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To allow the controlled yielding of mine walls in order to reduce rock-burst hazards and reduce maintenance caused by excessive squeezing forces. Approach Rock bolts that elongate and continue to sustain a load, have been fabricated and tested. This device is an adoption of a concept originally developed in South Africa for use where unusually adverse conditions may warrant the added cost. How It Works A coupling in the rock bolt allows controlled elongation if the load increases beyond the bolt's design strength. (The load can build up either slowly, as during heaving, or rapidly, as before a rock burst.) The elon¬gation of one or more rock bolts surrounding a mine opening, allows the rock to move from its original position to c new position in a controlled manner. This movement relieves the rock stresses, and the mine opening reaches a new state of equilibrium. The elongatible coupling of the rock bolt consists of a

Jan 1, 1977

By J. A. Organiscak

In the United States, respirable coal mine dust exposures are limited to a 2 mg/m3 time weighted average for a working shift. If the silica content of the sample exceeds 5 percent, the 2 mg/m3 standard is reduced according to 10- (% silica) to limit silica dust exposures to 100 µg/m3. Examinations of dust sampling data collected by the federal coal mine inspectorate showed that roof bolter occupations continue to be at risk for overexposure to respirable silica dust. Testing at the Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health assessed the effectiveness of a canopy air curtain for controlling occupational exposures to respirable silica and coal dusts. Initial testing found that zones of higher velocity airflow shrank as distance beneath the canopy increased. This suggested that protection from occupational dust exposures would likely decrease as distance beneath the canopy increased. Further testing revealed that coal dust reduction efficiencies were most affected by changes in interference air velocity and, to a lesser extent, changes in canopy air quantity. However, respirable silica dust percentages under the canopy were not affected by such changes and, in fact, were not significantly different from silica percentages measured outside the canopy. This implied that the air curtain was equally effective on both respirable coal and respirable silica dust particles.

By Akul Joshi, Ming C. Leu, Robert Guttenberg, Susan L. Murray

The aerospace and automotive industries are facing a significant risk for cumulative trauma disorders from high-repetition, long-duration tasks. Additional risk factors such as shocks, vibrations and sustained uncomfortable postures oftentimes contribute to musculoskeletal, neurological injuries associated with the hand-arm system. The power tools used for the operation reduce the comfort and working efficiency of the operators, thus lowering their health and safety and the quality of operation. This paper investigates the fastening operation on the assembly line of a major aerospace company for quantifying hand-arm vibrations with the objective of developing a dynamic model of the hand-arm system. The model will be used to ascertain the effect of the various risk factors on the quality of the operation. Experiment Setup A system of three tri-axial accelerometers is used to collect vibrations entering the hand-arm system and their positioning follows the ISO-5349 standard. Reaction force during the operation is measured using a force sensor. The posture of the hand-arm system is measured using two goniometers and one torsiometer. The pilot study conducted has two subjects and one pistol-grip power tool. The experiment setup and positions of various sensors is depicted in Figure 1. [ ] Analysis Method The analysis consists of transmissibility of vibrations and frequency weighted acceleration based on the recommendations of the ISO-5349 standard [1,2]. The transmissibility [3] was deduced in frequency domain after measuring data in time domain from the

Jan 6, 2006

By Michael A. Trevits

Since the promulgation of the MINER Act and the follow-up changes to the regulations governing mine seal construction and maintenance, mine operators must be acutely aware of the atmosphere in sealed mine areas and prepared to deploy control technologies when the conditions are warranted. On Site Gas Systems1 in Newington, Connecticut was awarded a contract by the National Institute for Occupational Safety and Health (NIOSH) to construct a novel in-mine nitrogen (N2) generation plant using pressure swing adsorption (PSA) technology. PSA technology utilizes carbon molecular sieve material and pressure to adsorb oxygen (O2) molecules while allowing N2 molecules to pass through the sieve material. The prototype PSA unit was tested at the NIOSH Safety Research Coal Mine (SRCM) where a 62,000 ft3 area of the mine was rendered inert during a series of two tests. The resultant data were then used to construct a CFD simulation of both injection tests. In addition, O2 depletion and gas leakage rates were quantified in the model and were compared to actual values. Once the model was calibrated, the sealed mine area was doubled and simulations were made with various injection rates and injection site locations to determine the impact on the time needed to render this area inert. This paper presents an overview of the PSA plant, the details of the gas injection tests and CFD modeling work.

