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By Mark Larson, Steve Iverson, Brian G. White

The authors hypothesize that excavation-induced extension fractures are caused by elastic shearing displacement that in turn causes tension oblique to a propagating shear zone. Such extension is manifested as tension on scales larger than that of microcracks. En echelon fracture patterns are a common result. FLAC modeling confirmed that localized tension is created near the corners of mine openings. In the model, tension was concentrated at the leading edge of a simulated fracture in a pattern that could promote the formation of an en echelon fracture. Particle Flow Code models confirm progressive formation of en echelon tensile failures with distance from an opening. The elastic displacements and the resulting fractures facilitate reduction in applied load at the expense of shear deformation and lateral dilation. Understanding the mechanics of fracture and deformation is vital for designing more effective ground support practices, a major objective of ground control research being conducted at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health.

Reduce longwall equipment transfer time between panels by utilizing a predriven recovery room, and thus eliminate the premove preparation associated with most equipment recovery methods. Background and Approach The recovery point for a retreating longwall is a predetermined position near the end of the panel where mining is terminated and equipment is disassembled and removed. However, to prepare for equipment removal at the recovery point, bolting and wire meshing arc required before the recovery point is reached. Usually, preparations for equipment recovery begin about 35 ft from the recovery point, significantly impeding the normal rate of advance of the longwall and, consequently, production. Recently, BethEnergy Mines, Inc., and the Bureau of Mines cooperated to evaluate the applicability of utilizing predriven recovery rooms to improve longwall equipment recovery. A predriven recovery room is an entry driven parallel to the longwall face at the end of the panel, having standard dimensions (for that particular mine) and supported with bolts, wire mesh, and supplemental support. The preparation of this entry is completed before it experiences mining-induced effects from the approaching longwall face. This enables the face to continue to mine at its normal rate of advance until the panel is completed. The supplemental support is required to control the loads imposed by the front abutment and is the most vital component of the recovery room.

Jan 1, 1989

By R. V. Ramani, V. T. Burgos, J. A. McClay

Cost Data Library The data retained in the Cost Data Library is of a semi¬permanent nature in that it is held in storage for immediate use with the program although its contents may require periodic evaluation to maintain it in a current status. The library is composed of six arrays containing both technical and cost data. The following description of the library input system provides the information necessary to maintain an active storage file. Array POWERA: FORMAT (8F10.0) - contains the step groupings of the power rate schedule for power cost computations. Four input data cards are required to fill this storage area. Card Column 1 1 - 10 Demand in Kilowatts for the First Step of the Demand Rate Schedule 11 - 20 Demand in Kilowatts for the Second Step of the Demand Rate Schedule y 41 - 50 Demand in Kilowatts for Fifth Step of the Demand Rate Schedule 51 - 60 Maximum Demand Level for this Rate Schedule 61 - 70 Percent Power Factor for this Rate Schedule 71 - 80 Unassigned 2 1 - 10 First Step Demand Charge, $/Kw 11 - 20 Second Step Demand Charge, $/Kw 4¬ 41 - 50 Fifth Step Demand Charge, $/Kw

Jan 1, 1975

Prevent collisions between large mine-haulage trucks and smaller vehicles parked in areas not visible to the haulage-truck operator, Approach Two electronic systems were developed to detect the presence of vehicles in the blind areas of a parked haulage truck. The systems can warn haulage truck operators of presence of vehicles that are blocked from view. The systems do not apply for trucks in travel. How It Works The systems use electronic transmitting techniques-one system is based on low-frequency radio waves and the other on very-high-frequency radio waves. Each system requires that a signal transmitter be mounted on the smaller vehicle to be detected. Continuous signals from this transmitter are sensed by receiving antennas mounted on the right front and rear of the large haulage truck. Upon receiving a signal, the receiver energizes warning lights and a buzzer in the cab of the haulage truck, alerting the operator to a possible collision hazard. Detection distance is adjustable, depending upon the size of the haulage truck, but a minimum of 30 feet was the design goal.

Jan 1, 1990

By K. C. Dean

Time and motion studies were made by the Federal Bureau of Mines on the hand and machine dismantling of scrapped auto starter motors, generators, and alternators for recovery of copper, aluminum, and iron. The studies showed that an individual with power handtools and convenient access to a hydraulic press, power bandsaw, acetylene torch, and power lathe could, in an 8-hour day, disassemble about 100 starters, or 150 generators, or 30 alternators. The scrap copper yield would be 280, 390, and 45 pounds, respectively, and the iron yield would be about seven times the copper weight. About 100 pounds of aluminum would be obtained from the alternators.

