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By Gabriel Esterhuizen, Tom Goodwin, Scott Schilling, Anthony T. Iannacchione

The Roof Fall Risk Index (RFRI) is a new method introduced by the National Institute for Occupational Safety and Health (NIOSH) to assist the underground stone mine operator in 1) assessing defects the mine strata and 2) rating the relative roof fall risk these defects pose. The RFRI utilizes observational techniques to identify defects in the roof strata caused by local geologic, stress, and mining conditions. Assessment values for ten defined defect categories provides the foundation for estimating a range of risk conditions between 0 and 100 that define the potential for a roof fall. This paper examines how the defect information is collected using two field verification sites and proposes methods to analyze the RFRI data. These examples provide information on how well the method replicates observed conditions and how it might be applied in practice.

By B. W. Gandrud

This report presents the data of one of a series of investigations of the washability of Alabama coals as indicated by float-and-sink tests made by the Bureau of Mines at the Southern Experiment Station in cooperation with the University of Alabama and Alabama coal producers The Klondyke mine, operated by the Blocton Mining Co., is about 1 mile east of West Blocton, Bibb County, Ala., near the southwestern extremity of the Cahaba coal field. The Bureau of Mines already has published three reports that deal with the washability of Cahaba coals - one a washability study of the Clark bed at Marvel4/, one on the tabling of fine coal from the Thompson and Woodstock bed , and the third a washablility study of the Henry Ellen bed at Acmar6/.

Jan 1, 1939

By K. Y. Haramy

Coal mine bumps involve the violent, rapid failure of coal and rock around a mine excavation. Deep coal mines with strong roof and floor rocks and high-stress conditions frequently experience face and rib bumps. The bump problem is becoming more severe as mining depth increases, prompting efforts to control high stress in advance of mining. This Bureau of Mines report presents a review of the most widely used methods to detect and destress high-stress zones along coal faces and an investigation of stress-related bump problems and destressing techniques at a cooperating mine. Geotechnical instrumentation and microseismic methods were used to better understand bump occurrences in underground coal mines. Laboratory tests of the drilling-yield method for high-stress detection were conducted to determine the correlation between the volume of cuttings obtained and the magnitude of the applied stress at various confining pressures. A three-dimensional, multiple-seam computer modeling program, MULSIM, was used to evaluate the effectiveness of stress-relief methods. Modeling results indicate that dangerously high-stress areas can be controlled by either proper planning or destressing. Proper mine planning guidelines and destressing methods such as volley firing, hydraulic fracturing, and auger drilling are discussed.

Jan 1, 1988

To reduce air be respirable dust generated from emptying dry dust collectors on small truck-mounted drills used at surface coal mines.

Jan 1, 1995

By Thomas M. Barczak

Roof support systems are necessary to provide stable mine openings and much research has been conducted to design a variety of roof support systems that will function in various manners to ensure that stable ground conditions are achieved. Despite these advancements in technology, mistakes continue to be made in the evaluation and/or installation that significantly degrade the support capability or lead to erroneous determinations of support expectations. The purpose of this paper is to discuss misconceptions about how roof supports perform and factors that impact their performance. The goal is to present practical information that will assist mine operators and engineers in selecting, installing, and evaluating roof support systems properly, and help them to avoid mistakes that can lead to erroneous expectations and potentially catastrophic results that may lead to roof falls. The paper is limited to a discussion of secondary roof support systems and powered roof supports such as longwall shields.

By Lucia Kuizon

The Pinnacles Wilderness Contiguous Wilderness Study Area (WSA) (CA-040-303) is 30 miles south of Hollister, CA, in San Benito and Monterey Counties. It is composed of five parcels of public land totaling 5,838 acres adjacent to the Pinnacles National Monument. The U.S. Bureau of Land Management later reduced the size of the Recommended Suitable Area (RSA) to 2,200 acres. U.S: Bureau of Mines personnel examined the entire WSA in May 1984. The WSA is underlain by Tertiary sedimentary and Cretaceous plutonic rocks. Diatoms occur in interbedded tuff, shale, and sandstones in the northern part of the WSA, but outside the RSA. In 1984, there were no mines, prospects, mining claims, leases, or mineral resources in or within one mile of the study area. No energy minerals were identified; however, an oil well was drilled in 1951 in the northern part of the WSA, but outside the RSA; it was a dry hole.

