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By Graham W. Gibbs

The current state of knowledge concerning mesothelioma risk estimates is reviewed. Estimates of the risk of mesothelioma exist for the commercial asbestos fiber types chrysotile, amosite and crocidolite. Data also exist on which to assess risks for winchite (sodic tremolite) and anthophyllite asbestos. Uncertainty in estimates is primarily related to limitations in measurements of exposure. Differences in the dimensions of the various fiber types and of the same fiber types at different stages of processing add a further complication. Nevertheless, in practical terms, crocidolite presents the highest asbestos related mesothelioma risk. The risk associated with sodic tremolite (winchite) appears to be similar. In chrysotile miners and millers, the mesothelioma risk has been linked with exposure to asbestiform tremolite. Exposure to chrysotile in a pure form seems likely to present a very low if any risk of mesothelioma. While the majority of mesothelial tumors result from exposure to the asbestos minerals, there are other well established and suspected etiological agents. While a practical threshold seems to exist for exposure to chrysotile, it is unlikely to exist for the amphibole asbestos minerals, especially for crocidolite. To date there is no indication of an increased risk of mesothelioma resulting from non-commercial fiber exposure in the taconite industry. © 2007 Elsevier Inc. All rights reserved. Keywords: Mesothelioma; Amosite; Grunerite; Taconite; Crocidolite; Tremolite; Anthophyllite; Winchite; Risk estimation; Etiology

Jan 1, 2007

By Geoffrey Berry

Exposure?response relationships between the relative risk of lung cancer and quantitative measures of exposure to asbestos are available from a number of epidemiological studies. Meta-analyses of these relationships have been published by Lash et al. (1997) [Lash, T.L., Crouch, E.A.C., Green, L.C., 1997. A meta-analysis of the relation between cumulative exposure to asbestos and relative risk of lung cancer. Occup. Environ. Med. 54, 254?263] and Hodgson and Darnton (2000) [Hodgson, J.T., Darnton, A., 2000. The quantitative risks of mesothelioma and lung cancer in relation to asbestos exposure. Ann. Occup. Hyg. 44, 565?601]. In this paper, the risks derived in these meta-analyses have been compared. Lash et al., concentrated on process and found that the risk of lung cancer increased as the asbestos is refined by processing. Hodgson and Darnton concentrated on fibre type and found that the risk was highest for exposure to amphibole asbestos (crocidolite and amosite), lowest for chrysotile and intermediate for mixed exposure. Some of the differences between the conclusions from the two meta-analyses are a consequence of the choice of studies included. The range of asbestos types included in the studies in the analysis of Hodgson and Darnton was wider than that in Lash et al., enabling differences between fibre types to be analyzed more readily. There are situations where occupational exposure to chrysotile asbestos has shown no detectable increase in risk of lung cancer. Taconite miners have shown no increased risk of mortality due to lung cancer. © 2007 Elsevier Inc. All rights reserved. Keywords: Mesothelioma; Amosite; Grunerite; Taconite; Crocidolite; Tremolite; Anthophyllite; Winchite; Risk assessment; Etiology

Jan 1, 2007

By Brent A. Elliott, J. Richard Kyle

Texas is a major producer of industrial mineral resources required by the state’s ever-growing population that now exceeds 28 million. Texas typically ranks in the top three states for the value of non-fuel mineral production with a total value of $5.2 billion in 2017, accounting for 6.9% of the total US mineral value. Almost 90% of current Texas industrial mineral value comes from the production of cement, crushed stone, industrial sand, and construction sand and gravel. Construction material consumption is focused in the 25 metropolitan areas of the state with populations of > 100,000 residents. Industrial mineral consumption is dominated by the four most populous regions of the state—Houston, Dallas-Fort Worth, San Antonio-New Braunfels, and Austin-Round Rock—with an aggregate population of more than 18 million. More than 11,000 employees work in Texas mining and processing operations. Texas produces more crushed stone than any other state from more than 200 quarries; a similar number of operations produce sand and gravel. Specialty industrial sand production for use as proppants in hydraulic fracturing for enhanced petroleum production serves as an excellent example of how developments in one industry sector can markedly affect another industry; the production of industrial sand in Texas has markedly increased over the past decade, reaching $1.3 billion in 2014. With Texas’ population projected to reach 50 million by 2050, continuing in-state development and production of industrial minerals will be required to supply its residential, commercial, and industrial users. Favorable geology and economic factors provide opportunities for identification and development of new industrial mineral production sites.

