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By Launa G. Mallett, Robert H. Peters, Barbara Fotta

Due to variations in the thickness of U.S. coal seams, there is great variability in the height of the roof where underground miners work. Restrictions imposed by low seam heights have important safety consequences. As the height of their workplace decreases, miners must stoop, duck walk, or crawl, and their vision, posture, and mobility become increasingly restricted. Low seam height also places important restrictions on the design of mobile equipment and other mining machinery. Using the employment and injury data reported to the Mine Safety and Health Administration (MSHA) from 1990 to 19% small underground bituminous coal mines with less than 50 employees were stratified by average coal seam height according to the following categories: low (? 42"), medium (43"60N), and high (? 61"). Injury rates for both nonfatal days lost and fatality cases were examined by seam height and leading type of injury incidents. The leading types of Incidents associated with fatalities were roof falls and powered haulage equipment. In comparison to high-seam mines, miners working in low or medium seams are at higher risk of being killed by powered haulage equipment, roof bolting machines, and falls of unsupported roof. The leading types of incidents associated with nonfatal injuries were handling materials and powered haulage. As mining height decreases, miners are at increasingly higher risk of having a nonfatal injury from incidents involving roof bolting machines, load-haul-dump equipment, personnel carriers, and powered haulage conveyors. As mining height increases, miners are at increasingly higher risk of having a nonfatal injury from slips and falls and incidents involving shuttle cars and roof and rib falls. Knee injuries are a particularly severe problem in low- seam mines. The rate of injuries to miners while crawling or kneeling is 10 times higher in low seams than in high seams

By F. W. Wood

Ingots of zirconium and other highly reactive metals such as titanium and hafnium produced by the consumable-electrode arc-melting process require conditioning before forging or rolling. A nondestructive, arc-conditioning technique has been developed as a substitute for lathe conditioning. The technique employs en electric arc under an inert atmosphere to fuse surface metal on the sidewalls of ingots without seriously affecting the general quality of the ingots. Advantages of the practice are Increased yields, lower accumulation of inferior scrap, and actual cost savings. The work cited in this report was done on zirconium. INTRODUCTION The consumable-electrode arc-melting process as practiced at the Bureau of Mines3 4/ has proved to be a technique for producing sound, homogeneous, commercial-size ingots of zirconium and its alloys. Ingots produced by this process, however, have as a characteristic a layer of partly fused metal on the sidewall to a depth of 3/16 to 3/8 inch. To prevent extension of surface imperfections during forging, the ingots are ordinarily conditioned by removing defective material in a lathe. If the metal were less reactive or the requirements less severe, the machine chips could be recycled and remelted. However, zirconium, being so oxygen sensitive, is contaminated by merely being machined despite extensive cooling of the tool bit. Further, being contaminated with oxygen, the chip metal upon remelting is 10 to 25 Brinell-hardnese numbers harder than the ingot from which it was machined. For this reason, the ingot specifications for naval reactor use have prohibited remelting machine chips, except as required for starting pads. Again, were zirconium less costly or less in demand this ever-increasing pile could be burned to oxide and recycled through the Kroll sponge process. Economics do not favor this, as melting feed stock has an estimated increase In value over oxide of about $8.80 per pound of contained zirconium. The efforts of the Bureau to solve the problem have been directed along two lines: To reduce the contamination of the machine chips produced and to reduce the quantity of the chips produced. This paper presents the technique developed to reduce the quantity of chips produced by arc-conditioning the remelted ingot.

