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By G. R. Rao, K. A. Natarajan, P. Devasia

The role of growth conditions and adhesion of Thiobacillus ferrooxidans on the leaching of chalcopyrite was investigated. Thiobacillus ferrooxidans grown on sulfur, thiosulfate and ferrous ion substrates was used in this comparative study. Growth on sulfur, a solid substrate, requires bacterial adhesion unlike that required in the presence of soluble thiosulfate and ferrous ion in a mineral-salts medium. Solid substrate-grown cells showed higher rates of leaching than those grown in liquid media. An initial lag period noticed during leaching by solution-grown cells was absent when solid substrate-grown cells were used. Such a behavior is attributed to the presence of an inducible proteinaceous cell-surface appendage on the sulfur-grown cells. This appendage aids in bacterial adhesion onto the mineral surfaces. Such an appendage is absent in solution-grown cells, as substantiated by electrophoretic measurements. The importance of bacterial adhesion and the direct mechanism in leaching by Thiobacillus ferrooxidans are demonstrated.

Jan 1, 1997

By A. Pratt, G. Deschênes

This paper quantifies the detrimental effects of pyrite and stibnite on gold leaching kinetics. Means to reduce the effect of these minerals by addition of lead nitrate and oxygen are presented. A significant retarding effect was observed when the pyrite concentration was 20%. A pretreatment with lead nitrate reduced the extent of gold surface coating by Ag, Fe and S. Stibnite, at a concentration as low as 20 ppm, significantly affected the gold leaching kinetics through forming a passivating film of Sb(V) oxide possibly Sb2O5. The most practical way to alleviate the effect of stibnite is to leach the materials at a moderate pH with addition of lead nitrate. A low temperature reduced the efficiency of lead nitrate to counteract the effect of stibnite. The increase of dissolved oxygen is not favourable to alleviate the coating of stibnite on gold.

Jan 1, 2004

By A. Goulsbral, D. Harrison, R. Dunne

A programme to reduce cyanide consumption at the New Celebration Gold Mine, situated 32kms South of Kalgoorlie, Western Australia, commenced in the latter part of 1990. Cyanide speciation studies at the time identified that the major loss and consequently consumption was due to the hydrolysis of cyanide, The use of artesian hypersaline waters of high magne­sium content on gold plants in Western Australian Goldfields has meant that economically viable operating pH values during cyanide leaching are around 8.9 to 9.5. The high ionic strength in these waters does to some degree retard the hydrolysis reac­tion. Notwithstanding this, the formation of hydrogen cyanide and its loss due to volatilisation is the cause of the major loss of cyanide on most gold plants in the Kalgoorlie Goldfields. This paper discusses the aspect of oxygen addition during cyanide leaching to decrease cyanide consumption and increase gold recovery.

Jan 1, 1996

By H. Mercado G., J. R. Parga T

Mexico continues to be one of the main producers of silver, lead and zinc; although this leadership is ending because of the use of obsolete technologies, which is reflected in low recoveries of these processes. The country therefore requires to develop on new technologies in the field of nonferrous metallurgy, particularly be'cause it is the second most important source of foreign exchange. A novel method, presented in this paper, demostrates that refractory gold and silver can be extracted from a complex sulphide concentrate by a one stage pressure oxidation in an alkaline cyanide solution, this is achieved by simultaneous liberation_ and solubilization of the precious metals. Both gold and silver extractions are greater than 97%. Factors affecting recovery efficiency, such as: pH, lixiviation time in the reactor, temperature, particle diameter, pressure, % of NaCN and pulp density, were investigated. A summary of actual plant operations is also be included.

