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By Helmut Hass, Michael S. Shultz

For many tunneling, deep shaft and deep excavation projects ground freezing is one of the best if not the only technique available to create a watertight and load bearing temporary support system in soft ground conditions. When appropriate attention is given to the details of the ground freezing system design, ground freezing is a very safe method and is economically viable with competing techniques and combinations of techniques. Recent innovative uses of the technique in Europe are highlighted in this paper and compared with current uses in North America.

Jan 1, 2005

By David E. Siskind

The Bureau of Mines studied airblast from surface mining to assess its damage and annoyance potential, and to determine safe levels and appropriate measurement techniques. Research results obtained from direct measurements of airblast-produced structure responses, damage, and analysis of instrument characteristics were combined with studies of sonic booms and human response to transient overpressures. Safe levels of airblast were found to be 134 dBL (0.1 Hz), 133 dBL (2 Hz), 129 dBL (6 Hz), and 105 dB C-slow. These four air-blast levels and measurement methods are equivalent in terms of structure response, and anyone could be used as a safe-level criterion. Of the four methods, only the 0.1-Hz high-pass linear method accurately measures the total airblast energy present; however, the other three were found to adequately quantify the structure response and also represent techniques that are readily available to industry. Where a single airblast measuring system must he used, the 2-Hz linear peak response is the best overall compromise. The human response and annoyance problem from airblast is probably caused primarily by wall rattling and the resulting secondary noises. Although these will not entirely be precluded by the recommended levels, they are low enough to preclude damage to residential structures and any possible human injury over the long term.

Jan 1, 1980

By R. W. Fedors, S. T. Green, G. R. Adams, C. Manepally, L. B. Browning

This paper provides estimates of large-scale temperature gradients that can be used to support modeling of natural convection and cold-trap processes in thermally perturbed drifts. Temperature influences estimates of the quantity and chemistry of water contacting engineered components (e.g., drip shields and waste packages) in a potential high-level waste repository at Yucca Mountain, Nevada. Temperature gradients drive natural convection and cold-trap processes, which could affect the distribution, quantity, and chemistry of liquid-phase water contacting drip shields (waste packages).The confluence of high temperatures, liquid-phase water, and high chloride may lead to corrosion of drip shields and waste packages. An overview of the evolution of environmental conditions in thermally perturbed drifts is presented to provide a context for the estimates of temperature gradients. A mountain-scale conduction-only model is used to estimate temperature gradients and temperature differences for a drift located at the center of a potential repository. Thermohydrologic models and heat transfer algorithms are used to evaluate the reasonableness of the conduction-only results. Estimates of temperature using an in-drift heat transfer algorithm account for the possibility of drift degradation and formation of a rubble pile on the drip shield. Temperature differences between the center and ends of the drift are estimated to rapidly increase to 80 °C soon after repository closure. That temperature difference decreases over time to 15 °C after 10,000 years. Local temperature gradients are generally estimated to be less than 0.2°C/m, though the gradients can be much larger near changes in lithology and near the end of the drift. The estimates of temperature gradients do not account for intermediate- and small-scale variations, such as those influenced by differences in heat loads between waste packages, intra-layer variations in thermal properties of the surrounding fractured rock, or localized drift degradation.

Jan 1, 2004

By H. L. Burmeister

This is one of a series of publications by the Bureau of Mines dealing with mining methods and costs at representative operations in the United States. The report describes all phases of the mining methods for the open-pit operation and milling practices employed at the Vermont Asbestos Mines in Lamoille and Orleans counties, Vermont. A brief history of discovery and development of these asbestos deposits is given, and the ore deposits are described. Methods employed in exploration, sampling, and estimation of tonnage and grade are outlined. A breakdown of available cost figures is summarized in the last section. All asbestos ore produced in this area has been won by the use of surface-mining methods. Two quarries, the Lowell and the "C" Area, are in operation. The quarries combined are producing and the mill is processing approximately 3,500 tons of ore per 3-shift day The average 40,000 tons of crysotile asbestos fiber produced at this plant annually accounted for 96 to 98 percent of the total fiber produced in the United States in 1958. The mine is located (fig. 1) approximately 4 miles north of Eden Mills village on the southeastern flank of Belvidere Mountain (fig. 2).

