Search Documents

By J. C. Yingling, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Much of the land reclaimed since enactment of the 1977 Surface Mining Control and Reclamation Act is over-compacted. Research has shown that excessive compaction in replaced growing media is detrimental to establishment of trees. If trees are to be grown on reclaimed surface mined sites, something must be done to alleviate this excessive compaction. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed growing media. The University of Kentucky has developed test cells on reclaimed sites at a surface mine in eastern Kentucky to determine the impact of tillage (ripping) on soil compaction and tree survival rate. The ripping methods being evaluated include shallow tillage using conventional farm equipment and deep tillage using a dozer with a ripping arm. The impact of organic soil supplements on soil physical properties and tree survival rates is also being evaluated at the site. The organic soil supplements being evaluated include application of hardwood bark and application of straw and mulch. Each test cell has been planted with various species of trees, and for the first two years, data have been collected at these test cells for soil dry bulk density, penetration depth and resistance, and survival rate of trees. These data are currently being correlated to determine how ripping and the application of organic soil supplements affects the relationship between soil compaction and tree survival rate.

Jan 1, 2002

By Daniel F. Meyer

INTRODUCTION The Metropolitan Boston Transit Authority (MIA) Red Line has served greater Boston commuter needs from its Harvard Square terminus since its opening in 1912. Since then, the population of Boston's northwest area has increased substantially, and with this growth have come dramatic changes in the type and distribution of urban land uses, including the number of households, jobs, shopping and recreational opportunities; these changes have created a need for improved transportation. Extension of the Red Line to better serve these communities has been a topic of discussion for nearly 40 years. In November of 1977, the Urban Mass Transportation Administration (UMTA) granted the MBTA approval and funding for the Red Line Extension Project. With funding in place, the MBTA proceeded with final engineering and construction of the section from Harvard Square to Alewife. When completed, the Red Line Extension will add 3.2 miles of new track to the MBTA system. Estimated final cost is about $400 million. On October 3, 1978, the MBTA received bids for the construction of Project 091-105, Harvard Square to Porter Square Tunnels and Shafts, which is part of the overall Red Line Extension. The Joint Venture of Morrison-Knudsen, White, Mergentime was the low bidder at $47,478,600. Official award of the contract came on October 25, 1978, with Notice to Proceed given October 31, 1978. The contract called for construction of two independent parallel concrete-lined tunnels in rock, soft-ground and mixed-face

Jan 1, 1983

The authors summarise the development and recent advances in the reconstruction and visualisation of three-dimensional objects from point data and describe applications to the reconstruction of orebody shapes from drill-hole and other data. In particular, Dijkstra's algorithm is proposed and implemented as a means of optimal reconstruction of complex orebody and topographical shapes from irregularly located sample data. The surfaces of the shapes are constructed from triangular tiles and the algorithms proposed by the authors are guaranteed to find the optimal set of tiles that "best" construct the surfaces on the basis of specified objective criteria. The algorithms are illustrated by applications to a complex silver/gold/zinc/lead deposit.

Jan 1, 2002

By C. Chamberlain

The mining industry continues to underpin the regional economy. Australia, benefiting from a weak currency, receives 27% of the total goods export value from non-energy mining lead by aluminium, iron ore, gold and nickel. Consolidation has eliminated CRA, Comalco, North, Savage, Acacia, Ashton, Great Central, Aberfoyle, Placer Pacific, Plutonic, Normandy and RGC leaving Rio Tinto, BHP-Billiton, WMC, MIM and, increasingly, the South African companies Anglo, Gold Fields and Harmony as dominant players. Exploration stagnates with expenditure dropping 40% in Australia and 80% in PNG from peak levels. Major new regional developments include Rio’s West Angles iron ore project, Newcrest’s Ridgeway gold-copper mine and Inco’s Goro nickel-cobalt project in New Caledonia.

Jan 1, 2002

By O. MacIntosh

The Round Mountain gold mine, located 90 km (55 miles) north of Tonopah, NV began large-scale production in 1977. During 2008 Round Mountain Gold Corp. (RMGC) relocated the primary crusher facility approximately 300 m (1,000 ft) to make room for the next phase of openpit mining activities. This facility was installed in 1988 and used a log-crib retaining wall and dump pocket. RMGC selected Hilfiker Retaining Walls and Collins Engineers, Inc. to provide design and materials for a new 17-m- (56-ft-) high mechanically-stabilized embankment (MSE) wall to support the haul trucks at the new location. The construction contractor was EarthTech West Ltd. of Norwood, CO. An MSE wall with a cast-in-place concrete face was chosen as a durable, yet less expensive alternative to the reinforced concrete dump pocket that was originally designed for the project. The arrangement of the MSE wall is of an unusual configuration to meet a variety of operational and maintenance requirements. This paper outlines the selection process, design and construction of the MSE wall.

