Search Documents

By R. Thierbach, W. Kahnt, Oberthür. T., D. Eisenburger, V. Gundelach

ABSTRACT: The ground penetrating radar (GPR) method was used in a platinum mine in Zimbabwe by members of the Federal Institute for Geosciences and Mineral Resources (BGR). The measurements were carried out in boreholes and drifts. Electromagnetic re?ections from a fault that consistently trends parallel to the mineralization zone permitted the mapping of the economically minable parts of the deposit. An introduction is given to the geology of the studied area and the application of the GPR method. The electrical parametres of the rocks are measured in situ, the GPR measurements are displayed with radargrams, and the visible structures are explained in illustrations.

Jan 1, 2010

By Rolf Schillinger

Transport of Small Quantities of Explosives Material on Public Roads The transport of dangerous goods on public roads is extensively regulated by EU and national law. The transport of explosive material is not only done by forwarders but also by small companies and private persons with the goal of their own use. The following article tries to explain what is allowed and what is not.

Jan 1, 2010

By Martin Herrenknecht

The world?s growing population and rapidly proceeding urbanization are boosting an enormous demand for new and high-capacity infrastructures to secure the mobility of goods and people. Densely populated areas face the challenge to provide efficient traffic infrastructure, such as a modern public transportation system. At the same time, the maintenance and modernization of supply and disposal structures for water, sewage, energy and communication are also essential. Additionally, supra-regional transportation routes such as long distance water diversion schemes are the challenges for the future. All these projects are as demanding as they are characterized by a tight time schedule.

Jan 1, 2010

By Rahul Sharma

Although, mining of minerals such as polymetallic nodules and sulphides from the deep sea floor has been delayed due to the combination of factors such as current availability of Cu, Ni, Co, Mn (and other metals) on land and their fluctuating prices; these deposits are still considered as the alternative source for metals in the 21st century. Exclusive rights for exploration in the ?Area? (beyond the national jurisdictions of any country) given to eight countries and consortia by the International Seabed Authority and the estimated resource of 300 million tonnes in a typical area of 75,000 km2 is expected to yield about $17.5 billion (at December 2008 metal prices) in 20 years life span of a single nodule mine-site. In order to recover 3 million tonnes of nodules, an area of 300 sq km only will be mined annually (i.e. <1 km2/day) for an optimum abundance of 10 kg/m2. However, during mining, large quantity (22 tonnes/day) of sediments associated with nodules would be resuspended that could lead to certain environmental impacts on the benthic ecosystem. Several small-scale benthic impact experiments in the Pacific and Indian Oceans, have given some insight into the possible environmental impacts and the restoration processes, but the possibility of extrapolating these findings to a commercial mining scale remains an issue to be considered. An estimated capital expenditure of $1.05 billion and operating expenditure of $4.2 billion for a single deep-sea mining venture will have to be weighed against the availability of mineral ores on land as well as the metal prices in the world market. None-the-less, development of technologies for mining and metallurgical processing, as well as formulation of regulations and guidelines for potential ?contractors? to mine these minerals have been progressing consistently. These coupled with recent efforts by certain ?entrepreneurs? to initiate mining of seafloor massive sulphides in the EEZ of certain countries, indicate the continuing interest and support the perception that such deposits could well be the future sources of metals. This paper analyzes the current status and discusses the economic, environmental, and technical issues that need to be addressed for sustainable development of deep-sea minerals.

Jan 1, 2010

By C. Hilton

Arch Coal Inc. has implemented and sustained Best Practices at its four western mines through utilizing foremen in ongoing time studies. A prime benefit is the unique opportunity provided to front line supervisors. To date, 48 supervisors have participated in this program. Each quarter a new team is assembled with members from each operation. During three month blocks the supervisors conduct studies at each mine and identify best practices to implement at their own mine. Ongoing Best Practice and Action Item lists are reviewed each study. Mine management edits, prioritizes and monitors the completion of the proposed action items.