Jan 1, 1955

By Maria I. De Rosa

Table 1 and figure 1 show the number of fires and fire injuries that occurred in underground metal/nonmetal and stone mines by state during 1990-2001. Table 1 also shows the injury risk rates, employees' working hours, and lost workdays. Overall, 65 fires occurred in 20 states; these include 2 fires and no injuries for contractors. Six of the fires caused nine injuries. The yearly average was 5.4 fires and 0.75 injury. Forty-one fires with 2 injuries occurred in metal mines, 14 fires with 7 injuries occurred in nonmetal mines, and 10 fires with no injuries occurred in stone mines. The underground mine fires required 25 mine rescue team interventions and 30 mine/section evacuations. The Ewhr value was 260 x 10° hr (Irr = 0.007), and the LWD value was 83. Idaho had the most fires (eight fires and no injuries), followed by Louisiana (seven fires and two injuries), Michigan (six fires and six injuries), and Missouri (six fires and no injuries). Of these states, Michigan had the highest injury risk rate value (Irr = 0.146). Table 2, partly illustrated in figure 2, shows the number of fires, fire injuries, risk rates, employees' working hours, and lost workdays by time period. The number of fires during the six time periods show an increase during the fourth period followed by a sharp decrease during the fifth period and a sharp increase in the last period. The number of fire injuries show an increase followed by a decrease during most of the periods, accompanied by a decline in employees' working hours during most of the periods; an increase is seen during the third and fourth periods. The In values follow patterns similar to those shown by the injury values. Tables 3-8 show the number of fires by ignition source, method of detection and suppression, equipment involved, location, and burning material by time period. Figure 3 shows the major variables related to fires for 1990-2001. Table 9 shows the number of fire injuries per number of fires causing injuries and total fires by year, ignition source, equipment involved, and location.

Jan 1, 2004

Develop an environmentally feasible method of mining shallow oil sands without removing overburden. Approach Oil sands are extracted through a single borehole by cutting into the sands around the borehole with a high pressure water jet, and pumping the resulting slurry to the surface. Although oil can be extracted from shallow fields by open-pit mining methods, this type of mining may create significant environmental impacts, including; (1) disruption of the surface, (2) accumulation of waste rock piles, (3) accumulation of tailings, (4) damage to the ground water quality, and (5) surface water pollution. The borehole mining system developed and successfully field tested by the Bureau of Mines offers a method for extracting oil from oil sand with minimal disturbance to environmental quality. (For examples of other applications of borehole mining, see Technology News Nos. 95, 63 56, and 48.) How It Works Prior to the start of mining operations, baseline conditions for ground subsidence and ground water quality are established at the test site so that the degree of subsidence and changes in ground water quality can later be determined. Oil sands mining is conducted using the Bureau of Mines borehole mining system. The borehole mining tool consists of a 12-inch-diameter pipe string and accessories capped with a three passage swivel terminated with a mining section. The mining section has an auger at the bottom. Four slurry inlet holes and an eductor are located above the auger, and a single cutting nozzle is located near the top of the mining section. The tool generates a high velocity water jet that erodes and slurrifies ores. The slurry is drawn into the inlet of the eductor which lifts the slurry to the surface where it is deposited into a slurry discharge sump. To detect evidence of subsidence, surveys of the land surface are made at regular intervals during, and until 30 days after, the termination of the mining operations. Samples of ground water from the borehole and two adjacent monitor holes are taken on alternate days during the mining operations, and are later analyzed to determine if any ground water contamination has occurred.

Jan 1, 1981

By S. H. Denny

"As the result of the work of an efficient safety organization, the Midwest Refining Co. at its various operations and particularly in the Salt Creek field has been able to show a definite accident reduction. Lost-time accidents during the past year have been reduced to a small number as compared with previous years, and infection cases have been almost eliminated.The accident-prevention work of the Midwest Refining Co. is in charge of the department of industrial relations, with a director as the administrative head; two safety men handle the work directly at Midwest, Wyo. A competent medical staff with a well-equipped hospital at Midwest is also an important factor in the prompt and proper treatment of injured persons when an employee is injured, he is given first-aid and then taken to the hospital with minimum delay.About 1,450 persons are employed in the 4 departments (production, gas, pipe lines, and electrical) and in the 34 districts of the Midwest Refining Co. The work at Midwest spreads over a considerable area, and new drilling operations, pipe work, and similar activities require the services of many small gangs of workers. Complete supervision, of each job, whether shall or large, is possible through the large number of superintendents, foremen, and gang pushers employed; thus, there are 20 superintendents, 78 foremen, and 115 gang pushers. The largest number of men under any one toss is approximately 15, and it is probable that much of the good safety record is due to this intensive supervision. These company officials, including the gang pushers, have been impressed with the idea that it is their duty to see that the men under them do not get hurt; the responsibility of instructing new employees in safety practices is placed directly upon them. Monthly meetings of the field officials, including superintendents, foremen, and gang pushers, and as far as possible the men, of each district are held with the safety engineer. Both officials and men are encouraged to bring up for discussion any practice or proposals looking to the changing of any conditions that will"