Jan 1, 1976

By J. Whyatt

A package of bench design programs is being publicly released by the National Institute for Occupational Safety and Health (NIOSH). These programs are designed to provide a probabilistic estimate of the likelihood that various widths of catch bench will be retained. Program modules address the mechanisms of plane, plane step path, and wedge failure. Results are drawn from statistical and geostatistical descriptions of fracture characteristics and other input parameters, and reported as the statistical chance that a given width of catch bench will survive, that is, that a catch bench will remain wide enough to catch rolling and sliding material and prevent such material from posing hazards to miners operating below. The capabilities and application of this software are demonstrated through a case example. Comparing bench width estimates obtained using geologic data with actual widths is a key step in verifying that a program is appropriate for particular site conditions and that proper statistical descriptions of fracture parameters for that site have been developed. Such verification efforts improve confidence, and hence usefulness, of this method for designing future slope benches. Development and release of these programs appears particularly timely given recent progress in photoanalysis methods, which promise to greatly reduce the cost of collecting fracture data.

Jan 1, 2004

SMCRA contains five principal regulatory provisions that form the basis for its implementation: Performance Standards Performance standard safe intended to ensure that all surface mining is conducted in a way that protects the environment and the public and ensures that the mined land is restored to productive use following mining. Permits Before developing a surface or underground coal mine, an operator must have a permit issued under SMCRA. An application for a permit to conduct a surface coal mining operation is a detailed document that consists of text and numeric data describing the proposed mining and reclamation. Information must be furnished on pre-mining environmental conditions, existing land use, proposed mining and reclamation, how the performance standards will be met, and the post-mining land use. This provides the regulatory authority with the information necessary to determine that the operation can be conducted in accordance with the regulations. Performance Bonds Before a permit can be granted, an operator must post a performance bond sufficient to cover the cost of reclaiming the site in the event the operator fails to complete reclamation. The bond is not fully released until all performance standards have been met and reclamation of the site has been determined to be successful after five years in the East and Midwest, and after 10 years in the arid West. However, the bond can be partially released as various phases of reclamation are completed. Inspection and Enforcement If a violation of SMCRA or of a state surface mining and reclamation law is observed, an inspector issues a notice of violation to the operator. The violation must be corrected within a specific time, and the operator may also have to pay a fine based on the severity of the violation. If the violation is not corrected, acessation order is issued to immediately stop active coal mining, and the operator must pay a fine. If a violation is especially serious (for example, creates an Following reclamation, the land was immediately put back into agricultural production. Today, grain and corn crop yields have continually exceeded targets. 2 imminent danger to public health or safety or causes significant damage to land, air, or water resources) the inspector immediately issues a cessation order. An operator must correct all violations in order to obtain permits for new mines. Lands Unsuitable For Mining Congress recognized that certain coal deposits cannot be mined without permanent damage to unique cultural or natural resources. As a result, SMCRA protects these resources in two ways: It prohibits mining within the boundaries of national parks, forests, wildlife refuges, trails, wild and scenic rivers, wilderness and recreation areas; in areas which will adversely affect sites listed on the National Register of Historic Places; and within a restricted distance of occupied dwellings, public roads, buildings, parks, schools, churches, and cemeteries; and Provides a process that allows anyone whose interests may be adversely affected by proposed mining to petition to have specific lands designated unsuitable for mining.

Jan 1, 1992

By R. S. Conti, C. D. Litton

This U.S. Bureau of Mines (USBM) report discusses the results of research conducted in the USBM experimental mine at its Lake Lynn Laboratory to determine the alarm times of smoke and carbon monoxide(CO) sensors, and a point type heat sensor (PTHS) to slowly developing coal-conveyor belt fires. The tests were conducted at air velocities of 0.44 and 0.97 m/s. The data clearly indicate that smoke sensors provide earlier warning of fire than 10 ppm CO sensors, and that 10 ppm CO sensors provide earlier warning than PTHS. A success rate of 1.0 (indicating detection of every test fire) was obtained for both smoke and CO sensors. For the PTHS, the success rate was 0.57 at the lower air velocity, decreasing to 0 at the higher air velocity. Data are also presented showing the sequence of fire events and detection events at the two air velocities as a function of time. Results show that early detection and warning of underground mine fires will improve the probability of miners’ escape.

