade iron ores of the Birmingham district is in progress. Certain experiments have demonstrated that the limestone may be floated from the magnetic log-washer tailing, and then incorporated in the iron concentrate.If the loss of lime could be prevented, some ores though low in iron and high in insoluble contain enough lime to make their concentrates self-fluxing. Since this loss in the magnetic log-washer can not be avoided, the Time must be recovered from the tailing by some method and added to the magnetic iron concentrate before sintering. Then the resulting concentrate will be self-fluxing.While seeking a suitable means of treating the tailing for recovery of lime, flotation was tried. It was at once evident that this method had possibilities, during the early part of the investigation, soap solution made from a common soap was used as a flotation reagent. The froth obtained was a fairly good lime concentrate. This result was an important clue, and led to tests with the use of such reagents as oleic acid and sodium oleate. Later, cresol, creosote, coal tar and other similar flotation reagents were tested in combination with the oleic acid and soap solutions. As a result, oleic acid and cresol used together were found to be satisfactory.The tailing from the magnetic log-washer is in excellent physical condition fur flotation. The iron ore had been ground in a ball mill to 100 mesh for magnetic concentration. Hence the bond between the lime carbonate and the other constituents of the tailing was well broken."

Apr 1, 1926

By W. J. Fene

"The prevalence of accidents in the coal-mining industry has prompted a study of the workmen's compensation laws of the various States and the statistics of accident costs, for the purpose of explaining to operators how the compensation laws are regulated and to show the cost of accidents.The subject of compensation laws and accident costs is by no means new, but the prevalence of coal-mine accidents would indicate that the mine operator in general is not thoroughly conversant with their importance. Unquestionably, compensation laws are a large factor in promoting accident prevention, and it is believed that a greater measure of success would be accomplished in preventing accidents if all mine operators were fully aware of their important bearing on the cost of production.Many operators seem to be indifferent to accident occurrence; possibly they do not real¬ize the seriousness of the accident hazards that exist in their mines, even after the hazards are brought to their attention. There is no question that material financial advantages are to be gained by the prevention of accidents and it would appear that when these advantages are thoroughly understood, operators would be anxious to eliminate, insofar as is feasible, conditions likely to cause accidents.The unsettled state of the mineral industry and the irregular operation of mines during the past several years has probably been an important factor in influencing the apparently indifferent attitude of the operator. The chaotic conditions in the mining industry and especially in coal mining are unquestionably a factor that tends to increase accidents, just as mine idleness increases roof hazards and results in deterioration in mechanical, electrical, and haulage equipment, and promotes disorganization of the personnel. During such times greater efforts should be exerted toward the prevention of accidents because of these increased hazards and of the financial advantages brought about by the various savings to be effected when mine accidents are held to a minimum.This report on accidents in the coal mines of Pennsylvania was made possible largely through the cooperation of William J. Maguire, director, Bureau of Statistics, Pennsylvania Department of Labor and Industry, and Rush N. Hosier, superintendent, Coal Mine Section, Pennsylvania Compensation Rating and Inspection Bureau, who made available their records and extended much assistance and numerous courtesies during this study."

May 1, 1932

Enhance coal mine worker safety and productivity by developing a means to control and predict coal mine mountain bumps. Approach The Bureau of Mines has been engaged in extensive research to understand coal mine mountain bumps and their effect on underground coal mining in the United States. Information was collected on the geologic conditions, mining techniques, and engineering parameters at five mountain-bump-prone mines. Although research has not yet evolved to the point where mountain bumps can be effectively predicted or controlled, such studies are invaluable for providing clues that can lead to the development of mountain bump mitigation technology. Case Study Results and Recommendations Mountain bumps in coal mines are explosions of the coalbed that violently release the strain energy stored within it into openings created by mining. Such an event is not only dangerous to mine workers, but can cause substantial amounts of damage to mine equipment, resulting in productivity loss and downtime. In a coal mine, the occurrence may cause coal to be expelled violently from the coal face or coal pillars or cause the mine floor to heave suddenly. Coal bumps are usually accompanied by a very loud noise and tremors or vibrations. Such ground failure:; usually occur in the vicinity of an active gob line in an active retreating room-and-pillar panel, or at or near the face in an advancing or retreating longwall mining panel.

Jan 1, 1989

Develop improved blasting practices that can help to curb overbreak in highwalls at surface mines, thereby reducing the hazards of rock-falls to workers and equipment, The Problem The serious hazard in surface mining is the falling of rock from highwalls. Poor highwall stability is caused in part by geologic conditions, but often is aggravated by faulty blasting practices, where the explosive energy not only fractures the rock to be excavated, but also damages the rock that borders the excavation. This reduces the general stability of the hlghwall and increases the rockfall potential. The probability of injury to mine workers or damage to equipment associated with exposure to the highwall increases with the height of the highwall and the extent of its overbreakage. Most rockfalls occur in the first 15 days after a new highwall is exposed. This statistic is significant since most of the work below a highwall is done during this period. The area of greatest hazard is within 25 ft of the toe for rocks that fall vertically, and up to 90 ft from the toe for falling rocks that are deflected by the highwall during their descent, The workers most frequently involved in such accidents are dozer operators, ground laborers, and shovel operators or oilers.

