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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 Marcia L. Harris

The National Institute for Occupational Safety and Health (NIOSH), as part of its continuing research program for evaluating coal dust explosion hazards, has investigated several areas in which current practices may need to be updated in order to adequately protect mines against coal dust propagated explosions. In the United States, current rock dusting requirements remained largely unchanged since 1969. US Title 30 Code of Federal Regulations Section 75.403 is based on a coal dust particle size survey performed in the 1920s and later was supplemented by full-scale testing of the rock dust ability to inert a coal dust explosion. NIOSH recently conducted a comprehensive survey of US underground coal mines to determine the range of coal particle sizes found in dust samples collected from the mine entries. Due to advancements in technology and modern coal mining techniques, the current coal dust particles in intake airways are significantly finer than those found in the mines in the 1920s. According to past full-scale dust explosion test results, the current rock dusting practices used in today?s mines to inert a coal dust explosion may not be adequate. Other closely related issues such as rock dust testing methods and sampling procedures are discussed.

Jan 1, 2009

By R. Karl Zipf, Z. T. Bieniawski

"Abstract. Based on the premise that understanding the fundamental mechanics of fine fragment formation in coal will lead to reducing coal dust problems in mines, a thorough study of the mechanics of crack propagation in coal was undertaken. Two approaches were considered in an attempt to understand and quantify the fracture process as it relates to fine fragment formation.In one approach, theoretical models are used which describe the size of the fracture process zone which may relate to the amount of structural damage and fine fragment formation on the new crack surface. The other approach is based on the relationship between crack tip stress intensity and new surface appearance for mixed mode crack propagation. Preliminary observations with a scanning electron microscope support the premise that fine fragment formation is related to fracture surface appearance and fracture initiation conditions.An experimental program designed to supply the input parameters for these approaches is presently underway. The experimentation features mixed mode fracture toughness testing, using a special mixed mode testing rig, and fracture velocity measurements with a crack propagation gage. The interpretation of this data via the approaches discussed will provide further understanding of the mechanics of fine fragment formation in coal."

Mar 1, 1989

By K. Zipf, Z. T. Bieniawski

"An extensive mixed-mode fracture toughness testing programme was conducted on coal from three coal fields. A special mixed-mode testing fixture for coal and other geologic materials was developed together with reliable specimen preparation procedures. Dynamic modulus measurements made on each of the 116 fracture toughness specimens showed that these coals exhibit certain degrees of anisotropy. The fracture toughness testing programme systematically varied the loading rate, specimen orientation and fracture loading mode. Loading rate did not significantly effect the fracture toughness over the quasi-static range tested. Orientation did have a significant effect on measured fracture toughness. In the coals tested, the divider orientation and arrester orientation had higher fracture toughness than the short transverse orientation. Data showed that one orientation could have almost twice the fracture toughness as another. The fracture toughness testing enabled certain evaluations of three mixed-mode fracture theories: maximum tangential stress, maximum energy release rate and strain energy density theory. Due to the extreme heterogeneity of the coals tested, definitive conclusions regarding the best mixed-mode fracture theory are not possible; however, data do tend to support the strain energy density theory. INTRODUCTIONThe major aim of this research is to ·develop a fundamental understanding of how fine· fragments of coal (respirable dust) are generated during a fracture process. In a related paper [l], a hypothesis was presented for the mechanism of fine fragment formation during a generic coal material/cutting tool interaction. In this hypothesis, fine fragments are created during coal material/cutting tool interactions that are best described as general mixed-mode fracture processes. Data are required on the mixed-mode fracture behaviour of coal, the physical character of the newly-created fracture surfaces and the character of the inherent flaw structure of the coal material. Accordingly, a test programme was designed that provided some information in each of these areas. The testing effort seeks to measure critical fracture toughness under mixed-mode loadings as a material parameter characterizing in part the tendency of various coals to generate undesirable quantities of fines and respirable dust."

Jan 1, 1990

By James M. Spear

The U.S. Bureau of Mines conducted a mineral survey of the Domeland Addition (5207) and Woodpecker (5206) RARE II areas during the summer of 1979. These study areas were examined to determine the presence or absence of mineral resources and reserves and where possible, to estimate values. The study areas are 9 air mi northeast of Kernville, California, and encompass 47,400 acres of primarily granitic rocks of the Sierra Nevada batholith with some scattered exposures of older metasedimentary, volcanic, and metavolcanic rocks. These other rock units partially surround the exposed batholith in the Domeland Wilderness and consist mostly of late Paleozoic quartzites, mica schists, marbles, and meta-volcanics, Mesozoic quartz diorite and gabbro intrusives, and local Tertiary basalt and andesite flows.

