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By John C. LaScola

The Bureau of Mines repeatedly surveyed a grid of monuments over an active longwall mine panel in southwestern Pennsylvania during a 1-year period. Both conventional ground surveying techniques and photogrammetry were used. The objective of this investigation was to compare elevation measurements of subsidence obtained from aerial and ground survey methods under dynamic ground conditions. The results of a statistical analysis of the survey data show that the mean of the differences between 372 matched pairs of elevation measurements was 0.20 ft (61 mm) with a 95-pct-confidence interval of 0.05 ft (15 mm). The mean of the absolute values of the differences was 0.38 ft (116 mm) with a 95-pct-con-fidence interval of 0.04 ft (12 mm). Ninety-five percent of the absolute values of the differences were less than 1.11 ft (338 mm).

Jan 1, 1988

By Gerrit V. R. Goodman, Charles D. Taylor, Edward D. Thimons

Future coal mining systems will be able to cut from crosscut to crosscut where advances could exceed 100 ft. However, limitations arise when ventilating such mining systems. In deep advance mining, there would be no workers at the face to advance ventilation tubing or curtain manually. Traditional methods also provide no means for maintaining face ventilation after the miner backs away from the face. U.S. Bureau of Mines research is studying means to provide effective ventilation at cut depths beyond the current limit of 40 ft. Several innovative ventilation schemes are currently being considered. One such method is the use of a jet fan to ventilate a deep cut. A jet fan is simply a freestanding fan using little or no ducting to direct the ventilation flow. Jet fan testing in a 90-ft entry revealed that higher exit velocities and greater penetration depth occurred when various configurations were used to confine and direct the air flow. Additional testing also indicated that 2,200 cfm of fresh air was delivered to the face 90 ft distant when a check curtain was used to limit entrainment around the fan. Without this curtain, this quantity dropped to only 1,000 cfm This testing indicated that a jet fan was capable of providing ventilation to a distant face area. It also highlighted potential problems, such as recirculation at the fan and reentrainment in the jet flow. Despite these potential problems, jet fans may be adequate for ventilating cuts exceeding 40 ft.

Jan 1, 1992

By Lewis V. Wade

This Bureau of Mines work was performed to theoretically determine the effects of specimen radius and specimen boundary conditions on the stress state in the rock near the anchor for rock specimens used to investigate expansion anchor behavior. Finite element analyses were performed on mathematical models of varying radius and boundary conditions. A review of the results of these analyses revealed a definite convergence of all stress measures considered as the specimen radius increased. There was, however, a significant variation in all stress measures as the specimen diameter increased from 8 to 12 inches.

Jan 1, 1973

By Walter W. Fisher

A kinetic investigation of copper cementation in a revolving drum was undertaken by the Bureau of Mines to explore the effects of a porous copper deposit attached to the iron surface and a fluidized slurry of copper particles surrounding the iron precipitant. The rate of cementation was found to be significantly enhanced by the increased cathodic areas provided by a porous copper deposit or the presence of a fluidized bed of copper particles contacting the iron precipitant. The cementation rate was found to be retarded by increased ionic strength, low pH, and the presence of oxygen. The cementation reaction was first order with respect to precipitant surface area. Copper cementation on iron is visualized to occur by two basic mechanisms. Precipitation may occur through a series of shorted electrochemical cells, whereby cupric ion precipitates on a growing cathodic copper deposit, or, deposition may occur via a fluidized cathode of copper particles contacting the ion precipitant.

Jan 1, 1976

Develop an inexpensive, reliable means of quickly detecting and locating trapped miners in underground coal mines, particularly after a mine accident. The Limitations Although the Bureau of Mines has performed extensive research on the use of electromagnetics for locating trapped miners, much of its research trends toward the development of long-range systems designed to locate an underground transmitter from the surface. Such location systems are beneficial; however, there are several limitations regarding their use. Two limitations are weight and cost of the equipment. Most long-range detection systems would be too heavy and cumbersome to be accepted by miners as part of their daily protective equipment. Since such long-range detection systems are usually expensive, it would not be economically feasible for every miner to be provided with a system.