Jan 1, 1993

By Daniel T. Hegyan

The employment of continuous rotary vacuum disc filters to filter refuse from the fine coal washing circuits has been increasing as it has become more important to close the water circuits and eliminate sludge holding ponds. This paper will discuss our past experience filtering refuse, effects of solids concentration in the filter feed, use of polymer flocculation aids, effect of flocculation devices, and effects of particle size and ash content on the filtration rate. Detailed tests were performed on existing installations utilizing coal refuse filters to determine optimum flocculant dosage, solids concentration, and disc rotation speed to form a dischargeable cake. Information was also obtained showing effect of flocculant addition on the moisture of the filter cake. Our test work has shown that the continuous filtration dry cake rates for fine coal refuse correlates very well with the data developed and presented by Silverblatt and Dahlstrom1 except that the curves have moved up the scale by use of polymer flocculant additions. These polymers were not available at that writing. Finally, our tests also confirmed the general premise stated by S. K. Mishra2 that controlled additions of polymer flocculants will reduce filter refuse cake moistures somewhat.

Jan 1, 1974

By Fred T. Towne

There are a number of air classifiers manufactured throughout the United States and the rest of the world. The classifiers manufactured by Alpine, A. G. of Augsburg, Germany, are unique in their abilities. It is this uniqueness that I wish to delve into and in this respect we will limit this discussion primarily to the classifiers as manufactured by Alpine. It has been reported in the past that these classifiers were introduced into the. United States in the late 50's. Until the introduction of the Alpine Classifiers, air classification seldom produced a satisfactory fractionation of a product below 45 microns (325 mesh) or above approximately 22 mesh. It has been a common practice to classify fine materials which used water as a carrier medium The use of centrifuges are today producing thousands of tons of finely partitive powders in the very small particle size range. The use of centrifuges in connection with wet grinding mills has increased the rates of production of these mills considerably.

Jan 1, 1965

By Thomas F. Stinson

Energy-producing states see severance taxes as attractive sources of increased revenues for otherwise tight budgets. Consumers in energy-poor states, however, protest that current rates are excessive and have moved to obtain a reduction. The US Supreme Court heard two cases questioning such taxes during its 1981 term, and Congress, in each of its last two sessions, has seriously considered measures placing a ceiling on severance tax rates. Although discussions usually focus on coal severance taxes levied by Montana and Wyoming, ramifications of changes in national policy are much larger, potentially affecting mineral taxes in all states. Severance taxes yield substantial revenues in some states, as illustrated in the accompanying table. In fiscal 1980, Texas collected more than $1.5 billion from such taxes, while Louisiana, Alaska, and Oklahoma collected $525 million, $507 million, and $436 million, respectively. Oil and natural gas production were the major items taxed. While the table shows only the 10 states with the largest severance tax collections, a total of 17 states had severance tax receipts exceeding $10 million in 1980. The enormous increases in severance tax revenue between 1970 and 1980 can be seen from the table by comparing columns A and B. For the 10 states shown, revenues increased from $650 million to $3.8 billion during that period, due to a combination of higher prices, increased production, and new or increased taxes. In most states, increases in prices and production were more evident than higher tax rates. Although the revenue increase is impressive, it understates the extent of changes occurring during the past decade. Since tax collections are shown for fiscal 1980, the full impact of the decontrol of domestic oil prices is not evident. Also, taxes on natural gas reflect controlled prices. When full de-control of natural gas occurs, significantly higher revenues can be expected in gas-producing states, even if tax rates, production, and world prices remain constant. These increases in severance tax revenues, coupled with further increases expected to accompany natural gas decontrol, have produced fears that a substantial transfer of income is taking place from residents of energy-poor states to those living in energy-rich areas. Others worry that increased severance tax revenues will be used to substitute for a substantial portion of state taxes that would have otherwise been collected from firms and individuals. The resulting improvements in tax climate, it is thought, may encourage firms and workers to migrate to energy-producing states. While these issues are often portrayed as pitting energy have-nots against the haves, such is not entirely the case. Much of the original impetus for limits on coal taxes came from Texas residents, the state collecting the most severance tax revenue. One way of gaining perspective on these concerns is by examining severance taxes per capita and as a percent of state tax collections (see columns C and D in the table). When this is done, Alaska, where 1980 taxes on oil and gas production totaled more than $1300 per capita (and 35% of all state tax collections), stands out as a special case. There, the state was able to eliminate some individual taxes, place revenues in a permanent trust fund, and consider offering a rebate of some previous income