Jan 1, 1962

By J. C. Duchon

The U.S. Bureau of Mines is conducting human factors research for the purpose of reducing accidents and improving the person-machine interface found in surface and underground mining operations. Miners are exposed to a variety of environmental stressors, e.g., extreme heat, noise, vibration, and adverse illumination, throughout the workday. Exposure to these environmental stressors has been noted in the literature to affect performance on vigilance tasks. Since impaired performance at vigilance tasks can lead to industrial accidents, further investigation of the effects of environmental stressors on human performance is warranted. A brief description of the environmental conditions present in the mining workplace is followed by a review of experiments dealing with the effects of environmental stressors on vigilance task performance. The applicability of past research to actual mining operations is considered.

Jan 1, 1989

By Nick Barton

When the Q-system was launched in 1974, the name referred to rock mass classification, with focus on tunnel and cavern support selection. Besides empirical design of support, the Q-value, or its normalized value Qc, has been found to correlate with seismic P-wave velocity, with deformation modulus, and with deformation. The Q-system provides temporary or permanent support for road, rail, and mine roadway tunnels and for caverns for various uses. It also gives relative cost and time for tunnel construction for a complete range of rock qualities. There are also indications that Q has captured important elements of the cohesive and frictional strength of rock masses, with Qc resembling the product of rock mass cohesion and rock mass friction coefficient.

Jan 5, 2007

By H. M. Lawrence

"The land-pebble district, the larger of the two producing areas of Florida, is situated in Polk County and in the eastern part of Hillsborough County. About 80 per cent at the phosphate rock produced in the United States in recent years has been mined from this area. The phosphate ores, locally termed matrix. are beds of sands and clays containing the phosphate pebbles, considered to be Pliocene in age, derived by marine action from underlying Miocene phosphatic marls, and are covered by practically barren sands and clays that have been deposited more recently. Open-pit mining is practiced; hydraulic mining, which has been intensively developed in this district, is used exclusively for mining the matrix and, by some companies for removing the overburden, although drag-line excavators have become established and are proving economical for stripping operations. From the pits the matrix is pumped to adjacent washing plants for beneficiation. The product of the washers. after drying, enters the world markets as Florida pebble phosphate.In this district recovery of the phosphate pebbles by the washing plants has not been particularly effective in the past. The screening, designed to effect a seperation at about 20 mesh (0.033 inches), has not been well controlled. Washer rejects discarded to the waste dumps have contained appreciable amounts of material analyzing above the minimum commercial grade - 66 per cent B.P.L. (bone phosphate of lime). Such losses of commercial fractions should be considered avoidable, and have been discussed at length in a previous paper.3"

Jul 1, 1930

By J. L. Holman

The Bureau of Mines has extended its previous development of cast Mn-Cu damping alloys to powder metallurgy (P/M) consolidation of alloys containing 55 to 75 wt-pct Mn. Blends of minus 200-mesh elemental powders were compacted cold in directional and isostatic presses. With 1 pct binder, typical green densities ranged between 76 and 80 pct of theoretical when pressing at 30 or 48 tsi. Green strength increased with compacting pressure and copper content. As-sintered tensile strengths ranged to 60,000 psi fox a hydrogen, sintered 60Mn-40Cu alloy, along with 5-pct elongation. Sintered densities ranged between 90 and 96 pct of theoretical. Sintering (a as effective when holding for 1 hr at maximum temperatures of 900° to 1,040` C, dependent on composition. Strength and ductility were considerably lower than for equiva¬lent cast alloys. When aged to the damping condition, alloys containing 60 to 70 pct Mn exhibited >40 pct specific damping capacity (SDC) at 5,000-psi stress, considerably higher than values reported for equivalent cast material. Effects of 1 or 3 pct Sn or Zn additions on SDC and other properties were assessed. Trials were conducted on consolidating rings and gears of the 65Mn-35Cu alloy on industrial-type P/M equipment.