Using mines in Canada, Boart Longyear, a leading provider of drilling services and products, has put its Stage 3 Coring Bit to the test and each time the bit has passed the test with great success. After more than a year in the field at a major mine operation in Sudbury, Canada, the Stage3 coring bit broke life records to become recognized as the most productive design in the industry. In addition to the proven advantage seen in regular bit life increases of as much as 300 percent in some cases, the design is quickly being recognized for its cost-saving operational impact. In Sudbury, the mine operation realized actual cash savings of more than C$45,000 within an eight-month period by making the switch to Stage3 bits. For years, the Sudbury Basin team has relied on the Alpha Extended Crown bit with the Express Waterway geometry option, ordering approximately 500 units per year. This 07 COM ECEX configuration performed well in medium-hard, non-abrasive to ultra-hard, non-abrasive formations with an average bit life of 150 m (490 ft). While satisfied with the performance of the Alpha Ex-tended Crown, the team agreed to put the new Alpha Stage3 to the test. Boart Longyear?s field engineers supplied five drill sites with Alpha Stage3 bits in a 07 COM configuration. After thoroughly testing the Stage3, the results were clear. Even with the well-known performance and versatility offered by the previously preferred configuration, the Stage3 set a new standard of bit performance. The new bit maintained its cutting edge for up to three times longer than the Alpha Extended Crown, a significant performance increase when compared to the 07 COM ECEX.

Jan 1, 2009

By J. M. Elder, W. S. Kow

Challenges to new heavy mineral deposit developments are presented. These include land use issues, particle fineness, declining grades, and particle coating, amongst others. Industry responses to these are presented as possible solutions.

Jan 1, 2005

By John E. Tilton

The ability of companies and countries to mine copper and other mineral commodities competitively and in the process to generate new wealth depends on their mineral endowment. Chile, for example, produces and exports copper because it is well endowed with high-quality, low-cost deposits. This production creates wealth that benefits mining companies and their stockholders, the government, local communities, as well as copper consumers around the world. The widespread perception that mineral endowment must largely determine competitiveness, or what economists call comparative advantage, must be true at any particularly moment. Countries with abundant reserves must be competitive. This follows from the definition of reserves — the quantity of a mineral commodity found in discovered deposits that are profitable to exploit under current conditions. As a result, it is a tautology and not particularly interesting. The important question is what causes reserves to change over time, producing in the process new wealth and shifts in competitiveness?

Jan 1, 2003

By Y. Boissonnas

INTRODUCTION, The transalpine rail routes in Switzerland are well over one hundred years old. As the established routes no longer meet the demands of the continually increasing volumes of rail traffic between north and south, two new routes through the Alps were planed. The old Gotthard rail line is in fact a mountain railway. The northern and the southern access ramps?with a maximum speed of 80 km/h and a maximum slope of 2.2%?reach the old Gotthard rail tunnel at an elevation of approximately 1,100 m above sea level. This is approximately 900 m higher than the city of Milan. In 1992, the Swiss electorate people voted with an overwhelming majority in favor of the project to build the new base routes through the Alps. The Swiss voted again in 1998 in favor of the financing proposal for the new infrastructure. Swiss Federal Railways together with the BLS Lötschbergbahn were commissioned for the realization and management of the Gotthard and Lötschberg routes. AlpTransit Gotthard Ltd., founded by Swiss Federal Railways, was given the task of managing the design and realization of the Gotthard route until the start of regular service. In the meantime the shorter Lötschberg Base Tunnel was open to traffic in 2007

By Stephen M. Smading

The Jinping-II hydroelectric project in China features four parallel headrace tunnels approximately 18-km- (11-mile-) long. Two will be excavated by tunnel boring machines (TBM) and two by drill-and-blast. A nearby fifth tunnel is being excavated by a 7.2-m (23.6-ft) TBM to draw down ground water in advance of excavating the headrace tunnels. Unique onsite assembly of a 12.43-m (40.7-ft) main beam TBM and backup system was completed on Sept. 18, 2008 in the remote mountains of the Sichuan province. The equipment was assembled onsite, without previously having been assembled and tested in a factory, using a method called onsite first time assembly (OFTA). This paper addresses the following topics: ? Project description including geology and terrain. ? The decision process leading to onsite, first time assembly, the assembly process and logistics, and lessons learned. ? Design features of the TBM and backup system. ? Operational history from startup to the writing of this article.