Jan 1, 1984

By Stephen C. Tadolini, Thomas M. Barczak

Roof support systems, longwall shields in particular, have persistently grown in size and capacity for the past 25 years. Why is this? Is it a good thing or is it unnecessary? What are the consequences of this “bigger-the-better” design philosophy? Rarely do we see a “one size fits all” approach to roof support except when it comes to longwall shields, where the historical trend for new procurements is to simply purchase the highest capacity support you can buy. Does high capacity ensure failures will not occur? The answer is no! The highest capacity tailgate supports are typically the ones that fail the most often. What does this tell us? It tells us that there are fundamental aspects of support design and ground control that we still do not understand or recognize when designing a support system. This paper provides an interesting evaluation of these issues and proposes a different approach to support design that attempts to match the support performance characteristics to the ground behavior. Along the way, some of the old premises of support design will be discarded, and new “controversial” ideas developed. Thinking outside the box never hurt any industry. Mining has made it a common practice.

By A. J. Rambosek

An evaluation of diamond-bit performance data accumulated from core drilling in quartzite shows that core recovery and physical characteristics of drill bits and diamonds have economic significance. Relatively inexpensive, low-quality, small Congo diamonds will perform as well as, or better than, other diamonds used as drill bart. M-type bits set with oriented Congo diamonds provide those engaged in core drilling with near optimum combination. Various factors that affect bit performance, including size of diamonds, size and type of bits, grade or quality of diamonds, and percentage of core recovered, are evaluated by means of tables, charts, and discussion.

Jan 1, 1958

Develop a method of dewatering ultrafine mineral waste that will increase water recovery from the waste and produce a dewatered material that eliminates the need for large settling ponds. Background In the hydrometallurgical treatment of many ores and concentrates to recover mineral values, slurries of fine particles are generated. Some of these slurries settle slowly and are difficult to dewater. This inherent property causes environmental and handling problems for the minerals industry. Examples of such problem wastes are clay wastes generated during the mining and beneficiation of phosphate ores, the processing of coal to produce a low-ash material, the cleaning of bentonite, beneficiation of potash, and the recovery of mica from clay-containing ores. At the present time these waste slurries are treated by techniques such as impoundment, thickening, and thickening followed by filtration. But factors such as new environmental regulations, the loss of mineral values in the waste slurries, the need to recycle water in the processing facility, and the lack of land suitable for impounding the waste have shown that new technology will be needed in the future to handle waste slurries.

Jan 1, 1986

By J. C. Edwards

The Bureau of Mines developed a mathematical model that decribes the interaction of an automated breathing and metabolic simulator, or lung, with a self-contained· self-rescuer that is supplied compressed oxygen. The model can be used to predict the gas partial volumes of 0z, Nz, and COz in the lung and in the self-rescuer breathing bag for a prescribed metabolic state that characterizes the lung. Nonlinear rate equations are used to describe the temporal evolution of the gas partial volumes. A numerical procedure was established with a FORTRAN computer program to solve these equations, which correspond to a given metabolic state. Examples are presented of applications of the model to predict bag volume and bag oxygen concentration changes with time when the bag is controlled by an automated breathing simulator. Under certain restrictive conditions, the model equations can also be used to analytically pre-dict the time required for the bag to reach a maximum or minimum volume. The model equation in this latter case was extended to transi-tions between metabolic states, with transitions described as exponential growth or decay processes.

Jan 1, 1985

Improve the effectiveness of person-wearable self-contained self rescuer (PWSCSR) training by enhancing the memory retention of trainees in proper donning procedures. Background In the fall of 1989, a total of 185 miners and inspectors were trained by Bureau of Mines personnel to don the SR-100 PWSCSR using the Bureau's 3+3 method. With the exception of a few individuals, miners were trained underground in an area set up within their working sections. The instructional protocol was as follows: (1) after placing an SR-100 simulator (equipped with a cleaned and disinfected mouthpiece assembly) on the mine floor in front of the worker, a researcher guided him or her step-by-step through the complete donning procedure, (2) the miner was required to perform each step slowly, methodically, and correctly while being talked through the sequence, (3) following this pre-practice instruction, the apparatus was repacked and the subject donned the device without coaching, while being evaluated, (4) if an error was made, the worker received corrective feedback, the unit was repacked, and the entire donning trial was redone. This procedure was repeated until the miner achieved a perfect 3+3 sequence.