Jan 1, 1979

By J. E. Lawver, B. J. Clingan, R. E. Snow

Response surface methodology is a well-known and powerful technique for determining optimum conditions in flotation systems. One disadvantage is the onerous task of the numerical calculations and curve plotting. This paper describes a system in which the investigator simply selects the range of several flotation variables after which the design of the experiment, data analysis, generation of response surface equations, and response surface plots are automatically carried out using a digital computer and a computer-driven curve plotter. Several typical response surfaces of important variables in phosphate flotation are presented as examples.

Jan 1, 1980

By Francis D. Leathers

Four friction pile load test programs, including 23 tension tests and 9 compression tests, have been performed as part of the Central Artery/Tunnel Project in Boston, Massachusetts. The tests, performed on both precast, prestressed concrete (PPC) piles and steel piles, yielded the following adhesion values: [Soil Type Clay Clay Glacial Till Interbedded Sand and Clay Interbedded Sand and Clay Pile Type PPC Steel Steel Steel PPC Adhesion (psf) 610 to 1,200 230 to 900 220 to 550 680 1,280 ] The adhesion appears to be affected by differences in pile material type, with PPC piles having higher adhesion than steel piles. However, part of the apparent difference for the clay may be due to differences in time between driving and testing. The significant range of test data means that the need for site specific testing to determine or verify design values of adhesion should be considered during design. Creep rates at loads near failure ranged from about 0.02 to 0.18 inches per log cycle of time, with most values in the range of about 0.04 to 0.08 inches per log cycle of time.

Jan 1, 1994

By Stephen R. Iverson

The U.S. Bureau of Mines made an economic appraisal of the Buttermilk study area, Inyo County, California in October 1980. Results of surveys indicate no potential for metallic, non-metallic, or energy resources in the area. However, glacial till covering most of the area prevented bedrock examinations by the appraisal teams or earlier prospectors. No mining claims are known to be in the area. INTRODUCTION Present Studies The U.S. Bureau of Mines, Western Field Operations Center, searched county mining claim records and other data available concerning mineral deposits, claims, leases, production, and mining activity in the area. The Bureau conducted field work in October 1980 searching for prospects and claim locations. Fourteen reconnaissance lode and placer samples taken from the area were analyzed for gold, silver, and tungsten; a spectrographic analysis also was run on selected samples.

Jan 1, 1981

By M E. Pierce, T V. Garza-Cruz

Rock mass strength and brittleness generally have a significant impact on both cavability and fragmentation. Variability in these properties across a panel or block footprint is of particular interest because stronger units have the potential to significantly impact cave shape. This paper describes how FLAC3D™ was used to examine the impact of variability in rock mass properties on predicted cave performance to aid in assessing potential risks associated with the proposed design.A case study orebody was subdivided into a number of domains to reflect the heterogeneity of the rock mass at the scale of a proposed inclined cave. The results suggest that the presence of stronger units has the potential to impact cave shape significantly in the southern half of the cave footprint and could increase the potential for cave stalling at shallow depths. If this unit is stronger and less brittle than expected, an overhang is predicted to develop in the southern half of the inclined cave at depth. The effective hydraulic radius is significantly reduced due to the overhang in the south, and the cave could eventually stall at shallower depths in the north.CITATION:Garza-Cruz, T V and Pierce, M E, 2016. Impact of rock mass strength variability on caving, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 359–368 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By M. F. van der Merwe

