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By Roger Storry, Arnaud Hochart, David Harris, Olivier Martin

"INTRODUCTIONThe Port of Miami Tunnel (POMT), designed and constructed by Bouygues Civil Works Florida between 2009 and 2014, was a Public Private Partnership between the Miami Access Tunnel Concessionaire, Florida Department of Transport, Miami-Dade County and the City of Miami. The project comprises dual 11.3m internal diameter, 1.27km long, twin lane road tunnels running between Watson and Dodge islands under the main shipping channel in Biscayne Bay. Five cross passages (CPs), spaced at 200m centre to centre, provide emergency access between the two tunnels, as shown in Figure 1.The CPs were constructed by open-face excavation methods but the particular geological conditions at the project site (loose and variable carbonate sedimentary strata with very high permeability) required specific ground treatment solutions to provide safe excavation conditions and to ensure the long term serviceability of the permanent works construction. Where access allowed, ground treatment was performed from the ground surface using deep-mixing techniques; however, at two locations (CP2 and CP3) surface access was restricted and ground treatment by freezing, performed from the tunnels, was required. The CPs are 12.3m long with an excavation diameter of 5.8m and are located up to 30m below the water table partly or wholly within the Key Largo limestone (termed Layer S7 in the ground model). Layer S7 is a coralline limestone having a metastable honeycomb structure and high variable porosity. At CP2 the upper portion of the excavation was within the overlying Anastasia Formation limestone (Layer S6), comprising a highly permeable coquina. The geological profile along the project is shown in Figure 2.This paper presents aspects of the freeze design and the risk mitigation necessary to successfully achieve the construction of the CPs in the unique geological conditions."

Jan 1, 2016

By R. Krog, M. Valente, R. Ochsner, W. Marchewka, R. Jensen, R. K. Zipf

A tube bundle system (TBS) is a mechanical system for continuously drawing gas samples through tubes from multiple monitoring points located in an underground coal mine for analysis and display on the surface. The U.S. National Institute for Occupational Safety and Health (NIOSH), in collaboration with Signal Peak Energy (SPE), LLC, Bull Mountains No. 1 Mine, operated a TBS during mining of two bleederless, longwall panels. This paper describes the gas analysis data and its interpretation. As verified by the TBS, coal at the SPE mine tends to oxidize slowly. It was known that a reservoir of low-oxygen concentration atmosphere developed about 610 m (2,000 ft) behind the longwall face. A bleederless ventilation system facilitates formation of an inert atmosphere in this longwall gob and decreases the likelihood of spontaneous combustion. Connections of the mine atmosphere to the surface through subsidence cracks could allow airflow into the longwall gob, revive coal oxidation and increase spontaneous combustion risk. The atmospheric composition of the sealed areas was homogeneous, except in the immediate vicinity of suspected ingassing points. The TBS verified that gases within the partially sealed, bleederless longwall gob expanded into the longwall tailgate area when barometric pressure decreased. The concentration of carbon dioxide in the back return airflow at the longwall tailgate was observed to increase by a factor of three and possibly up to 10 times the typical background concentration of 0.5 to 1.0%, depending on the size of the longwall gob and the magnitude of barometric pressure decrease. TBS have the inherent disadvantage of slow response time due to travel time of the gas samples and sequential gas analyses. A TBS or similar continuous monitoring system could be beneficial in detecting and providing warning of potentially hazardous gas concentrations, if the slow response time of the system is always understood.