Jan 1, 1985

Reduce the hazards to which mine personnel are exposed by providing safer procedures for removing dragline wire rope terminations. Background The termination points of wire ropes used on draglines consist of a wedge and socket that lock the rope in place through friction. These components must be separated when the wire rope is changed. At present, the cannon method is the most common procedure used to accomplish this. However this method, using a small cannon and primer (detonator) cord to propel a steel projectile that will knock the wedge out of the socket, has the potential of causing injuries to mine personnel and damage to equipment. The Bureau of Mines, has devised safer, and equally efficient methods of removing wire rope terminations. The Bureau began by studying the cannon method, its merits and draw-backs. Safety guidelines were then developed for the cannon method, and two alternative methods-the pendulum ram and hydraulic pusher-were devised and tested. The Cannon Method The steel projectile used to separate the wedge and socket in the cannon method was found to be very effective. However, the method poses the inherent hazards of any explosive de-vice-hazards that could be increased by lax work procedures. There is no strict uniformity in the manufacture of the cannon or in the work procedures used in the mines employing it. Hazards could be reduced, or even eliminated, with adaption of certain manufacturing and work-procedure guidelines, such as 1) making the cannon and projectile de-signs, as well the work procedures used, uniform, 2) ensuring separate loading of the charge and detonator with insertion of the detonator through a separate port, 3) connecting electrical firing circuits only after the charge and projectile are loaded and the cannon is placed in its final firing position, 4) using approved detonating devices, 5) anchoring the cannon before firing and, 6) placing armor netting over the cannon before detonation.

Jan 1, 1986

By E. W. Dean, W. A. Jacobs

"The petroleum division of the Bureau of Mines in its laboratory investigations, has had occasions to develop a number of types of electrical heating equipment. It was found that electric heaters could be used to particular advantage in the standard distillation test for gasoline. (Dean, E.W., Motor Gasoline, Properties, Laboratory Methods of Testing and Practical Specifications, Bureau of Mines Technical raper 214, 1919, 33 pages.) In order to assist in rendering this type of heater available for general use, a description of the apparatus developed by the Bureau was published. (Dean, E.W., A convenient electric heater for use in the analytical distillation of gasoline,. Jour. Ind, and Eng. Chem., Vol.10, 1918, page 823.) Shortly after the article was printed a chemical supply house undertook the manufacture of an electric heater suitable for gasoline distillation. A preliminary model was examined and tested by the Bureau and modifications were suggested that were incorporated in the type of heater that was finally marketed.Description of the Bureau of Mines-heater: The electric heater developed by the Bureau has an inverted conical resistance Plament surrounded by a layer of heat-insulating material and mounted in a metal case having a top of hard asbestos (Transite) board. The resistance element is a helix of nickel-chromium alloy wire held by a molded core of alundum. The Bureau heaters are generally of about 330 watts capacity and are used with stock types of regulating rheostats capable of reducing the effective wattage to about 43 the full-load maximum."

Jun 1, 1920

By Donald W. Mitchell, John Nagy, Edwin M. Murphy

Information is presented on remote sealing of a mine passageway through a borehole by five methods : PPnneeuummaattiicc injection of mineral wool and sand, ureaformaldehyde foam , balloons , urethane foam, and caving by blasting . An adaptation of the method using pneumatically conveyed mineral wool was tried in an operating mine . Further research is needed to simplify and to improve the techniques involved , as well as to explore the possibilities of other methods and combinations .

Jan 1, 1964

To permit better cap lamp positioning for users of dust helmets. Approach The present design of the dust helmet prevents use of the miner's cap lamp when the front shield is raised, When the shield is raised I the cap lamp is directed at the mine roof or back, making the lamp useless in the event the miner needs to wear his self-rescuer. A flip bracket was designed by the Bureau of Mines to correct this situation. How It Works The safety hat is modified by the addition of lamp clips, a bracket and a hinge on the cap lamp and face shield. Two clips hold the lamp cord firmly to the helmet. When the safety hat shield is raised, compressive force from the lamp cord causes the cap lamp hinge to swing open about 90%, allowing the lamp

Jan 1, 1984

"The Generic Mineral Technology Center on Respirable Dust was established in August 1983, at the request of the Bureau of Mines, to conduct research that affords ""...each miner the opportunity to work underground during the period of (his/her) adult working life without incurring any disability from pneumoconiosis or any other occupational disease"". The Center consists of the Mining and Mineral Resources Research Institutes (MRI) of The Pennsylvania State University (PSU) and West Virginia University (WVU) in association with the MRIs of the Massachusetts Institute of Technology (MIT) and the University of Minnesota (UMN). (FIGURE 34) Michigan Technological University (MTU) is also affiliated with the Center in the area of diesel particulates.The Center brings together experts concerned with particles causing potentially disabling or fatal diseases including pneumoconiosis (""black-lung""), silicosis, and asbestosis. The latter is of deep concern not just to workers in the mineral sector of the economy but also to the general populace. The primary goal of the Center is to reduce the incidence and severity of respirable dust disease through advancing fundamental understanding of all aspects of respirable dust associated with mining and milling, and the interaction of dust and lungs. The research program of the Generic Mineral Technology Center explores these scientific, engineering or medical concerns with the objective of refining existing strategies and developing new respirable dust control techniquesand technology that are consistent with the fundamental dust-lung interaction processes that lead to mine worker disability. The work concentrates on five areas (FIGURE 35):"