Jan 1, 2010

By James H. Rowland

The Mine Improvement and New Emergency Response Act of 2006 (MINER ACT) established a Technical Study Panel (The Panel) to provide recommendations on the utilization of belt air and new technology that may be available for increasing the fire resistance properties of conveyor belt used in underground coal mines. The Panel Report recommended use of the Belt Evaluation Laboratory Test (BELT) as the method for testing and approval of flame resistant conveyor belts used in underground coal mines. The research conducted to establish the correlation of the BELT with large-scale belt fire flammability tests was done using 36- to 42-in wide conveyor belt. Due to today?s coal haulage capacity, the mining industry is using 72-in and wider conveyor belts. The National Institute for Occupational Safety and Health (NIOSH) conducted a study to determine if the BELT will also qualify wider belts as fire resistant for use in underground coal mines. This paper describes the results of recent experiments comparing results from using the BELT and the large-scale tests for six different belts.

Jan 1, 2010

By T. Purushotham, B. Samanta

ABSTRACT; The shaft bottom junction in a mine ventilation system is an important source of shock loss due to the combined effect of bend and area change. The occurrence of high-volume ?ow rates through this con?guration can potentially result in high energy losses. The current research examines the process of shock loss at a characteristic shaft bottom junction of an underground coal mine. Investigations are per-formed on both laboratory-scale models and three-dimensional computational ?uid dynamics (CFD) simulations, under both exhausting and forcing shaft bottom conditions. The effects of the plat roughness and the shaft bottom length on the shock loss factor values are also examined. The studies show that the combined effect of bend and area changes that occur at the shaft bottom junction results in shock loss factors that are much higher than those values resulting from abrupt area change only. The transition from a smooth wall condition to an unlined rough airway condition (relative roughness, e/d = 0.112) can increase the shock loss factors by 40%. The effect of shaft bottom length on the shock loss factor has not been clearly established due to con?icting results produced by scale model studies and the CFD simulations.

Jan 1, 2010

By K. Y. C. Chung

A case study on foundation engineering through organic soils is presented. Located along the west shore of the Hudson River, site soils consist of random brick fill over a thick layer of peat and organic silts or clays. The organic layer is underlain by medium dense to dense sand with varying amounts of silt. Strong artesian pressures were measured in the sand. A pile foundation system was selected to support all structures. To avoid periodic flooding, new fill must be placed on the existing fill. Large total and differential settlements will occur due to consolidation and secondary compression of the organic soils. This settlement will reduce the allowable pile capacity due to the large negative skin friction in the organic layer; and will necessitate long-term maintenance of the final grade elevation. Pile load tests were performed to determine the allowable compression and uplift capacities, long-term capacities and pile driving criteria.

Jan 1, 2010

By Paul Staples, Chris Morley

"The development of the Cerro Verde, Amplats Mogalakwena and Boddington projects over the last few years has helped to establish the use of high pressure grinding rolls (HPGR) in comminution circuit designs in large-scale hard-rock applications. The increasing acceptance of this innovative and sometimes controversial technology has had the natural effect of prompting many other new projects to examine HPGR as an alternative to the established, usually SAG-based, comminution circuit design approach.At the current stage of development of the technology, HPGR-based circuit capital costs are generally higher than for the equivalent SAG-based circuit, so that HPGR must offer sufficient operating cost benefits to offset the additional capital costs over an acceptable pay-back period. It is usually necessary to undertake comprehensive project-specific trade-off studies to quantify this effect.This paper describes the processes involved in the execution of a typical SAG-HPGR trade-off study, from the preliminary assessment of ore characteristics and project criteria, through testwork, circuit modelling, equipment selection and cost estimates, to a project-economics comparative assessment of the options. The trade-off study determines both the technical feasibility of the respective technologies and their commercial viability in the given project setting.The paper concludes with a cautionary note to the effect that, while HPGR has many potential benefits, it is not a panacea, and that, for some ore types and project conditions, the more established conventional technologies are often more appropriate."