Jan 1, 1981

By Joseph L. Ritchey

The Trail Lake RARE II area comprises 1,300 acres (526 ha) in Lassen and Plumas Counties, California, adjacent to the Caribou wilderness. No mining claims, prospects, or quarries are reported within the study areas, and no evidence of potential mineral deposits was found during a field reconnaissance. Quaternary basaltic lava flows uniformly underlie the area. INTRODUCTION The Trail Lake (No. B5-095) RARE II further planning area occupies 1,300 acres (526 ha) adjacent to the Caribou Wilderness in Lassen and Plumas Counties, California. Susanville is about 30 mi (50 km) east and Chester is about 17 mi (27 km) south of the study area. Access from State Highways 44 and 36 is provided by well-maintained gravel roads.

Jan 1, 1981

By Thomas J. Peters

A mineral survey of the Sill Hill RARE II area (No. 5304), covering 5,200 acres (2,100 ha) of the Cleveland National Forest, San Diego County, California, was conducted by the U.S. Bureau of Mines and the U.S. Geological Survey. This survey was in conformance with the Resource Planning Act (RPA) of 1974, as amended by the National Forest Management Act of 1976, to provide mineral resource information for study area classification. Bureau of Mines personnel made an economic appraisal of mineral deposits by searching pertinent geological and mining publications as well as U.S. Bureau of Land Management, U.S. Forest Service, and U.S. Bureau of Mines files and records. Known mines, prospects, and mineralized localities were examined during 1981, and sampling and mapping were done where warranted. The Geological Survey 'did geologic mapping, geochemical sampling, and geophysical surveys to aid this study.

Jan 1, 1983

By Andrew M. Leszcykowski

In 1984, personnel from the U.S. Bureau of Mines examined 41,550 acres of the North Fork Owyhee River Wilderness Study Area for mineral resources. This study area, in southwestern Idaho, is underlain by tuffs and basalt of Tertiary age. There are no known mines, claims, or prospects in or near the area. The northeast and southwest corners of the area are covered by oil and gas leases or lease applications, but no known exploration has been conducted. On Nickel Creek and Pleasant Valley Tables, in the southern part of the area, thin flows of vesicular, moss-covered basalt occur that are suitable for use as decorative building stone. The stone available for exploitation crops out over several square miles. However, more suitable material, outside the study area, is closer to potential markets.

Jan 1, 1986

By Michael M. Hamilton

In 1984 and 1985 the U.S. Bureau of Mines performed a mineral survey of the South Jackson Mountains Wilderness Study Area covering 60,211 acres of mountainous terrain of Humboldt County in northwestern Nevada. Approximately 550 lode claims have been located within or adjacent to the study area from 1900 to the present. Total recorded production for the area is 28.19 ounces gold, 1,105 ounces silver, 959 pounds copper, 6,016 pounds lead, and 12,446 pounds zinc; an additional two carloads from one mine contained an unknown amount of metal. In early 1986, there were eight active properties with a total of 126 claims. Wescord Resources and Long Lac Exploration (Texas) Inc. are involved in a joint exploration of the Jackson Mountains for volcanogenic massive sulfide deposits. Development at the Claudia mine continues in 1986. Results of the survey indicate that there are no identified mineral resources or reserves within or adjacent to the study area. Twenty-two properties have mineral occurrences containing gold, silver, copper, lead, zinc, iron, antimony, vanadium, and cobalt, with silver, copper, and iron being the most abundant.

Jan 1, 1987

By Fredrick L. Johnson

In 1984, at the request of the U.S. Forest Service, the U.5, Bureau of Mines began a study of the 94,370-acre Arc Dome study area (4-667) in order to appraise its mineral resources, The Bureau of Mines mapped and sampled mines, prospects, and mineralized sites in and near the area, The study area is located in the Toiyabe National Forest, about 54 mi north of Tonopah, Nye County, NV, It is estimated that over 500 claims have been staked in the study area since the mid-1800?s. In January 1986, there were 108 active mining claims completely inside and 59 on the boundary. Another 283 active claims were outside the study area but within 1 mi of the boundary, In addition to the large number of claims staked, exploration activity is also reflected by the almost 700 inactive workings that were found during field investigation.