Jan 1, 2013

By A. M. Marabini, G. Belardi, V. Alesse, M. Acosta

Sotiel mine is situated in the Iberian Pyrite Belt in southern Spain, some 40 km north of the port of Huelva. Although mining operations at the site date back to Roman times, the present mine came into production in 1983 and 5.6 million tonnes of ore had been extracted by 1993. The orebody is volcano-sedimentary and consists of fine grained copper, lead and zinc minerals in massive pyrite surrounded by slates and volcanics. Prior laboratory research had resulted in the synthesis of a new collector, belonging to the MercaptoBenzoOxazole (MBO) class that acts selectively towards Cu and Zn minerals after activation with CuS04. The MethylMercaptoBenzoOxazole (MMBO) version of this collector had been used for the laboratory flotation of Cu minerals and sphalerite activated by CuS04. This resulted in identification of the optimal physicochemical conditions for laboratory-cell flotation of the two minerals from samples of complex sulphide ores, and subsequently the reagent has been tested in the Sotiel plant (Spain). The plant has three flotation sections. With conventional re-agents, the first section yields a Cu concentrate grading 21% with a total recovery of 29%, and the second one yields a 40% Pb concentrate with total recovery of 34% and a 47% Zn concentrate with total recovery of 78%. Application of the new synthetic reagent in the copper and zinc circuits produces a more selective process with a decrease in re- agent concentration grade and recovery are increased by 2 and 9 points respectively in the case of Cu and by 1 and 3 points where Zn is concerned. Moreover, the penalty elements in the Cu concentrate are halved.

Jan 1, 1995

By Jodie Robertson, Isabel Barton, Cristian Caro

Prior to mining, all rocks contained in a mineral deposit must be placed in one of several categories known as ore types. Each ore type describes a different way that the rock will behave in processing. The ore type determines which process stream a particular mined unit will be sent to, sets expectations for process engineers and metallurgists, and forms the basis for recovery predictions and production estimates. At first, ore types are assigned mainly by geologists based on visible geological criteria (dominant ore mineralogy, estimated grade, rock type, alteration type). As metallurgical tests are carried out and process data accumulate, the resulting criteria may be factored into the ore typing process, typically as assays and recoverable metal using the relevant process(es). Other variables may also be incorporated into ore typing at operations if they are particularly important, such as grindability, preg-robbing, gangue reagent consumption, and the presence of especially deleterious minerals such as talc or smectite. The mine operation department may also redefine ore types and/or process destinations based on economic criteria. A “best” ore type is designated that (in theory) best describes how the rock will behave in processing. Codes representing this ore type are entered into the drill hole database, then interpreted on cross sections and level plans, and finally added to the block model. Ore types are iteratively reexamined and adjusted over the life of a project. Major difficulties in effective ore typing are (1) lack of communication between geologists and metallurgists, (2) the imprecision inherent in imposing clean categories on messy natural systems without discrete divisions, (3) the need for ore types to provide useful information for a wide range of processes, (4) difficulties in scaling up laboratory test results to mine production, and (5) conflict among geological, metallurgical, and economic criteria for ore typing.

Nov 8, 2023

By Tim Neil, O&apos

Copper price rebounds A worldwide scramble for diminishing supplies of copper has pushed the red metal's price to more than $2.20/kg ($1 per lb), the highest level since 1980. The first nine months of 1987, world copper production was down 1% from a year ago, while consumption rose 7%. Demand has been fueled by economic strength in several countries, particularly Japan, South Korea, and Taiwan. The price has also been helped by interest rate declines that have prompted manufacturers to build up inventories. In addition, China is expected to be a major buyer in 1988 as it stocks up for its five-year industrialization plan. There appears to be no sign of any significant increase in copper supplies until later 1988 or early 1989. This means supplies probably will remain tight for some time even if world economic activity slows. Strikes and other production problems slowed world output of copper in 1987. As a result, copper supplies are the lowest they have been in 14 years. World inventories currently total 625 kt (690,000 st). That is not much above the 585 kt (645,000 st) level reached in 1974 when the price of copper rose to a record $3.84/kg ($1.74 per lb). This makes all the more interesting what Chile, the world's largest copper producer, has been doing lately. Chile has been the world's largest copper producer since 1982, when it overtook the United States. Table 1 shows Chile's copper grades, reserves, and production at its mines. Chile contains roughly one-fifth of the world's copper reserves. At present production rates, these reserves would last for more than 100 years. In 1986, Chile produced 1.4 Mt (1.5 million st) of fine copper, up 3%. Chile accounted for 17% of the world's copper output.