Jan 1, 2010

By Robert F. Chaiken

The U.S. Bureau of Mines conducted an experimental and theoretical study of coupled chemical kinetic and mass transport processes during leaching of pyrite from coal in a counterflow, "trickle-bed" column reactor. Spatial and temporal data on reactant and product concentrations were used as solutions to appropriate continuity equations, which in turn define chemical kinetic reaction rates. Data from four 180-by 30-cm column leaching experiments using coal, coal waste, and air-water and air-FeC13 lixiviants have been analyzed. The rate of leaching was found to be diffusion limited (probably by Fe3+) and not controlled by bacterial action. Rates of pyrite oxidation were found to vary with elapsed time (80 to 225 days) and followed a bell-shaped curve, sometimes with a delay before start of reaction. Maximum rates of reaction ranged from 3 to 10 (mmol/d)/L (column) for coal waste and 0.4 (mmol/d)/L (column) for coal. Reaction was 30 to SO pct complete, probably due to precipitation of product salts (e.g., jarosites), which impede transport of oxidant through the coal. An absorption-desorption model of solids leaching, which considers the role of heterogeneous porosity in solids leaching, was used to describe time-dependent leaching rates.

Jan 1, 2010

By John C. Edwards

Standard smoldering and flaming combustion tests using smaIl coal samples have been developed by the U.S. Bureau of Mines as a method to evaluate the response of a smoke detector. The tests are con-ducted using a standard smoke box designed and constructed according to Underwriters Laboratories. The tests provide a standard, easily reproducible smoke characteristic for smoldering and flaming coal combustion, based upon a comparison of the smoke optical density and the response of a standard ionization chamber to the smoke. With these standard tests, the range of threshold limits for the response of a smoke detector and the detector&apos;s reliability can be evaluated for nearly identical smoke visibility and smoke physical characteristics. The detector&apos;s threshold response limits and reliability need to be well defined prior to the instrument&apos;s use as part of a mine fire warning system for improved mine safety.

Jan 1, 2010

By Jian Zhang

From the standpoint of quality, surface cracks normally pose more of a problem than internal cracks. Hypo-peritectic (HP) steel grades are well known for their proneness to surface longitudinal cracking (SLC) during continuous casting. This study analyzed the influences of chemical composition, technique parameter and secondary cooling on the surface longitudinal cracks. Based on the optimized the first and secondary cooling zone water distribution in the process of continuous casting, low cooling water distribution at solidification initial stages and uniform cooling at secondary cooling zone were suggested, which can be used to effectively control the surface longitudinal cracks.

Jan 1, 2010

By Ronald S. Conti

A new U.S. Bureau of Mines 6.8-L ignitability furnace was used to study the thermal autoignitability of dust clouds. This furnace has a quartz window to allow observation of the early stages of the ignition process and to allow measurement of the dust explosion temperature. Thermal ignitability data were obtained for various carbonaceous and metal dust clouds, with particular emphasis on various ranks of coal dusts. One of the reasons for the construction of the new 6.8-L furnace was to evaluate the effect of chamber volume on the measured autoignition temperatures. Therefore, data from the 6.8-L furnace were compared with data measured earlier in a 1.2-L furnace. The conclusion is that the autoignition temperatures measured in the 6.8-L furnace were only slightly lower on average than those from the 1.2-L furnace. These data on the minimum autoignition temperatures of various materials will be useful in analyzing the thermal ignition hazards of dust clouds in the mining industry and other industries that manufacture, process, or use combustible dusts.