Jan 4, 1982

By Fred T. Towne

Recent developments in fine grinding by the means of mechanical impaction are the result of continuing improvements in modern machine construction. This is especially true when related to the bearings and mechanically operated parts of impact mills. These improvements allow manufacturers to increase the speeds of the impacting members Most of the more common forms of size reductions, such as percussion, pressure, friction and sectioning, or cutting were at one time accomplished by human hands. These actions were transferred to machinery. Originally of limited application, their use widened as industrial materials and construction became more sophisticated.

Jan 1, 1965

By I. Longson

As a longwall coalface advances a caved goaf or waste region is left behind. Air flow takes place through this permeable goaf due to the pressure differentials existing across it and en route this leakage air picks up both heat and moisture. A marked deterioration in climatic conditions occurs in the face area at all points downstream of where this leakage air rejoins the main air-stream. This goaf heat source can make a very significant contribution, typically 30-40% to the rate of total heat pickup on an advancing UK longwall coalface with a VST of 40°C and hence on the climatic conditions that prevail at the return end and in the return gate of the face. The magnitude of the rate of heat collection from the goaf depends on a number of factors but it has been established that it is particularly influenced by the prevailing virgin rock temperature and the total flow rate of the leakage air. This paper proposes a model for the goaf based on a packed bed analogy and other assumptions required in order to evaluate the rate of heat pickup are identified. The outlet condition of the leakage air predicted by the model have been shown to correlate with underground measurements taken for a range of different production patterns with the face cutter at various locations on the face. The sensitivity of these predictions to variations in the input data has been tested and is commented on. At this stage of the development the capabilities and predictive limitations of the model are discussed. Further areas of investigation are suggested in order to improve the predictive ability and to extend the versatility of the model.