Jan 1, 1988

By Slavoljub D. Maksimovic, Steve J. Page

The Bureau of Mines measured respirable dust emission rates from overburden drilling at a surface coal mine and the transport of this dust to downwind locations. The emission rates were estimated by using multiple gravimetric dust samplers mounted on a cross-shaped tripod located immediately downwind of the drill. The transport of this dust was measured at more distant downwind locations by a combination of respirable gravimetric sampling and integrated bag sampling of sulfur hexafluoride (SF6), which was used as a tracer gas. Two modes of sampling were used: (1) At five sampling locations arranged in a semicircle around the drill. The radius of this arc ranged from 15.85 m (52 ft) to 71.32 m (234 ft). (2) In-line sampling at downwind locations with samplers located at intervals of either 10.67 m (35 ft) or 15.24 m (50 ft) for a total distance of 76.20 m (250 ft). Samples were taken 1 .22 m to 1.52 m (4 to 5 ft) above ground level. Test results for the semicircular test arrangements showed that at any downwind location, the maximum contribution of respirable dust due specifically to the drilling operation was 42%; the average for eight tests was 13.6%. In general, there was no correlation between the downwind distance of this maximum contribution and the maximum contribution itself because of changing wind direction. Test results for the in-line arrangements indicated that the transport of the dust from the drilling operation usually decreases rapidly with distance and that, even though the drill dust may produce significant health hazards for the drill operator and drill helper (or other personnel in the immediate vicinity), the exposure of downwind personnel to drill-generated dust may not be a significant problem.

Jan 1, 1987

By N. Champigny

The geostatistical estimation of the reserves of an ore deposit is highly dependent on the quality and stability of the variograms of the sample grades. Gold deposits commonly show a skewed grade distribution. The few high grades at the tail end of the distribution produce unstable variograms that are difficult to model. If these grades are cut to a lower grade value or removed, more stable variograms are obtained. However, outlier grades may make a deposit economically viable, and their cutting or removal should be treated with caution. To reduce (but not to eliminate) the effect of high grades, a transformation of the raw data can be performed. Most commonly used transformations are: logarithm, gaussian anamorphosis, rank and indicator. Variograms of the transformed grades are resistant to high grades and present a clear structure. The weak point of data transformation appears when grades are estimated by kriging; the estimates are very sensitive to slight variations in the parameters of the back-transformation. More robust variogram estimation procedures can also be used, but often these procedures are not suitable for skewed grade distributions as they are based on an assumption of a contaminated normal distribution. The Porgera gold deposit in Papua New Guinea has a highly skewed grade distribution, with grades ranging from 0.01 to 3500 g/t and a coefficient of variation greater than 5. For the geostatistical estimation of the high grade zone of the deposit, the influence of the high grades was quantified by calculating and comparing the following variograms: raw grades, raw grades with the highest grades removed and transformed grades. The study confirmed that there is no general method for handling high grades in a geostatistical reserve study. Several methods should be tried to quantify the influence of high grades.