Jan 1, 1985

By R. C. Wang, W. M. McKewan

The behaviour of wire ropes used in mine hoisting is not well understood. In an effort to improve this understanding, the structure of round-strand wire ropes was analysed. This report provides a generalised mathematical model that completely describes the geometry of the wires. It consists of two sets of vector equations and is valid for any round-strand wire rope. One set of equations is used to trace the paths of wires that have the form of a single helix. The other is used for the paths of double helical wires. The specific model for a 33-mm 6x1 9 Seale, IWRC, right regular lay wire rope was presented as an example. The paths and the geometric properties of the wires which include the path length per lay of strand, the curvature, and the torsion were determined from this model. In future work, the model could be used to conduct stress analysis for the wires in the deformed rope at a given rope strain and also to study the effect of wear and breaking of wires on strength loss for the various round-strand wire ropes used in mine hoisting.

The largest producing coal field in Alabama, the Warrior Coal Field, was discovered in 1821'. Since then, coal has become Alabama's leading industrial mineral, both in production and income. Alabama has traditionally been one of the nation's major coal-producing states. This level of production is expected to continue due to Alabama's high-quality, low-sulfur coal. Alabama produces both bituminous and lignite coal. The bituminous coal is mined by underground and surface methods from four major coal fields in 24 counties. Alabama's lignite deposits, which are located in the southern part of the state, are not presently being mined. However, Alabama lignite is high-grade, and deposits are very shallow and easily surface-mined. Alabama gained primacy when its regulatory program was conditionally approved May 20, 1982. The program was fully approved July 5,1984. Alabama's Abandoned Mine Lands program was approved May 20,1982, and its emergency program was approved January 23, 1991. Although a Federal Lands Cooperative Agreement between Alabama and OSM became effective August 30,1985, no coal mining is currently taking place on federal lands in the state.9

Jan 1, 1992

In 2001, 14,623 mining operations reported employment statistics to the Mine Safety and Health Administration (MSHA). This was an increase of 210 mining operations compared to 2000. Almost half (49%) were sand and gravel mines, followed by stone (29%), coal (15%), nonmetal mines (5%), and metal mines (2%).

May 1, 2003

By M. M. Jones

A procedure for the spectrophotometric determination of uranium has been developed in support of minerals research being conducted by the Bureau of Mines. Uranium is separated from the sample by tributylphosphate extraction from acid solution containing added aluminum nitrate and (ethylene dinitrilo)-tetraacetic acid solutions. The colored uranium-dibenzoy1methane complex is developed in the organic phase by adding an ethanol solution of dibenzoylmethane buffered with triethanolamine. Absorbance is measured at 410 nanometers, and the response is linear up to at least 100 micrograms U30S in the aqueous aliquot taken for analysis. Aliquots containing as little as 8 micrograms U30S may be analyzed with relative errors no greater than ±5 percent. For aliquots containing at least 35 micrograms U308, relative standard deviation at the 95-percent confidence level is about ±2.2 percent. Appropriate procedures are given for analyzing a wide variety of samples.

Jan 1, 1980

By Thomas M. Barczak

State-of-the-art longwall roof supports provide effective strata control, but failures of these support systems still occur. To identify failure mechanisms and the impact these failures have on the safety of the support system, the U.S. Bureau of Mines has been conducting research on shield mechanics in the Bureau's unique mine roof simulator, as well as field studies of in situ support loading and investigations of longwall failures, Three types of failures are discussed: (1) inadequate support capacity, (2) structural failure, and (3) instability. Hypothetical situations with proposed courses of action and case studies of actual longwall failures are described. This information is intended to assist the Mine Safety and Health Administration (MSEIA) and industry mining personnel in safety evaluations of longwall roof support systems.

Jan 1, 1989

By R. Karl Zipf, David Newman

The objective of this is paper is to review the current state of knowledge and practice in highwall mining (HWM). HWM has become a widely-applied method in surface mining, commonly used alone or in conjunction with contour or slot mining. It provides 800-feet to 1,200-feet of additional recovery when the economic stripping ratio is reached in contour mining or in slot mining when surface access to a reserve is limited. A significant attribute of the highwall miner is its versatility. HWM has been used successfully to mine abandoned pre-reclamation law highwalls, points or ridges uneconomic to mine by underground or other surface methods, outcrop barriers left adjacent to underground mines, separate benches of the same seam where the parting thickness or quality differences between benches render complete extraction uneconomic, previously augered areas containing otherwise inaccessible additional reserves and close or widely spaced multiple seams. The theory and design methods to assess roof, pillar, and floor stability are presented followed by three case histories. Simple design charts for sizing HWM web and barrier pillars are also presented. A recommended web pillar width may be obtained from the design charts given the overburden depth, the HWM cut width, and the mining height. Given the depth and panel width for a set of HWM cuts, another set of charts gives a suggested barrier pillar width. The case histories, from Northern and Southern Appalachia are used to illustrate the application of rock mechanics to quantify the stability of the highwall, roof, web pillars, and floor. The case histories involve 1) mining through a previously augered highwall, 2) mining under back-stacked spoil and 3) selective mining of closely spaced benches of the same seam. Because each site is unique, the appropriate pre-mining geotechnical analyses range from the calculation of roof, web pillar, and floor bearing capacity stability factors to detailed numerical modeling of the auger and underground mine workings. When operating in the vicinity of existing underground mine or auger workings, the determination of ground deformation and strains resulting from highwall mining is a necessary facet of a ground control investigation.