Jan 1, 2010

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 John F. Wiss

A series of controlled experiments was conducted at four surface coal mines to study the effects of certain blast parameters upon the ground and air vibration. Preliminary scale-model blasts were conducted at a quarry to provide basic data. It was found that the amplitudes of the ground and air vibration were controlled by the maximum explosive weight per delay. Either cube root or square root scaling could be used for the seismic amplitudes, and cube root scaling could be used for the overpressure amplitudes. Both amplitudes were not significantly affected by the total charge weight per blast, the attitude of the boreholes, or the charge length or diameter. The overpressure amplitudes were affected by the charge depth, the use of cover over surface detonating cord, and the use of adequate stemming. The length of the delay intervals and the spacing of holes were important in determining' the potential fur reinforcement of the amplitudes in certain directions from the blasts. In downwind directions from the blast, the attenuation of the overpressure with distance decreases. Surface terrain did not significantly affect the overpressure amplitudes within the range investigated. The type of overburden affects the generation of both amplitudes and the propagation of the seismic amplitudes. Spectral analysis of the ground and air vibration is reported. A bibliography of pertinent literature is included as an appendix. A scaled distance of 300 ft/lb1/3 should produce a peak particle velocity of less than 1 ips and an overpressure of less than 128 dB linear peak. For square root scaling, a scaled distance of 75 ft/lbl/2 should limit the ground vibration to less than 1 ips.

Jan 1, 1978

By Wilbur I. Duvall

In a review of so 40 papers on damage to residential structures resulting from blasting, only 3 were found that present data on the observed amplitude and frequency of the vibration levels produced by blasting together with an observed degree of damage to a residential structure. The data from these three reports have been analyzed statistically to determine if one of the quantities, displacement, velocity, or acceleration, is more reliable than the others for estimating the degree of damage to a residential structure. From this analysis the conclusion is drawn that a given degree of damage to a structure is most closely related to the magnitude of the particle velocity of the wave motion passing thru the earth at the structure location. On the average, only minor damage it observed for peak particle velocities of 5.4 inches per second, and major damage is observed for peak particle velocities of 7.6 inches per second. When the spread of the data is taken into consideration, the following statement can be made: Wave motions that have a peak particle velocity in excess of 2 inches per second have a fair probability of producing some damage to structures, whereas wave motions that have a peak velocity less than 2 inches per second have a very low probability of causing any damage. Therefore, the recommendation is made that vibration levels in the vicinity of residential structures should be maintained below a peat particle velocity of 2 inches per second. The above criterion for safe blasting is considered to hold over a wide variety of soil and rock conditions because the original data were obtained for a wide range of soil and rock conditions and on various types of residential structures. INTRODUCTION Ever since explosives were discovered and developed for mining purposes, there has existed the problem of what effects the air and ground vibrations resulting from blasting have on structures of various types. This problem is

Jan 1, 1962

By J. A. Organiscak

This paper examines methods for limiting occupational silica exposures for roof bolting personnel in underground coal mining. A canopy air curtain and an air tube were evaluated as means to provide filtered air over the breathing zone of these personnel. Laboratory testing showed that dust reductions beneath the air curtain and air tube approached 60 percent and 40 percent, respectively, with low interference air velocities. The data also showed that dust reductions were highest for positions closest to the device and that these levels decreased with distance. This paper also evaluates a metal rake, a flexible insert, and a rigid insert for cleaning the roof bolter dust collector box. Less dust was produced when using the rigid insert. Surprisingly, the flexible insert was sometimes no better than scraping or raking the dust onto the mine floor. However, little dust got on the coveralls when using either of the inserts.

By Sam S. Taylor

[The discovery of many oil fields in Illinois since 1936, and their rapid development have brought the problem of brine disposal to the foreground in that State. The ultimate magnitude of the problem is not yet known, but already it is treat enough to warrant technical investigation. The Bureau of Mines, therefore, has made a general survey of the methods of handling oil-field b brines in Illinois rend has studied in detail three subsurface disposal systems.]

