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More than 100,000 people are expected to be in Las Vegas, NV in March for ConExpo-Con/Agg 2002, the largest exhibit of its kind in the Western Hemisphere. This triennial event features equipment, services and technical sessions geared toward the global construction aggregates and ready mix concrete industries. ConExpo-Con/Agg 2002 will take place March 19-25, 2002 at the Las Vegas Convention Center. For registration information, contact the show offices, phone 800-867-6060, 414-298-4141, or 301-587-3140, Website www.conexpoconagg.com.

Jan 1, 2002

By A. Moskowitz, L. S. Redmerski

The corrosion resistance of stainless steels can be strongly affected by surface treatments. Changes in corrosion resistance can relate to surface composition, integrity and stability of the passive film, and to surface profile (roughness). Operations producing oxidation at the surface, such as annealing, heat treating, and welding, can result in a chromium-rich scale and a chromium-depleted metal surface. In order to restore full corrosion resistance, chemical or mechanical clean-up techniques must remove not only the oxide, but also a very thin layer of metal. Laboratory and field test studies show that these factors are particularly significant in less highly alloyed steels. Annealing stainless in a reducing atmosphere (bright annealing) avoids chromium depletion, but as-bright-annealed material does not display optimum corrosion resistance in certain environments. Electro passiva-tion can be applied to improve pitting resistance without significantly changing bright surface appearance. Potentiometric studies show that electropassivated material also displays significantly greater resistance to breakdown of passivity in acid solutions. The application of special surface finishes for appearance purposes can affect corrosion resistance. Roughness is a key factor. Samples of related appearance but with different surface profiles can show significant differences in corrosion resistance. Thus nonreflec-tive stainless with a relatively smooth surface produced by a special rolling process is much superior to material chemically etched to a similar low reflectivity. THE corrosion resistance of a stainless steel is affected by other factors in addition to its bulk composition and metallurgical structure. These other factors include those relating to the specific chemical and physical condition of the steel's surface. This paper will consider certain aspects of surface condition in relation to corrosion resistance. In particular, studies will be described on the effects of oxidation encountered in heat treating or welding operations, of passivation after bright annealing, and of different surface finishes. EFFECTS DUE TO OXIDATION When stainless steels are exposed to high temperature in an oxidizing environment, as in annealing or welding, the oxides formed are relatively rich in chromium. As a consequence of oxidation, the metallic layer directly beneath the scale may be low in chromium to some very thin but finite depth.1"8 Such a change in chromium content could lower the corrosion resistance at the surface, whether or not the oxide layer is removed. Studies were performed relating to the effect of oxidation and chromium depletion produced during annealing and welding on the corrosion resistance of stainless steels. The nominal compositions of steels used in this study and others are given in Table I. A) Annealing Studies on 17 pet Cr Steels. 1) Effects of Pickling Treatments. Studies were performed to investigate the corrosion resistance of air annealed type 430 stainless as a function of the amount of electrolytic pickling after annealing. The material used in this study had been air annealed and electrolytically pickled in the mill. All scale had been removed, and yet the material showed unusually poor corrosion resistance. Laboratory electrolytic pickling studies were performed to determine whether additional metal removal from the surface would improve corrosion resistance. Electrolytic pickling was performed in a sulfuric acid bath using various conditions of bath acidity, temperature, time, and current density. The samples were then rated for corrosion resistance in a ferric chloride spot test. For this spot test, a solution was prepared by dissolving 10 g of FeCl3 . 6H2O, 5 g of NaCl, and 2.5 ml of concentrated HC1 in 200 ml of water. An area on a specimen was cleaned and a drop of test solution was placed on the prepared area. After 5 min, the drop was rinsed off and the area wiped dry. The spot was then rated between 1 and 5 by visual comparison with standard spots. The numerical rating of the standard spots can be described as follows: 1—No clouding of surface; 2—very slight clouding of surface; 3—slight clouding of surface; 4—moderate clouding of surface; 5—strong clouding of surface. A rating of 1 or 2 was considered to have passed the test, a rating of 4 or 5 represented failure, and a rating of 3 was considered borderline. The severity of etching in this test has been related to the actual chromium content at the surface.4 Etching (clouding) occurs on type 430 stainless (rating of 4 to 5) when the surface chromium content is 14 pct or less. The effects of current density and retention time when electrolytically repickling this material in 6 pct sulfuric acid are shown in Fig. 1. Increasing the cur-rent density or retention time improved corrosion resistance as measured by the spot test. Similarly, increasing acid concentration of the bath or bath tem-perature was found to improve corrosion resistance. The conditions making for improved spot ratings resulted in increased metal removal, regardless of specific pickling conditions used, Fig. 2.

