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Safety Factor Characteristic Curves. Their Application to Mine Hoisting Ropes. (Paper by W. A. Boyer, Transactions AIME, 199, 989; Mining Engineering, October 1954. Discussion by B. E. Grant.) ............................................................................................................................. 1101 The Use of Wooden Rock Bolts in the Day Mines. (Paper by Rollin Farmin and Carville E. Sparks, Transactions AIME, 196, 922; Mining Engineering, September 1953. Discussion by Edward Thomas.) ................................................................................................................................. 1101 An Analysis of Mine Opening Failure by Means of Models. (Paper by Bernard York and John J. Reed, Transactions AIME, 196, 705; Mining Engineering, July 1953. Discussion by J. P. Zannaras.) ... 1102 B — Minerals Beneficiation Flotation and the Gibbs Adsorption Equation. (Paper by P. L. de Bruyn, J. Th. Overbeek, and R. Schuhmann, Jr., Transactions AIME, 199, 519; Mining Engineering, May 1954. Discussions by W. E. Ewers and Masayoshi Wada.)........................................................................................... 1103 Manganese Upgrading at Three Kids Mine, Nevada. (Paper by S. J. McCarroll, Transactions AIME, 199, 289; Mining Engineering, March 1954. Discussion by J. Bruce Clemmer, J. B. Rosenbaum, and C. H. Schack.)............................................................................................................. 1105 A Physical Explanation of the Empirical Laws of Comminution. (Paper by D. R. Walker and M. C. Shaw, Transactions AIME, 199, 313; Mining Engineering, March 1954. Discussions by Dimitri Kececioglu, George B. Clark, and Fred C. Bond.) ......................................................... 1106 F — Coal Underground Electrocarbonization of Coal and Related Hydrocarbons. (Paper by T. C. Cheasley, J. D. Forrester, and Erich Sarapuu, Transactions AIME, 199, 908; Mining Engineering, September 1954. Discussions by John G. Tripp and James L. Elder.)....................................................... 1108 Longwall Mining and Mechanization, with Special Reference to Nova Scotia. (Paper by Frank Doxey, Transactions AIME, 199, 701; Mining Engineering, July 1954. Discussion by Louis A. Turnbull.) ........................................................................................................................................ 1109 Cleaning Various Coals in a Drum-Type Dense-Medium Pilot Plant. (Paper by M. R. Geer, W. A. Olds, and H. F. Yancey, Transactions AIME, 196, 696; Mining Engineering, July 1953. Discussion by John Griff en.)................................................................................................................................. 1110 Frontiers in Heat Extraction from the Combustion Gases of Coal. (Paper by Elmer R. Kaiser, Transactions AIME, 199, 304; Mining Engineering, March 1954. Discussion by G. A. Vissac.) ............ 1112 Exploration of the Oaxaca Coal Fields in Southern Mexico. (Paper by Luis Toron and Salvador Cortes-Obregon, Transactions AIME, 199, 505; Mining Engineering, May 1954. Discussion by John D. Price.).................................................................................................................. 1113 H — Industrial Minerals Alkali Reactivity of Natural Aggregates in Western United States. (Paper by William Y. Holland and Roger H. Cook, Transactions AIME, 196, 991; Mining Engineering, October 1953. Discussions by Dexter H. Reynolds and W. L. Merritt.) ......................................................... 1114 Characteristics of Titaniferous Concentrates. (Paper by L. E. Lynd, H. Sigurdson, C. H. North, and W. W. Anderson, Transactions AIME, 199, 818; Mining Engineering, August 1954. Discussion by D. R. Grantham.)........................................................................................................................ 1116

Jan 1, 1955

By Harry L. Brown, James M. Dickinson, Philip E. Armstrong

The elastic stiffness coefficients of niobium have been rneaslrred from -150°C to over 650 C and ave in accord with the anomalous temperature dependence previously observed for Young's modulus. This unusual behavior has been shown to be the result of changes in the relative values of the shear elastic coefficients. The bulk modulus remained essentially constant over the temperature range studied, while changes in the shear coefficients produced a more nearly isotropic behavior as the temperature increased. A number of investigators have reported data on the temperature dependence of Young's modulus of polycrystalline niobium. The values cited for the room-temperature modulus ranged from 0.71 to 1.17 x 10" dynes-cm-' (10.3 to 17.0 x lo6 psi) and in each case the modulus was observed to decrease with increasing temperature. In our recent study,8 both polycrystalline and single-crystal samples of essentially strain-free high-purity niobium showed a Young's modulus whose temperature dependence as well as magnitude was strongly dependent on specimen orientation. This was shown to be the result of changes in the relative magnitude of the two shear moduli, C and C'. Young's modulus of polycrystalline samples with strong [110] textures and Young's modulus of single crystals whose orientations were away from the [loo] actually increased as much as 12 pct between room temperature and 1000°C. While studies on the residual effects of previous fabrication, thermal treatments, and impurity contents will probably resolve the problem of the widely differing Young's modulus values observed in polycrystalline niobium, a more complete description of the elastic properties requires an evaluation of the single-crystal elastic constants. A knowledge of these constants can provide a clearer picture of the nature of the temperature dependence, as well as establish a basis for predicting the modulus behavior of polycrystalline niobium, both in the randomly oriented condition and with various fabrication textures. The effects of residual strains on the elastic behavior then can be separated from orientation effects. EXPERIMENTAL METHOD Thin rod-resonance techniques were used to obtain both the Young's modulus and shear modulus of single-crystal specimens. The determination of these moduli as functions of the crystallographic orientation of the specimen axis provided sufficient information to permit calculation of the single-crystal elastic constants. The necessity for torsional as well as longitudinal measurements led to the design and assembly of a vertical-tube vacuum furnace incorporating probes for the simultaneous determination of both longitudinal