Jan 1, 1989

By Fred N. Kissell, George H. Jr. Schnakenberg

INTRODUCTION A variety of instruments are available for measuring or monitoring the performance of underground mine-ventilation systems. In general terms, the instruments may be classified as those that measure air velocity and those that measure gaseous concentrations. All costs herein are in terms of 1978 US dollars. The mention of a specific manufacturer or device is not intended to be an endorsement by the US Bureau of Mines. AIR-VELOCITY INSTRUMENTS The basic instruments used for measuring the air velocity in mines are the vane anemometer and the smoke tube. Vane Anemometer Of the air-velocity instruments, the 102-mm (4.0¬in.) vane anemometer is the most common and is available as either a low- or high-speed type. The low-speed anemometer generally is the most suitable for measuring the velocities in ordinary airways. For a rough check of the velocity in an airway, it usually is satisfactory to hold the anemometer by hand, positioning it in the center of the airway for 30 sec. However, the resultant error may be as high as 25% , and such a hand-held approach is unsuitable when accurate or reliable measurements are required. To obtain more accurate measurements, the proper procedure is as follows: 1) Since holding the anemometer by hand generally causes the instrument to read about 15% high, it is mounted on a 0.6-m (2-ft) extension rod. 2) The airway is divided into equal right and left halves. A 1-min traverse is used in each half, moving the anemometer smoothly up and down in a zigzag pattern so that the entire half is covered within the allotted minute. 3) The manufacturer's correction table is applied to the readings to adjust the velocity calculation as necessary. Whenever possible, anemometer readings should be obtained in a long straight section of airway that has a constant cross-sectional area. Bends and obstructions should be avoided, since they cause turbulence and other discontinuities in the airflow and can degrade the accuracy of the velocity measurements. Although a series of velocity measurements at one location usually corresponds to within a few percent, this is not an indication that the airflows calculated from those readings are completely accurate. One reason is that the correction table provided with the instrument generally is not for that specific instrument; instead, it represents the average correction for all such instru¬ments made by the particular manufacturer. Most cor¬rection tables specify a correction factor of from 0 to 15%, depending upon the velocity. However, even after correction, the instrument error still may range from 3 to 5%. At low velocities such as those below 0.76 m/s (150 fpm), the instrument error can be two or three times greater than this, ranging from 6 to 15%. The new ball-bearing anemometers generally perform somewhat better at low velocities than did the older conventional anemometers. Another source of error is introduced when measur¬ing the cross-sectional area of the airway or entry. Under the best of circumstances, measurement errors, instrument errors, and a host of other minor errors all combine to cause a total error of at least 10% in the velocity calculation. The vane anemometer also can be used with reason¬able accuracy to measure airflows in mine-ventilation ducts. In this application, the anemometer is mounted on a rod and is held at the center of the duct end. For a duct that is discharging air, the average velocity in the duct is 85% of the centerline reading (Northover, 1957). For a duct that is taking in air, the average velocity is 70% of the centerline reading (Haney and Hlavsa, 1976). To measure the airflow discharged from a regulator or from a small hole in a stopping or bulk¬head, a correction factor for the area is necessary. A good approach in this situation is to traverse the area of the regulator or hole, holding the anemometer with an extension rod. This provides an average velocity that is multiplied by 85% of the measured area of the regulator or hole. In all cases, the manufacturer's instrument cor¬rection table must be used and applied properly. For accurate results, the anemometer should be returned to the manufacturer for periodic cleaning and checking. If it is in daily use, the anemometer should be returned about once per year, and proportionally less frequently if the usage is less frequent than on a daily basis. Smoke Tube The smoke tube may not appeal to individuals who believe that good measurement results can be obtained only with expensive, complicated, and fragile instru¬mentation. Nevertheless, smoke works about as well as anything for the routine measurement of low air velocities in mines. The following procedure yields reasonably good results: 1) Two marks are scratched 7.6 m (25 ft) apart on the floor of the airway. 2) The smoke tube is used to release a cloud of smoke in the center of the airway, about 0.9 m (3 ft) upstream of the first mark on the floor. 3) A timed interval begins when the leading edge of the smoke cloud passes over the first mark, and the interval stops when the leading edge of the cloud passes over the second mark. 4) A factor of 20% is subtracted from the cal¬culated velocity to determine the true average velocity, providing a correction for the centerline and for the spreading effect at the front of the cloud. Velocities calculated with the preceding method generally are accurate to within 10 to 15%. In some instances, the cloud from a conventional smoke tube

Jan 1, 1982

By L. K. Holder

"The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), commonly known as Superfund, mandates evaluation of remediation alternative using nine criteria: (1) overall protection of human health and the environment, (2) compliance with ARARs (applicable or relevant and appropriate standards), (3) long-term effectiveness and permanence, (4) reduction of toxicity, mobility or volume, (5) short-term effectiveness, (6) implementability, (7) cost, (8) state acceptance, and (9) community acceptance. Many states have adopted these or similar criteria for remedy selection under state laws. Although not explicitly addressed in the CERCLA criteria, consideration of sustainability can be incorporated into these criteria. This paper explores how sustainability can be evaluated for remedy selection using the CERCLA criteria. INTRODUCTION Sustainability considerations can be incorporated into all phases of site remediation: • Site investigation (remedial investigation). • Remedy selection. • Remedial design. • Remediation construction. • Operations, maintenance, and monitoring. This paper focuses on remedy selection. Many have looked at remedy selection using sustainability criteria. However, CERCLA and corresponding State programs require remedy selection using mandatory criteria. This paper shows how sustainability can be explicitly considered using the mandatory criteria. REVIEW OF CERCLA CRITERIA First, we review the definitions of the CERCLA criteria. We then explore how sustainability criteria can be fit into the CERCLA criteria. Overall Protection of Human Health and the Environment This criterion addresses the degree to which each alternative is protective of human health and the environment, considering both long-term and short-term risks. Overall protectiveness is a ""threshold"" criterion, in that alternatives that do not achieve adequate protection of human health or the environment are eliminated from further consideration. Evaluation of this criterion is derived from the evaluation of the other criteria (e.g., long-term effectiveness and permanence, and short-term effectiveness). It is not an independent criterion, but more a summary of the overall evaluation."