Jan 1, 1970

By William H. Schiffbauer

The Bureau of Mines is conducting research that is aimed at making the mining industry more efficient in term of both productivity and the health and safety of the worker. As part of this research the Bureau of Mines has integrated a testbed composed of computer and related peripheral hardware to form an intelligent base for performing autonomous mining machine experiments. Although this particular application was con- figured for use on a Joy 16 CM mining machine, its generic structure facilitates its attachment to a variety of mining machine types. The multitasking multiuser computer can be set up for other applications by changing a bubble memory cartridge. The Joy 16 CM implementation includes 96 digital input-output (1-0) ports, 32 analog inputs, 8 analog outputs, 2 serial data channels, and 1 printer port. Operation of the machine can be performed either through a local terminal or remotely through a modem hookup. This report describes a testbed for autonomous mining machine experiments (TAMME)--its hardware, software, and complete system integration--so that it can be used as a foundation for other applications.

Jan 1, 1988

By Christof Metzger

This paper discusses the process utilized by the Kiewit?Bilfiger Berger Joint Venture (Contractor) to select, design, and procure the largest mixshield tunnel boring machine (TBM) ever implemented in North America. The mixshield will excavate the 8,534 linear m × 6.7 m ID (28,000 linear ft × 22 ft ID) tunnel for the City of Portland Oregon?s, Bureau of Environmental Services (Owner) East Side CSO Tunnel Project. TBM selection was conducted under a preconstruction contract in which the Contractor, Owner, Construction Management Consultant and Designer collaborated on TBM selection prior to commencement of construction. This paper focuses on TBM design considerations, including the use of one versus two machines, machine configuration,extended-wear protection, hyperbaric interventions, boulder digestion, and erection of a steel-fiber-reinforced segmental lining

By T. Braun, J. Parker

On June 25, 1999, BHP Billiton (BHPB) announced the suspension of operations at the BHP Copper Inc.(BHP) San Manuel copper mine in Pinal County, Arizona. Subsequent to this announcement, BHPB aggressively pursued a number of alternatives for the underground mine and open pit facilities, including continued curtailed operations, sale to a qualified mining operator and closure of the property. After consideration of these various alternatives over a 2.5-year period, BHPB announced final closure of the mine site on January 15, 2002.This paper describes how the BHPB charter and HSEC policy apply during the closure process.

Jan 1, 2004

By Thierry Bernard, Phillipe Cappello, Jean Marc Laboz

"The main reasons of the emergence of electronic detonators are linked to:-Local urban development close to mining operation sites-Environment regulations"

Jan 1, 1995

By John C. Machisak

INJURY and employment figures for nonmetal mines and mills in 1959 are presented in this publication. Data for nomnetal mines are presented separately from those for nonmetal mills. The Bureau of Mines is authorized to send questionnaires to the nonmetal mining industry each year requesting their voluntary submission of injury experience and employment data. The voluntary response to these requests has contributed greatly toward the promotion of safety in the industry, and every effort has been made to make the information as complete as possible.

Jan 1, 1963

By David Dardick

Tround International Inc. is developing rock excavation and drilling devices which utilize a simple patented mechanism for firing frangible projectiles. This system launches a salvo of three projectiles with every shot in automatic sequence. Studies conducted by Physics International Inc. have demonstrated that firing projectiles into hard rock such as granite creates fragmentation which is much faster and cheaper than conventional drilling and blasting. The Tround salvo approach enhances this further by a controlled stresswave interaction created by a slight time difference during impact of the individual projectiles. The University of Maryland is conducting additional studies to optimize these parameters.

Jan 1, 1981

By P Bellairs

The Hamersley Province is located 1000km to the North of Perth the Capital City of Western Australia and is of major economic significance due to the mining of extensive deposits of Haematitic Iron Ore for both domestic and export use. A small but significant proportion of the waste associated with these deposits presents problems due to its ability to spontaneously combust and react with explosives resulting in premature detonations.

Jan 1, 1996

By Georgene Renner

With more than 800 booth spaces sold and 540 exhibiting companies displaying their wares, there was something for everyone on the exhibit floor of the 2014 SME Annual Meeting in Salt Lake City, UT Feb. 23-26. The following is a sample of what was offered at the 2014 meeting.