Apr 1, 1928

By Van H. Manning

EXPLOSIVES RESEARCH. As the physical laboratories of the explosives section of the Pitts- burgh experiment station were equipped for testing the physical properties of explosives, both the Army and Navy Departments for many years had requested the Bureau of Mines to make such tests. Chemical control of the physical tests through analyses, heat tests, analyses of gaseous products of combustion, and sand tests was exer- cised through the explosives chemical laboratory. Often an investigation was cooperative between two laboratories. The explosives chemical laboratory also aided the work of the Ex- plosives Regulation both by chemical tests and investigation of acci- dents in explosives plants. COOPERATIVE WORK FOR ARMY AND NAVY DEPARTMENTS. The explosives chemical laboratory devised, at the request of the Bureau of Ordnance of the Navy, a more economical method of making hexanitrodiphenylamine. This problem was assigned to the Bureau of Mines by Dr. C. E. Munroe, chairman of the committee on explosives of the National Research Council, acting as the depart- ment of science and research of the Council of National Defense. Before the United States entered the war the following reports of investigations were submitted to the Army or the Navy: 1. Report of sensitiveness and relative efficiency of TNT and ammonium picrate, dated February 6, 1913, undertaken at the re- quest of the Chief of Ordnance. 2. Report of tests and examination of two samples of TNT and one of TNA for the Ordnance Department of the Army, dated August 5, 1915, was undertaken at the request of commanding officer, Frankford Arsenal. 3. Report of tests for sensitiveness to detonation of mercury ful- minate of 21 samples of TNT crystallized from various solvents, for the Bureau of Ordnance, Navy Department, dated June 17, 1916. 4. Report of tests of two samples of mercury fulminate for Frank- ford Arsenal, dated December 2, 1916, undertaken at the request of the commanding officer, Frankford Arsenal. After the United States entered the war the following reports of investigations were submitted: 5. Report of pendulum friction and large impact tests on two samples of "sodatol" and two samples of "amatol." The final report was dated July 20, 1918; and the preliminary report, May 15, 1918. This investigation was undertaken at the request of the Ordnance

Jan 1, 1919

By M. J. Friedel, D. E. Scott, T. J. Williams

Rock masses in deep level mines are subject to high stresses, which can result in unexpected failure of rock into mined-out openings. Historically, various independent methods have been used to discern the causes of rock bursts and to evaluate stress conditions in rock masses susceptible to violent failure. 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 the 4600 levels of the Sunshine Mine, Kellogg, ID. The team evaluated the current state of stress in the pillar and the most likely cause of the rock burst by studying the seismic history of the pillar, examining the geology, analyzing the available in situ stress data, calculating possible fault-plane solutions for the burst, and performing a seismic velocity tomographic survey. The results of the study showed that post-rock-burst seismicity was concentrated about 15 to 30 m west of and about 15 m above the rock-burst location. The pillar is composed of a very hard sericitic-to- vitreous quartzite of a type rarely found in the mine, but that is often found in other district mines having a history of seismic activity. In situ stress analysis of the pillar and the surrounding rock mass showed a probable stress rotation from northwest-southeast to east-west. Of four fault plane solutions, the most probable was either a left-lateral, strike-slip movement with a compressive principal stress oriented nearly north-south, or a right-lateral, strike-slip movement oriented east-west. Finally, tomographic images showed low-velocity areas (interpreted as areas of low stress) associated with the crosscuts and haulageways, and high-velocity areas (interpreted as areas of high stress) associated with the rock-burst location. High velocities were also found in a planar area oriented in an elongate northeast-southwest direction.