Jan 1, 2009

The theme of the 2012 North American Tunneling conference (NAT) was ?Tunneling: Driving Value.? This theme best reflects where the tunneling and underground construction industry is to-day. Major advances that have been made in technologies have provided tremendous improvements in productivity, which, in turn, have allowed the industry to deliver more cost-effective and less disruptive solutions to the nation?s infrastructure needs. Despite a weak economy, domestically and globally, cities and states continue to spend billions on infrastructure improvements. For the underground construction industry, that means more transportation and water, wastewater, storm water projects and other underground structures. And, for each project completed, underground construction and tunneling technology grows. The NAT conference, put on by the Underground Construction Association (UCA) of SME, provides an outlet for technology transfers among professionals. This year?s conference, held in Indianapolis, IN June 24-27, attracted 918 attendees, up from 803 at the last NAT in 2010. The accompanying exhibit also featured 116 exhibitors occupying 140 booths. That was up from 108 booths in 2010. So, the meeting continues to grow as underground construction professionals throughout the world seek to learn from their peers.

Jan 1, 2012

By Jill Murray

This study focuses on the amosite mining region in South Africa and associated health effects, compared to other mined asbestos fiber types. Historically, dust and fiber levels were high in the amosite mills and mines, and many miners and members of the surrounding communities were exposed to the fibers. Research has shown that amosite produces both benign and malignant disease. Nevertheless, the mesotheliomagenic potential of amosite is several fold lower than crocidolite. The risk of disease associated with amosite exposure is difficult to quantify. Reasons for this include the scarcity of available information, including fiber measurements, and case ascertainment, as well as the juxtaposition of the amosite and crocidolite asbestos seams in South Africa. © 2007 Elsevier Inc. All rights reserved. Keywords: Amosite; Mesothelioma; Crocidolite; South Africa; Asbestos

Jan 1, 2007

By Georgene Renner, William R. Yernberg, Steve Kral

Agapito Associates (AAI) provides consulting services in geo-engineering, mining engineering and related disciplines. Founded in 1978, the firm operates out of offices in Grand Junction, CO, Golden, CO and Lombard, IL. Members of the staff include mining, civil and geological engineers, physicists, geologists, numerical analysts, computer specialists, instrumentation specialists, plus administration and technical support personnel. AAI has provided consulting and engineering services to mining companies producing base metals, precious metals, coal, potash, trona, limestone, oil shale and salt, and to defense and nuclear-waste disposal industries. AAI also provides services for measuring in situ horizontal stresses using an advanced biaxial overcore stress downhole measurement system developed by Sigra of Australia. Since 1978, AAI has measured in situ stress in copper, oil shale, molybdenum, trona, limestone and coal mines, and in tunnels and concrete structures. Since 1994, the staff has completed 527 overcore stress determinations. AAI has the equipment and personnel for overcoring, sample coring and instrumentation installation in limited access, surface and underground mines. Portable Longyear CP-65 drills, borehole deformation gauges and strain indicators are used for difficult-access overcoring and are permissible for use in gassy mines.

Jan 1, 2006

By Gregory T. Ziegler

A complex soil profile and high water table, together with a below-grade active subway tunnel, an above-ground elevated railway line, and the heavily travelled Northern Boulevard all passing above the tunnel alignment, combined to make mining of New York?s Northern Boulevard Crossing what is widely considered to be the most challenging portion of the multi-billion-dollar East Side Access project. The Northern Boulevard Crossing is a vital link in this project which, when completed, will connect the Long Island Railroad to Grand Central Terminal in Manhattan. How the sequential excavation method (SEM) tunneling was successfully accomplished, despite the obstacles, was a textbook exercise in practical innovation coupled with close cooperation between the owner, the construction manager, Hatch Mott MacDonald, the designer, Parsons Brinckerhoff, the contractor, Schiavone-Kiewit, and spe-cialty geotechnical contractor, Moretrench.

Sep 1, 2013

The National Institute for Occupational Safety and Health conducted laboratory and field tests to evaluate the effectiveness of dust collector bags for reducing dust liberation and operator exposure from a roof bolter?s dust collection system. The laboratory tests evaluated the bag?s effectiveness to contain dust and the effect on canister filter loading in both a bag and bagless condition. The dust emissions from the collector?s exhaust were also measured in each condition during laboratory testing. Laboratory results show that nearly 100 percent of the test dust fed into the collector was captured by the dust bags. Loading and pressure drop on the dust collector?s canister filter is greatly decreased when using the bags, enabling longer periods of drilling without filter removal/cleaning. The field results showed that, even though dust standards were met, respirable dust in exhausted emissions was reduced around the bolter. Laboratory and field results show that benefits from use of the bags are realized in all areas of operator exposure.