Nov 1, 1988

By F. C. Turin, K. M. Cornelius

1. INTRODUCTION Underground mining in the USA has undergone significant change in the past 20 years. Two key elements have been increased mechanization and a more educated work force in spite of these changes, many jobs continue to be labor-intensive and repetitive in nature. They entail tasks that, performed over time, can take a toll on the soft tissues and joints. The problem may be compounded by an aging mining workforce. In 1996 the mean age of the coal mining work force was 45 years and the median total years of experience was 20 (NMA 1998). As a person ages, the body resilience to chronic wear and. tear is reduced, which may cause a worker to pay an increasingly higher health price for performing the same task. Mining companies, like many others, are becoming more aware of cumulative effects to the worker as reports of these types of injuries rise. . Conducting a job analysis is an important step when considering a job redesign or modification to reduce worker cumulative trauma exposure. A basic approach to job analysis is to examine the types of aches and pains reported, the tasks performed, and work site conditions. The US Bureau of Mines (USBM) conducted an evaluation of roof-bolting tasks performed at an underground coal mine concerned about early warning signs of cumulative trauma. This evaluation will comprise the primary focus of this chapter. The approach used for the roof-bolting race study may be applicable to other work environments. 2. FUNDAMENTALS OF CUMULATIVE TRAUMA EXPOSURE Musculoskeletal injury is a term used to describe a wide range of soft tissue disorders that affect the nerves, tendons and muscles. Common examples include lower back pain, tendinitis and carpal tunnel syndrome. The majority of these injuries are not the result of sudden mishaps, but usually develop gradually from repeated wear and tear. Symptoms may not appear immediately, but can take weeks, months or even years. Symptoms may result from many types of activities, performed at work or at home, and it is often difficult to attribute there to a single event. In fact, it is more common to identify factors that may have contributed to the development of the condition. The terms repetitive strain injuries or cumulative trauma disorders (CTD) have been commonly used to refer to disorders that have occurred due to work-related activities. Three main risk factors contribute to CTD: force, repetition and awkward postures. Any one or combination of these may contribute to the development of CTD. Therefore, the design of equipment in conjunction with the required tasks should be evaluated when attempting to reduce these risk factors. Examining the layout of the work area to help identify tasks which may contribute to cumulative trauma is necessary. The following list (Putz-Anderson 1988), describes ergonomics concerns that, overall, should be minimized at the work area: • Crowding or cramping the worker: a work area layout may unnecessarily constrain movements of the worker. • Twisting or turning: placement of tools and materials may require the worker to twist the spine to fulfill the requirements of the job. • Repeated reaching motions: the layout of the work area may require the worker to lean to reach and grasp the necessary tools and controls. • Misalignment of body parts: the arrangement of the work area may require the worker to frequently have one shoulder higher than the other or have the neck or spine bent to one side. While many of these concerns are a function of equipment design and environmental conditions, making workers aware of these issues may help them to adapt their work habits to reduce risk of injury. Additionally, this information is useful when conducting an ergonomic evaluation of a work area and associated tasks. 3. UNDERGROUND MINING ENVIRONMENT The underground mining environment is a unique challenge. It is more difficult to develop controls for an underground mine site as compared with a factory setting where equipment and facilities can be more easily designed to reduce worker force, posture and repetitive exposures. In an underground mine, workers are required to perform labor-intensive tasks that often cannot be avoided due to environment constraints. The dynamic nature of the environment does not allow easy implementation of mechanical assists to reduce force exposure. Many of the tasks performed by workers are repetitive. Restrictive work areas due to low ceiling height, low lighting levels and large pieces of equipment cause workers to perform these tasks in postures that are not desirable. Designers of underground mining equipment can control how a machine will function, but not the environment in which it will be used, Hazards in an underground mine cannot be completely removed by redesigning the system. There are many hazards and information sources that must be continually monitored by workers including their position in relation to large pieces of mobile equipment and unpredictable geological anomalies. Thus, immediate dangers may take priority over awareness of ergonomic considerations while performing a job. 4. CASE STUDY OF UNDERGROUND ROOF BOLTING 4.1. Roof Bolting and Cumulative Trauma Exposure In an underground coalmine, after an area is mined it is necessary to support the roof to keep it from collapsing. Since 1950, the primary method for supporting the mine roof has been installation of roof bolts. Long bolts installed into the roof compress the layers of strata achieving a uniformly distributed support anchorage. Roof bolts, typically 6-8 feet long, are installed by workers using large roof-bolting machines. There are different types of machines