By Linda L. Chasko, Larry D. Stowinsky, Ronald S. Conti

Mine operators often rely on mine rescue teams to save lives during an underground emergency such as an underground fire, explosion or roof fall. It is extremely important that team members are provided with adequate exploration equipment and that training simulations are conducted in a realistic manner. A series of mine rescue training exercises was developed, conducted and evaluated by the National Institute for Occupational Safety and Health (NIOSH) in cooperation with the Pennsylvania Department of Environmental Protection, Bureau of Deep Mine Safety. The exercises were conducted at NIOSH’s Lake Lynn Laboratory during 1995 to 1998 and resulted in improved technology and training for mine rescue teams. For example, existing technologies were identified to help rescue teams during exploration. These included chemical light sticks to identify team members and mark crosscuts and mine materials, strobe lights for mapping out escape ways, and a helmet mounted thermal imaging system to see through smoke. A hands-free communication system showed potential for enhanced communications between team members and the fresh air base. A new high-visibility team lifeline that allows for flexibility of movement between team members was developed. A positive-pressure inflatable escape device (IED) was used to isolate the “hazardous” environment from fresh air and allow rescue team members to traverse through. An inflatable feed-tube partition that can rapidly block large openings such as underground passageways and simultaneously provide a feed-tube for high-expansion foam generators was also deployed for several simulations. During the simulations, mine rescue team members donned self-contained breathing apparatuses (SCBA) and traversed more than 305-m of mine passageways filled with nontoxic smoke. Visibility ranged from 0.3 to 0.9-m. In one area of the mine, a kerosene heater was used to simulate a fire and reduce the oxygen concentration. In another area, a 1.5 pct methane zone was established. The team members searched for "victims,” mapped the passageways, built temporary stoppings and ventilated the smoke-filled entries. The teams indicated that the simulations were challenging and very informative.

By Michael J. Pazuchanics, Thomas J. Fisher, John J. Sammarco, Jeffrey H. Welsh

This report (An Introduction to Safety) is the first in a nine-part series of recommendations addressing the functional safety of processor-controlled mining equipment. It is part of a risk-based system safety process encompassing hardware, software, humans, and the operating environment for the equipment's life cycle. Figure 1 shows a safety framework containing these recommendations. The reports in this series address the various life cycle stages of inception, design, approval and certification, commissioning, operation, maintenance, and decommissioning. These recommendations were developed as a joint project between the National Institute for Occupational Safety and Health and the Mine Safety and Health Administration. They are intended for use by mining companies, original equipment manufacturers, and aftermarket suppliers to these mining companies. Users of these reports are expected to consider the set in total during the design cycle. • 1.0 Safety Introduction.—This is an introductory report for the general mining industry. It provides basic system/software safety concepts, discusses the need for mining to address the functional safety of programmable electronics, and includes the benefits of implementing a system/software safety program. • 2.1 System Safety and 2.2 Software Safety.—These reports draw heavily from International Electrotechnical Commission (IEC) standard 61508 and other recognized standards. The scope is "surface and underground safety mining systems employing embedded, networked, and non-networked programmable electronics." System safety seeks to design safety into all phases of the entire system. Software is a subsystem; thus, software safety is a part of the system's safety. • 3.0 Safety File.—This report contains the documentation that demonstrates the level of safety built into the system and identifies limitations for the system’s use and operation. In essence, it is a "proof of safety" that the system and its operation meets the appropriate level of safety for the intended application. It starts from the beginning of the design, is maintained during the full life cycle of the system, and provides administrative support for the safety program of the full system. [ ]

Jan 4, 2001

By Barbara Fotta

According to the Bureau of Labor Statistics (BLS), workforce estimates of median age suggest that the median age of the mining workforce, which has been experiencing overall declines in numbers of employees, is rising more rapidly than for the overall U.S. civilian labor force. In the absence of detailed demographic data for the mining industry, the current study uses injury and illness data reported to the Mine Safety and Health Administration (MSHA) to examine differences, over time and by commodity, in the proportions of injured or ill workers aged 45 years and older. These data indicate that from 1988 to 1998, the percentage of injured or ill older workers (aged 45 years and older) have been steadily increasing. The most notable increase occurred at coal mining operations where the proportion of injured/ill older workers increased from 24 to 44 percent. A more detailed breakdown of the industry by commodity for 1998 showed the highest proportions of older injured/ill workers (over 40%) occurring in coal, iron ore, alumina mills, cement, and trona operations. In coal operations, as the employment size of the mine operation increased, so did its proportion of older injured/ill workers. Also, higher proportions of older injured/ill workers were observed at surface coal work locations than at underground locations. The distribution of older injured/ill miners by occupation for several select commodities shows the highest proportions for supervisors, electricians, mechanics, and surface equipment operators, and the lowest proportions for surface laborers and for underground coal roof bolters and scoop operators. With few exceptions, older injured workers have the highest median number of days lost per injury when examined by type of mining operation and by occupation. Given the high proportions of older injured or ill workers in many sectors of the mining industry, health and safety programs must consider the physiological changes associated with aging when evaluating job tasks and the working environment.