Jan 1, 1989

By David A. Benjamin

In 1989 and 1990, the Bureau of Mines conducted a mineral resource investigation of the 122,000-acre Trinities study area, located in the Trinity Mountains of south-central Idaho. No identified mineral resources were delineated during this study. There are 58 lode mining claims within the area. Five localities contained elevated metal concentrations which may indicate precious metal mineralization at four localities and molybdenum-precious metal mineralization at another. Four of the five localities appear to form a northwest trend through the center of the study area. Twenty-eight individual sites contain anomalous concentrations of gold, silver, bismuth, molybdenum, and beryllium.

Jan 1, 1991

By Sam McNary

The U.S. Bureau of Mines used the East Fork Pine Creek watershed to conduct a pilot study for an inactive and abandoned mine lands inventory, during which techniques and methodologies would be developed for subsequent inventories. A total of 177 waste dump samples, 191 mill tailings samples, and 36 stream sediment samples were collected. Water samples were collected from 18 sample sites during five sampling events. Waste dump, tailings, and stream sediment samples were analyzed for antimony, arsenic, cadmium, copper, iron, lead, mercury, and zinc. Results indicate a multidisciplinary approach is necessary: disciplines should include geology, geostatistis, geochemistry, geophysics, biology, hydrology, and remote sensing; small prospects do not generally contribute to watershed contamination, major mine and mill sites may contribute metal enriched sediment of metal enriched water; speciation studies and bioavailability studies are important.

Jan 1, 1995

By Russell A. Schreiner

In conjunction with the Geological Survey, the Bureau of Mines conducted a mineral investigation in 1981 and 1982 of the Santa Rosa Mountains Wilderness Study Area (WSA), Riverside County, California. The Bureau of Mines is responsible for the mineral survey of mines, prospects, and mineralized areas in and near the WSA. A literature search was completed to obtain information concerning mineral occurrences and mining activity that relate to the WSA. A field investigation inside, and up to 1 mi outside, the boundary of the WSA, disclosed one prospect. This prospect was surveyed by compass and tape, and five samples were taken to determine the representative mineral content. No attempt was made to expose concealed mineralization or to re-open caved workings. All five samples were analyzed by fire assay for gold and silver and by colorimetric methods for tungsten. Two of the samples were analyzed by semi quantitative spectrographic methods to determine if any unsuspected elements were present. All analyses are furnished in this report except for the semi-quantitative spectrograhic analyses. Complete sample analyses are available for public inspection at the Bureau of Mines, Intermountain Field Operations Center, Building 20, Denver Federal Center, Denver, CO 80225.

Jan 1, 1983

By Nicholas T. Zilka

Mineral resource studies by the Bureau of Mines indicate three areas within the Selway Bitterroot Wilderness have mineral resource potential. Regional studies suggest that a granitic stock on the south side of the Wilderness has high potential for a Climax-type stockwork molybdenum deposit (pl. 1, no. 8); but detailed surface investigations failed to recognize a deposit. The Elk Summit area on the north side of the Wilderness contains subeconomic resources of columbium (niobium)-bearing ilmenite in placers (p1. 1, no. 19). Subeconomic silver-copper-lead resources occur in a vein on the northeast side of the Wilderness at the Clift Mine (pl. 1, no. 2-5). The study area has no known deposits of oil and Haas, coal, geothermal resources, or other energy-related commodities.

Jan 1, 1982

By Michael S. Miller

During U.S. Bureau of mines mineral investigations, in 1981 and 1983, no mines, prospects, or mineral resources were identified in the Little Sand Spring Wilderness Study Area (WSA). Placer gold values in near-surface samples from alluvial fans within or near the WSA contained no more than 66 cents gold per cu yd, at $400 per troy ounce gold price. Sand and gravel and carbonate rocks occur in large quantities, but transportation costs to distant markets preclude their classification as resources. Nitrogen, lithium, clay, pumice, perlite, aragonite, and agate occurrences in the WSA are small or low-grade. The Silvia Mine, adjacent to the WSA contains gold-, silver-, copper-, and lead-bearing shear zones which strike toward the WSA. INTRODUCTION The Little Sand Spring WSA, encompassing 33,500 acres, is approximately 56 mi east of Big Pine, California, by paved and graded dirt roads (fl;. 1). Elevations range from 2,600 ft in Death Valley Wash to 5,600 ft along the California-Nevada boundary. The nearest permanent facilities are at Grapevine Ranger station and Scotty's Castle (Death Valley Ranch), about 9 and 11 mi, respectively, south in Death Valley National Monument.

