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By Doris M. Hyde

New mineral activity focused on increased petroleum exploration activities, while the established construction-oriented minerals sector operated without substantial change from previous years. After showing a 1 % real growth in the $154 million II gross domestic product (GDP) for 1983, preliminary estimates for 1984 indicated that the same growth pattern prevailed. The negative trade balance at midyear had worsened over the negative balance for the same period in 1983. An upward trend in import costs partly reflected the impact of Mexican inflation, which made that country's goods more ex-pensive and led to increased imports from North America and Europe. On the other hand, by midyear, the reexport trade with Mexico indicated an upward climb from the 1988 low of $12.7 million.

Jan 1, 1986

By J. M. Singer

Approximate equations were used to compute the radiant heating of float coal dust by approaching flames for various combinations of particle size, dust path length (flame travel distance), flame temperature, dust concentration, flame speed, and flame length. The computed values of degree of radiant heating and flame travel distance for preheating the coal dust should be useful for estimating the increased fire hazard of different coal dust-flame parameters. Some findings relating to coal mine disaster control are-- 1. Coal dust clouds cannot be preheated to ignition temperatures by flame radiation alone when deflagration speeds are greater than about 10 m/sec. Thus it appears unlikely that radiation alone will cause flames propagating in dust clouds to accelerate to detonation velocities. 2. Small particles in the radiation flame zone caused by burnout and soot formation increase the degree of preheat significantly. 3. The concentration of float coal dust (radii = 3 to 40 microns) for maximum radiant heating usually peaks in the range 50 to 200 mg/liter of air.

Jan 1, 1970

By B. T. Brady

Results of a study are presented of the effect of low radial reinforcement pressure on the postfailure characteristics of two types of granite, a sandstone, and marble. The low radial reinforcement pressure is applied to the rock surface by a gooch rubber sleeve. The gooch rubber sleeve provides a radial pressure of less than 1 psi pressure to the rock surface. This method of support gives an average strength increase of approximately 8 percent to the fractured rock sample.

Jan 1, 1973

By A. N. Styler

As part of its water-jet assisted rock cutting research, the Bureau of Mines has initiated a study into the mechanism of rock fragmentation by water-jet-assisted mechanical tools. The objective of this research is to increase coal extraction efficiency by seeking an improved understanding of the synergistic relationship between mechanical cutters and water jets, enabling the design of more effective cutterheads. Rock chips collected during laboratory traverse speed jet-assisted cutting tests were analyzed with respect to the size distribution of the chips and the forces measured during cutting. As the water-jet pressure was increased, the size distribution of the product became coarser with V-face type cutting tools producing less fine material than conical cutting tools. Fracture mechanics theory accounted for less than 10 pet of the energy consumed during fragmentation of the rock. The energy consumed by processes other than rock breakage decreased with the use of water jets and increasing advance rate.

Jan 1, 1987

By John R. M. Hill

The Bureau of Mines performed elastic-plastic, finite-element analyses to investigate the support performance of hydraulic backfill. A mathematical model was developed for two vertically adjacent stopes separated by a sill pillar. An exact duplicate of a working stope was not intended; however, the model did simulate a working stope to the extent that field measurements from an active stope could be used for comparative purposes. Using a predetermined mining sequence, the computer analysis simulated the mining operation as a series of incremental cut-and-fill steps. Computer results included a complete history of stope closure and pillar stresses throughout the mining sequence. With the mining sequence and rock properties held constant, three separate analyses were made using varying backfill properties. These cases included no fill,-low-to-medium-quality fill, and medium-to-high-quality fill. Results of these analyses show decreases in stope closure and pillar stresses as the backfill quality increases, thus reducing the possible occurrence of rock bursts. Predicted stresses within the backfill compare favorably with field measurements. A relationship between maximum stress normal to the stope wall and the ratio of relative fill stiffness to relative rock stiffness was also indicated.

Jan 1, 1974

By C. H. Elder, Maurice Deul

Coal degasification boreholes drilled from the surface have been success - fully hydraulically stimulated to increase the flow of gas from the coal. This Bureau of Mines report describes the hydraulic stimulation procedure for a coalbed, the equipment required, and design criteria for the treatment. Three examples of stimulation treatment show from fivefold to twentyfold increases in gas production. The tests were conducted in the Pocahontas No. 3coalbed, Buchanan County, Va., the Pittsburgh coalbed, Washington County, Pa., and the Mary Lee coalbed, Jefferson County, Ala. Two sites where the coal was hydraulically stimulated and exposed by subsequent mining show no adverse effect on mining operations through the treated zones. The induced vertical partings were confined to the coalbed and did not in any way affect either roof or floor rock.