Jan 1, 1940

By Elaine T. Cullen

Miners, like many skilled blue-collar workers, are not traditional learners. They have not always been successful in classroom-type settings, preferring to learn on the job in a hands-on environment. U.S. law requires that miners have a minimum of 8 hours of safety training annually, plus 40 hours for underground miners and 24 hours for surface miners when they enter the industry. However, miners rarely view this training time positively. In fact, it has been called “safety jail” by many, who regard it as a time to get a little extra sleep While mining has become far safer in the past 100 years, it is still a dangerous occupation. The Office for Mine Safety and Health Research, a part of the National Institute for Occupational Safety and Health (NIOSH), has funded a project for the past 4 years to address this challenge. The purpose of the research was to find a way to develop effective safety training for these people. Miners are born story tellers. They share “near miss” stories, stories about master miners they have known, and stories about how things used to be. These stories not only pass along information about what will happen if a miner fails to respect the mining environment, they also instruct listeners in the culture of mining and the values that it embraces. Stories, it seems, are a way to get safety messages across to miners, especially inexperienced ones, and using older, wiser miners in these stories is an obvious choice. This paper will discuss how a series of training videos was developed, how “master miners” and story lines were chosen, and how the resulting videos have been received in the mining industry.

By Radford Schantz

In 1990, the Bureau of Mines (BOM) conducted a mineral investigation of the mines and prospects in the East Mojave National Scenic Area (EMNSA). San Bernardino County. California During field work. BOM identified 701 mines and prospects in EMNSA for which the geology, mineral resources, and mining history were compiled and summarized. Analytical results for 1.188 rock samples collected are tabulated. Total value of identified resources in EMNSA is $5.0 billion. Twenty-four mines and prospects were deemed profitable under current economic conditions. Development could generate considerable economic benefits to San Bernardino County. Potential economic benefits from mining the deposits were evaluated under the following access restrictions for EMNSA: 1) fun access, 2) HR 3460, and 3) S 11/HR 780. Under the full access scenario, cumulative mine revenues are $3.0 billion, cumulative personal earnings at mines and supporting industries are $0.94 billion, and annual jobs at mines and supporting industries are 2,379. Under HR 3460, mine revenues, personal earnings, and annual jobs are $2.9 billion. $0.88 billion, and 2,165, respectively. Under S 11/HR 780, mine revenues, personal earnings, and annual jobs are $1.0 billion, $0.32 billion, and 936, respectively.

Jan 1, 1990

By T. M. Ruff

A prototype mucking machine designed to operate in narrow-vein stopes was developed by Foster- Miller, Inc., Waltham, MA, under contract with the U.S. Bureau of Mines. The machine, called a compact loader-trammer, or minimucker, was designed to replace slusher muckers in narrow-vein underground mines. The minimucker is a six-wheel-drive, skid-steered, load-haul-dump (LHD) machine that loads muck at the front with a novel slide-bucket system and ejects it out the rear so that the machine does not have to be turned around. To correct deficiencies of the tether-remote-control system, a computer-based, radio-remote-control system was retrofitted to the minimucker. Initial tests indicated a need to assist the operator in guiding the machine in narrow stopes. An automatic guidance system that used ultrasonic ranging sensors and a wall-following algorithm was installed. Additional tests in a simulated test stope showed that these changes improved the operation of the minimucker. The design and functions of the minimucker and its computer-based, remote-control system are reviewed, and an ultrasonic-sensor-based guidance system is described.

Jan 1, 1992

By J. C. Edwards

The National Institute for Occupational Safety and Health (NIOSH) implemented a real-time neural network system which can discriminate mine fires from nuisance diesel emissions as part of an atmospheric mine monitoring system in NIOSH?s Safety Research Coal Mine. The real-time response of a neural network to fire sensor outputs was demonstrated for coal and belt combustion in the presence of diesel emissions. The fire sensors consisted of an optical path smoke sensor, a carbon monoxide (CO) sensor, and two types of metal oxide semiconductor (MOS) sensors. The real time neural network was trained with coal, wood, and belt fire experiments with and without diesel emissions background. The trained neural network successfully predicted mine fires with these combustibles in the smoldering stage prior to the onset of flames.

