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Improve the safety and reduce the cost of longwall entry support. Approach Replace the conventional wood cribbing with stronger, non-rotting and lower cost cribbing made of steel-fiber-reinforced (SFR) concrete. How It Works Conventional concrete can suddenly fail under excessive compression loads, but adding steel fibers to the concrete, before it is mixed with water, changes the failure mode to a gradual and controlled failure characteristic similar to wood. A system for making SFR concrete crib blocks was designed and developed (or use in constructing walls and cribs to support coal mine roofs. The SFR concrete cribbing is stronger and stiffer than wood, and avoids wood's disadvantages of: flammability, deterioration under chemical or bacteriological attack, methane generation, and relatively high cost. Use of SFR concrete also allows freer movement of miners, equipment, and ventilation air, because much less volume of SFR concrete is required than wood for a given amount of support, and because the roof-to-floor closure is greatly reduced by the stiffer supports.

Jan 1, 1981

By Anthony Iannacchione

One of the more pressing engineering problems for deep longwall mines in the Southern Appalachian Basin is to design longwall systems that will eliminate catastrophic coal pillar failure from the working environment. The purpose of this study is to quantify the behavior of a particular size abutment pillar prone to burst or bump. Because the 24.4-111 (80-ft) square abutment study pillar is within the pillar size commonly used in this region, understanding the behavior of this pillar should aid in future efforts to design optimum mining strategies. This research has attempted to construct the pillar stress and roof-to-floor convergence profiles in order to evaluate the ultimate strength, deformation modulus, visco-elastic deformation, and violent failure characteristics of the pillar during longwall mining. This information reflects the overriding influence of the local geologic characteristics on bursts, provides the field measurements needed to verify concurrent modeling studies, and suggest some basic mechanisms associated with the coal pillar bursts discussed in this paper.

By R. W. Nash

This report describes the design and operation of a digital instrumentation package for the Bureau of Mines improved torsion pendulum, a scientific instrument that measures the vibration damping of metallic materials. The new design eliminates manual analog-to-digital conversion, reduces the data acquisition time, and increases the precision of the measurements. The digital output can be coupled directly to a micro-processor or computer to produce the final data in real time.

Jan 1, 1983

By Daniel C. Boteler

Data from 68 entrained-bed carbonization tests were treated statistically by the Bureau of Mines, and several useful relationships were developed among the major variables. Nine coals, ranging in rank from lignite A to high-volatile A bituminous, were carbonized in two entrained-bed carbonization pilot plants. The carbonizing reactors employed were vertically mounted cylinders, internally heated, refractory-lined, and 10 inches ID. The range of carbonization temperatures was from 825° to 1,600° F. Using a regression-analysis computer program, empirical equations were developed by which carbonization temperature, air-to-coal ratio, devolatilization of coal, char yield, and volatile matter content of product char may be predicted.

Jan 1, 1973

By George J. Conroy

Techniques for locating trailing-cable faults are discussed, particularly those techniques suitable for use in underground coal mines, which have been the subjects of Bureau of Mines research. The discussion concerns precautions and suggestions for locating faults, rather than detailed descriptions of apparatus.

Jan 1, 1979

By S. H. Katz, J. J. Bloomfield

Fires in zinc dust have sometimes given particular trouble owing to their resistance to extinguishers and the liability of explosions . Similar problems , notably with aluminum dust* , have previously been subjects of investigation by the Bureau of Mines .

Mar 1, 1922

Use instantaneous sampling to pinpoint dust sources and to Improve dust control on longwalls. Approach Use a dust monitor developed under a Bureau contract. How It Works Sampling can be done by either a moving or a stationary method. In the "moving' method, the dust monitor is carried by a survey engineer walking at the midpoint of the shearer Dust levels and face position (support number) are taken during all phases of the mining cycle while the shearer is cutting. These measurements can show how changes in airflow along the face, face specific; (rock partings) and cutting sequence (cutting the wedge) variables affect dust levels. In the "stationary sampling" method, the survey engineer stands with the RAM at a fixed location on the face. As the shearer approaches, the dust level and the distance to the shearer are recorded at 10-second intervals. Typically measurements start when the shearer is 20 feet from the sampling position and continue as the shearer passes the position until it is 20 feet away on the other side. Dust profiles around the machine are obtained at several fixed locations along the face only while the shearer is cutting.