Jan 1, 1995

By John P. Gooch

Data for the ternary phase diagram for the system 1,1,2,2-tetrabromoethane/water/2-propanol at 25° C have been measured. Experimental methods used are described, and the complete ternary phase diagram is presented. A simple example is given to review the use of the ternary diagram.

Jan 1, 1972

By H. H. Hill

"The wide publicity that is given to the discover; of new oil fields has led many people to believe that our supply of crude petroleum is practically in- exhaustible and that in order to keep pace with the demand for petroleum products, it is only necessary to drill a few more wells in some of the south-western states. It is not generally realized that, although many famous fields have been developed in Oklahoma, Kansas, Texas and Louisiana during the past few years, the production of crude oil in 1919 was not sufficient to meet the demand and it was necessary to import approximately 53,000,000 barrels from Mexico.Continued efforts are being made to recover a larger percentage of the oil underground by improvements in methods of drilling and in handling producing properties. Improvements are also being made in methods for handling the oil after it has reached the surface which will result in reducing losses through leakage and through evaporation. These methods for cutting down waste in production and storage, if universally adopted, will no doubt result in appreciable increases in our supply of crude oil."

Nov 1, 1920

By A. B. Hooker, L. C. IlsLey

The greatest hazard of early mining was from explosions of methane ignited by open lights . With the advent of safety lamps and forced ventilation this hazard was greatly reduced until the application of electricity to modern mining not only multiplied the sources of gas ignition but the accompanying , machines and haulage systems increased the amount of explosive dust , through which a methane explosion is more liable to become a major mine disaster , and thus greatly furthered the need of adequate ventilation to keep down the concentrations of methane . Adequate ventilation is still the best preventive of such explosions . However , even with a well laid out and controlled ventilating system the amount of air passing through entries and rooms is liable to vary within wide limits because of open doors , falls of rock , or other accidental causes . The percentages of methane under normal conditions should therefore be kept so small that they will not be increased to explosive proportions by short interruptions in ventilation . Mine ventilation and methane detection are inseparable safety precautions . The increasing importance of ventilation necessitates more accurato determinations of the methane concentrations throughout the mines . This paper discusses in detail some of the steps in the development of methane detection and specially notes the more accurate detectors now available . One of the earliest means of detecting methane was by a candle . About 1835 , John Buddle , Sr. , a noted mining man of his period , when questioned by a Parliamentary Committee as to the safety of using candles , replied :

Jun 1, 1933

By M. J. Ankeny

The expression "firing open, unconfined shots," as used in this circular, means the firing of explosive charges not confined in boreholes. Examples are the so-called mudcap shots, adobe or dobe shots, or bulldozing shots consisting of explosive charges placed on, under, or between rocks for the purpose of breaking them. The practice of firing open, unconfined shots is not uncommon in coal mines, despite the fact that numerous mine explosions and dust ignitions have resulted from this practice. The usual method of preparing such shots is to place the explosive with its detonator on top of a piece of rock or coal and cover it with clay, loam, sand, or road dust; frequently no covering of any kind is used. In some mines, an open charge of explosive is placed on timbers to dislodge them or in crevices in the roof to break down loose rock that cannot be dislodged with a bar or pick. The explosive charges may be made and fired singly, although sometimes several charges are placed on one large piece of rock with a detonator in each charge, and all charges are fired simultaneously. Although it is general practice to use permissible shot-firing devices, which will not ignite gas or dust to fire these charges, electric power from the regular mine circuits is sometimes used. When the shot is fired, any coal dust that may be present is thrown into suspension by the blast and may be ignited by the intense hot flame of the explosive or by an arc or spark at the leg wires or the end of the firing leads if power from the regular mine circuit is used to fire the shot. Even if there is not enough coal dust present to form a dust cloud, open, unconfined shots can readily ignite methane.

