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By W. Blake, J. Whyatt

Sixty years of rockbursting in the Coeur d’Alene district has taught painful lessons and led to a number of practical advances in controlling rockburst hazards. This paper summarizes those lessons, concentrating on practical measures that have been successfully adopted to reduce hazards. These lessons are explained in the context of district mining history and current understanding of rockburst phenomena. Overall, the paper provides the practicing mine engineer with an appreciation of rockburst hazards and an overview of practical measures that can be used to control these hazards in the context of Coeur d’Alene district experience.

Measure tattling in cemented backfill when installation of bore-hole extensometers is not feasible. Problem To evaluate the amount of load that backfill carries during pillar recovery, information about how much the backfill settles after placement is often required. However, the composition of some backfills makes them difficult to drill and the installation of borehole extensometers almost impossible. Approach Bureau researchers have developed a vertical fill extensometer that can be cast in place as a stope is being filled. It consists of a baseplate, sections of steel pipe enclosed in loosely coupled polyvinyl chloride (PVC) pipe, and a top anchor assembly that contains a displacement transducer (fig. 1).

Jan 1, 1990

By George D. Dub, FREDERICK G. MOSES

The Bureau of Mines, in connection with the investigations of war minerals it conducted, examined the graphite deposits of this country, studied the methods of mining and preparation used, and sought to devise more efficient methods for the preparation of do- mestic graphite, and to standardize the quality of the product. The graphite investigations covered three general phases, as follows: 1. An examination of the deposits in Alabama and other States, and a survey of the methods of mining and preparation used. In this connection methods of sampling and analysis were noted and ex- periments made to determine a standard method of sampling and a rapid but accurate method of analysis. 2. Experimental work on the concentration and refining of domes- tic crucible graphite to improve the quality of the product and to lessen waste. 3. Experimental work in crucible manufacture to determine the properties of domestic flake and the maximum proportions that might be used without impairing the quality of the crucibles. This work was accompanied by photomicrographic study of crucible structure. In this bulletin are presented the results obtained in the first two phases of the work outlined above. The bulletin is in two parts. The first part describes the methods of mining and milling used, suggests a standard method of sampling finished graphite, and de- scribes a rapid and convenient method of analysis developed at the Pittsburgh station of the Bureau of Mines, to which had been as- signed the analytical and microscopic work. The second part describes experiments on the concentration and milling of graphite, which were made at the Salt Lake City, Utah, station. As soon as the reports incorporated in this bulletin were ready, mimeograph copies were distributed to those persons most interested in order to make the results immediately available. The experimental work on crucible manufacture, assigned to the Columbus, Ohio, station, yielded results which were made known to the industry. Á report on this work will be published later as a separate bulletin.

Jan 1, 1920

By E. J. HOFFMAN, L. A. SCHOLL, J. c. W. FRAZER

The danger from coal dust in mines has been thoroughly demon- strated by experiment, and consequently the study of the inflam- mability of coal dust suspended in air, that is, the readiness with which a cloud of coal dust inflames, is of decided importance to those engaged in coal mining. Much knowledge has been gained from the work done in the large galleries constructed at official and semiofficial stations in this country and abroad, but the study of the coal-dust problem in these galleries requires so much time and is so costly that there is need of a reliable laboratory method for obtaining a classi- fication of the great variety of dusts that occur in mines. The investigation described in this paper was an attempt to devise such a method. It was a preliminary investigation, and work in the same direction is being continued by the Bureau of Mines. As Mr. Frazer has severed his connection with the bureau, it is deemed advisable to publish the results of his study substantially as he prepared them, with little attempt to draw conclusions or to show the bearing of the results on other studies now in progress. The results of these studies and a full discussion of the significance of the laboratory investiga- tions will be published in future reports of the Bureau of Mines. The reader should remember that any laboratory method, since it involves conditions that differ so greatly from those of actual mining, should be thoroughly tested, and the results obtained by it should be confirmed by experiments conducted on a scale simulating mining conditions before final conclusions are drawn. The need of a laboratory method has long been felt, and several investigators have devised apparatus and methods. The work done by Vital, Holtzwart and Von Meyer, Bedson and Widdas, Le Chate- lier, and that of the British Coal Dust Commission is of great interest in this connection. Bureau of Mines Bulletin 20 contains a sum-

Jan 1, 1913

By Charles Enzian

This report is issued by the Bureau of Mines as one of a series dealing with methods of increasing safety and efficiency in mining operations. It is intended purely as a preliminary statement of the present development of hydraulic mine filling as conducted in the anthracite region of Pennsylvania. A discussion of different methods, their variations and modifications, as well as their probable extension as a result of amplified tests of the various roof-supporting materials, will be presented in a future bulletin. The history of the development of the anthracite-mining industry, from the time when the Indian tribes in the Wyoming and Lacka- wanna Valleys first discovered the existence of "stone coal," on through subsequent events-the purchase of lands containing enor- mous deposits of coal for insignificant sums of money, the develop- ment of the first mine, the formation of the first company, the build- ing of canals and railroads-up to the present time when the industry has become of such tremendous importance to the prosperity of north- eastern Pennsylvania and of the Nation itself, is intersprinkled with romance, tragedy, and pathos. The great economic lessons to be learned from a study of mining operations in the anthracite region suggest to the person interested in the efficient utilization of natural resources the need of applying such methods as will make possible the conservation to posterity of this invaluable deposit of coal that has resulted from the operation of the processes of nature during probably hundreds of millions of years. It is the opinion of many prominent mining men familiar with mining operations in the United States and abroad that under certain conditions the most practical way of preventing loss of unmined coal in pillars and of protecting surface property from damage by sub- sidence is by filling the workings with refuse material. This bulletin aims to present a general discussion of hydraulic mine filling, its origin, development, and practicability in anthracite mining.