Jan 1, 1982

By J. J. Cummins

Green River oil shale previously extracted by benzene was heated at 150°, 200°, 250°, 300°, and 350° C for 0.5 to 360 days to determine the rate at which kerogen degrades to thermal products, the types of thermal products formed, and the effect of prolonged low-temperature heating (preheating) upon subsequent assay yields. Thermal decomposition of kerogen at 150° to 350° C is treated as a first-order reaction. The specific reaction rate for kerogen decomposition increases from 2.2 X 10-4 per day at 150° C to 2.0 X 10-1 per day at 350° C. The calculated kerogen activation energy is 19 kcal. Variations in the rate of formation of individual type components of the pyrolytic products were found. Carbon balances show an increase in the amount of kerogen converted to bitumen and oil (from assay of preheated oil shale) as the temperature of preheating increased from 150° to 350° C. Total product from shale preheated at temperatures of 150° and 200° C gave less than 100 percent of Fischer assay yields while the total products from shale preheated at temperatures of 250° to 350° C gave greater than 100 percent of Fischer assay yields.

Jan 1, 1972

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

B 4 Description of Subroutines There are thirteen subroutines in the program: PROGIO HOIST MINER SMOKE STENCH MSMOK

Jan 1, 1976

By M. K. Larson, J. K. Whyatt, R. B. Langston, J. C. Johnson, H. Kirsten, T. M. Brady

An experiment is described in which hollow inclusion cells (HICells) were used to measure stress in a jointed rock mass during drift development at the Stillwater Mine, Nye, MT, USA. Two HICells were installed in the footwall approximately two drift widths ahead of the face. One HICell was over cored and then immediately tested in a biaxial chamber. The other HICell was left in place and monitored as the drift was excavated in three advances, each one-half the width of the drift. Strains were recorded hourly by a datalogger. Results show that there was little stress change during the first and second drift advances, but that a large stress change occurred after the third advance. The measurements also showed that the in situ principal stress directions lined up with regional geologic structures. Stress changes during face advance were likely caused by deformation along localized joint sets and inelastic deformation near the face.

Design a high-production coal mining machine with inherent low dust generation and low frictional ignition potential. Approach Constant depth linear cutting (CDLC) provides a longterm solution to excessive dust generation from shearers and continuous mining machines through new design of the rotary drum culling system. Problems with rotary drum systems, which must be eliminated to control the dust generation at the source, include the effect of a con¬stantly varying depth of cut using fixed bit spacing, secondary fragmentation of already broken coal and, frictional heating of bits and entrainment of dust by fanning action due to high drum rotational speed, Each bit on a rotary drum enters the coal face at zero depth of cut, goes to some maximum depth at the horizontal centerline during sump, and exits at zero depth.

Jan 1, 1989

In the past, mine management has been concerned with removing water from active mining sections primarily because it hampered the movement of mining equipment and aggravated the working condition of the miners. Pumping water to sumps and gravity drainage by ditching have proven successful in mines for minimizing section down time due to water influx. However, with the advent of more strict pollution laws the mining engineer must now be concerned with keeping water out of the section and also with preventing it from causing pollution. A review of the handbooks and textbooks used in the mining engineering curricula reveals that little has been written concerning acid mine water prevention or control in underground coal mines. Additionally, the review of the curricula of mining schools indicates they are not teaching the engineering students the necessary techniques of mine water management as they relate to the abatement of mine water pollution.