Jan 1, 1990

By Thys B. Johnson

A three-dimensional dynamic programing method is presented for determining the optimal ultimate open pit limit. The method given is based on the block concept and is an extention of the two-dimensional Lerchs-Grossmann approach. The three-dimensional technique presented herein is fast and simple and may be used for an initial open pit evaluation when only limited data are available or as a more refined model when the entire deposit is well delineated. The method is illustrated by simple numerical examples and is also presented in algorithmic form. A computer program was written in Fortran IV which implements the three-dimensional algorithm and some computational aspects are discussed.

Jan 1, 1971

By Carlton E. Brown

In 1935 , Brown and Yant / described a microprojector ( microscopic arrangement for projecting images on a screen ) for use in counting and measuring the size of dust particles in Owens - jet dust - counter and simila dry samples of dust collected from the air . In 1938 Brown and others , described a modification of this microprojector that could be used also in counting dust in impinger samples . Microprojectors of this second type have been set up by many mining companies and others and have been made commercially available . Hamly and Pullen5/ described a modification of this microprojector for use in making rapid comparative estimates on konimeter samples and other determinations . This report contains information on still another modification named the "midget microprojector " because of its small size .

Sep 1, 1944

By H. S. Chiang, S. S. Peng

"SummaryAir velocity distribution surveys on four mechanized longwall faces are presented and discussed. Although there are discernible patterns in the velocity distribution, there are wide differences in distribution in the cases examined. This can be attributed to differences in mining and face geometry. An important factor is air leakage into the goaf.IntroductionOver the past two years several intensive air velocity surveys have been carried out in West Virginia coal mines as part of a programme aimed at understanding dust transport mechanisms on mechanized longwall faces. These are presented here and some of the patterns of velocity distribution are discussed.Ventilation survey methodologyThe air velocity vector consists of three mutually perpendicular subvectors; the vertical subvector is directed toward the roof, one of the horizontal subvectors is parallel to the coal face and the other pointing to the gob. The air velocity which was measured in this paper is the horizontal subvector parallel to the coal face.To record the velocity distributions at the longwall faces, the surveying stations and the surveying points were established as follows.(1) The first station usually was set at the third support from the headentry T-junction. Within the first few supports, the air coming from the intake airway encounters a sharp right-angle turn at the T-junction, and forms a turbulent region close to the coal face. The intake air in this region is also influenced by the motors that drive the face conveyer. But when the air reaches the different. But for the same face the number was the same. The main air-travelling area was divided into six to 12 equally sized sub-areas, and each surveying point was situated approximately at the centre of the sub-area.The velocity survey was carried out by two persons, one reading the meter and the other taking down the readings. A complete survey at one station took about 5-8 min. Usually, the dimension of the cross-sectional area was measured during that time.A third person used the smoke tubes to observe the following: (I) the air movement patterns at different locations; (2) the extent and the direction of the air leakage; and (3) the machines' influence on the main airflow. At the same time he observed and recorded the roof conditions and the compactness of the roof-caving in the gob."

Mar 1, 1989

By Stephen C. Tadolini, Thomas M. Barczak

Western mines have had limited choices for standing support. Wood cribs were often too soft and unstable. The introduction of the Can support in the early 1990’s provided a very effective alternative and remains the dominant form of tailgate support. Water-filled prestressing cells are now used to cap the Can and preload it to provide an active roof load. The Cluster Prop, consisting of three timber wedge props bundled together, provides more capacity than an equivalent sized Can support and improves transport efficiency. However, the Cluster Prop is less stable and does not maintain a consistent load throughout its loading profile. Pumpable roof supports are another alternative support, but they have not been proven in high deformation environments. Alternative supports are also being used in longwall recovery operations. These include the Rocprop and Omni Prop, which are extendable support systems. They also provide active roof loading which can be beneficial in these applications. Specialty supports, such as the Sand Prop and Spider Prop, have also been introduced into western longwall operations. This paper compares the performance characteristics of these various support systems.