Jan 1, 2005

By R. H. Grau, R. Krog

The National Institute for Occupational Safety and Health (NIOSH) has conducted research to improve the ventilation of large-opening mines. The research has demonstrated that the ventilation of large-opening mines improves significantly by including ventilation requirements in the mine planning process and implementing somepractical techniques during mining. Planning the location of long pillars to reduce the number of crosscuts between intake airways and return airways, positioning auxiliary fans in their proper locations, and establishing ventilation stoppings with minimal leakage all significantly improve the ventilation of large-opening mines. Mine operators that adopt these techniques in the mine ventilation plan will reduce mineworkers’ exposure to airborne contaminants.

By A. George Stern

The literature dealing with the drilling of oil wells has become extensive during the last few years, and oil men can find much information relating to drilling muds in the technical literature of the petroleum industry. Although large tonnages of clay are used in preparing drilling mud (also known as drilling fluid), almost no information has been published to apprise the clay industry of the types of minerals used, with their requirements and limitations. It is from this point of view that the present report has been prepared.

Jan 1, 1941

By C. P. Mabie

This report summarizes studies by the Bureau of Mines in developing a simple method for estimating the phosphorus pentoxide (P205) content of finely ground sedimentary phosphate ores and beneficiated products. The method used involved leaching, filtration, and precipitation. The Bureau found that measurement of the volume of ammonium phosphomolybdate precipitate obtained from samples containing 16.8 to 37.7 percent P205 and the use of an appropriate calibration curve permitted estimates of percentage of P205 content accurate within ± 1.1 to ± 2.6 percent, respectively, at the 95-percent confidence limits. Incidental to mineral dressing and petrographic investigations of western phosphate ores in 1959, the Bureau of Mines undertook development of a simple process-control method for rapid on-the-spot evaluation of phosphate-mineral recovery. Because of the fine-grained and obscure character of western phosphate ores, chemical, rather than microscopic or petrographic, techniques were investigated. The described method involves acid decomposition of the ore or product, filtration, addition of ammonium molybdate reagent to the filtrate, and centrifuging and measuring the volume of yellow ammonium phosphomolybdate precipitate produced.

Jan 1, 1961

By Michael E. Henderson

Presented in this report are the experimental results of coarse coal slurry degradation data obtained from the Hydraulic Transport Research Facility (HTRF) at the Pittsburgh Research Center (PRC), Bruceton, PA. The facility is operated by Boeing Services International, under Bureau of Mines Contract No. J0333956. Presented in this report are the experimental results of coarse coal slurry degradation data obtained from the Hydraulic Transport Research Facility (HTRF) at the Pittsburgh Research Center (PRC), Bruceton, PA. The facility is operated by Boeing Services International, under Bureau of Mines Contract No. J0333956. This particle degradation report is a summary of the particle distribution data obtained at the HTRF for the period 26 November 1982 to 1 October 1983. The testing covered herein is for coarse Pittsburgh Seam coal in the 6-in (150 mm) and 12-in (300 mm) pipelines, at velocities ranging from 5 to 18 ft/s (1.5 to 5.5 m/s), and at concentrations by weight ranging from 15 to 55 pet. Particle size distribution samples were taken systematically throughout the testing.

Jan 1, 1985

By L. R. Herrmann

The research described in this report is the first phase of a comprehensive program for the development of a characterization for the structural properties of rock masses. The mathematical expression of the characterization is especial' tailored for use in conjunction with modern structural analysis procedures. The objective of the first phase of the project is to determine the feasibility of representing the structural properties of rock masses in terms of the analysis of an appropriate "representative volume" the results of this investigation are described in detail in the body of the report. The current state-of-the-art concerning the understanding and description of the fundamental mechanisms of rock behavior are determined from a survey of existing literature. The development of a representative volume that captures the most important of these mechanisms is described, In order not to unduly obscure the fundamental aspects of this development, the mathematical analysis of the representative volume is limited to plane strain conditions. A subroutine for the numerical evaluation of the proposed model (i.e., the analysis of the representative volume) is presented. The steps necessary for the incorporation of the subroutine directly into existing two-dimensional finite element structural analysis programs are described. Comparisons between the predictions of the proposed characterization and published results of simple laboratory tests are presented and discussed. Finally recommendations are given concerning suggested improvements of the model and the extension of it to the general three-dimensional case.