Jan 1, 1975

By Kenneth M. Earl

The purpose of this investigation was to obtain subsurface information on the John Burdette barite-fluorite deposit, Garrard County, Ky. The deposit was intersected in each of five inclined diamond-drill hales aggregating 1,163 feet. All holes were drilled from the hanging wall of the deposit; the inclinations varied from minus 41° to minus 75°. Disseminated metallic sulfides were noted in the drill cores from holes 1, 2, 4, and 5. The deepest drilling was hole 5, which intersected the deposit at approximately 490 feet down dip. Visual inspection of the cores did not indicate mineralization of economic importance; therefore, no chemical analyses were conducted. Condensed logs of diamond-drill cores are included in this report. All drill cores were shipped to the Bureau of Mines core library in Minneapolis, Minn., for future reference,

Jan 1, 1959

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 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 Travis Q. Lyday

The Other South Pacific Island states extend from Palau, also called Belau, near the Philippines in the west, to French Polynesia in the east. However, a number of countries and territories have been omitted, from this chapter because their mineral production was insignificant to the local economy. These include the French over-seas territories of French Polynesia and Wallis and Futuna Islands; independent states, including Kiribati, Marshall Islands, Micronesia, Palau, Tonga, Tuvalu, and Vanuatu; the New Zealand freely associated state of the Cook Islands, and the New Zealand dependency of Niue. What mineral production existed in these islands was limited to construction materials such as coral reef limestone, crushed stone, and sand and gravel in minor quantities solely for domestic consumption. FIJI The mineral industry of Fiji continued to be dominated by gold, although this sector contributed less than 1 % to the gross domestic product (GDP) of the country. Gold and silver together ranked second in value among the country's exports. Fiji's economy contracted 11% during the 8-month period following the first, on May 14, of two military coups. Although the island nation had been a member of the British Commonwealth of Nations since its independence on October 10, 1970, Fiji's membership terminated with the emergence of the Republic or Fiji on October 15.

Jan 1, 1989

By Ann G. Kim

The Bureau of Mines investigated factors that influence the formation of methane and other hydrocarbon gases in coal, which is an integral part of the coalification process. Coalification begins with a biogenetic stage in which plant debris decomposes and peat is formed; methane and CO2 are the predominant gases produced during this stage. During the diagenetic stage of coalification hydrogen and the hydrocarbon gases methane, ethane, ethylene, propane, propylene, butene, iso-and normal butane, and pentane are formed by dissociation of the organic material. Methane may also be produced by a secondary reaction of hydrogen with unsaturates or by the reduction of CO2. The gas contained in coalbeds is a mixture of methane, C2 through C5 alkanes, CO2, O2, N2, H2, and He; its heating value is equivalent to that of natural gas. The gas content of coal depends on many variables, but an empirical relationship between adsorptive capacity, rank, and depth has been observed.

Jan 1, 1978

By John Nagy

The Bureau of Mines examined explosion development in a closed spherical vessel, mathematically correlating flame travel, pressure, and time with parameters defining the reaction. The model assumes that burnt and unburnt zones are separated by a thin, radially moving flame front. Isothermal and adiabatic systems are considered. Correlation with gas and dust explosion data is better for the adiabatic system, but the isothermal development is simpler and in reasonably good agreement. Interpretation of the explosion phenomena is facilitated by expressing the rate of mole change in the flame front in terms of elementary parameters. This expression is developed by examining the components of spatial-flame velocity.

Jan 1, 1969

By E. J. Kloos

Bureau of Mines-approved self-contained breathing apparatus of the compressed air demand type were evaluated for performance at low temperature. Apparatus durations, breathing resistances, and airflow rates were measured on machine tests at room temperature and -25° F. Man tests under actual wearing conditions verified the machine test results. Many serious functional changes in apparatus performance occurred at low temperature. Pressure regulators malfunctioned when diaphragms lost flexibility. Under certain conditions frozen condensed moisture sealed exhalation valves and fogged eyepieces. High-pressure leaks, not encountered at ordinary temperature, developed at low temperature. Tests results are discussed generally and specifically for each apparatus. Recommendations are given to obtain optimum performance from demand type breathing apparatus at low temperatures.