Jan 1, 2004

Three -dimensional boundary value problems are difficult to solve. Indeed, while the separation of the scalar wave equation can be effected in 11 different coordinate systems, an analytic solution requires that the boundaries, both external and internal, possess the same symmetry as the coordinate system. Numerical methods are thus of great importance for the solution of such problems; however, despite the availability of high-speed, large memory digital computers , the solution to a significant three -dimensional problem is by no means trivial. It is unfortunate that the results reported here by Jones are invalid. Jones discusses a model in which a three-dimensional island lies off a linear coastline where all the interfaces lie in the coordinate planes in a Cartesian system. A downward plane em wave polarized with the electric field parallel to the linear coastline, and two of the islands coast, is incident downward. This, of course, requires that the incident electric field is perpendicular to the other faces of the idealized Cartesian island. The significant equation used by Jones for his finite difference calculations is [ ] where n2 = sµ? . is the conductivity, µ=µo is the permeability of the appropriate medium, and w is the angular frequency of a Fourier component of the incident field. We see that the displacement current term is omitted, which is an excellent approximation for the parameters of interest in this model. In the similar equation for the y- component of the diffusion equation, the same considerations which we are about to discuss are equally valid. It can be seen from the equation that the field components are related and thus any errors introduced will be propagated into all three components. The difficulty arises when Ex or E is perpendicular Y to one or other of the surfaces of discontinuity in s. The continuity of current at the air-earth interface (upper surface), e. g., jy, requires

Jan 1, 1973

By James Westfield, S H. Ash

Because of the increasing shortage of fuel in the United States, especially of residential fuel in the Eastern and New England States, it was essential that the maximum production of anthracite be obtained to help win the war and to prevent human distress. The nine railroads that depend on the anthracite region for a substantial portion of their business were not congested unduly with other traffic, because the region was not participating in industrial activities to the same degree as in many other sections of the United States; consequently, transportation of anthracite to the New England States, New York, New Jersey, and eastern Pennsylvania over a shorter rail haul than for any other fuel was desirable. The prevention of floods that would cause a loss of anthracite production was important to the war program. Every shutdown deprives the northeastern section of the United States of anthracite that is needed badly. Failure to prevent inundation of anthracite mines halts production, endangers the lives of workmen, damages, sometimes beyond repair, vital underground equipment, and threatens the permanent loss of a large portion of the Nation’s anthracite reserves. Funds were made available to the Department of the Interior, Bureau of Mines, for the fiscal year ended June 30, 1945, through a supplemental appropriation for anthracite investigations, one of which was to conduct inquiries and scientific and technologic investigations that have a bearing on the anthracite mine-flood problem. As part of the investigation, the Bureau proposed to obtain the cooperation of the anthracite-mining companies and the State in effecting a program to prevent the inundation of mines in the anthracite region. No large engineering projects were undertaken by the Bureau during the fiscal year ended June 30, 1945, on the anthracite mine-flood problem. Small projects were chosen that could be completed within 1 year to prevent loss of anthracite production at a critical time. It was believed that such projects would lessen the chance that flood water would inundate active mine workings.