Jan 1, 2008

By A. Moergeli

The Swiss are building the world’s longest tunnel, the 57-Kilometer (35-mile) long Gotthard Base Tunnel. Lot 252, Tunnel Amsteg: Two Hard Rock Tunnel Boring Machines (TBM) crossed hydro-thermally decomposed granite. While the East TBM advanced slowly but steadily, the West one got stuck for five months and had to be recovered by special means and methods. Both TBMs have finished their more than 11-Kilometer (7 miles) long drives successfully. Lot 360, Tunnel Sedrun: For the first time in tunneling, roadway support machines are used through most challenging, squeezing geology. They constantly advance in full face mode for about one Tunnelmeter/24 hours.

Jan 1, 2007

By T. M. Barczak

Stoppings are required to resist lateral forces on the face of the structure to control pressure differentials created by ventilating air. The design criteria in other parts of the world, including Australia, exceed this requirement by specifying over pressurization control to as much as 14 kPa (2 psi) in the active sections and 35 kPa (5 psi) in the main ventilating control areas. This is done to provide protection to the mine workers from explosive or air blast events within the mine that can create this over pressurization. The National Institute for Occupational Safety and Health (NIOSH) has been conducting research to develop a new testing protocol for rating mine ventilation stoppings. The premise of this work is that arch-loading conditions more accurately reflects the transverse load capabilities of stoppings in underground coal mines than the freestanding flexural strength test specified in the current Code of Federal Regulations (CFR). This work clearly shows that the transverse load capabilities of dry-stacked, mine ventilation stoppings are dependent upon the material strength of the block and the height and thickness of the wall, none of which are part of the current CFR criteria based on ASTM E-72 specifications. This paper compares the transverse load capabilities of several block materials and wall dimensions commonly used in stopping constructions based upon simulated three-hinge, rigid-arch loading tests of half-wall constructions in the NIOSH Mine Roof Simulator. The results indicate a wide-range of transverse load capacities, ranging from as low as 21 kPa (0.3 psi) to as much as 117 kPa (17 psi) for the conditions evaluated in this study. The current CFR criteria do not distinguish between applications of these stopping designs despite their wide variance in transverse load capabilities, which is not conducive to employing ventilation control strategies that isolate certain sections of the mine to prevent injury to mine workers.

Jan 1, 2009

By T. L. Owen

Since 1993 Cyprus Amax has brought $2.5 billion dollars of greenfield and expansion projects into production, taking it from a mid-sized domestic minerals company into a major international minerals organization. The near simultaneous development of these multiple mineral projects in different locations around the world provided the opportunity for Cyprus Amax to develop a formal project management approach based, in large part, on an outsourcing philosophy. This formal project management system along with its outsourcing philosophy has served the growth agenda of Cyprus Amax extremely well. These preceding factors, coupled with the in-house retention of a core project group that fully understands the breadth of skills and abilities needed to undertake development of multiple large projects successfully, have been the cornerstone of Cyprus Amax’s project development success.

Jan 1, 2000

By Joel Nonnweiler, Rafael Castro, Ross Webb

The three thousand foot long 66-inch diameter Folsom East Interceptor Section2B was completed accident free, on time and under budget with no measurable surface settlement. The tunnel passed through nested cobbles, highly abrasive sands and gravels, and abandoned mine workings with less than five-feet of cover at times. Preventing settlement was critical since the tunnel passed under a heavily traveled state highway. A pilot project to test microtunneling and pipejacking methods in the same ground conditions abandoned both drives before completing the planned drive lengths. This paper discusses performance of the conventional tunneling method selected to excavate the ground and the effectiveness of the ground modification techniques employed.

Jan 1, 2001

By Sohta Takatsu, Hachiroh Mizubata, Shigeki Kudoh, Kazuya Takekuni, Yoshinori Yamada

A special type of shotcrete is used to improve the performance of open-type TBM in difficult situations. The Hakamagoshi and Johana tunnels are expressway evacuation tunnels of 3.2 km and 5.1 km in length, respectively (total 9.1 km) that were excavated by one open-type TBM. The geological conditions at the sites were estimated to be good before excavation. However, 95% of the rock turned out to be two ranking orders worse than the estimated classes. Therefore, we used a special shotcrete for bad rock conditions, and succeeded in excavating the tunnel at an average rate of 270 m/month.