Jan 1, 1983

By Michael Sokaski

The Cliff Springs prospect in the northern part of the Slate Range Wilderness Study Area (WSA) contains only minor amounts of gold and silver. Clay near this prospect contains insufficient aluminum to be of economic interest, although alunite claims are recorded in the vicinity. Mineralized rock at the Crescent Mine adjacent to the WSA contains gold, silver and lead occurrences. The host rock may be present in the extreme southwestern part of the WSA, which is covered by alluvium. Substantial sand and gravel deposits are present but these occurrences are remote from markets. Much of the USA is underlain by volcanic rocks and alluvium and consequently the mineral resource potential there remains unknown.

Jan 1, 1983

By Stephen R. Iverson

Manganese deposits exist in the Wonder Mountain RARE II area (fig. 1). The manganese mineral is primarily bementite, a silicate. It occurs with Jasper and manganese oxides in tabular or irregular lenses along the contact between red limestone and basalt. There are about 11,000 tons (10,000 t) of indicated sub-economic resources in the northeast part of the study area. Of this, 10,700 tons containing 27.1 percent manganese is at the Apex Prospect and 300 tons averaging 24.8 percent is at the Brown Mule Mine (fig. 1). Another 1,000 tons (900 t) containing 27.0 percent manganese is at the Steel Creek deposit 0.5 mi (0.8 km) west of the area (Wiebelt, 1942, p. 1, 2). Each of these deposits is subeconomic due to small tonnage and high estimated recovery costs. They are in a regional belt of manganese occurrences trending northwesterly through the area. Pardee (1921) reports that manganese ore was shipped from the Triple Trip (Brown Mule) Mine in 1916.

Jan 1, 1982

By J. Douglas Causey

No mines are active in the Hunter Mountain Wilderness Study Area (WSA), and no mineral resources have been identified in the WSA. However, the Monarch Mine has low potential for silver, copper, tungsten, and gold resources in quartz veins; the Shirley Ann Group and Sal Group have moderate and low potential, respectively, for silver, lead, and copper resources in skarn; claims overlying the Eureka Quartzite have low potential for silica resources; and the Tourmaline N1-4 Prospect has low potential for tourmaline resources in quartz monzonite. Copper, lead, silver, tungsten, molybdenum, wollastonite and garnet occur in skarn zones between monzonitic and carbonate units. Silver, tungsten, and copper also occur in quartz veins within monzonite. Known metallic mineral deposits are small, erratic and discontinuous. The J. 0. Mine, adjacent to the northeast corner of the WSA, may contain as much as 26 million tons of subeconomic wollastonite resources. The crest of an open pit to produce that resource would extend into the WSA. No information exists on geothermal potential because no exploration has been done in the area. No occurrences of energy minerals are known within the WSA.

Jan 1, 1983

By John R. Benham

The Windigo Theilson RARE II area has a low mineral potential. There are no mines or claims in the area. The only observed results of mining activities were five prospect pits near Tolo Mountain. Samples from these pits contained no significant assays. The study area contains more than 190 million cu yds (145 million m3) of cinders in 17 cones. Development of these cinders is unlikely because their locations are remote, and other sources supply area needs. The Geological Survey has classified the area as prospectively valuable for geothermal resources. However, there has been no geothermal exploration activity.

Jan 1, 1982

By Lawrence Y. Marks

During the mineral survey of the Bob Marshall Wilderness and study areas by the author in 1971, 1973, 1974, and 1976 (Marks, 1978), the area designated Reservoir-North (RARE II No. H1-485) in January, 1979, (U.S. Forest Service, 1979) was examined, along with other lands adjacent to the earlier study areas. However, the 1978 open-file report covered only areas originally designated for study. The present report on Reservoir-North is based on earlier work. No work has been done in the area since 1976. Mineral Appraisal Reservoir-North RARE II area (No. H1-485) is in the Northern Disturbed Belt which has been identified as having high potential for natural gas accumulations and lesser potential for oil accumulations (Mudge, 1978). Oil and gas lease applications in the area, indicate interest by oil companies.

Jan 1, 1981