Jan 1, 1968

By Kathleen Madland Kowalski

In recent years the issue of human stress response in emergency workers has begun to receive attention. This paper presents a rationale for considering human stress as a significant factor in the management of emergencies It discusses the concept of stress, Critical Incident Stress in emergency responders, and intro¬duces the Critical Incident Stress Debriefing (CISD) process. It is suggested that in a disaster, the CISD process can improve the effectiveness of response teams on site, their turnaround time on site, and post disaster time off the job. This paper, prepared by a US Bureau of Mines research psychologist, offers some ideas to the mining industry in general, mine rescue trainers and more universally, to those responsible for developing emergency management plans.

Aug 1, 1998

By Michael J. Brnich

Since 1991, Pittsburgh Research Center (PRC- formerly part of the Bureau of Mines) researchers have recorded extensive interviews with 30individuals who are experts in the area of mine emergency response. These individuals, who have an average of 35 years of mining experience and 29 years of mine emergency response experience, related stories and observations from events that they experienced during their combined 850 plus years in mine emergency response. The purpose of this effort was to gather information that could be passed onto both today?s and tomorrow?s mine emergency responders to train and guide them in handling future events. This is the second of two articles which report experts responses to questions about training for future mine emergencies. During the interviews they discussed how training should be conducted, who should be trained, and what topics should be included. This article will cover the third area: Topics that should be included in training for mine emergency response managers.

Jan 1, 1997

By R. D. Leitch

From time to time the Bureau of Mines has received requests from persons who wish to destroy unwanted explosives, and although the information that follows has been accumulated from sources considered reliable,4/ the. Bureau of Mines assumes no responsibility for accidents that may result from following the suggestions offered. Explosives to be destroyed may be fresh material from damaged packages, usable material for which there is no further need, or material that has deteriorated either from natural aging or from improper storage to the point where it is unfit for use.

Jan 1, 1945

By C. M. McCulloch

Examination of several coalbeds in Walker County, Ala., Cambria, Greene, and Fayette Counties, Pa., and Raleigh and Wyoming Counties, W. Va., indicates that cleat orientations are similar throughout a vertical sequence of strata. Studies of cleat orientation were carried out in underground mines that are operating in separate coalbeds vertically above one another. The data show that over a vertical separation of 100 to 400 feet, the average difference in coal cleat orientation between mines is 04° for the face and 08° for the butt cleat. Variations of coal cleat direction between coalbeds examined in strip-mined areas show similar values. Cleat orientations measured at outcrops agree well with the directions measured underground, suggesting that the amount of vertical separation between coalbeds has little effect on the resulting differences in cleat directions. The largest variation of cleat directions between adjacent coalbeds occurs where a large horizontal distance separates two sample locations. Cleat orientations for deeper coalbeds are most reliable where the data are taken from directly above.

Jan 1, 1976

By E. C. Lane

The motor gasoline that is being marketed in the United States this winter (1928-29) is slightly more volatile than that gold a year ago. This characteristic is shown by a slight lowering of the distillation temperatures, particularly at the average initial and 20 per cent boiling points. Daring the past mine and a half years the Bureau of Mines has made semi annual surreys of the gasoline marketed in the United States; the Survey just completed is the nineteenth in the series. The 12 cities in which samples have been collected were chosen as representative of the more important marketing territories, as it was obviously impracticable to obtain a sample of every gasoline sold in the entire country.

Jan 1, 1929

By D. E. Hirsch

A systematic procedure for separation, characterization, and semiquantitative analysis of high-boiling petroleum distillates was developed by the Bureau of Mines and applied to a 370° to 535° C distillate of Wilmington, Calif., crude oil. Separation procedures employed were isothermal and molecular distillation, chemical treatment, silica-alumina adsorption, and gel permeation chromatography. Characterization and analysis were accomplished by gel permeation chromatography correlations and mass and nuclear magnetic resonance spectrometry. These data should be useful in improving petroleum processing and utilization and in achieving the energy conservation inherent therein.

Jan 1, 1974

By Philip A. Holland

The Bureau of Mines has developed a method for determining helium in water for use in sampling and analyzing surface and subsurface waters for geochemical survey work. The accuracy of the analytical method is within ±10 percent for samples containing above 20 x 10-8 cm3 He (STP)/cm3 H20. The minimum detectable helium-in-water concentration is calculated to be 2 x 10-8 cm3 He (STP)/cm3 water. Water samples are collected in 500-cm3 stainless steel cylinders. The dissolved gases are extracted into a cylinder of equal volume containing a known quantity of neon. The resulting gas mixture is subsequently analyzed for helium and neon-21 by mass spectrometry. The volume of helium in the sample is calculated from the mass spectrometric determination of the helium-to-neon-21 ratio, the known quantity of neon used, and the extraction efficiency of helium.

Jan 1, 1981