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The original work statement of this contract was entitles: 'A Accident Analysis Model for Use in Underground Coal Mines.' The contract was scheduled for a duration of 26 months and was to be in three phases: Phase I - Model Development, Phase II - Application of the Model, and Phase III - Installation, Monitoring and Evaluation of the Model. Alter three months in Phase I, it became apparent that much of the needed data for the model was nut available and could not be made available within the original study schedule. Proceeding as plumed would have resulted in a model of limited utility. Personnel from Theodore Barry and Associates and the Bureau discussed the problem in detail and mutually decided to utilize the majority of remaining funds to assist the Bureau in solving these data problems and develop a stronger ongoing capability for safety analysis within the Bureau. Both tie contractor and the bureau officials involved believed that this decision greatly enhanced the Bureau's ability to develop future accident prediction models, whose rigor would greatly exceed what was currently possible.

Jan 1, 1972

By Richard Mainiero

In any construction project involving explosives, care must be taken to protect workers from carbon monoxide (CO) generated by blasting operations. CO is an odorless, colorless gas that can cause illness and death by asphyxiation. In general, the first symptoms include headache, fatigue and lightheadedness. At higher exposures to CO, skin flushing, rapid heart rate, and lowered blood pressure occur. At ever, higher exposure levels, decreased attention span is followed by nausea, vomiting, unpaired coordination, fainting, coma, convulsions and, finally, death. The detonation of explosives in blasting operations generates a range of toxic fumes, but CO is the most insidious because it is colorless, odor less, and is long lasting, since it is not readily removed try reaction with ground water, soil or rock. Additionally CO is generated in relatively large quantities compared to other toxic: fumes. CO may continue to seep out of blasted material long after the odor commonly associated with detonated explosives has dissipated. It is never safe to assume as confined space in the vicinity of a blast is clear of toxic fumes. CO may be present even if the area looks Clear and many hours have passed since the last blast.

Jan 1, 2000

By O. C. Blade

This report on the properties of motor fuels sold through service stations in the United States was made in accordance with a cooperative agreement between the American Petroleum Institute and the Bureau of Mines of the United States Department of the Interior. This paper is a continuation of a series made in cooperation with the Coordinating Fuel Research (CPR) Committee of the Coordinating Research Council (CRC), Inc. The first of this series of reports presented data on motor gasolines sold during the winter of 1935-36, and succeeding reports described motor gasolines sold during the summers and winters to and including the summer of 1941. No reports were made on motor gasolines sold during the winter of 1941-42 and during the summer of 1942. However, starting with the winter of 1942-43, the semiannual reports were resumed.

Jan 1, 1949

MFIRE is a computer simulation program that performs normal ventilation network planning calculations, and dynamic transient state simulation of ventilation networks under a variety of conditions. The program is useful for the analysis of ventilation networks under thermal and mechanical influence. MFIRE simulates a mine's ventilation system and its response to altered ventilation parameters, external influences such as temperatures, and internal influences such as fires. Extensive output enables detailed quantitative analysis of the effects of the proposed alteration to the ventilation system Network simulation using digital computers has become widespread throughout the mining industry in recent years. However, as the sophistication of the simulator increases (MFIRE, for example), the complexity of input data requirements and interpretations of results requires more skill and knowledge from the users. Perhaps the most difficult part of using MFIRE is to construct the data set describing the mine's physical layout and its ventilation properties. The initial attempts to get the data set running often reveal unknown or ignored aspects of the mine's ventilation. MFIRE was written in Fortran 77 and compiled with Microway1 Fortran for the Intel 80386 based computers with a 80387 math co-processor. The source code is portable and available for users who wish to modify the source code to operate on other computers. This user manual describes the development of MFIRE, the input format and requirements, the output, common errors, fire parameters, and examples MFIRE application. Valuable reference material is included in the appendices. Knowledgeable users may skip directly to the PROGRAM INSTALLATION AND OPERATION section to begin using MFIRE immediately.