By Lianyang Zhang

For optimal design of rock socketed shafts used to support axial loading, it is important to predict the end bearing capacity. The existing empirical methods for determining the end bearing capacity of rock socketed shafts use the empirical relations between the end bearing capacity, qmax, and the unconfined compressive strength of intact rock, sc. Since rock socketed shafts are supported by the rock mass (both intact rock blocks and discontinuities separating them) not just the intact rock, one should consider not only the intact rock properties but also the influence of discontinuities when determining the end bearing capacity. Although the effect of discontinuities may have been implicitly (partially) included in the empirical relations derived from the results of load tests, it is not clear how big the effect is and how much of it has been included. In this paper, a database consisting of 50 test shafts, 25 of which contain the RQD (rock quality designation) value, is developed. Using the database, the applicability of the existing empirical relations is evaluated and two new empirical relations between the end bearing capacity, qmax, and the unconfined compressive strength of rock mass, scm, are derived. The new empirical relations explicitly consider the effect of discontinuities by using scm which is directly related to RQD. Finally, an example is presented to demonstrate the application of the newly derived relations.

Jan 1, 2008

To meet the energy requirements, hydroelectric projects are planned and executed in many countries. Though these projects requires a high capital investment, the returns are regular with minimum maintenance after commissioning of the project and are ecofriendly. Bhutan is situated in the eastern Himalayas and covers an area of 38,394km2 (14824.01sq. miles. It is bordered by India in East, South and West and by Tibet in the North. The hydropower potential of the country is estimated at 30,000MW, out of which around 5% has been harnessed.

Jan 1, 2016

By F. Habashi

Asbestos, an extremely useful natural resource, has been studied extensively mineralogically and for industrial application. Its extraction from ores has been greatly improved with respect to safety in the work place. In spite of that, there is a decisive effort in many countries to ban its use on the grounds that it is a toxic substance. This action resulting in drastic decrease in production and the possibility of destroying the industry. The chelation of asbestos with organic dyes seems to be a promising way to abate its toxicity. Dyeing can be done when the fibers are slurred in water at ambient conditions in the same way as textile fibers.

Jan 1, 2009

This publication summarizes, for potential contractors and other interested parties, the research, development, and demonstration contract projects programed by the Bureau of Mines for fiscal year 1979 (October 1, 1978-September 30, 1979) under its Mine Health and Safety Research program. The objective of these projects is to provide an ordered and sequenced series of advances toward the Bureau's overall goal of providing the system technology required to create a healthier and safer working environment for the Nation's miners.

Jan 1, 1979

By Seong-Taek Yun, Chil-Sup So, Seung-Jun Youm

The greisen-bordered quartz veins are spatially, temporally and genetically associated with a late Cretaceous granite intruding an early Palaeozoic, limestone-rich formation. Paragenetic data indicate three stages of hydrothermal mineralisation, the first typically in or within 500 m of the granite stock and showing vertical zoning between deeper Mo and higher W, the other two more abundant in the upper and outer parts of the mineralised area. Fluid inclusion and stable isotope data indicate that hydrothermal veins formed over a temperature range of 120-395 degrees C from low-salinity fluids. Early wolframite and molybdenite deposition in stage I occurred at temperatures of 300-395 degrees C from magma-derived, low-salinity, CO2-rich fluid, mainly as a result of fluid boiling and associated CO2 effervescence. Progressively larger volumes of local meteoric water entering the system led to the successive deposition of scheelite in stage I vugs, stage II base-metal sulphides and stage III fluorite-carbonates. Remobilisation of W and its later deposition of scheelite in the outer and shallower portions of the system occurred at 215-275 degrees C and stage II and III mineralisation from lower-temperature fluids that became progressively lighter in stable isotopes. It is concluded that the influx of meteoric water increased with distance from the cooling pluton

Jun 18, 1905

By G. Kang

The ferroalloys industry has generated historically substantial solid waste. The accumulated waste causes serious problems to the environment. However, it is possible to transform the solid waste into an environment-friendly resource to serve the human being. Consequently, the construction of plants that are ?environment-friendly? and that accommodate ?recycling? has become a target of most ferroalloy producers in the world to ensure sustainable development. This paper introduces the practice of Shanxi Jiaocheng Yiwang Ferroalloys Works, the biggest manganese metal producer in China, in the development of an ?environment-friendly and recycling? process. The process includes power generation using coal gangue, waste from local coal mines; hollow bricks manufacture using slag and fly ash from the power station; cement production using slag from ferroalloy smelting; recovery of ferrous and non-ferrous elements in the dust from the furnace gas cleaning system; application of silica dust in construction and so on. The final objective of the plant is to realize zero discharge of solid waste. The profit of the ?environment-friendly and recycling? process compensates in part for the operational expense of the environment facilities.