Jan 1, 1970

Design, fabricate, and test a machine capable of operating in coal seams 48-inches and thicker that can reduce the time, expense, and injury potential inherent in extending and retracting mine-wide section belt conveyors, while eliminating the need to use additional machinery or equipment in accomplishing such moves. The Problem Many underground coal mines use a belt haulage system to move cut coal from the face to the loading area. This system usually consists of a main line belt conveyor fed by section belt conveyors. A shuttle car at the face carries the coal cut by a continuous mining machine to a feeder breaker that breaks the large lumps of coal into smaller, transport-able pieces and unloads them onto the tail piece of the section conveyor. This tail piece is skid-mounted so it can be readily moved as needed. The conveyor is kept close to the face during mining in order to shorten the haul distance of the shuttle cars. Section belts can be lengthened by adding belting, wire rope, and support hard-ware. During pillar retreat mining, these section belts are shortened to keep pace with pillar extraction operations. However, these belt moves, either the extensions or retractions, usually require six to eight workers and three to eight hours to complete. In addition, a 100-foot belt move requires workers to handle up to 4,000 lbs. of material, not including the tail section. Strain and sprain injuries can be incurred during this heavily labor-intensive task. The time required to move the section belt can also create losses in the mine's production. To help solve this problem, the Bureau of Mines

Jan 1, 1984

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

5. General Escapeway Requirements 5.1 Escape Routes Present escapeway regulations state "Every mine shall have two separate properly maintained escapeways to the surface which are so positioned that damage to one shall not lessen the effectiveness of the other, or a method of refuge shall be provided when only one opening to the surface is possible." "Escape routes shall be a. Inspected at regular intervals and maintained in safe, travellable condition, b. Marked with conspicuous and easily read direction signs that clearly indicate the ways of escape." "Application. "Regular" intervals means at intervals no greater than monthly where conditions are stable and oftener where conditions may change." "Designated escapeways inclined more than 30* from the horizontal shall be equipped with stairways, ladders, cleated walkways, or emergency hoisting facilities." As can be noted in present and proposed regulations there must be two separate properly maintained escapeways. In most operations, the escapeways will consist of one route that is the normal travelway used in day to day operations. The second route is usually a return airway through old work areas. Based on this generally accepted practice, we will designate the two types as primary and secondary.

Jan 1, 1976

By E. E. Remmenga

Often a collection of analytical data, which should reasonably be expected to follow the normal distribution, contains too many extreme values, which the experimenter is inclined to eliminate according to some arbitrary procedure. The stepwise computer procedure described for this purpose is similar to many other truncation procedures; however, because truncation of a basically normal distribution causes a downward bias in the estimated variance, this procedure provides a graphical method to compensate for the bias.

Jan 1, 1971

Improve the efficiency of stainless steel pickling (chemically cleaning) operations by providing the industry a quick and convenient method to estimate pickling solution behavior and to estimate recommended ranges of nitric and hydrofluoric acid concentrations for effective pickling of stainless steels. Background Iron, chromium, and nickel in stainless steels react with nitric and hydrofluoric acids during pickling. Ions of these dissolved metals complex or combine with the acid anions. When the total metal concentration reaches about, 50 grams per liter of pickling solution, the solution no longer serves its purpose and is considered spent. Knowledge of cation and anion species in these pickling solutions contributes an insight into pickling chemistry and allows estimates to be made of the most effective ranges of acid concentrations. The Bureau developed a computational model of the complex equilibrium chemistry occurring among iron, chromium, and nickel and the pickling solution. Total concentrations, in grams per liter, of nitrate, fluoride, iron, chromium, and nickel were used as input; output was 17 cation and anion molar concentrations. The model, in the form (if an equilibrium program on a mainframe computer, was used extensively to facilitate Bureau research by determining chemical complexes in numerous stainless steel pickling solutions. However, the program's availability to members of the stainless steel industry, its intended users, was limited because of lack of mainframe compatibility and the difficulty of program maintenance.