Jan 1, 1995

By C. M. Harrer

The location, features, qualities, and extent of iron occurrences and the associated resources--limestone and dolomite, bentonite, coal-lignite, petroleum and natural gas, power, and water--are evaluated. The results of pioneer beneficiation tests on South Dakota taconite are discussed. In addition, pertinent features of taconite development, cost factors, the Western and Central United States trade area and markets are reported. The State's production of iron ores until 1963 has been small and for purposes other than the manufacture of iron. This investigation disclosed the probability of large resources of taconite in Pennington and Lawrence Counties. The average iron content is 29 percent, and a 65-percent or better iron concentrate might be produced. Ample resources are available for mining and processing taconite. An investment of at least $26 million would be required for a plant capable of turning out 1 million tons of agglomerated iron concentrate per year. The feasibility of such an enterprise is indicated, but intensive investigation and research must be completed to justify such an investment,

Jan 1, 1966

By John C. Machisak

THIS CHAPTER of the Minerals Yearbook (volume III) contains overall injury experience and employment data at bituminous-coal, lignite, and anthracite mines, coking plants, metal and nonmetal mines, metallurgical plants, and stone quarries in the United States for the calendar year 1956. Volume I of the Yearbook includes injury experiences and related employment data in the metal, nonmetal, and quarrying industries, and in the milling operations connected with the mining of those commodities. Volume II contains the injury and related employment experience of the coal mining, coking, and oil and gas industries. Reporting is voluntary on the surveys conducted by the Bureau of Mines to collect injury and employment data in the mineral industries, except in the coal-mining industry, where operators are required by Federal law to furnish the information requested.

Jan 1, 1958

By C. M. Harrer

The location, features, qualities, and extent of iron occurrences and the associated resources--limestone and dolomite, bentonite, coal-lignite, petroleum and natural gas, power, and water--are evaluated. The results of pioneer beneficiation tests on South Dakota taconite are discussed. In addition, pertinent features of taconite development, cost factors, the Western and Central United States trade area and markets are reported. The State's production of iron ores until 1963 has been small and for purposes other than the manufacture of iron. This investigation disclosed the probability of large resources of taconite in Pennington and Lawrence Counties. The average iron content is 29 percent, and a 65-percent or better iron concentrate might be produced. Ample resources are available for mining and processing taconite. An investment of at least $26 million would be required for a plant capable of turning out 1 million tons of agglomerated iron concentrate per year. The feasibility of such an enterprise is indicated, but intensive investigation and research must be completed to justify such an investment.

Jan 1, 1966

A new personal respirable dust monitor developed by Rupprecht & Patashnick Co., Inc. in a multi-year project funded by the National Institute for Occupational Safety and Health (NIOSH) generated promising results in underground coal mine testing performed by NIOSH and industry representatives during the summer of 2003. The mine data showed that the personal dust monitor (PDM) performed similarly to co-located manual reference samplers for full-shift samples at all four underground coal mines at which the evaluation took place. The technology that forms the heart of the PDM, called the tapered element oscillating microbalance (TEOM system), is unique in its ability to collect suspended particles on a filter while simultaneously determining the accumulated mass with National Institute of Standards and Technology traceability. Because the monitor measures the true particle mass collected on its filter, its results do not exhibit the same sensitivity to water spray as do optically based measurement approaches. The technique achieves microgram-level mass resolution even in the hostile mine environment, and reports dust loading data on a continuous basis. Using the device, miners and mine operators have the ability to view both the cumulative and projected end-of-shift mass concentration values, as well as a short-term 15- or 30-minute running average. During underground mine trials in the summer of 2003, technical personnel used the readings from the PDM to identify and correct several abnormal dust generating scenarios. These events demonstrated the potential of the PDM to be used as an engineering tool to evaluate the effectiveness of various dust control strategies. In a separate evaluation performed by CONSOL Energy, Inc., the mine operator evaluated the benefit of a proposed new water spray-based dust control system. Engineers measured the dust concentration upstream and downstream of a production location under different dust control scenarios using two PDM units. By evaluating the change in the dust loading between the upstream and downstream monitoring sites, the company was able to determine in a few hours which hardware configuration would yield the greatest benefit to the workplace environment. BACKGROUND Measuring underground coal mine dust concentrations is an essential part of protecting miners' health. The U.S. Secretary of Labor and the Federal Advisory Committee on the Elimination of Pneumoconiosis among Coal Mine Workers has recommended that better monitoring of coal miner dust exposures be used as a method to improve miner health. In consultation with labor, industry, and government, NIOSH issued a contract to Rupprecht & Patashnick Co., Inc. (R&P), Albany, N.Y., to develop a one-piece PDM. The object was to miniaturize TEOM technology into a form suitable for a person-wearable monitor that would enable accurate end-of-shift dust exposure information to be available to miners. Furthermore, any person-wearable dust monitor should minimize the burden to the wearer by incorporating the monitor into the mine worker's cap lamp battery, with exposure data continually displayed during the shift to enable workers and management to react to changes in dust exposure. In the summer of 2003, NIOSH conducted extensive testing of the PDM to determine its laboratory and in mine performance. In addition, anecdotal information collected in the mines showed several occasions where miners were able to identify situations that produced high levels of respirable coal mine dust The PDM's response to unplanned changes resulted in action being taken to keep dust exposures as low as possible. In another case that demonstrated the PDM's versatility, a mine was seeking to find a better dust control solution on its longwall headgate stageloader. In this instance, the PDM was used as a diagnostic tool by the miners to quickly evaluate the control technology. [ ] HOW DOES THE PDM WORK? The PDM is configured to provide accurate respirable dust personal exposure information in a form that is as convenient to wear as a normal cap lamp (See Figure 1). Respirable dust exposure data displayed by the device has two main objectives: providing the miner and mine operator with timely values to avoid overexposure to dust, allowing them to make any necessary changes during the course of a work shift; and computing an accurate end-of-shift statistic for a miner's average respirable dust exposure. The mass sensor embedded in the PDM, holds the key to the accurate, time-resolved dust concentration measurements. The inertial, gravimetric-equivalent, mass measurement technique used in the device typically provides a limit of detection on par with that of the most sensitive laboratory-based microbalances.