Mar 1, 1946

By J. Ankrum, T. Xia1, D. Wilder, K. Spratt

The human lumbar spine is inherently an unstable structure and requires sophisticated neuromuscular control to maintain its stability and for performing physical tasks. As a consequence, it is important to understand the potential health effects on human operators of mechanical stimuli such as shock and vibration.1 Impact applied to a vehicle operator combines the risk of sudden, unexpected load with the mechanical stress of the seated posture.2 Because many work environments contain the potential for multiple, unexpected impacts, it is important to understand how the trunk muscles respond to complex conditions. We believe the results have implications for isolation design and standards development. Methods Muscle activity was recorded during simple and complex impacts, applied randomly and without warning, while subjects sat on an air-suspension truck seat located on a man-rated 6-DOF motion platform (Rexroth-Hydraudyne). Simple (single) impacts consisted of 100 ms quarter-sine jolts in the side-to-side (L and R) and vertical upward (V) directions with peak amplitude at 0.4 g. Complex impacts consisted of combinations of two simple (single) impacts in sequence (LV, RV, VL, VR), separated by 100 ms. Twelve right-handed males (23.7 ± 7.8 years old) were tested without a blindfold under 2 posture conditions (supported while leaning back and unsupported, sitting upright) and 2 seat suspension conditions (present or absent). Each type of impact was repeated three times under each posture and suspension condition, resulting in 84 impacts in total. Surface EMG signals from the left and right erector spinae (ES), rectus abdominis (AR), external obliques (EO) and internal obliques (IO) were recorded and transformed to 25ms RMS values. The response time, defined as the time the muscle activity exceeded the mean + 2 STD of the pre-impact resting period, peak response amplitude, and time were then derived. A mixed-model repeated measures analysis of variance was used to evaluate statistical significance, where type I error rate was set at .05. Results One question we asked of these data was whether there were differences in responses related to simple single strike impacts (L, R, or V) and complex, double-strike impacts (LV, RV, VL, VR). There are 21 possible combinations of comparisons of simple and complex impacts to each other. The differences found are listed in Table 1.

Jan 6, 2006

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

"The town of Monson in Piscutaquis County, Maine is the, center of an important site industry. Monson slate has a nation-wide reputation, particularly for electrical switch boards, and the deposits have been worked for the manufacture of such products for many years. Open-pit quarrying is the method most commonly employed in obtaining slate. Underground methods have been used in the Peaon Bottom district near Delta, Pennsylvania, but the quarries that were thus operated are now abandoned. Underground methods have been used more extensively in foreign countries, the most famous example being the slate mines at Angers in France, where an over-head stoping method has been employed successfully for many. It is only under special conditions that underground methods can be successfully used. If the deposit is wide and relatively thin, or if the material is too unsound to constitute a safe roof, open-pit methods must be used, for slate is too low-priced a commodity to justify the heavy expense of any timbering methods. It is only where the deposit is relatively narrow, of great depth, and sufficiently sound to afford a strong roof that ordinary mining may be employed.The best slate beds in two of the three quarries operated at Monson are no worked by underground methods. The chief bed worked by the PortlandMonson Slate Co. is 10 feet thick, stands vertical and strikes N. 63º F. The slaty cleavage is vertical and crosses the strike of the beds at an angle of 5 to 10°. The grain or second direction of splitting is vertical and perpendicular to the cleavage. In addition to the 10-foot bed, to 2-foot beds and one 5-foot bed are available but are not now utilized. In theMonson Maine Slate Co. quarry (the old Pond quarry) a greater number of beds available, but at present quarrying is confined to a single bed about 9 feet thick which dips 30º S.E. and strikes N. 47ºF. The slaty cleavage is vertical and strides N. 45º F., while the grain strikes N. 45-50º W. and is also vertical."