Jan 1, 2015

By R. Froidevaux

Geostatistical estimation techniques were customized to enable forecast of production figures at the Silver Bell uranium mine (Uravan District). Surface drill hole data were used to provide a block model of kriged estimators of average uranium grades. The recoverable figures, such as ore-waste ratio and ore grade, are then deduced from regressive curves previously obtained from underground information and production data. Cross-validations of the entire model were performed and were found positive.

Jan 1, 1981

By Stuart M. Lipofsky, Norm Hutchins

The Metropolitan Water District of Southern California has undertaken the Lake Mathews Outlet Facilities project to replace the existing outlet facilities. In the late1990s, consulting engineers for the District determined that the Lake Mathews Outlet Facilities were susceptible to a catastrophic failure during a seismic event. To ensure a reliable supply of water to Metropolitan’s customers in the Los Angeles area, the District decided to construct new outlet facilities. This Project consists of excavating a large diameter junction shaft, a 6.10 m (20 ft.) horseshoe tunnel, three short 4.88 m(16 ft.) horseshoe bypass tunnels, and a large excavation within a cofferdam that were all driven in difficult rock conditions. Additionally, a new concrete outlet tower was constructed and connected to the existing tunnel by the new bypass tunnels and through the junction shaft. The J.F. Shea Co., Inc. of Walnut, California, is currently finishing the construction of the Lake Mathews Outlet Facilities Project for Metropolitan. The large diameter junction shaft is 50.60 m (166 ft.) deep, excavated 16.15 m (52 ft.) in diameter and lined with a61 cm (2´-0?) thick steel reinforced concrete lining to a finished diameter of 14.63 m (48ft.). The shaft was excavated full face with one stationary shaft three-boom jumbo, modified for the large diameter. The shaft also consists of four sets of gate guides extruding from the shaft wall towards the center of the shaft that provide the ability to operate up to four mechanical gates at any time, to open or close each tunnel. This paper will present the junction shaft excavation and concrete construction techniques, including the innovative slip form method utilized to construct the junction shaft.

Jan 1, 2003

By E. W. Geist, W. J. Bronkala

PRINCIPLES OF MAGNETIC SEPARATION The application of magnetic separators relies on the different behavior of individual mineral particles under the influence of magnetic forces. When exposed to a magnetic field, all materials are affected in some way. According to whether materials are attracted or repelled by the magnetic field, they are designated paramagnetic or diamagnetic, respectively. Paramagnetic materials are attracted along lines of magnetic force from points of lower magnetic field intensity to points of higher magnetic field intensity. The very strong response of some materials to a magnetic field is sometimes designated ferromagnetic and the particles attracted frequently retain magnetic properties after the applied magnetic field is removed. Diamagnetic materials are repelled along the lines of magnetic force from points of high magnetic intensity to points of lower field intensity. Only limited commercial use of diamagnetic effects has been made. For practical applications, the paramagnetic groupings are: 1. Strongly magnetic (ferromagnetic) 2. Magnetic 3. Weakly Magnetic 4. Non-magnetic The limits of these groupings are not well defined and will vary in some mineral species. Only a few minerals are ferromagnetic (magnetite is an example) and arbitrarily some investigators have selected 10,000 gauss, or 1 Telsa, as the dividing line between low and high intensity magnetic fields. I. S. Wells has developed a table indicating the magnetic intensity required to separate a selected grouping of minerals which is shown in Table 1 on page 2. A similar table has been developed by Carpco Inc. of Jacksonville, Florida in conjunction with the use of its high tension separators. This table, Table 2 on page 3 shows other minerals grouped in the broader categories cited above. Magnetic separation methods are used either to separate valuable minerals from nonmagnetic waste or magnetic impurities or other valuable magnetic minerals from bulk nonmagnetic values. Magnetically susceptible mineral particles occur as either individually discrete particles,