Jan 1, 2010

By F. Freme

For the second time in four years, the coal industry was brought to the forefront of the nation’s consciousness in 2006, as two separate events unfolded which involved coal miners trapped underground. Unfortunately, the tragic results of the 2006 incidents were not the same as in 2002 when the trapped miners were all successfully rescued. In January, two different incidents, both in West Virginia, focused the public’s attention on the dangers that miners face on a daily basis. As a result of these unfortunate events new legislation requiring improvement in safety in underground mines passed both at the federal and state level. In 2006, a total of 47 miners died on the job, matching the total number that occurred in 1995, and more than double the 22 killed in 2005. Notwithstanding those tragic events, coal production in the United States reached another record level in 2006, ending the year at 1.05 Gt (1,161.4 million st) according to preliminary data from the U.S. Energy Information Administration (Table 1). Production in 2006 was 27.1 Mt (29.9 million st) higher than the prior record set in 2005 of 1.03 Gt (1,131.5 million st). Although coal production rose in 2006, U.S. total coal consumption actually declined for the year. Coal consumption decreased in the electric power sector by 1.1 percent, while coking coal consumption decreased slightly. Only the other industrial sector had higher coal consumption in 2006, increasing by 0.3 percent. (Note: All percentage change calculations are done at the short tons level.) U.S. coal exports declined slightly in 2006, while coal imports again reached a record level. The excess production over consumption allowed total coal stocks to increase significantly during the year, as electric generators rebuilt their stockpiles that had fallen substantially in 2005 because of missed shipments in the second half of that year.

Jan 1, 2007

By D. William Tedder

Several bauxite residue sands and muds produced by Bayer plants in the U.S. and overseas have been fractionated using dry and wet magnetic separators. The magnetic sand fractions typically contain about 60 wt% iron and the bulk of the radioactivity in this waste. The muds are more difficult to process than the sands, but some fractionation is possible using a combination of flotation and magnetic separation techniques.

Jan 1, 1984

By Joseph Irons, David Westfall

Three rock tunnel sewer systems are underway in the Chicago Area. (Figure 1) The three are designed to act independently and to be later connected to the future tunnels of the master plan. The tunnel excavation for each of the systems has been completed. One is in the Northwest area within the City being built by the City, known as the Lawrence Ave. System. Another is in the Southwest suburbs, known as the LaGrange-Brookfield Sewer or Southwest 13A, being built by the Sanitary District, the third is in the South suburbs called the Crawford Avenue sewer or Calumet 18-E, Ext. A- being built as a joint venture between the City and the District. The three are similar in that they have the same purpose, the same component parts and their tunnels were constructed in the nigaran limestone using a mechanical mining machine. The purpose of each of the systems is two-fold. First to provide flood relief for existing inadequate sewer systems, and second to reduce the pollution load to the waterways caused by combined sewer overflows. The existing systems in the areas to be relieved are combined sewers built many years ago. The main outlet for the Village of LaGrange, for example, was built in 1908, is badly in need of repair and lacks the capacity to handle the flood flow from the heavily urbanized area it now serves. The dry weather flow from the area is taken off by intercepting sewers. However during