Jan 1, 2004

By David D. Davidson

Commodities remain hot for the time being, but for how much longer? The bulls point to global economic growth lead by China?s insatiable demand for raw materials. To further emphasis the bullish view they point to the emergence of India for follow through demand. The bears remain convinced China?s growth is unsustainable and with higher interest rates and high oil prices, the United States economy is poised to slow. Both groups can make a convincing argument and both will be proven right in the fullness of time. Profitability and balance sheet strength for the mining industry has rarely been better. Is this a time to be bold or cautious? In this paper, the author will address the dilemma facing today?s management as they pursue growth and try to minimize risk.

Apr 1, 2005

By D. J. Adams, W. K. Rymon-Lipinski

Rock engineering plays a crucial role in contributing to sustainable development in South African mining. A framework for this has been created through legislation and structures to encourage the mining industry to have a long and prosperous future. However, rock engineering input is an essential element to achieving success. The most accessible deposits have been mined in South Africa and although large reserves still remain, many of these are difficult to access and will require excellent rock engineering knowledge and skill in the future. This is borne out by the fact that more than 50 % of fatal accidents are related to rock engineering issues. Many of these may be addressed with rock engineering solutions which are not beyond current rock engineering technology. A reduction in fatalities and injuries contributes to a sustainable mining industry.

Jan 1, 2003

By Clifford S. Gibson

THE Workmen's Compensation Ace defines Silicosis as "a fibrocic condition of the lungs caused by the inhalation of silica dust sufficient co produce a lessened capacity for work". This fibrocic condition muse exhibit a specific appearance in the X-ray picture of the chest-an appearance which is not characteristic of several lung conditions which can cause lessened capacity for work and which are not due co silicosis. The layman is sufficiently familiar with this subject co know chat, as far as our knowledge goes, quartz is one of the principal objectionable factors in the production of this condition. He should also know that silicosis respects neither geographical nor industrial boundaries. It is as much a factor in some industrial processes (e.g. foundry work, sandblasting) as it is in mines handling ores containing quartz. Its development co a recognizable stage is usually a matter of many years. As yet, its cure is unknown. Its prevention is possible in varying degrees. The layman should also know that the development of fibrosis may be accelerated by breathing in, or living in, any atmosphere containing dust. Few normal adults, particularly those above a certain age, have clear lungs, and fibrosis in varying degrees is noted in the farmer, the steel worker, the clerk, and many others in varied occupations. It is not restricted to miners. Medical and industrial journals, and at times the press, are crammed with data pertaining to this subject, much of which is misinformation. This is particularly true of certain !laces where the preventive and compensation measures for the good o those earning their livelihood in an industry in which silicosis may be contracted are not so far advanced as in our own Province. A great many of these publishings are alarming to the layman. They leave him with the impression that he is taking his life in his hands if he elects to work underground, particularly in a gold mine-that he has at once sold his heritage of health and chat sooner or later he will succumb to the ravages of this ailment. Nothing could be farther from the truth. Actually, under present conditions in Ontario mines, a very small percentage of the men employed ever become impaired by silicosis to the extent chat they must withdraw from the industry. I propose to tell you briefly something of this subject as it affects our mines.

Jan 1, 1937

A number of mineral deposits occur in close proximity to the Pacific plate fronts. Among these deposits are gold-silver and the base metal sulphide deposits of copper, zinc and lead. Gold deposits that commonly occur in these areas are of hydrothermal origin. Of these the epithermal deposits have attracted the attention of the exploration geologists as well as the metallurgists. One vital aspect of the activity of the geologists is the development of models for epithermal gold mineralisation in the Pacific Rim. These models can also be used by metallurgists for predicting gold extraction processes. This paper reviews the mineralogy, fineness and the host minerals of gold and examines the data in the light of gold mineralisation in the southwest Pacific Rim. The gold mineralisation models proposed for the Pacific Rim have been used to predict gold extraction processes suitable for the various mineralisation types. Discussed also are the mineralisation and treatment processes of some selected epithermal gold deposits and gold-rich porphyry copper deposits in Indonesia, Papua New Guinea, Solomon Islands, Fiji and New Zealand.

Jan 1, 1999