By J. Mitchell Linnet

Bureau of Mines personnel examined mines, prospects, and mineralized areas to determine the mineral resources and potential of deposits in the Bucks Lake and Chips Creek RARE II areas in Plumas and Butte Counties, California. These areas lie along the west slope of the Sierra Nevada on opposite sides of the North Fork Feather River and encompass an area of 62,800 acres (25,400 ha). Metasedimentary and metavolcanic rocks of the Pennsylvanian Calaveras Formation are intruded by plutons of Mesozoic age. Mineral; of economic iterest are in quartz veins in metasediments close to these plutons; they are principally gold and silver with minor amounts of copper, lead, and zinc minerals. Molybdenum, copper, silver, and tungsten minerals occur in tactite along metasedimentary-granitic rock contacts. In both areas, auriferous Tertiary channel gravels have been extensively developed. Asbestos occurs in ultramafic rocks in both areas, and a limestone deposit was explored in the Chips Creek area. Gold is the principal economic mineral in the Bucks Lake RARE II area. The Shenandoah Mine (fig. 1, no. 19) contains 7,500 tons (6,800 t) of indicated and inferred subeconomic gold resources in sulfide-bearing, silicified metamorphic rocks of the Calaveras Formation (table 1). Similar rocks have yielded gold at the Edman and Megowen Mines, adjacent to the area. A high potential exists for additional lode resources in the area around the Shenandoah Mine. Callahan Mining Corporation personnel believe a multi-million ton disseminated gold deposit underlies the property.

Jan 1, 1983

By J. Douglas Causey

In 1987, at the request of the Bureau of Land Management, the U.S. Bureau of Mines studied 13,374 acres of the 14,994-acre Ireteba Peaks Wilderness Study Area (NV-050-438) in order to evaluate its identified mineral resources. The study area is located in Clark County, NV, about 4 miles south of Nelson, NV. No identified resources were found within the Ireteba Peaks study area, although there are identified subeconomic resources just outside of the study area boundary. Most of the area is underlain by Tertiary granitic rocks, which apparently postdate mineralization. The area is virtually surrounded by mining districts with mines developed in older rock units. On the north side, quartz monzonite, volcanic tuff, and tuffaceous sediments in the Eldorado mining district host deposits of gold, silver, copper, zinc, and mercury. On the south side, Precambrian gneiss, intrusive andesite porphyry, and hornfels in contact with Quartz monzonite in the Searchlight mining district host gold, silver, copper, and lead deposits. The Newberry mining district to the southeast had copper, gold, and silver mineralization in Precambrian gneiss and andesite.

Jan 1, 1988

By William R. Wayment

The objective of this investigation was to obtain data on friction-head losses of sand slurries during their transport in pipelines. The data ultimately will be used in designing hydraulic transport systems. Information that was incidental to the primary objective was gathered on degradation, changed percolation characteristics, and critical velocities of the slurries~ Tests were made in a closed-circuit pilot plant, with one type of tailing, through horizontal 2-, 3-, and 4-inch-pipe test sections at various pulp densities and flow velocities. Tests were made in a closed-circuit pilot plant, with one type of tailing, through horizontal 2-, 3-, and 4-inch-pipe test sections at various pulp densities and flow velocities. Approximately 2,000 tests were run in the pilot plant. The ranges of flow velocities used in the experiment were 2.8 to 19 f.p.s. in the 2-inch line, 4 to 14.5 f.p.s. in the 3-inch line, and 4 to 11 f.p.s. in the 4-inch line. Velocities were varied in increments of 0.5 f.p.s. through the entire velocity range in each pipe size. Densities were varied in 3-percent increments from 40 to 70 percent solids by weight except for one series of tests in the 2-inch line; in this series, densities were varied in 5-percent increments from 5 to 65 percent solids by weight.