Jan 1, 1997

By Gregory D. Savage, Bruce M. Everett

Introduction The growing role of Colombia as a major supplier of internationally traded steam coal has been widely discussed in the industry. Although Colombian coal has been produced and exported in small quantities for a number of years, the country's position as a major coal exporter began in earnest in 1985 with the first commercial exports from the Cerrejon North Block Project. The mine is located on the Guajira peninsula in northeast Colombia, about 145 km (90 miles) from the coast (Fig. 1). In addition to the mine itself, the project involves construction of a dedicated railroad and port. This forms a modern, efficient, and integrated system. The project is embodied in a 50-50 association contract between International Colombia Resources (Intercor), a wholly-owned subsidiary of Exxon, and Carbocol, the Colombian state coal company. Intercor and Carbocol share investment and operating expenses equally. Intercor has the additional responsibility of managing operations on behalf of the partners. Each partner is entitled to 50% of the coal produced, and each markets its share separately. The project is a multi-seam, truck and shovel operation, based on large reserves (2 to 3 Gt or 2.2 to 3.3 billion st) of high quality bituminous coal. Exports began in the first quarter of 1985, at modest levels through what is called Early Coal Facilities. The permanent coal handling system began operation in February 1986. Production will increase rapidly in each of the next few years, reaching the design capacity of 15 Mt/a (16.5 million stpy) in 1989. Based on available resources, however, the resource will support expansion, and continued growth in production into the 1990s is feasible. Importance of transportation The success of a new coal export venture, such as Cerrejon, depends heavily on efficient transportation. In the international coal industry, overland and ocean transport can in some cases account for 40% to 50% of the final value of the product. Many coals, such as western US subbituminous coals, cannot reach export markets at all because of their low heat content and great distance from export markets. By the same token, low-grade resources are often commercially attractive for local markets even in the face of competition with much higher quality coals from distant sources. Figure 2 shows the growth in steam coal imports into Europe, the largest trading market. Through

Jan 6, 1986

By R. M. G. Machunter

Computer models of metallurgical circuits are extensively utilised in design, and prediction of overall plant separation performance. As always, in the final optimised flowsheet design there is a compromise between the recovery of values and grade of the circuit output. This paper mathematically examines various circuit options for the generation of a heavy mineral concentrate from a generic mineral sands wet concentrator plant. Based on data derived from testwork, any particular mineral sand has a unique release curve describing the separation performance of the heavy mineral suite. Models are constructed that combine particular stage output streams as feed to other stages in various configurations. The ramifications of each option are discussed and reasons why one particular option is selected over the others examined.

Jan 1, 2005

By L. K. Marshall

The importance of high quality underground mine ventilation is readily apparent. The principles of primary and auxiliary mine ventilation, however, are sometimes less readily apparent. The first article in this two-part series discusses some general aspects of primary and auxiliary ventilation. Next month's article will detail considerations involved with auxiliary mine ventilation.

Jan 1, 1982

By E. Bauer, S. Moore

Technological advances in underground coal mining have led to a reduction in fatalities. This study demonstrated that the percentage of cumulative injuries remained largely unchanged across two decades of technological advances (1983-1984: 37%; 2003-2004: 33%). Furthermore, it was demonstrated that the average number of lost days due to cumulative injuries has increased (36±55 days and 62±82 days, respectively) which may have been due to the increased age of the work force or an increase in length of employment meaning that the mine workers injured in 2003-2004 had been exposed to ergonomic risk factors longer than those in 1983-1984. It is recommended that ergonomics processes be implemented as a means to systematically identify, prioritize, and resolve the root causes of these cumulative injuries.

Jan 1, 2007

By M. M. Rajkovich

Just prior to the close of the century, the Federal Mine Safety and Health Review Commission issued its long-awaited decision in Berwind Natural Resources, et al v. Secretary of Labor, to usher in the new millennium. The case arose as a result of a mine explosion in Eastern Kentucky resulting in MSHA’s issuance of 225 citations, not only to the contractor, but to four affiliated entities of Berwind Corporation. While an Administrative Law Judge dismissed those citations as to three of the Berwind entities, both MSHA and the remaining Berwind entity appealed the case to the Commission. Although the Commission effectively left intact the Administrative Law Judge’s decision, it announced a new theory of liability that would apparently be applied in the future, namely the Unitary Operator Theory. This presentation will provide an in-depth look into the Berwind decision and explore the means under which MSHA might impose liability for contractor violations upon other entities in the future.

Jan 1, 2001

Thallium is an uncommon heavy metal that may be found in concentrations that exceed regulatory limits in mining influenced water associated with processing cadmium, copper, gold, lead, and zinc ores. This study evaluated cost-effective modifications to lime precipitation treatment to reduce thallium concentrations to below the EPA drinking water MCL of 2 ppb. The oxidative precipitation of Tl+ to Tlß+ by potassium permanganate was explored for thallium removal at low concentrations (1 ppm initial thallium). Laboratory batch tests were performed to evaluate the removal of thallium from synthetic solutions. Three ratios of potassium permanganate to oxidizable metals in solution were used (one-half, one and two times stoichiometry). Thallium was removed to less than 1 ppb for all stoichiometric ratios evaluated within 10 minutes of reaction. The efficacy of oxidative precipitation for thallium removal is presented.