Jan 1, 1952

By D. Harrington

"Since its establishment in 1910 the Bureau of Mines has consistently recommended the rock-dusting of bituminous and lignitic coal mines as a preventive of widespread explosions. As with many other proposed innovations, the response to the bureau's recommendation has been slow; but during the past 10 years many coal mines have done some rock-dusting, even though probably fewer than 50 of the country's approximately 6,000 coal mines are thoroughly rock-dusted. Notwithstanding the inadequacy of the rock-dusting which has been done in most of the mines which have adopted the new system, numerous cases are at hand. indicating the well-founded basis of the bureau's claims regarding the effectiveness of rock-dust in stopping explosions. Very brief descriptions will be given of several cases in which explosions in coal mines of the United States are fairly definitely known to have been stopped by rock-dust during the past 5 or 6 years; in addition, several cases are cited in which explosions were stopped through the agency of rock-dust and moisture.A rock-dusted mine is one in which the floor, roof, and sides of every accessible working place, including haulage ways, airways, manways, and rooms and connections have an application of rock-dust - for instance, limestone - such that the incombustible content of the aggregate dust on those surfaces is over 60 per cent. The dust in these workings should be sampled at regular intervals to determine whether the incombustible matter in the coal-dust is less than the necessary minimum of 60 per cent; another application of rock-dust should be given when the incombustible percentage is less than 60. (As an example of thorough rock-dusting, see Bureau of Mines Information Circular 6578, 1932, which describes how rock-dusting is done in Alabama at a cost of 1.8 cents per ton of coal for a thorough application; Report of Investigations 3060, February, 1931, Rock-Dusting In A Pennsylvania Coal Mine; or Information Circular 6244, 1930, giving data, including costs, on rock-dusting in coal mines in New Mexico.)An explosion may be started by the ignition of gas, even when rock-dust is present; hence it is not correct to say that rock-dust will prevent an explosion of gas; however, if rock-dust has been applied to a working place which has present an explosive mixture of me-thane and air, and if an open light is used or a blown-out shot or an electric arc occurs, although there will very likely be an ignition and possibly an explosion, the rock-dust will certainly prevent ignition of the coal-dust nearby, and unless the general atmosphere has an explosive gas mixture, the rock-dust will stop propagation of the flame throughout the mine. In other words, if an explosion is started by gas or by coal-dust and the mine has been rock-dusted as defined, the rock-dust will prevent widespread extension of the explosion, unless the general atmosphere contains methane and air in explosive proportions.With these definitions clearly in mind, instances are now given where rock-dust has played a prominent part in the stopping of several explosions. No cases have been included where there was any reasonable doubt that rock-dust had taken a definite part in the limiting of the explosions."

Apr 1, 1932

To cost-effectively reduce noise and vibration in newly manufactured mantrip vehicles. Approach Previous Bureau of Mines research demonstrated that noise controls could be in-stalled on existing mantrip vehicles, thereby substantially lowering noise levels inside the mantrip. Under Bureau sponsorship, a manufacturer of mantrip vehicles agreed to incorporate similar noise controls into a new vehicle during manufacture. Throughout this project, durability, maintainability, and cost were considered to be as important as noise reduction. How It Works The following noise-control features were included in the new mantrip: (a) Suspension Isolation- The suspension components were isolated by inserting elastomeric materials between them and the vehicle frame.

Jan 1, 1982

To reduce operator exposure to drilling noise from roof bolting machines. Background Noise-induced hearing loss (NIHL) is a prevalent occupational illness in the United States. Studies indicate that 70%?90% of miners have NIHL significant enough to be classified as a hearing disability. Mine Safety and Health Administration studies indicated that roof bolting machine operators are among those overexposed to noise. Field studies support the premise that, on average, drilling is the loudest noise source to which a roof bolting machine operator is typically exposed and contributes greatly to the operator?s noise exposure. The National Institute for Occupational Safety and Health (NIOSH) has further determined that the drill steel and chuck radiate a significant amount of noise during drilling. To address this noise hazard, NIOSH developed a collapsible drill steel enclosure (CDSE) to encapsulate the drill steel during the drilling portion of the roof bolting machine duty cycle. In addition, NIOSH is collaborating with J. H. Fletcher & Co. in the continued development of a CDSE.

Sep 1, 2008

By R. V. Ramani, A. S. C. Owili-eger

The origin of gaseous hydrocarbons in coal, predominantly methane, can be traced to the natural processes of coalification. The higher rank coals or the more deeply buried seams retain more gas than low rank coals or shallow seams. It is estimated that up to 460,000 cubic feet of all types of gases are produced during the formation of one ton of coal (Cervik, 1969). The chief components of these gaseous products are methane, carbon dioxide, nitrogen and water vapor. Most of these gases escape during the various stages of decomposition but with eventual presence of overlying impermeable beds, there may be as much as 2,000 cubic feet of gas retained per ton of coal. Over geologic time, diffusion and other processes such as geologic disturbances in the earth's crust remove all but 500 to 2000 cubic feet of gas per ton of coal (Cervik, 1969). It is this residual methane which is of primary concern when mine openings are made in coal measures. Extensive data compiled by the United States Bureau of Mines reveal that some coal mines in this country emit up to 20 million cubic feet of methane per day (Spencer, 1970; Irani et al, 1972). Toxic, poisonous and respirable gaseous pollutants and explosive gases, predominantly methane, are injected into the ventilation stream from active sections and gobs. The liberation of methane in gob areas may, under certain circumstances, become extremely large. In some instances it may constitute up to 70 percent of the total yield of gas in a mine. The basic physical factor which determines the yield of gas into the mine environment is the gas content of the seam. The influence of the gas content of a seam on the overall yield of gas