Jan 1, 1991

By Richard R. Radel, Jack Barry

Contract required excavating 2,000 If of 14' horseshoe tunnel in rock, a 95' deep work shaft on shore, and a 50' deep intake shaft located in the middle of the Niagara River just above Niagara Falls. Large quantities of H2S were encountered in the range of 20 PPM with ventilation. Peak levels of 40 PPM were recorded. The original designed ventilation system required only a volume of 10,000 CFM to meet OSHA requirements. The volume of air was increased to 50,000 CFM to dilute the H2S to al- low workmen to work and comply with OSHA H2S action levels. The second phase of the tunnel consisted of placing 72" ID X 20 foot long concrete reinforced pipe in the tunnel. When the tunnel was holed through and both shafts were open, a substantial amount of work was required to take place in the shafts which eliminated the possibility of placing a bulkhead to secure proper ventilation. The ventilation team designed a jet system airlock. The design of this system was to bring fresh air down the work shaft in two duct systems; one 30" diameter and one 24" diameter. Following the excellent work of Jan Wolski (7th Mine Ventilation Symposium chapter 58) our design incorporated nozzles located approximately 100' in by the work shaft. The velocity of the 24" diameter duct was 6,365 FPMD2.2 MPH. The velocity of the 30" diameter duct was 6,117 FPMl69.5 MPH. Both systems were on blow and being that air expands at 3112 degrees per side this high velocity of air expanded and created an air bulk head through which men and the large sections of concrete pipe could be passed without any delay or additional cost to the project.

Jan 1, 1997

By Milan Yekich, Emanuele Cauda, Justin Patts, Cody Wolfe

A worker’s personal exposure to respirable dust in occupational environments has traditionally been monitored using established methodologies which entail the collection of an 8-hour representative sample that is sent away for laboratory analysis. While these methods are very accurate, they only provide information on the average exposure during a specific time period, generally a worker’s shift. The availability of relatively inexpensive aerosol sensors can allow researchers and practitioners to generate real-time data with unprecedented spatial and temporal granularity. Low-cost dust monitors (LCDM) were developed and marketed for air pollution monitoring and are mostly being used to help communities understand their local and even hyper-local air quality. Most of these integrated sensing packages cost less than $300 per unit, in contrast to wearable or area dust monitors specifically built for mining applications which have been around for decades but still average around $5,000 each. At the National Institute for Occupational Safety and Health (NIOSH), we are leveraging the power of high-volume data collection from networks of LCDM to establish baseline respirable hazard levels and to monitor for changes on a seasonal basis as well as following any application of control technologies. We have seen the effective use and advantages of monitoring live data before, during, and after events like shift changes, operational changes, ventilation upgrades, adverse weather events, and machine maintenance. However, many factors have prevented a systematic adoption of LCDMs for exposure monitoring: concern for their analytical performance, the complexity of use, and lack of understanding of their value are some factors. This contribution outlines a one-year case study at a mine in Wisconsin USA, covering the installation, maintenance, data visualizations, and collaboration between NIOSH researchers and the industrial hygiene professionals at the mine.

Feb 1, 2024

By S. B. Bhagwat

The United States has abundant coal resources that could last at least another century. and probably longer at present consumption rates. Geographically, the coal resources are distributed over the entire nation including Alaska, although there are no coal deposits in the highly populated areas on the two coasts. This allows free access to the coal, but makes transportation more expensive. Not all coals can be utilized equally because they differ vastly in quality. The sulfur content of coals, considered as the most detrimental acid rain-causing element, varies from as low as 0.3 percent in some areas of the western U.S. to 5 percent or more in parts of the Midwest. The chlorine content, which causes corrosion of plant hardware, also varies regionally. The 1990 amendments of the Clean Air Act of 1963 (CAA) require that emissions of sulfur be restricted and rolled back in two stages by the year 2000. There have been a number of reports expressing concern about the future of the industry in the states where high sulfur coal is produced. The remedies devised by the federal government and many coal-producing states in the past to "se-cure" the future of the regional coal industries have focused on the physical task of removing sulfur rather than the economic challenge of doing so at a cost that will enable high-sulfur coals to survive and compete. The past remedies, generally, were not specific enough to account for the characteristics of regional coal deposits and did not look at the coal market as an integrated national and international entity. The State of Illinois has, in recent years, taken a more comprehensive approach to the solution of the problem.