By D. R. Babich, E. R. Bauer

National Institute for Occupational Safety and Health (NIOSH) researchers are conducting a cross-sectional survey of equipment noise and worker noise exposures in the mining industry. Surface and underground limestone is one commodity recently surveyed. The sound levels of mining and processing equipment were recorded to identify noise sources. Full-shift worker noise exposures were completed to determine the exposure of various occupations. This paper presents the results of the noise research conducted in both underground and surface limestone mines, detailing the equipment likely to cause worker overexposures, and the occupations experiencing overexposures. Implications for worker noise exposure reduction are also reported.

By Gerrit V. R. Goodman

A laboratory study assessed the impacts of water spray pressure, face ventilation quantity, and line brattice setback distance on respirable dust and SF6 tracer gas concentrations around a continuous mining machine using a sprayfan or directional spray system. Dust levels were measured at locations representing the mining machine operator and the standard and off-standard shuttle car operators, and in the return airway. The results showed that changes in all three independent variables significantly affected log-transformed dust levels at the three operator sampling locations. Changes in setback distance impacted return airway dust levels. Laboratory testing also identified numerous variable interactions affecting dust levels. Tracer gas levels were measured on the left and right sides of the cutting drum and in the return. Untransformed gas levels around the cutting drum were significantly affected by changes in water pressure, face ventilation quantity, and setback distance. Only a few interactions were identified that significantly affected these concentrations. Gas levels in the return airway were grouped by face ventilation quantity. Return gas levels measured at the low curtain quantity were generally unaffected by changes in water pressure or curtain setback distance. At the high curtain quantity, return airway gas levels were affected by curtain setback distance. A field study was conducted to assess the impact of these parameters in an actual mining operation. These data showed that respirable dust levels may have been impacted by a change in water pressure and, to a lesser extent, by an increase in curtain setback distance. A series of tracer gas pulse tests were also conducted during this study. The results showed that effectiveness of the face ventilation was impacted by changes in curtain flow quantity and setback distance. Laboratory testing supported similar conclusions.