Jan 1, 1974

By Steven J. Page

Overexposure to airborne respirable crystalline silica dust can cause disabling or fatal respiratory disease, and mine worker exposure to silica dust continues to be an ongoing occupational health concern. Exposures of surface coal mine rock drillers to respirable crystalline silica are of particular concern. On surface coal mine drills, bailing air flushes the cuttings out of the drill hole. Conveyor belting material is typically used to fabricate a shroud around the drill deck in an effort to contain the drill dust so that it can be captured by a collector. Dust leakage from the drill shroud is usually the worst dust source problem on most drills. The focus of this work is drill shroud dust leakage and the relationships of various drill parameters on this leakage. Experimental data were obtained and used in combination with dimensional analysis to establish these relationships. In general, it is found that airborne respirable dust (ARD) concentrations vary in a direct relationship with shroud leakage area and in an inverse relationship with drill deck cross sectional area and shroud height. This work expands the testing and dimensional analysis previously reported for collector/bailing air flow ratios ranging from 2:1 to 4:1 to include ratios approaching 1:1. A semi empirical mathematical model has been developed and expanded to describe ARD generation on surface coal mine drills. Geometric parameters included are drill deck height and cross sectional area, shroud leakage associated with the deck shroud, and the operational parameters of bailing airflow and dust collector airflow. The relationships can be described by logarithmic functions and yield predictive ARD values, which fall in the range measured on operating drills for collector/bailing air flow ratios greater than 2. However, at values of collector/bailing air flow ratios of approximately 1.1, the amount of ARD shows minimal response, if any, to drill deck shroud improvements that do not result in near perfect seals. This is a condition that can occur in actual operation and is a substantially different result than previously expected and reported. Application of these results should provide mine operators with sufficient information to determine (1) the relative magnitude of their dust emissions, (2) where they should focus their efforts to reduce ARD emissions and (3) the improvement they could reasonably expect to achieve. Given that exposures of surface coal mine rock drillers to respirable crystalline silica are of particular concern, substantial reductions of airborne silica dust during drilling may be estimated and achieved through use of the analysis presented. Keywords: drill; dust; model; dimensional analysis

Jan 1, 2008

By Paul M. Tyler

The alkali metals , sodium and potassium , and more particularly sodium , occur abundantly in chemical combination with other elements . The elements themselves are available in metallic form but are so active chemically that they oxidize rapidly in contact merely with the air . Potassium will even catch fire spontaneously in air , and both the metals will decompose water with explosive violence . Inasmuch as they are almost as soft as wax they are not suitable for the structural or other mechanical uses characteristic of ordinary metals , and consequently the uses of these elements even in the metallic condition are based upon chemical rather than physical qualities . Sodium metal is used largely as a commercial reducing agent , but potassium metal is rarely found outside of chemical laboratories . Numerous salts and other compounds of these elements enter largely into world trade and are commercially very important , but none of these compounds except sodium peroxide and sodium cyanide are made economically from the metals . Sodium is generally considered as rather an uncommon metal , but in point of annual tonnage produced it is far more important than mercury , magnesium , molybdenum , bismuth, cadmium, cobalt , gold , silver , or the various rarer metals .

Apr 1, 1932

Modify conventional mining practices to reduce significantly the amount of material brought to the surface from underground mines, or to ?re-mine? existing surface mine dumps by backfilling empty underground stopes.

Jan 1, 1994

The Bureau of Mines Minerals Information organization collects worldwide data on virtually every commercially important nonfuel mineral commodity. These data form the base for tracking and assessing the health of the minerals sector of the U.S. economy. This data collection activity was instituted by the 47th Congress in an appropriations act of August 7. 1882 (22 Stat. 329), to place the collection of mineral statistics on an annual basis. The most recent authority for the Bureau of Mines Minerals Information activity is the National Materials and Minerals Policy, Research and Development Act of 1980 (Public Law 96-479, 96th Congress), which strengthens protection for proprietary data provided to the U.S. Department of the Interior by persons or firms engaged in any phase of mineral or mineral-material production or consumption.

Jan 1, 1985