Jan 1, 1989

By Fred N. Kissell, R. J. Bielicki

In this report the importance of diffusion in controlling the emission of methane in mines is examined. An in-situ diffusion parameter is defined and calculated for a hypothetical unfractured lump of coal in the Pittsburgh and Pocahontas No. 3 coalbeds. The values obtained are similar to those obtained with lump coal in laboratory experiments.

Jan 1, 1972

Analyze variably saturated flow in mining and other environmentally sensitive settings through the use of personal computer (PC) based software. The Problem There is an increasing need for mining companies to quantify water contaminants and their migration in the unsaturated zone. New and innovative computer models are therefore necessary to more accurately assess the potential impact of mining activities on groundwater resources and the environment. Applications for unsaturated flow modeling include (1) assessment of the impact of surface or underground extraction mining on flow conditions; (2) assessment of various hydrologic designs for resource recovery, such as in heap leaching or in situ leach mining; (3) assessment of the transport of conservative nonrcactive constituents in response to migration from spoil piles, or acid mine drainage; and (4) assessment of any combination of the above to facilitate expeditious permitting for mining operations. Since the mid 1970's there has been a proliferation of mathematical models and procedures for solving unsaturated now problems; however, few of these approaches have been integrated into software for public use. Commercially available unsaturated flow software models typically are limited to a single application and have restricted approaches. For example, computer codes that solve the unsaturated flow problem based on an analytic expression arc restricted to a simple geometric shape, homogeneous and isotropic materials, and provide only information regarding pressure and flow conditions in specified wells. The variably saturated computer codes that take advantage of the finite difference or finite element approach arc often restricted to either steady state or transient solutions; utilize one specific moisture-retention relationship and moisture-dependent permeability function; do not account for hysteresis; and are used with specific hardware such as a mainframe or work station. This restricts their use because they arc hard to interface, and arc often poorly documented, support dependent, and expensive. The mining community needs a flexible, more broadly based, variably saturated fluid flow simulator for the PC-platform to more accurately predict fluid movement in the mining environment.

Jan 1, 1991

By Ronald D. Hill, Elmore C. Grim

The removal of overburden often exposes pyritic materials (iron disulfide). As shown in equations 1 and 2, the oxidation of this material results in the production of ferrous iron and sulfuric acid. The reaction then proceeds to form ferric hydroxide and more acid, as shown in equations 2 and 4. [ ] Consequently a low pH water is produced (pH 2-4.5). At these pH levels, the heavy metals such as iron, manganese, copper, and zinc are more soluble and enter into the solution to further pollute the water. Water of this type supports only limited water flora, such as acid-tolerant molds and algae; it will not support fish life, destroys and corrodes metal piers, culverts, barges, etc., increases the cost of water treatment for power plants and municipal water supplies, and leaves the water unacceptable for recreational uses. The amount, and rate of acid formation, and the quality of water discharged are a function of the amount and type of pyrite in the overburden and coal, time of exposure, characteristics of the overburden, and amount of available water(l). Crystalline forms of pyritic material are less subject to weathering and oxidation than amorphic forms. Since oxidation by oxygen is the primary reaction during early acid formation, the less time pyritic material is exposed to air, the less acid is formed. Thus, a positive preventative method is to cover pyritic materials as soon as possible with earth, which serves as an oxygen barrier. In terms of mining, this step is accomplished by current reclamation techniques and small open pits.

Jan 1, 1974

By D. R. Tesarik, M. K. Larson, J. P. Dunford, E. G. Zahl

Western coal mines are operating under increasingly challenging ground conditions. Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health are cooperating with mines to evaluate how these conditions affect mine opening stability and related miner safety. A system was developed to monitor rock and coal stresses during mining of an entire longwall panel. The system was designed to generate data in near real time to evaluate rock behavior in roof strata and the onset of hazardous conditions as overburden stress was redistributed over working entries during gob formation. Computer simulations and in-mine evaluations were used to optimize instrument placement. A prototype packer assembly was designed and tested for installing sensitive instruments in a mine roof. This paper provides background information on the stress monitoring concept and focuses on the development of instrument placement techniques and the prototype packer assembly.