Jan 1, 1913

Homans [1950] offered a working definition of group that is useful for this research: "We mean by a group a number of persons who communicate with one another often over a span of time, and who are few enough so that each person is able to communicate with all the others, not at secondhand, through other people, but face-to-face." This chapter begins with a discussion of the group concept in reference to the hypothesized escape groups mentioned earlier. It then moves to an examination of analysis techniques used by the authors. Finally, the subjects themselves are profiled according to their demographic characteristics. The Nature of Groups Warriner [1956] took a realist approach to understanding groups: "(1) the group is just as real as the person, but (2) both are abstract, analytical units, not concrete entities, and (3) the group is understandable and explicable solely in terms of distinctly social processes and factors, not by reference to individual psychology." Warriner's realist position merely holds that "group" occupies a different domain in which it is no more or less concrete than "person." At this group level the unit of analysis will be those relations that indicate social rather than individual behavior. It is possible to investigate these group properties empirically-if a researcher avoids confusing conceptual entities with concrete ones. Most people seem to accept that group attributes must somehow be inferred, but think personal attributes will be directly manifested, requiring little or no interpretation [Snizek 1979]. In other words, nobody would equate physical components of an underground working section with the actual work group, yet social scientists (as well as laypeople) very often confuse real individuals with notions of the person. In actuality, neither groups nor persons are directly disclosed to the senses; both are inferred by experience and observation. One can "see" a group just as clearly as one can "see" a person, given the proper perspective from which to do so. It is necessary, in developing this perspective, to begin with a sound definition of the thing being examined. Besides communication, or more generally, social interaction, Homans [1950] included three other components of group makeup. "Sentiment" is characterized as the feelings people tend to form about one another when they interact often. These feelings include not only friendliness and dislike, but attitudes such as approval or disapproval. A "norm" is an idea, held in common by group members, that specifies how people ought to behave in given circumstances. In lay terms, norms are simply those informal rules individuals abide by in order to get along together in social situations. Finally, "activity" refers to those things persons do with others. In work groups, as an example, many of the activities are cooperative and goal-directed.

Jan 1, 2000

Jul 1, 2003

By Thomas V. Falkie, R. Venkataramani

Table 15. Summary of Physical Characteristics of Coal and Shale from Channel Samples. Table

Jan 1, 1972

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

Table

Jan 1, 1977

By J. Walden, S. Rhoades, R. E. Miller, R. Gibbs, P. Boman

Accelerometers and pressure transducers mounted in suspension components can be used to monitor the ride of haulage trucks. Presently, it is difficult to tell what caused a jolt to the truck using either pressure or acceleration data alone. When information horn a Global Positioning System is recorded at the same time as shock pressures or acceleration data, then the exact location of an event can be determined. Mine management can then determine what caused the jolt to the truck.

This is the final report on Project CR-102 under the auspices of the Department of Environmental Resources, Commonwealth of Pennsylvania .1 The project was activated on January 5, 1970, with financial support from Bituminous Coal Research, Inc., the Pennsylvania Coal Research Board, and the Water Quality Office of the Environmental Protection Agency (WQO-EPA)2 through Grant 14010 EST to the Commonwealth of Pennsylvania Work on the project was conducted according to the procedures outlined in BCR Research Program Proposal RPP-164R, dated April 24, 1969, and a subsequent Revulsion of Scope, dated February 25, 1970. This report covers the entire project period from January 5, 1970, through March 25, 1971.

Jan 1, 1971

By George T. Faust

The Southern Experiment Station of the Bureau of Mines, United States Department of the Interior, in cooperation with the University of Alabama, is investigating the various types of clays to be found in the Southern States. In connection ,with this work, the petrographic laboratory is called

Jan 1, 1940

By E. Aamland

Preparation of high-purity magnesium-yttrium alloys by electroreduction of Y2O3 dissolved in a YF3-LiF bath and the subsequent deposition of yttrium in a molten magnesium cathode was investigated in laboratory-scale apparatus. Parameters such as temperature, current density, and electrolyte density were studied. Electrolysis was conducted in a specially designed MgO diaphragm cell at temperatures ranging from 780° to 970° C. Alloys containing up to 55 weight-percent yttrium were prepared at cathode current efficiencies of 21 to 60 percent. Cell design and operation are described, and some of the limiting conditions pertaining to the method are discussed.

Jan 1, 1973

By John C. Edwards, Fred N. Kissell

Experimental work by the Bureau of Mines indicates that when a coalbed is degassed by boreholes, the flow of methane may actually increase with time. This phenomenon appears to be the result of a relative-permeability effect; that is, the coalbed permeability to the gas increases sharply with decreasing water saturation. This report reviews the background of experimental evidence indicating a relative-permeability effect, and presents the results of a computer simulation of two-phase flow in coal.

Jan 1, 1975

By C. M. Frost

Crude shale oil prepared by gas-combustion retorting of Colorado oil shale was hydrogenated over a cobalt molybdate catalyst at an operating pressure of 1,000 psig, temperatures of 781° and 761° F, and liquid hourly space velocities of 0.10 and 0.05 Vo/Vo/hr, respectively. The yields of total liquid products and the amounts of nitrogen and sulfur removed were comparable with those obtained at an operating pressure of 3,000 psig and a liquid hourly space velocity of 1.0 Vo/Vo/hr. Approximately 1.5 times as much gasoline was produced at the lower pressure and space velocities.

Jan 1, 1973