Jan 1, 1962

By Terry R. Neumann

The Olallie RARE II study area has volcanic cinder deposits with a sow potential for development. No mining claims or prospects are known within the study area, and except for common construction materials such as volcanic cinders and stone, no mineral deposits were identified. An evaluation of the geology indicates that metallic mineral deposits are unlikely to exist. No significant metallic concentrations were reported in samples from the area. The only resources in the study area are about 30 million cu yds (23 million cu m) of cinders in three cones. The cinder deposits in the study area cannot compete economically with enormous deposits of similar material in more accesible areas closer to markets. At the present rate of consumption, resources outside the area are adequate far into the future. The geothermal potential of the study area is being evaluated by the U.S. Geological Survey.

Jan 1, 1983

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

APPENDIX B - DEVELOPMENT OF FOAM-CONCRETE SLURRY MINE SEALANT 1. Introduction This appendix describes the results of an experimental development and laboratory evaluation of foam-concrete as a rapid setting, lightweight, self-supporting mine sealant material. Foam concrete, otherwise known as Aerated Concrete, is a form of lightweight concrete whose structure consists of air bubbles held together by a hardened cement mortar. Its principal applications are found in roofing, insulation, shock absorbing, and backfill. The air bubbles in foam concrete are formed either by chemical reaction in the wet, placed mortar, or by introducing a stable foam into the mortar during mixing. The mortar is usually a cement slurry with fine sand or fly ash as filler. Our attention focused on preformed foam concrete, since this is most adaptable to field applications. Equipment is available,* which simultaneously mixes and pumps a slurry of foam concrete. Such a slurry can be produced at a rate of up to 50 yards/hr and has been pumped in a 2-inch-diameter hose 1000-feet horizontally and 250 feet vertically up without significant bubble deterioration. One very attractive feature associated with the use of foam concrete concerns site logistics. Foam concrete can be generated with densities as low as 20 lbs/ft3, and hence the total number of

Jan 1, 1973

By L. B. Pankratz

Enthalpies were determined for synthetic chalcopyrite (CuFeS2) between 298° and 1,050° K and for synthetic bornite (Cu5FeS4) between 298° and 1,100° K by copper-block drop calorimetry. Two transitions were found for each compound. The lower transitions were both crystal transformations from tetragonal (low-temperature form) to cubic (high-temperature form). The chalcopyrite transformation occurred at 830' K with a heat of transformation of 2,405 cal/mole; the bornite transformation was at 485° K with a heat of 1,430 cal/mole. The other transitions were of the second order and were presumed to be magnetic in character. The second-order transitions for chalcopyrite occurred at 930° K, and the one for bornite at 540° K. Enthalpy increments, entropy increments, and heat capacities are tabulated at even temperatures above 298.15° K. Equations of enthalpy are also given.

Jan 1, 1970

The 53 countries that constituted Africa in 1993 accounted for a significant portion of total world output of a number of mineral commodities. For the continent as a whole, world shares of most commodities showed little change from those of 1992 although most output volumes showed a slight decline. There were no significant production increases, but there were significant decreases of cobalt and copper because of political instability in Zaire and production problems in Zambia, of chromite resulting from cutbacks in South Africa and Zimbabwe, and of phosphate rock owing to a lower output by producers in general. (See tables 1 and 2.) Among the most significant mineral commodities produced in Africa, ranked by portion of world production in 1993, were diamond, cobalt, chromite, gold, phosphate rock, manganese ore, uranium and petroleum. Others of importance in world trade were andalusite, antimony, asbestos, bauxite, coal, copper, fluorspar, lithium minerals, platinum-group metals (PGM), titanium minerals (ilmenite and rutile), vanadium, vermiculite, and zircon. Several of these-chromite cobalt, diamond, and manganese-were not produced in the United States.

Jan 1, 1995

By Travis Q. Lyday

During 1983, Ecuador's gross domestic product (GDP) decreased by a reported 3.3% in real terms, the second consecutive decline in the economy after more than a decade of growth generated mainly by petroleum export revenues. The slowdown was due, in part, to the effects of the world recession, lower foreign demand for oil, depressed world oil prices, and reduced demand and prices for Ecuador's traditional agricultural exports. Inflation accelerated to an estimated 55% annual rate. The sucre was devalued in March, for the second time in less than a 12-month period, by 27% after remaining unchanged during the previous decade. In addition, continuous adjustments were made every weekday, effectively devaluing the sucre another 30% by yearend. Ecuador's production of crude petroleum increased almost 12% in 1983 compared with that of 1982. Average daily production was 237,100 barrels per day (bbl/d), up from 211,300 bbl/d in 1982.

Jan 1, 1985