Anglogold Ashanti?s Kopanang Gold Plant (previously No. 9 Gold Plant) treats ore from Kopanang and Tau Lekoa shafts. The plant is twin streamed and has dedicated treatment circuits, from milling to final product, for each shaft. Waste rock material is used to compensate for the mill gap on both streams. Each stream consists of three 4.85 m x9.15 m ROM mills in closed circuit with a single stage hydrocyclone, milling an average of 7 000 t per day. The liner configuration in each mill consists of six rows of 30 grid liners along with rectangular lifter bars. The topic of gold lock-up is not new and has been investigated and reported on many times, both within Anglogold Ashanti and the broader mining industry. Although the lock-up mechanism is understood, its measurement is neither practical nor precise. The initial lock-up in a new liner and the release as the liner wears down cannot be accurately quantified. Previous test work carried out on Kopanang Gold Plant (with a ?gold scanner?) measured the natural gamma radiation emitted by uranium. This radiation is in proportion to the mass of concentrate locked up in the grid liner pockets, as well as between the cast-on backing plate and the shell. The ratio of concentrate lock-up was estimated as 35% behind the liners and65% in the pockets. Mill gravity concentrates are recovered during routine relining operations from behind the grid liners at Kopanang Gold Plant. Prior to relining, the liners tend to release the concentrate from the pockets as the liners wear. Historical Kopanang data from actual ?mill gold? smelted indicates that an average of 29 kg gold is recovered from behind each row. This indicates a total lock-up of 250kg gold per mill. This locked-up gold should preferably be minimizedor eliminated for the following reasons: ?The cyclic build-up and release of gold in mills complicates accounting ?Gold concentrate arising from liners is a security risk and creates a major mechanism for gold theft ?Loss of interest on the value of 250 kg fine gold is significant and was a major driver for the project. These factors led to the need to develop techniques to eliminate or at least minimize the gold lock-up in the mills. Wave liners, with rubber inserts, have been successful in eliminating lock-up, and were tested at Kopanang Gold Plant in November 2000. However, due to increased load-slip and high wear rates associated with these liners, this option proved less economical in terms of liner wear. Grid liners, with rubber-filled pockets, demonstrated a very high wear life and eliminated pocket lock-up. This system was successfully trialed in January 2003, but unfortunately did not prevent lock-up behind the liners. Current developments have resulted in a system that eliminates both pocket and backing plate lock-up. The conventional grid liner design has been modified to remove its steel backing plate. Rubber inserts that are integrated onto a rubber backing plate, have been designed to be used with the newly modified grid. The backing plate and grid pockets are now completely occupied by rubber, thus completely eliminating concentrate build-up around the new grid liner system installed in November 2003. Results to date are promising and liner life is expected to exceed conventional performance.

Jan 1, 2005

Industrial minerals and rocks are those which are economically important because of desirable physical and/or chemical properties rather than metal or energy content. The evaluation of these resources for investment purposes in general follows established procedures after due consideration of well documented input data. However, in view of the sensitivity of many industrial mineral projects to specific inputs they require very careful analysis. The characteristics of the industrial minerals and the industrial minerals industry are reviewed and the significance of logistics, customer requirements, technology and marketing are discussed. Implications in relation to resources/reserves terminology are considered with phosphate rock used as an example. It is concluded that industrial mineral projects as a consequence of technology and market dependence in particular can give a high level of investment risk. The industry, however, offers most interesting and challenging employment opportunities for geologists, mineral engineers and economists.

Jan 1, 1988

By Ronald T. Mayerle

A mineral survey of portions of two contiguous WSAs (Wilderness Study Areas) along the South Fork Owyhee River in southwestern Idaho and north-central Nevada was done by the U.S. Bureau of dines in 1984. The portions of the WSAs, known as study areas, have a combined area of 47,610 acres. The Idaho study area consists of 42,430 acres of the 42,510-acre South Fork Owyhee River WSA (ID-16-53). The Nevada study area consists of 5,180 acres of the 7,840-acre South Fork Owyhee River WSA (NV-010-103A). The Idaho study area is within the Boise District of the Bureau of Land Management, and the Nevada study area is within the Elko District. In the Nevada study area, no claims or hard rock mineral occurrences are known.