Jan 1, 1986

By J. Stoll

In May 1998, Hanson Aggregates Midwest, as an outcome of mine planning, offered a 10-acre tract of land containing the famed fossil-bearing Silica formation, to the City of Sylvania, OH. in the form of a 99-year lease agreement. The Olander Park System, and Ohio code park operating within Sylvania Township, was then approved by Hanson and the City to manage and fund the park. All parties signed the lease in August of 1999. In November 2001, local residents voted to fund the park by a margin of 2 to 1. The park will consist of a shallow (approx. 20 ft.) former cement production quarry that is 700 ft. long by 300 ft. wide. Hanson’s motivation and vision for the park was fivefold: 1) the site was located away from long-term reserve access; 2) it would serve nicely as buffer property for the active quarry; 3) it had become an area of illegal dumping by locals in the past; 4) trespassing and safety issues would be limited by allowing supervised usage; and 5) the shallow outcropping contains the world famous, fossil-bearing Silica shale. Hanson will supply shale to the park perpetually via stripping activities in the process of uncovering quality construction aggregate limestone and dolomite reserves. Thousands of enthusiastic fossil hunters have already combed throughout the shale in their quest for “treasures”. The park’s master plan also features nature trails, picnic areas, a fossil-themed play area, amphitheater, visitor’s center and gift shop. Given the natural and people resources that Sylvania Fossil Park will have to offer, Hanson is confident that it will become the premier invertebrate fossil hunting site in the United States. It will also remain a solid community relations vehicle for years to come.

Jan 1, 2003

By Aurel Goodwin

I chose the title "Let's Clear the Air" for this afternoon's presentation because it has two meanings, the literal and the figurative. Most of you know what MSHA is. Most of you know what MSHA does. And, for the most part, most of you know why. What I hope to accomplish today is to "clear the air" around our health standards, to clarify for you how MSHA views its congressional mandate under Title I Section 101(a)(6), (7), and (9) of the Mine Safety and Health Act. Asbestos, silica, radiation, noise, welding fumes, carbon monoxide, lead, hydrogen sulfide, nitrogen dioxide - the list of physical and chemical hazards encountered in the metal and nonmetal mining industry is as diversified as the industry itself, possibly even more so. In addition, miners are often exposed to several of these health hazards simultaneously.

Jan 1, 1980

By A. Bascetin

The human requirements have increased rapidly depending on population density and urbanization thus industrialization has grown steadily. As a result of the situation, the greenhouse gas emissions into the atmosphere and the global warming have increased slowly. Today this effect has continued to increase. Therefore, the effects of greenhouse gases in all areas of production must be controlled. The study presents the methods of determination the CO2 emissions (CO2-e) and energy consumption in aggregate production. The aggregate constitute approximately 70% by volume of concrete that has widespread use as construction material in the world. One of the most important elements in today's terms is sustainable use of resources and minimum CO2 emissions (CO2 + CO + NOx + CH4.vb.) at every stage of production of aggregate. Therefore, these elements must be taken into consideration in the aggregate production standards. The choice of production method of aggregate is very important for optimum use of energy and effects of greenhouse gas emissions. So the properties of the aggregate material must be known well to obtain the target. Within the scope of this study, the unit value of CO2-e that release when the production of aggregate in different formations is determined for our country. Thus, the effects of green house gas emission can be evaluated according to the characteristics of material in aggregate production planning. In this study, energies consumed during the production of aggregates at a quarry in Istanbul Cendere region were investigated by taking the different formations encountered at the quarry into consideration. The unit CO2 emission values per ton of produced aggregates were calculated as a result of this investigation. Besides, energy consumption values of previous months at this quarry were taken and the unit CO2 emission values were also calculated.