Jan 1, 2001

By Richard L. Stotlar

Introduction During the last decade, the metallic minerals segment of the industry could be categorized as a "feast-or-famine" business. It is no secret that metallic minerals are cyclical. Employment opportunities greatly depend on the supply and demand for its mineral products. It is also not unusual for there to be a lag between the industry's manpower requirements and academia's ability to produce new graduates. Due to this lag, there will be years with manpower shortages, as in the mid-1970s. At other times, supply will exceed demand. The question is where will the jobs be in the years to come? This presentation will review reasons why employment opportunities have declined within the metallic minerals industry. It will also predict future demand for mineral engineering graduates. And it will outline strategies for obtaining an employment offer. Historical Review - Employment From 1977 through 1983, about 75% of all metal mining employees were directly engaged in production activities, down from 83% in 1965. This decline reflects increased use of labor saving equipment, and more government regulation and foreign competition. Metal mining's employment decreased from 74,000 jobs in 1982 to fewer than 68,000 in 1983 - an 8% decline. The overall industry is having these problems because of the general downturn in the economy. For example, at the beginning of this decade, US automobile and steel industries were in trouble. Interest rates were too high and volatile. This adversely affected construction, housing starts, and manufacturing. All these industries, being large users of base metals, drastically affected the metals industry. US copper companies are still having problems. Reports indicate that many copper employers have cut production, laid-off workers, and permanently closed mines, refineries, and smelters. A decline in the demand for US produced metal products, such as copper, obviously affects some mineral engineering employment opportunities. Other factors to consider when looking at employment opportunities and why it has become difficult for US metal producers to compete in the world market include: • The grades of ore bodies of many US minerals are considerably lower than the grades of ores being mined elsewhere in the world. • The grades of ore bodies currently being mined in the US are steadily declining. • Foreign producers are largely government controlled and are not necessarily subject to the realities of supply and demand. • US environmental regulations have considerably added to production costs. Foreign producers in most countries do not have to worry about these additional costs. • US mines are getting deeper. This adds to the cost of production because of the increasing distance the ore has to be transported. • Plants and equipment are outdated. Many companies find themselves operating with equipment and plants that need modernizing or replacing. This obviously hinders competitive productivity. • Labor and management have had problems. Work stoppages in certain mining businesses and high wage and benefit costs in relation to foreign producers place US producers at a disadvantage. • Much land is unavailable. The US government owns most of the land considered to have the best potential for minerals development. Most of this land is unavailable for mining or exploration. Therefore, it appears that finding employment with a company whose primary business is mining and processing most metals, such as copper, in the US will be quite restricted and competitive. Future Demand It is difficult to anticipate what key employment opportunities within the next few years will be available to mineral engineering graduates. The Engineering Manpower Commission estimated that US engineering schools awarded 72,471 undergraduate degrees in 1983 vs. 66,990 in 1982. This was the eighth consecutive year in which the number of baccalaureates awarded has increased. On a brighter note, the US government's Occupational Outlook Quarterly stated that the growth rate through 1995 for all engineers is an encouraging 49% over present levels. The estimated number of engineers employed in 1982 is 1.2 million. The numerical in-

Jan 2, 1985

By D. Bour, C. Nyikos, R. Curtice

Fire in a coal mine can be disastrous on many levels. In most cases, when a fire is detected, mining operations cease and all personnel are evacuated. Underground coal-mine fires are difficult to extinguish, can burn for a long time, and often result in an extended period of lost production. In a worst-case scenario, the mine is permanently sealed and abandoned, resulting in lost jobs, lost natural resources, and possible devastation of the local economy. In some cases, seals placed within the mine to isolate the fire could eliminate the need for sealing the entire mine and the subsequent extended delay in returning the mine to full operation. Previous attempts to place remote seals to extinguish mine fires in active mines have been largely unsuccessful. The West Elk mine experienced an underground fire in early 2000. The fire could not be accessed and extinguished from the active mine workings. A method of constructing seals remotely by drilling boreholes into the affected area was needed to help isolate and extinguish the fire. This paper describes the process by which remote seals were constructed that successfully isolated the fire and provided a means of extinguishing the fire by flooding the area with water. The period of lost production in the West Elk mine was considerably shorter than is typical in similar situations.

Jan 1, 2002