Jan 1, 1992

By W. Burger

For the development of deep, hard rock, mines fast access to the orebody is critical. In some cases the mineralized area is more than 1,500 m (5,000 ft) below surface. Excavation of shafts or declines is typically on the critical path of the project schedule. Saving time on those activities can significantly increase the net present value of the mining project. Mechanical excavation methods are a step-change in excavation performance and labor safety compared to drill-and-blast operations. In hard rock conditions, roadheaders cannot be used effectively, so disc cutting is the first choice. For excavation of declines, tunnel boring machines (TBM) can be used in many cases. These provide, in certain rock conditions, considerably higher production rates com-pared to drill-and-blast excavation. Herrenknecht AG has developed a vertical shaft sinking machine (VSM) that is able to excavate shallow shafts in soil and medium soft rock. The ground is excavated by a roadheader boom. The muck is removed by a slurry system or a pneumatic system in combination with hoisting of skips. These machines have been applied successfully on shafts down to 100 m (300 ft). A pre-sink for a deep mine shaft has been excavated by this technology. For deep, hard rock shafts, a new shaft boring system has been developed by Herrenknecht AG in collaboration with Rio Tinto. Based on proven technologies, the system uses a unique arrangement of existing proven technologies. The system integrates excavation, mucking, primary rock support, installation of the final lining and shaft infrastructure. This new system improves the health and safety of shaft construction. Detailed performance estimates indicate significantly higher shaft construction rates are possible compared to conventional shaft sinking methods.

Jun 1, 2010

By Oleg N. Tikhonov

A new extraction method which includes a combination of gravity and alternating electromagnetic fields with interfriction of mineral particles was proposed (Tikhonov O.N., 1979) and tested in lab conditions at Mineral Processing Department of St. Petersburg Mining Institute. At the beginning of the work the main goal was to find an efficient alternative to traditional extraction methods (like shaking table, etc.) used for concentration of fine alluvial gold particles. After the method and a series of gradually improved lab separators (Tikhonov, et al., 1983) were positively tested for gold (Tikhonov, et al.. 1986) the efficiency of the method was also proved for extraction of and other heavy minerals from alluvial and ground ores in experimental work at the St. Petersburg Mining Institute. The fine heavy minerals were separated to concentrates with high technological indices (Andreev et al., 1987), (Tikhonov, Gladkov, 1987), (Tikhonov, Gladkov 1989). In parallel a semi-industrial gravi-electro- magnetic separator was made and several technological flowsheets were designed for testing the method in industrial conditions (Tikhonov O.N., Miazin B.N., 1987), (Tikhonov O.N., Tolstunov S.A., Jebelev V.V.,1989). A series of industrial tests accompanied with complete sampling and standard technological measurements were performed at several alluvial deposits, with good technological indices. Thus the method and the flowsheets displayed high additional recovery of fine alluvial gold particles during elkrated industrial experiments in Siberia (Aldan province). At higher concentrate grade this method, even in one-stage operation, increased gold recovery more than by 25% compared with shaking table (for particles -0.10 mm gold recovery was 82% vs. 55% by shaking table, for particles - 0.25mm the recovery was 97.5% vs. 61.8%). Experiments were performed by joint team of St. Petersburg Mining Institute and the Irkutsk Institute of Rare Metals (Tikhonov O.N., Gladkov S.A., Tarasova T.B., 1991).