Jan 1, 2004

By G. M. Kintz

"Methods and costs of rock-dusting bituminous coal mines have been discussed in various publications by the United States Bureau of Mines and others.3 This paper discusses the present methods and cost of dusting at the Swastika mine of the St. Louis, Rocky Mountain and Pacific Co., Raton, N. M.In the Swastika mine the recommendations of the United States Bureau of Mines with regard to rock-dusting are followed at least as well as in any mine in the States of Wyoming, Colorado, and New Mexico. This mine is located at Swastika, N. M., approximately 4 miles west of the town of Raton and is in the Raton coal seam. The mine is rated as gassy and produces approximately 1,000 tons of coal per day.A mining system known as the ""room-and-pillar with cut-offs"" is used which results in recovery of nearly 100 per cent of the coal. The mine employs approximately 250 men.Ventilation is maintained by a Sirocco fan so arranged that the air current may be reversed and exhausting approximately 130,000 cubic feet of air per minute at 3 inches water gauge. This fan is supplemented by two auxiliary fans for emergency use. Three main entries penetrate the hill in a straight line for approximately 8,000 feet. The haulage is through the center entry, which is also used as the intake in conjunction with a two-compartment concrete-lined shaft located at the end of the entries. The main return for 3,000 feet inby the fan is 12 feet wide and 7 feet high. For this distance the ribs have been reinforced by a wall made of coke-breeze blocks plastered over with cement. Solid concrete blocks are used for the top row of blocks of the wall. Steel 10-inch I-beams spaced 40 inches apart center to center are supported on these solid blocks and thus support the roof. The next 1,000 feet inby has the same area, but the cement blocks extend to the roof, as no crosspieces are needed. The airways are kept clean and well rock-dusted.A rather unique system is used to handle gas feeders along the intake and haulage entries. There these feeders occur in the roof or where gas is apt to collect in high points along the haulage, tin funnels as large as 3 feet in diameter are placed near the roof. From these a 2-inch or other suitable-sized pipe is run into the return through the wall of the nearest break-through. A valve on this pipe line controls the amount of air pulled. These devices keep the high places clear of any gas, even when strong feeders are encountered.Fifteen-ton electric trolley locomotives are used on the main haulage and approximately 30 roller-bearing oars, each having a capacity of approximately 3,000 pounds of coal, compose a trip. All loaded tripe carry steel drags on the last car, and automatic derails are located at advantageous points throughout the mine.All loaded trips are thoroughly sprinkled on the sectional partings and at the main parting. The track is sprinkled every idle day, or if needed, every day; from a large tank mounted on a truck hauled by a motor. Neither nozzle nor spray is used, as these were unsatisfactory. The water leaves the tank. through a 11/2-inch valve and is permitted to flow on the road through a horizontal 11/2-inch T. Water is obtained from filling stations located throughout the mine. It is stated by the officials that the use of this method of sprinkling permits the entire haulage roadbed to be wetted down in two hours."

Mar 1, 1930

By Lulie H. Crump

Salient historical data on consumption of fuels and energy have been summarized by State and census district for the years 1960 through 1972. This Information Circular covers States west of the Mississippi, and Information Circular 8704 covers States east of the Mississippi. These data replace previously published compilations of energy consumption statistics by States and districts. Future annual studies are planned using the same Btu conversion factors applied in these two Information Circulars.

Jan 1, 1976

By Victor E. Kral

"SUMMARYFollowing a magnetometer survey on the McCoy iron deposit, a trenching and drilling program was carried out by the Bureau of Mines in August 1944.This deposit is 32.3 miles southwest of Battle Mountain in the McCoy Mining District, Lander County, Nevada, and lies on the east flank of the Fish Creek Mountains at an altitude of 5,400 feet, about 1 1/2 miles south of the gold camp of McCoy.Total production from the deposit has been 400 tons of magnetite, mined by hand and shipped to the west coast for ship's ballast.Bureau drilled two holes to a total depth of 92 feet and excavated 12 feet of trenches. Both holes were drilled in the same ore body and engineered magnetite ore 14 and 11 feet thick. Trenching was used successfully to show the lateral limits of the ore.Magnetite ore bodies were found to occur as replacements of a limestone bed in quartzite. They outcrop near and parallel to the exposure of a diorite entrusting that forms a long westward-trending ridge. Although magnetic outcrops can be traced for 5,000 feet trenching definitely proved the ore bodies to be disconnected to have little or no lateral extent beyond their outcrops. Only two ore bodies more than 10 feet thick were found; one of these is the inaccessible to and the other was drilled by the Bureau."

Jan 1, 1947

By Thomas O. Glover

The mining industry of Cameroon continued to be dominated by crude petroleum. Crude petroleum production has become the most important facet of Cameroon's economic development. Oil production was estimated to be 6.3 million tons in 1983 compared with 5.2 million tons in 1982 and 4.3 million tons in 1981. Over two-thirds of its export income was attributed to crude oil. The country's only refinery, dedicated in 1981, has a production capacity of 2 million tons. Cameroon has become self- sufficient in petroleum products since commissioning the refinery. The oil sector contributed approximately 13.5% to Cameroon's gross domestic product in 1982-83. Oil production was expected to rise from 125,000 barrels per day in 1983 to 156,000 barrels per day in 1985 when output peaks. Cameroon's ultimate recoverable reserves have been calculated at 100 million tons, or 750 million barrels of oil.