By Richard J. Bielicki

Poor mixing of methane and air at coal mine working faces causes fluctuating methane concentrations. If these fluctuations are large enough, methane levels can periodically exceed safe limits, even though the time average methane concentration may be satisfactory. Concentration fluctuations measured underground can result both from variations in methane emission rate and poor mixing. The present paper reports on a statistical analysis of fluctuations at a constant methane emission rate, that is, on fluctuations due only to poor mixing. A full-scale model of a working face was used. Both peak heights and elapsed times between peaks were evaluated. Good mixing was indicated by normal, Poisson, and exponential distributions while poor or incomplete mixing was indicated by log-normal or gamma distributions.

Jan 1, 1974

By Janet Torma-Krajewski, Pauline Lewis, Paul Gust, Lisa Steiner, Kean Johnson

Since 1990 and the publication of the Ergonomics Program Management Guidelines for Meatpacking Plants by the US Occupational Safety and Health Administration, numerous reports of companies implementing ergonomics program have been published. However, despite these numerous reports, no examples of implementing an ergonomics program in the mining industry have been reported. In 2000, NIOSH initiated a long-term project to demonstrate the implementation of an ergonomics process designed to identify and reduce exposures to ergonomic risk factors found in mining. The mine selected for this project was the Jim Bridger Mine, a surface coal mine located 35 miles northeast of Rock Springs, Sweetwater County, WY. This paper discusses how a large, surface coal mine implemented an ergonomics program and the lessons learned while doing so.

Generate less respirable dust during mining by reducing the clogging and downtime of the water sprays on mining machines, especially on continuous miners. Approach An improved filtering system, having commercially available components, has been designed and tested. How It Works The improved filtering system shown opposite is mounted on the mining machine, where It traps particles of coal and pipe scale which cause most clogging of the water sprays. Water entering the system first flows through a ?Y" strainer, which screens out particles larger than 1/8 inch diameter. Next, the water whirls through a small hydrocyclone. Most of the remaining smaller particles are removed and pass Into the accumulator compartment built into the hydrocyclone. The water also flows through a final filter. This filter catches particles that might pass the hydrocyclone, especially during water spray start-up and shut-down, when the speed of the water flow is not sufficient for

Jan 1, 1976

By C. M. Mason

Mechanical mining produces large quantities of very fine coal dust called float dust. The associated increase in hazard requires a reexamination of the Bureau of Mines method of evaluating the incendivity of explosives in coal dust-gas-air mixtures. A technique recently developed by Bureau of Mines laboratories for evaluating the incendivity of explosives in coal dust-air mixtures was applied, with modifications, to coal dust-air-natural gas mixtures. A series of permissible explosives were evaluated by this modified technique. Results indicate that the modified technique could be the basis of a more discriminatory procedure than that presently in use.

Jan 1, 1968

By J. H. Perry, Joseph Cervik, G. N. Aul

The Bureau of Mines is conducting research to determine the effectiveness of long holes in degasifying an area of the Upper Split of the Lower Sunnyside coalbed at Kaiser Steel CO.'s Sunnyside No. 1 mine. These holes were drilled from the two outside entries of a section that was closed to mining because of excessive methane emissions. Two holes drilled to 430 and 450 feet produced initial gas flows of 160,000 and 127,000 cfd, respectively. Sixteen days after the completion of the second hole, the total gas production declined to just over 144,000 cfd. In 9 months of degasification, over 35 MMcf of commercial-quality gas has been removed from the coalbed. The combined gas flows declined to 106,000 cfd in the 9-month period. The two holes have reduced face emissions by about 40 pct.

Jan 1, 1978

By J. G. Walters

The method for predicting coke strength developed at Steinkohlenberg-bauverein, Germany, in which experimental parameters are readily determined by small-scale laboratory tests, was found to be applicable to cokes produced from industrially used blends of American coals. Predicted 1-inch ASTM tumbler indices for four industrial blends were found to be in excellent agreement with the experimentally determined values. The laboratory determined prediction parameters include the proximate analysis of the coal the size consist of the coal, and Ruhr dilatometer test data.

Jan 1, 1971