Jan 1, 1995

By Giovanni Toniatti

Brazil is a country with continental dimensions. It hosts many different varieties of terranes and geological environments in its 8.5 million km2 (3.28 million sq miles). This mineral endowment has been important for the country's economic and social development process since the early colonial period, leaving Brazil with a legacy of almost 400 years of mining tradition. Mining in Brazil started in the early 17th century with diamond and gold discoveries. The made the country the leading producer of both for more than a century. This phase faded by the late 18th century when the alluvial deposits were depleted. It finally yielded to competing countries where technology and capital were being applied more efficiently. This period of mining dormancy lasted from the late 19th century until the first decades of the 20th century when Brazilian mining picked up. There was growing pressure on mineral resources by the affluence of the industrial society. The fast-growing demand resulting from the two world wars had brought the Brazilian mineral wealth back to the scene. This second Brazilian mineral boom made the country a leading producer of iron and manganese ore, quartz crystals and other strategic minerals. This expansion in Brazil's mining industry provided the basis for the country's industrialization process. This was led by the Brazilian steel and petroleum industries. Unfortunately, the thrust provided by this modern industrial basis was not properly used as a lever for further industrial development. The upstream industrialization process was not supported by the proper development of the raw materials supplying basis. The resulting industrial model was heavily dependent on imports of raw materials. It did not support the economic growth and faced fierce industrial competitiveness and sophistication that emerged with the postwar economic boom.

Jan 1, 1997

By Henry R. Tiedemann, Eugene H. Skinner, George E. Wickham

The need for ground support research in underground excavation has been well identified in recent years by many studies in the subject area (1, 2, 3, 4, 5). A typical conclusion from these reports (1, 2) is that the drill-and-blast (D & B) mining or the mechanical tunnel boring machine (TBM) methods are expected to be continued in use for the needs of tunneling in the immediate future. The Organization for Economic Co-operation and Development (OECD) sponsored in June, 1970 advisory conferences on Hardrock and Soft Ground Tunneling (3,4). These two reports were based on the combined response received from approximately six hundred inquiries from 17 nations in the summer of 1969 and which concerned all aspects of present-day inadequacies of, and the needed improvements in the technology of tunneling. Some specific problem areas in ground support and tunnel linings were: 1) the ability to successfully predict rock loads that must be carried by the support system; and 2) inadequate methods for determining the load-carrying capacity of the various support systems. Therefore, the problem area is clearly defined by these two objectives: 1) To find means of predicting rock loads; and 2) To develop methodology for determining safe, efficient, and economical ground support design practices. Noting these research needs from a great number of sources, the United States Bureau of Mines, Spokane Mining Research Center (SMRC), acting as agent for the Advanced Research Projects Agency (ARPA), undertook contract research effort in these problem areas. Work by Jacobs Associates has studied a methodology for specification of temporary artificial support based on the dependent sequence of mining operations and prediction of various rock conditions in the pre-excavation stage. The major thesis is that rock behavior is the

Jan 1, 1997

By Lawrence W. Teufel

Knowledge of in situ stress and natural fracture distribution at depth improves our ability to stimulate and produce low permeability reservoirs. The focus of this study is three closely spaced, 2.5 km deep vertical wells in the Piceance Basin of Colorado. The wells were completed through the tight lenticular and blanket gas sands of the Mesaverde Group. In situ stress directions and magnitudes were determined from hydraulic fracture tests and anelastic strain recovery measurements of oriented core. The distribution, orientation, and characteristics of natural fractures in the subsurface were determined from detailed observations of over 1300 m of core, of which 400 m was oriented. Stress measurements clearly show that horizontal stresses are strongly influenced by lithology. In a sandstone/shale sequence at a depth of about 2.0 km in situ stresses in sandstone formations are anisotropic, with the average ratios of the minimum and maximum horizontal stresses to the overburden stress being 0.82 and 0.96, respectively. In sharp contrast bounding shale formations are lithostatic. This stress contrast between sandstones and bounding shale formations could act as a barrier to hydraulic fracture propagation during stimulation and impede vertical fracture growth. Natural calcite-filled fractures are present in over 7 percent of the core, with several horizons having a much higher frequency of fractures. Fractures are found primarily in sandstone. The fractures have a strong preferred orientation of N 1060E[+]110, which is aligned with the maximum horizontal stress and direction of hydraulic fracture propagation. The interaction between a well developed fracture fabric and anisotropic stresses in sandstone formations produces a permeability anisotropy, with the maximum permeability aligned with the fracture fabric and maximum horizontal stress.