Jan 1, 2011

By Stephen G. Hardcastle

3D-CANVENT is a software package that integrates advanced computer aided design (ACRD) true 3D graphics with a mine ventilation simulator. The package runs as a Windows(tm) application to access its printer drivers environment and does not need third party CAD software. It is composed of two primary modules: DMVENT and MINEDESIGNER. DMVENT is a traditional Fortran coded Hardy-Cross iterative ventilation network solver written in 1980 with thermodynamic capabilities. This module is relatively unchanged with the traditional data input options for branch type, specified or calculated resistances, fixed flows, and fixed or variable pressure fans. MINEDESIGNER is the graphics engine that optimizes the ventilation design process. It performs the front-end transformation of input data entered in the graphical interface into the correct format for the solver. At the back-end it reconverts the historically standard tabular data output from the solver into an easily viewed graphical format. ACRD features of MINEDESIGNER are used to generate a 3D wire-frame node and branch network of the mine's ventilation system. The network can be displayed in up to 4 views orientated to XYZ planes or a 3D view. All the views have zoom, pan, slice and rotate options. The graphical interface efficiently permits data entry and editing via a mouse with pick-and-point item selection. Branches can be found or added with "search" and "join" options. Visual interpretation is enhanced by the 16 colour options for branches and numerous graphical attributes. Network locations are readily identified by alpha-numeric names for branches, junctions and fans, and also the logical numbering of junctions. The program is also readily expandable for pollutant simulation and control/monitoring applications.

Jan 1, 1995

In April 2012, work started on one of the most ambitious construction projects of Austria?s ÖBB-Infrastruktur AG ? the New Semmering Base Tunnel. Scheduled for completion in 2024, the 27.3 km (17 mile) tunnel through the Semmering range will cut the journey time on the south railway connecting Lower Austria and Styria. Before con-struction can begin at the entrance portal and tunnel bores, the work concentrates on the above ground sections with the clearance and excavation of the entrance ramp site. The slope is currently being excavated by the Baubeteiligungsge-sellschaft m.b.H. BBG-GRAZ. The cut face is shored up with shotcrete and permanent self-drilling anchors produced by Minova MAI, an economical bolting solution for softer rock formations. After completing the surface construction work, the twin-bore, single-track tunnel will be cut through the Semmering by conventional and continuous excavation beginning in 2015. Once completed, the New Semmering Base Tunnel will be one of the longest rail tunnels in Austria. It will act as a vital link on the route crossing Europe?s heartland from Northern Germany to Italy, which currently has to climb the steep Semmering pass between Gloggnitz and Mürzzuschlag on a historic mountain railway recognized as one of the UNESCO World Heritage sites. The old route imposes considerable limitations on heavy freight trans-port, and passenger trains have to slow down to a speed of around 50 kph (31 mph). The New Semmering Base Tunnel will bypass this bottleneck and cut 30 minutes off the journey time between Vienna and Graz. It represents a particular advantage for freight traffic, since the new route?s minimal incline of 8.4 percent removes all obstacles for even heavy freight trains.

Jan 1, 2013

By B. K. Gupta

Arch Mineral's Captain Mine has used the Bucket Wheel Excavator System(BWE) for over 3 years in conjunction with a 180 yd3 (138M3) stripping shovel. The bucket wheels prestrip the soft overburden ahead of the shovel. This soft overburden is brought to the spoil side through a series of shiftable conveyors and placed by a spreader over the ungraded or partially graded shovel spoils. The placement of the soft overburden and top soil is accomplished in a manner that meets the reclamation mandates. The prestripping by the BWE has reduced the incidence of the highwall and spoil slides, depth the stripping shovel has to dig and the volume handled by the pullback draglines.

Jan 1, 1984