Jan 1, 1985

By Keith A. Heasley, John L. Ellenberger, Paul W. Jeran

In this paper, a state-of-the-art, three-dimensional, full waveform, microseismic system was used to analyze the rock failure around a deep (> 750 m (2500 ft) of cover) bump-prone longwall panel. The microseismic system consisted of both underground and surface geophones coupled through radio telemetry and a fiber-optic network to produce pseudo real-time detection and location of seismic events surrounding the coal seam. This was the first microseismic installation of this scope at a U.S. coal mine, and the system was intended to help determine the exact strata mechanics associated with the redistribution of stress and the associated gob formation at one of the U.S.’s deepest longwall mines. Overall, 5,000 calibrated seismic events were recorded during the mining of one panel, including a Richter magnitude 4.2 event which occurred inside of the array. Analysis of these events provides a number of notable insights into the rock mass behavior. For instance, the longwall panel was widened during the retreat process, and the mining-induced seismicity shows a distinctly different behavior between the start of the panel, the mining of the narrow part of the panel and the mining of the wider part of the panel. Also, in itself, the acquisition of the ML 4.2 event was a major milestone in geomechanical and bump research. This is the first time that such an event has been recorded with this detail and accuracy at a bump-prone coal mine in the U.S. The analysis of this single event has set distinct new limits on the relationship between mining seismicity and coal bumps.

By Thomas M. Barczak

Secondary roof support systems play a vital role in preserving the safety of underground mine workers by preventing the unintentional collapse of the mine roof. Hundreds of thousands of standing roof supports are constructed each year in underground coal mines. Historically, wood and concrete cribs and timber posts have been used for secondary roof support. These support constructions require the handling of heavy and bulky materials, causing numerous injuries to the mine workers and resulting in more than 40,000 lost workdays in the past 9 years. Since 1993, various alternative support technologies have been developed. These new support technologies not only provide superior roof support, but many also have significant material handling advantages by using smaller and lighter weight materials, fewer components, mechanically installed support systems, and pumpable support systems. The National Institute for Occupational Safety and Health (NIOSH) has conducted extensive material handling research and has developed recommended lifting thresholds to reduce material handling injuries. An analysis of roof support construction reveals that conventional support materials used in wood and concrete cribbing exceed the recommended lifting thresholds, while the engineered support systems are closer to the recommended weight thresholds. Finally, recommendations are made relative to proper lifting techniques and material handling practices to prevent injury to mine workers when constructing roof supports in underground coal mines.

Jan 10, 2000

By Sean Gallagher, William S. Marras, Alan S. Litsky, Velimir Matkovic, Deborah Burr, John Landoll