Jan 1, 1986

By S. G. Malghan, W. H. Moyer

In reference to the section "Excess pyrite," the author discusses difficulties in separating chalcopyrite from pyrite. A technique does exist, and has been used commercially, for the flotation, separation, and recovery, if desired, of both chalcopyrite and pyrite. The method was described in Mining Engineering, March 1966, "An Improved Flotation Method for Cornwall Sulfides." While it was not used on a porphyry copper ore, it was used on a chalcopyrite- pyrite-containing ore and might well have application. Both sulfides, chalcopyrite and pyrite, were floated simultaneously using xanthate as a collector and MIBC frother to produce a cleaned sulfide product. This concentrate was then thickened and conditioned at high solids with aeration and lime to a pH above 12.0 for a period of 1.5 to 2 hr. A supplemental suppressant, such as cyanide, could be used if necessary to sharpen the subsequent separation; however, it was not required at Cornwall. The conditioned sulfides were floated with two stages of cleaning to produce a high- grade chalcopyrite froth product and a pyrite sink product barren in copper. The separation at Cornwall gave a 28.6% Cu grade chalcopyrite product and a pyrite analyzing 0.06% Cu. A desliming step on the raw ore initially used at Cornwall for a period of time was later discontinued. Advantages to be found in using a strong sulfide collector, such as a xanthate, is the rapid flotation it induces and, generally, an ability to float at a coarser grind. A following regrind circuit could be used to give maximum liberation and produce a clean sulfide concentration. The "differential" separation is concerned primarily with grade and with assuring a barren pyrite for maximum recovery.

Jan 1, 1987

By K. G. Tsakalakis

The Greek Cement Industry is a vital sector of our economy. With an annual production of cement over 15.5 million tonnes, it contributes significantly to the national gross domestic product (G.D.P.). The cement industry, as other mineralogical transformation process industries (lime, glass, ceramics, extractive metallurgy etc.), is high energy intensive. Each tonne of cement produced requires not only large amounts of fuels (coal, fuel oil), but additionally a significant quantity of electrical power as well. All fuels consumed by the Greek Cement Industry are imported and energy accounts for one third of the cement production cost. Therefore, it is of interest of the community and the industry to increase energy efficiency, to reduce the quantities of fuels consumed in the cement manufacturing process. It is also known that like almost all manufacturing processes, the cement industry produces large amounts of CO2 (combustion of fuels, de-carbonization of limestone and use to electricity). The utilization of wastes (principally as alternative fuels, scrap tires, spent solvents etc.) is compatible with the general principles of waste management and it is also a common practice in other European and developed countries. In the present paper the economic, social and environmental benefits provided by the recycle process of the various wastes in the Greek cement plants are extensively analyzed. From the whole work, it was concluded that such a practice: - replaces a significant percentage of imported fossil fuels in the cement manufacturing process, - maximizes the recovery of energy and also ensures their safe disposal, - produces overall environmental benefits by reducing releases to air, water and land, - prevents resource depletion of valuable non-renewable fossil fuels, - overcomes the need for the construction of dedicated incineration facilities, - contributes positively to the principles of the sustainable development.

Jan 1, 2003

By Vernon Miller

In 1986, a subsidiary of Echo Bay Mines Ltd. purchased the McCoy property, 55 km (35 miles) southwest of Battle Mountain, NV. Echo Bay then launched a two-year, $1 15-mil lion capital program to build a mill to extract gold and silver from high-grade ore mined in two open pits - the original McCoy pit and a more recent discovery, the Cove. Engineering on a new mill began in 1987 with the facility coming on line in 1989. It was comprised of a semiautogenous (SAG) mill and ball mill grinding, leaching, flotation, counter current decantation (CCD) and Merrill-Crowe processes. The mill started up on McCoy ore, a rocky material that settled very well in the new CCD thickener system. Production levels were maintained at about 7.2 kt/d (8000 stpd). The situation changed as the McCoy ore played out and increasing amounts of material from the Cove pit-with its oxide, sulfide and carbonaceous ore - were fed to the mill. The problem was the high clay content of the Cove ore. The new ore immediately created production problems, mainly loss of control on the CCD thickeners. With the McCoy pit slated to be shut down in early 1991, it was essential to find a way to efficiently process the Cove ore. Initially, the only way to regain control of the thickeners was to slow down the processing rate and increase flocculant usage, thereby getting the solids to settle in the thickeners. But this had its cost. Production dropped to about 5.9 kt/d (6500 stpd), additional operators were needed and flocculant costs, on occasion, would reach an unacceptable $80,000 per month. Overfloccing led to viscous