Jan 1, 2011

By Steve Kral

The Society for Mining, Metallurgy and Exploration’s origins can be traced back to 1871. This was when 22 Pennsylvania coal mining engineers founded the American Institute of Mining Engineers (AIME). The organization’s objective was to “promote the arts and sciences connected with economic production of the useful minerals and metals, and the welfare of those employed in those industries by all lawful means.” Metallurgy and Petroleum were added to the AIME name in 1919 and 1956, respectively. Divisions of AIME were formed throughout the following years in recognition of the increasing trend toward specialization among mineral industry engineers. At the time, SME’s divisions consisted of the Coal Division (1930, now known as the Coal and Energy Division), the Industrial Minerals Division (1935), the Mineral and Metallurgical Processing Division (1948) and the Mining and Exploration Division (1949). The Environmental Division was created in 1997.

Jan 1, 2007

By Frank P. Frandina, Diane R. Hirsch, David P. Field, Colin R. Weeks

To accommodate growth in air service and to follow the Master Plan for long-term airport development, the Metropolitan Washington Airports Authority established thed2 Development Program at Washington Dulles International Airport. A sub-surface Automated People Mover (APM) System is under construction to replace the Mobile Lounges as the primary people mover system at Dulles. To minimize disruption to airport operations the majority of the APM System’s crossings of Taxi lanes will be undertaken using Tunnel Boring Machines (TBM) or the New Austrian Tunneling Method (NATM). This paper explores the planning and design of these shallow tunnel segments for future generation aircraft loads, within the constraints of minimal construction access under post 9/11 security requirements and the context of the overall airport expansion program.

Jan 1, 2005

By H. I. Kim

The leaching of a complex matte in chlorine and chloride media was studied. The matte was prepared from manganese nodules by the reduction smelting-sulfidation route. From XRD analysis, the major phases of the matte were identified as CuFeS2, CuS2, (FeNi)9S8, (FeNi)S2, Ni9S8, Ni3S2, (CoFeNi)9S8 and Co metal. Investigated were the chlorine, hydrochloric acid, hydrochloric acid-oxygen, ferric chloride, ferric chloride-oxygen, cupric chloride and cupric chloride-oxygen systems. The results are discussed in terms of reagent concentration, retention time, leach temperature and gas sparging rate. The chlorination process resulted >99% metal extraction efficiency within a short retention time and at atmospheric temperature. However, there were no preferential extractions of Cu, Ni and Co with respect to Fe. The cupric chloride-oxygen system produced leach liquors with the lowest Fe content and with a high base-metal extraction. Sulfide sulfur was converted to mixtures of elemental sulfur and sulfate in all the studied systems.

Jan 1, 2009

By T. S. Bomar, C. J. Wood

Heavy media cyclones (HMCs) are efficient, high-tonnage devices suitable for upgrading run-of-mine coal in the 50 to 0.5 mm size range. Unfortunately, industrial HMC circuits are often not optimized due to problems such as incorrect operating pressures, poor feed distribution, excessive media contamination, mismatched components, and improper density control. To avoid these problems, operating guidelines have been provided in this article that are useful for optimizing the performance of HMC circuits. The validity of these guidelines has been assessed by means of density tracer tests carried out at several coal preparation plants.

Jan 1, 2002

By Fernando Humberto Muge

One of the problems that arises in the early stages of the mine planning before the determination of the mining exploitation method is to predict what will be the recoverable ore reserves in tonnage, grade and metal quantity, if the select ion is based upon block grades. The estimation of these recuperation or recoverable functions can act as an important planning tool in what concerns the appraisal of the consequences of ore-waste discrimination of individual blocks in a selective mining operation. Estimation methods of all these functions are discussed together with cross validation tests using the available information concerning a preliminary drilling campaign accomplished during the exploration stage of an iron orebody located in the North of Portugal (Moncorvo Orebody).

Jan 1, 1982

By L. A. Weakly, D. A. Weiss, R. B. Crookston

A presentation of experience gained from using mechanical and conventional equipment for excavating shafts, raises, tunnels and other openings in various Colorado oil shale mining properties.

Jan 1, 1983