Study Design. Survival analysis techniques were used to compare the fatigue failure responses of elderly motion segments to a middle-aged sample. Objectives. To compare fatigue life of a middle-aged sample of lumbosacral motion segments to a previously tested elderly cohort. An additional objective was to evaluate the influence of bone mineral content on cycles to failure. Summary of Background Data. A previous investiga¬tion evaluated fatigue failure responses of 36 elderly lumbosacral motion segments (average age, 81 ± 8 years) subjected to spinal loads estimated when lifting a 9-kg load in 3 torso flexion angles (0°, 22.5°, and 45°). Results demonstrated rapid fatigue failure with increased torso flexion; however, a key limitation of this study was the old age of the specimens. Methods. Each lumbosacral spine was dissected into 3 motion segments (L1-L2, L3-L4, and L5-S1). Motion segments within each spine were randomly assigned to a spinal loading condition corresponding to lifting 9 kg in 3 torso flexion angles (0°, 22.5°, or 45°). Motion segments were statically loaded and allowed to creep for 15 minutes, then cyclically loaded at 0.33 Hz. Fatigue life was taken as the number of cycles to failure (10 mm displacement after creep loading). Results. Compared with the older sample of spines, the middle-aged sample exhibited increased fatigue life (cycles to failure) in all the torso flexion conditions. Increased fatigue life of the middle-aged specimens was associated with the increased bone mineral content (BMC) in younger motion segments (mean ± SD, 30.7 11.1 g per motion segment vs. 27.8 ± 9.4 g). Increasing bone mineral content had a protective influence with each additional gram increasing survival times by approximately 12%. Conclusion. Younger motion segments survive considerably longer when exposed to similar spine loading conditions that simulate repetitive lifting in neutral and flexed torso postures, primarily associated with the increased bone mineral content possessed by younger motion segments. Cycles to failure of young specimens at 22.5° flexion were similar to that of older specimens at 0° flexion, and survivorship of young specimens at 45° flexion was similar to the older cohort at 22.5°. Key words: biomechanics, low back disorders, fatigue failure, age, motion segments, vertebral endplate fractures, torso flexion, lifting, bone mass. Low back disorders (LBDs) are a major cause of both short- and long-term occupational disability in the United States, and it is clear that workers in certain occupations are more susceptible to LBD.2-5 Specifically, epidemiologic studies have shown that jobs involving heavy physical demands such as construction,2,3 mining,2,4 and farming,5 engender increased risk of back pain. These occupations are thought to experience high LBD rates as a result of their extreme postural and manual lifting demands. Studies have shown that jobs involving significant lifting 6-9 and jobs that involve frequent bending10-12 are associated with increased LBD risk. Workers in the mining industry, in particular, often have to lift heavy materials in restricted workspaces that compel torso flexion. An understanding of the impact of repeated loading of the spine in flexion on fatigue failure of spinal tissues is thus a critical issue for our research agency, which is concerned with reducing the pain and disability associated with LBD in the mining industry. It is well accepted that loads experienced by the spine during manual lifting tasks are sufficient to cause fractures in the endplates of lumbar vertebrae, particularly on repeated loading. 13-15 Endplate fractures may not be painful in and of themselves 16; however, evidence suggests that the process of internal disc disruption and disc degeneration may be initiated via endplate fractures. 16,17 It has been shown that endplate damage will alter the distribution of stress in the disc, resulting in buckling of the lamellas of the internal anulus.17 Once this process has been initiated, repeated spine loading will cause additional disruption of the anular fibers, resulting in formation of significant fissures or tears. 11-21 If these tears occur near or extend close to the outer portions of the anulus, a wound healing process is initiated, which involves infiltration of mast cells, macrophages, and re¬lease of cytokines and growth factors. 21 The presence of these infiltrates has been strongly linked to discogenic low back pain. 21,22 Indeed, for patients experiencing chronic low back pain, the prevalence of internal disc disruption is at least 39%,19 which represents the most

By P. G. Clites

This bulletin summarizes the results of Bureau of Mines research on the development of the inductoslag melting process. Inductoslag melting is an induction melting technique using a segmented, water-cooled, copper crucible. The process was developed as part of the Bureau's work on effective utilization of reactive metal scrap, and the process has been applied to melting Ti, Zr, Cr, Co, Fe, Ni, and V. Construction details are given for the segmented crucibles and for both an ingot furnace and a casting furnace. The melting process is described, and results of tests conducted with a variety of reactive metals are given.

Jan 1, 1982

By Thomas M. Barczak, Dennis R. Dolinar, Gabriel S. Esterhuizen

Longwall mines typically use some form of standing support for secondary roof support in longwall tailgate entries. Although there have been several new support products developed for this application, there remains no universal design criteria to optimize the application of these support technologies. The requirement for optimization and proper support selection is to understand the degree of control that the support has on the ground behavior. The ground reaction curve and numerical modeling was used to evaluate the impact of standing support on ground behavior. LaModel was used to evaluate the impact of standing support on main roof and floor behavior and pillar yielding. 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. However, it is imperative that this “uncontrollable convergence” be considered in the support design to prevent premature failure of the support. A FLAC model was used to evaluate the near-seam roof and floor behavior in conjunction with the global vertical and horizontal stresses. The model suggests that standing roof supports can have some impact on the ground behavior as the elastic response of the rock is exceeded and rock structure deteriorates from the stress concentrations that develop around the tailgate opening. During this phase, the capacity and stiffness of the standing support can be critical to the stability of the opening, as eventually the rock mass will be transformed into a partially detached structure whose weight must be supported by the standing support. This work is part of a ground control program of research at the National Institute for Occupational Safety and Health (NIOSH) aimed at improving mine safety by reducing roof fall injuries and fatalities.

To provide operators of large-opening mines with a ventilation planning tool that will help them develop a healthier, safer, and more efficient ventilation system in the underground workplace.

Jan 3, 2006