Jan 1, 2010

By Winthrop F. Watts

The U.S. Bureau of Mines evaluated the performance of a catalyzed diesel particulate filter (CDPF) and a CDPF combined with a diesel oxidation catalyst (DOC) at two metal mines. This report describes the results from the two field evaluations. The CDPF-DOC was installed on a load-haul-dump (LHD) powered by a 175-kW, prechambered, turbocharged engine. This system reduced diesel particulate matter (DPM) concentrations by 71±28 pet, as determined by size-selective sampling with gravimetric analysis, and by 71±29 pet, as determined by respirable combustible dust (RCD) analysis at the vehicle operator&apos;s location. The CDPF was installed on a diesel-hydraulic, roof-bolting jumbo, powered by a 172-kW engine. The CDPF reduced DPM concentrations by 72±21 pet, as determined by size-selective sampling with gravimetric analysis, and by 62±25 pet, as determined by RCD analysis at the vehicle operator&apos;s location. Underground evaluation was more difficult because of frequent movement by the roof-bolting jumbo, variation in daily workload, tremendous fluctuation in ventilation airflow rates, and use of a high sulfur diesel fuel, which promotes the formation of sulfate particles, decreases filtration efficiency, and hastens the deterioration of the catalyst.

Jan 1, 2010

By W. G. Miller, J. D. Scott, D. C. Sego

ABSTRACT An overall study was conducted to evaluate the properties and processes influencing the rate and magnitude of consolidation for oil sands fine tailings produced using different extraction processes. As part of the overall study, a comprehensive description of physical and chemical characteristics of fine tailings generated by caustic and non-caustic processes was carried out. Ultimately, the influence of these fundamental properties on the compressibility, hydraulic conductivity and shear strength properties of the fine tailings was assessed. The characteristics of the fine tailings are presented in terms of index properties, mineralogy, specific surface area, water chemistry, liquid limits, particle size distribution and structure. A difference in water chemistry was concluded to be the cause of substantial differences in particle size distributions and degree of dispersion of the comparable caustic and non-caustic fine tailings. The degree of dispersion was consistent with predictions for dispersed clays established by the sodium adsorption ratio (SAR) values for these materials. A linear variation of increasing dispersion with increasing SAR up to a SAR value of about 40 has been suggested, above which fine tailings are completely dispersed. The observed dispersed or flocculated structures (viewed using a scanning electron microscope) supported the predictions based on SAR values.

Jan 1, 2010

Keeping an eye on the future while honoring the past, Frank McAllister, chief executive officer of Stillwater Mining Co., and life member of the National Mining Hall of Fame and Museum, gave the keynote address to a packed house during the 23rd National Mining Hall of Fame and Museum Banquet in Leadville, CO on Sept. 11. McAllister?s company made news just days before the induction ceremony, when it was announced that Stillwater Mining would acquire Marathon PGM Corp. for $118 million (ME, Oct. page 14).

Jan 1, 2010

By David C. Oyler

The U.S. Bureau of Mines studied the interaction of longwall shield supports and adjacent strata at the Meigs No. 31 Mine in southeastern Ohio. Twenty-three legs of twenty shields at midface were instrumented with pressure transducers and monitored for 11 weeks. During the project, leg setting pressures were reduced twice to determine the effect of setting pressure on shield-strata interaction. No correlation was observed between setting pressure and leg loading rates. The shield loading profiles were consistent with a model in which the roof consists of two zones, a thin immediate roof loading the shields well below the typical setting force and a main roof zone essentially supported by the coal and gob and loading shields through its convergence. This model was used to develop an equation for estimating average loading rates at the site. The only variable of the equation is time, and the equation consists of an exponential term to account for the immediate roof loading and a linear term to account for main roof loading. The equation gave good correlation with average loading rates, but the variation in loading from cycle to cycle was too great for the equation to give good predictions of individual cycle loading rates.