Jan 1, 1993

By Gürkan Bacak

Study area is located on the NorthWestern of Yatagan-Yenikoy and placed in the units of the crystaline Menderes massif of Eagen, Turkey. Stratigraphically gneissic, migmatitic and metagranitic rocks are found at the base. Garnet schists, phyllitic rocks lie unconfirmitelly upon the basement rocks. Permian aged marbles can be observed as diferrent sized lenses within the schists. Triassic, Jurassic and Cretaceous aged gray colored dolomites and pure crystaline calcite bearing marbles lie upon the Permian aged schists. Neogen series, mainly composed of conglomerates, claystones, marl and limestones unconformly cover the other basement series, mentioned above. Pure calcite bearing marble occurances are found at 2 locations in the study area. These are known as Berber Quarry and Kavuk Quarry. Samples numbered as N7, N8, NA from the Berber Quarry, mineralogically composed of Calcite (97-99%)+iron oxide (1-3%) and chemically contain CaCO3 (97,98%), Fe2O3 (0.5-1%), SiO2 (0.025%) N9 and N10, sampled from the Kavuk Quarry-mineralogically composed of Calcite (94,95%)+iron oxide (2-3%)+albite-Quartz (1-2%) and chemically contain CaCO3 (92-93%), SiO2 1.49%, Fe2O3 0.42%. Especially in plastic and paint sector albite and quartz are unwilling minerals due to their hardness. Approximatelly 1/20 of the study area (87.500 km2) contains industrial calcite occurances. Moreover about 100 billion Tons geological, 1.86 billion tons runable (possible) calcite reserve calculated. It can be expected the calcite quality will be increased with depth. During the running stage of the quarries over burden removel and hand sorting processes will positive affect of the quality.

Jan 1, 2005

By Edward H. Opitz

Much has been written recently about the Henderson Mine Project in Colorado being developed by American Metal Climax, Inc. To briefly recap the project, AMAX has an ore body, containing about 300 million tons of proven and probable molybdenum ore which is located under Red Mountain on the eastern slope of the Continental Divide. The mill, however, will be located on the western slope in the Williams Fork Valley where water and space for waste disposal are more available. AMAX will carry the ore by remote controlled trains from a gathering level underground at the mine, through a ten (10) mile tunnel under the Continental Divide and thence along a five (5) mile surface railroad to the mill site. One of the more challenging facets of the project is the western portion of the ten (10) mile tunnel being driven by Dravo Corporation through difficult ground conditions, downgrade, toward the Continental Divide. The tunnel is a 16'-6" wide by 15' high horseshoe, which runs in a straight line and drops at a constant three percent (3%) grade from the West Portal to the ore zone. Dravo's portion is anticipated to be about 6 1/2 miles long and includes permanent pumping stations located every 4,900 linear feet (lf) permanent rectifier stations every 12,5001f, and one (1) 1,560 ventilation shaft. The western portion of the tunnel lies in the Idaho Springs formation, a mixture of gneiss and schist with some granitic intrusions. Toward the Continental Divide a transition into Silver Plume Granite is expected to occur. Preconstruction geologic information indicated the Idaho Springs and Silver Plume formations to be basically competent with some faulted and altered areas. It

Jan 1, 1974