Jan 1, 1974

By Suresh K. Bhatt, Christopher Mark

Fatalities caused by highwall/spoil bank failure in the surface mines, coal and non-metal, increased to an alarming rate of seven during 1999. To determine the causes of slope failure and successful mining practices, the National Institute for Occupational Health and Safety undertook a study. The study included: 1.A review of accident statistics; 2.A review of Federal and state mining laws pertaining to surface mining; 3.A literature review, and; 4.Mine visits. The study emphasized surface mines in the states of West Virginia, Ohio, and Pennsylvania. The review of a decade’s accident statistics using the mine Safety and Health Administration’s (MSHA) database showed that approximately 40% of all ground control related incidents reported to MSHA occurred in just four eastern states: Kentucky, West Virginia, Pennsylvania, and Ohio. The comprehensive literature search provided a historical perspective of highwall stability issues. Eleven mines we visited to obtain data on their mining practice or design. Commodities included coal, sandstone, and limestone. Based on the visits, five case studies were developed to represent typical mining methods and effective ground control practices used in eastern surface mines. Benching was found to be a common technique to reduce the overall highwall slope angle. Decking in the softer zones, such as shale, proved useful in controlling damage due to blasting.

By Ren G. Dong, John Z. Wu, Daniel E. Welcome, Kristine Krajnak

Although the exact mechanisms underlying vibration white finger (VWF) are not clear, it has been speculated that VWF is associated with variations of the blood flow patterns due to the physical damage and/or degeneration in neural and vascular tissue caused by vibration loading [1]. Excessive dynamic deformation of the soft tissues in the fingertip under vibration loading is believed to induce multiple occupation-related hand/finger disorders. However, the in vivo distributions of the dynamic stress/strain of the tissues in the fingertip under vibration conditions have not been studied because they cannot be measured experimentally to date. The goal of this study is to analyze, theoretically, the location and frequency-dependent dynamic deformation of the soft tissue in the fingertip during vibration exposures. [ ] Methods The fingertip considered in the model is the distal phalanx, the portion from the distal end of the fingertip to the distal interphalangeal (DIP) joint articulation (Fig. 1). The external shape of the fingertip was determined using a smooth mathematical surface fitting to the observed fingertip shapes. The fingertip surface was then scaled to the dimensions of a typical male index finger: length 25 mm, width 20 mm, and height 18 mm. The fingertip was approximated to be symmetric, such that only a half of the fingertip was considered in the FE modeling. The fingertip was assumed to be composed of outer and inner skin layers, subcutaneous tissue, bone, and nail. The soft tissues (inner skin layer and subcutaneous tissues) were assumed to be nonlinearly elastic and viscoelastic, while the bone, nail, and outer skin layer were considered as linearly elastic. The simulations were conducted using a displacement-controlled protocol in two stages. First, the fingertip was statically pre-compressed. The contact plate was first displaced towards the finger to achieve a predetermined value of tissue deformation (i.e., 0.5, 1.0, 1.5, and 2.0 mm). Second, the steady-state dynamics responses of the fingertip were analyzed using a linear perturbation procedure. The fingertip was subjected to a continuous harmonic excitation (magnitude 0.5 mm) from the contact interface. The dynamic analysis was performed in a frequency domain ranging from 16 to 2000 Hz. The frequency-dependent distributions of the vibration magnitude and dynamic strain magnitudes in the soft tissues are investigated. Results Typical simulation results for the frequency-dependent distributions of the vibration magnitude in the soft tissues are shown in Fig. 2 (figures show the results with a pre-compression of 2.0 mm). The vibration magnitude at the contact surface is 0.5 mm (specified) for all frequencies, while the vibration magnitudes in the soft tissues are location- and frequency-dependent. It is clear that the fingertip has a major resonance around 125 Hz, at which the vibration magnitudes in the soft tissues are over four times greater than that of the contact plate (0.5 mm). It is interesting to observe that, at this resonant frequency (125 Hz), the soft tissues at the tip has the maximal vibration magnitude while the regions near the contact

Jan 6, 2006