Jan 1, 2010

By Robert Kimutis, Ke Yang, Yi Luo, Jianwei Cheng

"Surface subsidence processes, especially those associated with a longwall mining operations, could cause operational and/or safety problems to railroads. For railroads with normal amounts of traffic, both the limited time window between traffic and the limited space available make the efforts to return the railroad back to its original state nearly impossible. In order to ensure the safe operation of a subsiding railway, the partial lifting method has been developed and applied. This paper describes the principle and application of the method. A case of applying this method to mitigate subsidence effects on a long section of railway has been demonstrated.INTRODUCTIONMaintaining an operational railway as it is experiencing a longwall subsidence process is not an easy task. The subsidence process may induce sufficient strain and curvature to cause problems to the railroad structures. Localized subsidence-induced slope often is significantly larger than the permissible ruling gradient of 0.7% for a locomotive to haul a loaded train reliably. In order to ensure safe operation, it would be ideal to instantly lift the railroad track back to its original level as it is subsiding. However, it is often impractical to do so due to the limited time windows available between railway traffic and the available space on the railroad base.A partial lifting method has been developed to keep the railroad operational under such limitations. The subsiding railroad track is raised by only a determined, partial amount of the occurred subsidence at a given time. By making such a determined adjustment, the railroad track can be maintained on a smooth and operational profile, and the high strain and curvature on the railroad structures can be reduced as well. To define a smooth railroad track profile in a subsided section the following two conditions should be met: (1) the maximum railroad gradient should be less than the permissible ruling gradient, and (2) the recommended amount of adjustment should be able to be made by the repair crew within the available time windows between scheduled railway traffic.The subsidence effects on a long section of railroad over two longwall panels have been successfully mitigated using the partial lifting method. The railroad experienced a maximum subsidence 89 of about 5 .0 ft (1.5 m) with the average subsidence along the entire length being about 3.45 ft (1.05 m). However, the average adjustment due to lifting that was made along the entire length of the subsidence-influenced railway was only 0.5 ft (152 mm)."

Jan 1, 2010

By D. R. Tweeton

The U.S. Bureau of Mines has developed tomographic computer programs for geophysical applications and is distributing them as part of a Bureau plan to facilitate the transfer of technology to potential users. These programs were developed for predicting and monitoring the flow pattern of leach solution during in situ mining. The Bureau has also applied them to assessing high-wall blast damage and examining the integrity of mine-related geological structures. This report describes the curved ray program BOMCMTR (Bureau of Mines curved ray tomographic reconstruction), tells how to run it, and gives examples with synthetic and field data. BOMCRATR provides optional mathematical constraints to counteract the nonuniqueness of tomographic reconstructions with crosshole data. These constraints include limiting the maximum and minimum velocities, fixing the velocity at any point to any value, and establishing layers in which velocity does not vary with horizontal position. The user can test for nonuniqueness by varying the initial velocity pattern, The program can perform either curved or straight ray analysis. Ray paths are calculated analytically in triangular pixels, which is faster than incremental numerical approximations,

Jan 1, 2010

By H. J. White

The effect of alloying elements on the mechanical properties and weldability of wrought gamma prime strengthened nickel- base superalloys is well known. An understanding of the basic guidelines concerning alloying additions has led to the invention and development of HAYNES® 282® alloy for applications in aircraft and land base gas turbines and other high-performance high-temperature environments. The alloy combines exceptional high temperature properties with good weldability and fabricability. At high temperatures (~ 900 °C), the alloy is stronger in creep strength than Waspaloy alloy (UNS N07001) and it approaches the creep strength of R-41 alloy (UNS N07041). Because the alloy has better thermal stability, fabricability, and weldability than Waspaloy and R-41 alloys, it is currently being considered as a candidate universal consumable for welding/ repair welding of gamma prime strengthened nickel based superalloys and it is also being considered as a suitable replacement for applications where R- 41, Waspaloy, and 263 (UNS N07263) alloys are currently being used. The alloy was designed to have improved resistance to strain age cracking, a problem common to gamma prime strengthened nickel based superalloys. In this paper, we present (1) results from hot ductility testing of annealed and annealed/aged material; (2) results from Time Resolved X-ray Diffraction (TRXRD) studies during a welding thermal cycle of annealed and annealed/aged material, and (3) gas metal arc (GMA) and gas tungsten arc (GTA) welding of annealed and annealed/aged material.

Jan 1, 2010