Nov 1, 1920

"Minimizing Particle Contamination During Generation of Fresh Dust for Inhalation Studies J. Abraham, MS, Mechanical and Aerospace Engineering, West Virginia University, 1995Correlating Lung Crackle Using Holographic Interferometry Ali Afshari, MS, West Virginia University, 1989Effect of Bit Wear on Dust Generation Mudassar Ahmad, MS, West Virginia University, 1992 The Effect of Surfactants on Suppression of Non-Wettable Particles Ali Alaboyun, MS, Mineral Engineering, The Pennsylvania State University, 1989 Geochemical Characterization of Kerogens, Shales, and Coal Refuse Associated with Allegheny Formation of Cases of Northern West Virginia Dick Andre, MS, West Virginia University, 1987Size and Mass Characterization of Airborne Particulate Matter in Underground Coal Mines Using Diesel-Powered Equipment Indranil R. Bardhan, MEM Report, The Pennsylvania State University, 1992Size and Mass Characterization of Airborne Particulate Matter in Underground Coal Mines Using Diesel-Powered Equipment I. Bardhan, R. V. Ramani, and J.M. Mutmansky, Mining Engineering, The Pennsylvania State University, University Park, PA, Final Report to the U.S. Bureau of Mines, April, 1994Particle Concentrations in a Hazelton Inhalation Chamber Shahram Bavani, MS, West Virginia University, 1985Use and Potential of Lazer Holographic Interferometry and Subsidence Model- Study of an Underground Room and Pillar Mine Richard Begley, MS, West Virginia University, 1984Development of a Mechanistic Model for Prediction of Subsidence in a Longwall Mine Richard Begley, PhD, West Virginia University, 1990Redesign of Micro-Orifice Uniform Deposit Impactor Steve Behm, MS, University of Minnesota, 1991Evaluation of a Two-Phase Spray System for Dust Suppression B. Belle, MS, The Pennsylvania State University, 1996Evaluation of a Two-Phase Spray System for Dust Suppression B. Belle and R.-V. Ramani, The Pennsylvania State University, University Park, PA, Final Report, September 9, 1996A Fracture Mechanics Study of Crack Propagation Mechanism in Coal: The Mechanics of Fine Fragment Formation Z.T. Bieniawski and R. Karl Zipf, Jr., Mining Engineering Department, The Pennsylvania State University, University Park, PA. Final Report, October l, 1988A Mathematical Model for the Prediction of Ambient Dust Concentrations in Mine Atmospheres R. Bhaskar, MS, Mining Engineering and Operations Research, The Pennsylvania State University, 1984Spatial and Temporal Behavior of Dust in Mines-Theoretical and Experimental Studies –R. Bhaskar, PhD, Mining Engineering, The Pennsylvania State University, 1987"

Jan 1, 1998

By Andrew B. Cecala, Edward D. Thimons

"The Bureau of Mines has recorded a number of different background dust sources that significantly contaminated the air breathed by bag machine operators. These background sources, observed at five different plants over the past 2 years, can expose bag machine operators to more significant dust concentrations than the filling process itself. To keep bag operator exposure within acceptable dust levels established by the Mine Safety and Health Administration, U.S. Department of Labor, the significance of these background sources must be realized, and the sources must be identified and controlled. The purpose of this work is to identify common background dust sources and show the significant effects that they have on the bag operator's overall dust exposure. INTRODUCTIONThe purpose of this report is to identify some common background dust sources in and around the bag-filling area. Although these background dust sources are of ten unrecognized, they can be more significant sources of contamination than the dust generated from the bagging process.The bagging of mineral products into 50- and 100-lb paper bags is common throughout the entire mineral processing industry. Bagging is performed by a bag operator who sits in front of a two- or four-station fill machine. The bagger's function is to attach empty bags to the fill nozzles as filled bags are ejected from the machine. If the product being bagged is extremely fine (smaller than 200 mesh), the bag operator's dust exposure is usually one of the highest in the plant.The bag operator is exposed to two primary dust sources. The first is product blowback during the bag-filling cycle. This occurs as excess pressure is released from around the fill nozzle during filling. As the excess air forces its way out of the bag, product is forced out with it. This blowback of product leaving the bag creates a considerable amount of dust. The second major source is the ""rooster tail"" of product thrown from the bag valve and fill nozzle as the bag is ejected from the fill machine. Since the bag is pressurized as it leaves the machine, product spews out of the valve for a few seconds."

Jan 1, 1986

By C. J. Tsai, K. Olson, R. Caldow, B. Cantrell, D. Y. H. Pui

"The amount of new surface generated during fracture of coal and rock has been found to be directly proportional to the amount of energy associated with the fracture. To confirm this and study the relationship between the new surface and dust aerosol formed during fracture the U.S. Bureau of Mines has conducted experiments simulating fracture as it occurs during mining operations. In addition to fracture energy measurements, fragment size distributions were determined over a size range of 0.5 microns to 1 inch. The size measurements accounted for the mass of the original sample. Material studied was Illinois No. 6 coal, coal from the Taggart seam of Virginia, and Berea Sandstone. The experiment employed a chamber to confine sample fracture fragments and a combination of particle measuring systems. Measurement methods included aerodynamic sizing of entrained dust aerosol with optical counting and inertial impaction techniques, physical sizing of non-airborne fragments by sieving, and optical sizing of fragments using optical counting and scanning electron microscopy.Results of the size distribution measurements indicate that a single size distribution law does not adequately describe the entire fragment size distribution. A combination of two size distribution laws, such as the Rosin-Rammler and log-normal distributions, is necessary to describe this size distribution. New surface created by fracture is primarily found 1n particulate between 2 and 50 microns with a mean size of 12 microns. It was also found that the specific energy of fracture can be linearly related to the .concentration of aerosol in this size range.Only a .small fraction, between 0.02 and 0.16 pct, of the dust particles .generated during fracture become airborne. The remainder adhere to the new surface created during fracture. An entrainment fraction, defined for a given particle size is the ratio of the mass of airborne particles to that of the total particles generated in that size range. This experimental entrainment fraction is related to the Van der Waals adhesion force and the electrostatic forces operating during fracture and is used to derive empirical parameters to model these two processes."