Jan 1, 1986

By Raymond M. Stateham

Infrared and displacement studies were made of an unsupported roof in Kaiser Steel Corp.'s York Canyon coal mine, Raton, N. Mex. Monitoring of the roof continued until the roof over the area was caved. Loose slabs in the roof, about 6 inches thick, were detected by means of associated thermal anomalies, using remote-sensing infrared instruments. Displacement measurements taken during the study indicate that roof movement was cyclic in nature; the cycles appear to have been related to the mine work cycle (work days to idle days).

Jan 1, 1974

By F Pirajno

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. China’s mineral deposits are the result of metallogenic processes associated with the geodynamic evolution of tectonic plates and eventual amalgamation into their modern configuration. The principal tectonic provinces of China comprise the North China Craton, Yangtze Craton, Cathaysia Craton, Tarim block, Altay-Tianshan-Hinggan orogens (part of the Central Asian Orogenic Bel), Central China orogens, Songpan-Ganze orogen and Alpine-Himalayan fold belts, which are part of the huge Tethysides. These tectonic elements are testimony to a complex geological history spanning more than 3000 million years. This contribution will focus on selected areas of the Altay-Tianshan, the fold belts surrounding the North China Craton and Yangtze Craton and the mineral systems along the Ailaoshan-Red River fault zone. Mineral deposits in these provinces include gold, copper, molybdenum, tin, antimony, nickel, platinum group elements, lead and zinc.CITATION:Pirajno, F, 2015. Metallogeny and related tectonic settings in China , in Proceedings PACRIM 2015 Congress, pp 17–24 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By R. Frim, S. D. Ukeles

The present U.S. production of bromine is from inland brines located in Arkansas and Michigan. The most concentrated domestic brines (up to 5,000 ppm bromide)are situated in Arkansas. Less concentrated brines(about 2,500 ppm bromide) are located in Michigan. The amount of bromine sold or used in the United States came from three companies operating in those two states. Its value was $191 million. In 2004, the estimated U.S. bromine production was 222 kt (244,000 st). That compared with 216 kt (238,000st) produced in 2003.

Jan 1, 2005

Geophysical surveys are currently being carried out over mineral prospects all around the Pacific Rim. Many of these surveys are successful in locating mineralisation in porphyry intrusives, mesothermal environments, and epithermal vein systems. A number of examples of surveys in Indonesia and Papua New Guinea are presented, which show the successful application of various geophysical techniques to the discovery of mineral deposits on the Pacific Rim.

Jan 1, 1999

By Rudolf E. Greuer

This report contains the practical application of a computer program for the simulation of ventilation systems under the influence of mine fires and other emergencies on five hardrock mines. The introduction describes the need for such a program, its basic features, and the range of its applicability which is mainly a function of the available ventilation data. The second chapter discusses program modifications, whose necessity or desirability was, during the application, discovered. The following five chapters, which comprise the major portion of the report, give the detailed description of the program application on the five mines. For every one of the selected mines, the ventilation system, the source of the used ventilation data and their preparation for computer simulations are outlined. Based on data for the airflow distribution solely, fumes concentrations in the mines are calculated for several assumed fire locations. Based on data for airflow and pressure distributions, ventilation disturbances caused by fires as well as the resulting fumes concentrations and temperatures are determined. The consequences for escape routes and the possible means to keep them free of fumes are discussed. To investigate the capabilities of the program, other contaminant sources and other potentially dangerous ventilation factors, like fan failures and changed surface temperatures, are simulated also. The results of the calculations have been entered into ventilation plans which makes them easier to scrutinize. All significant computer printouts have been attached.

Jan 1, 1981