Jan 1, 1989

"Health standards in the U.S. are among the highest in the world. Achieving these standards have often had an impact on productivity, slowing output, and raising prices to levels that make it difficult to compete with many foreign industries. The answer to many of these problems lies in the development of new and advanced control techniques. This overview has identified some of the major respirable dust technological hurdles that have been overcome, and provided some insight into current and future approaches underway to remove these obstacles and to provide the United States with the most advanced state-of-the-art mining industry in the world from a respirable dust standpoint. The necessary developmental research is costly and time-consuming. The long-term, high-risk aspects of this effort are being addressed by the Bureau and the Generic Center on Respirable Dust, with support by industry. This should be recognized as one of the principal agents through which the great mineral potential of this Nation can be realized, and our international status as a mining power be assured without compromising the health and welfare of those who ensure it.The problem of more stringent dust standards will continue to grow. To date, approximately 40 pct of the coal mining industry has been placed on more stringent dust standards due to quartz. Control techniques must be improved if mandated levels are to be met. As longwall production increases, dust levels will also increase. In light of the industry trend toward longwall mining, if no new control technology is available, the Federal dust standard will act as a constraint on future output per hour. The Bureau has recently completed a survey of 18 coal preparation plants; 50 pct of these operate at dust levels which exceed 2.0 mg/m3; future work will be directed toward solutions in this area. The 2.0 mg standard for respirable dust is for dust particles which are below 10 pm in diameter. Recent studies have shown that dust in the range between 10 and 25 pm can cause obstructive airway disease. The Bureau is currently determining the extent of exposure to dust in this size range from various mining operations."

Nov 1, 1988

By Clarence Hall, Spencer P. Howell

The tests and studies begun by the United States Geological Survey in the fall of 1908 with a view to lessening the accidents attending the use of explosives in coal mining are being continued by the Bureau of Mines at the Pittsburgh experiment station and in the field. One hundred and six applications for the testing of 209 different explo- sives had been received at the Pittsburgh station prior to March 1, 1913, and on that date 97 explosives that had passed the required tests were on the "permissible" list issued by the bureau. This bul- letin gives the results of tests of all permissible explosives tested between May 15, 1909, and March 1, 1913. Bulletin 15 entitled "Investigations of Explosives used in Coal Mines" contains the results of tests of 17 permissible explosives tested prior to May 15, 1909. A copy of the test requirements and the names of explosives on the per- missible list dated March 1, 1913, are appended to this bulletin. An explosive is considered permissible for use in coal mines when it is similar in all respects to the sample that passed the tests required by the bureau, and when it is used in accordance with the conditions prescribed. The physical tests reported in this bulletin were conducted by Messrs. H. F. Braddock, A. J. Strane, J. W. Koster, A. S. Crossfield, A. J. Hazlewood, A. B. Coates, and J. E. Tiffany at the Pittsburgh experiment station of the bureau. The act of Congress making appropriations for sundry civil ex- penses of the Government for the fiscal year ending June 30, 1912, authorized the Secretary of the Interior to charge a fee covering the actual necessary expenses involved in making such tests by the Bureau of Mines as might be approved by him. After careful consideration had been given to the actual necessary expenses involved in the test- ing of explosives to determine their permissibility for use in coal mines, the sum of $150 was approved by the Secretary of the Interior as a reasonable charge for each complete official test. During the first year this law was in effect the fees collected amounted to more than $6,000.

Jan 1, 1913