Jan 1, 1967

By S. M. McDeavitt

Waste form alloys are being developed at Argonne National Laboratory for the disposal of remnant metallic wastes from an electrometallurgical process developed to treat spent nuclear fuel. This metal waste form consists of the fuel cladding (stainless steel or Zircaloy), noble metal fission products (e.g., Ru, Pd, Mo and Tc), and other metallic wastes. The main constituents of the metal waste stream are the cladding hulls (85 to 90 wt%); using the hulls as the dominant alloying component minimizes the overall waste volume as compared to vitrification or metal encapsulation. Two nominal compositions for the waste form are being developed: (1) stainless steel-IS wt% zirconium for stainless steel-clad fuels and (2) zirconium-8 wt% stainless steel for Zircaloy-clad fuels. The noble metal fission products are the primary source of radiation in the metal waste form. However, inclusion of actinides in the metal waste form is being investigated as an option for interim or ultimate storage. Simulated waste form alloys were prepared and analyzed to determine the baseline alloy microstructures and the microstructural distribution of noble metals and actinides. Corrosion tests of the metal waste form alloys indicate that they are highly resistant to corrosion.

Jan 1, 1996

By A. S. Atkins

The interest in the use of micro- organisms in the leaching of sulphide minerals has been traditionally exploited as a scavenger process for the recovery of valuable metal by- products from waste ore dumps. Environmental concern on sulphur emission from conventional pyrometallurgical plants together with the cost of stack cleaning systems to comply with legislative control also indicate baccerial leaching to offer a low cost treatment for the processing of sulphide minerals. The paper describes the effect and limits of relatively coarse particles on the complete leaching of pyrite and its importance to the practical application in dump leaching operations of sulphide minerals. It has also been demonstrated that static leaching techniques have encouraging economic potential for process plant operations compared with agitated leaching systems.

Jan 1, 1984

By Bob Drew, Alfred Spanring, Kirschen. Marcus

"Increasing material conversion and energy efficiency, and decreasing carbon dioxide emission levels are crucial for sustainable production processes in the aluminum, cooper, and steel industries. RHI supports these targets by providing a diverse range of solutions including high quality refractory linings, optimum lining maintenance, and process improvements. In this paper examples are provided of process improvements and increased energy efficiency in copper refining, potential energy savings during electric arc furnace and ladle operations in the steel industry, and increased energy efficiency by improved heat transfer in anode baking furnaces in the aluminum industry. In all cases, RHI’s expertise in close collaboration with the customer resulted in an improved performance of the reactor lining and the actual high temperature process with a positive impact on the material conversion and energy efficiency and as a result a decrease in specific carbon dioxide emission levels.IntroductionRefractory linings play an important role in heat transfer during high temperature processes in for example the aluminum, copper, and steel production industries. Due to constantly increasing energy prices worldwide and the increasing demands for environmental and climate protection, improving the energy efficiency and decreasing emission levels of these energy intensive production processes is of significant importance. In this paper, the contribution of modern RHI lining technologies to energy saving measures and the corresponding reduction of specific carbon dioxide emission are described. The type of current refractory solutions for energy intense processes are illustrated with four examples: Optimization and increase of material conversion and energy efficiency in copper refining, energy saving potentials in both electric arc furnace and transport ladle operations in the steel industry, and heat transfer improvements during the carbon anode annealing process in the aluminum industry. These examples focus on particular production processes operating with a high proportion of recycled copper, steel, and carbon anodes. Increased energy efficiency directly decreases the specific energy related carbon emission levels whereas improvements to the metallurgical processes aim to increase material conversion efficiency and, therefore, decrease specific process related carbon emission levels. Significant energy savings can be achieved by maximizing the refractory campaign length through a combination of appropriate refractory material selection, grade zoning, correct installation, careful preheating, and effective maintenance strategies. Besides the efforts to improve the performance and energy efficiency of customer high temperature processes, RHI continuously promotes the development of new low emission carbon-containing refractory bricks and unshaped products."

Jan 1, 2008

By Ann G. Kim

The Bureau of Mines investigated factors that influence the formation of methane and other hydrocarbon gases in coal, which is an integral part of the coalification process. Coalification begins with a biogenetic stage in which plant debris decomposes and peat is formed; methane and CO2 are the predominant gases produced during this stage. During the diagenetic stage of coalification hydrogen and the hydrocarbon gases methane, ethane, ethylene, propane, propylene, butene, iso-and normal butane, and pentane are formed by dissociation of the organic material. Methane may also be produced by a secondary reaction of hydrogen with unsaturates or by the reduction of CO2. The gas contained in coalbeds is a mixture of methane, C2 through C5 alkanes, CO2, O2, N2, H2, and He; its heating value is equivalent to that of natural gas. The gas content of coal depends on many variables, but an empirical relationship between adsorptive capacity, rank, and depth has been observed.

Jan 1, 1978

By Robert E. Mead

During the past three years the New York Trap Rock Corporation has been restricting blasting operations to days when favorable atmospheric conditions prevailed. By favorable atmospheric conditions is meant the absence of temperature inversions or isothermals in the lower atmosphere or under 6,000 feet altitude. Strong wind and wind shear can also cause conditions unfavorable for blasting. As a result of this practice, there has been a marked decrease in the number of blasting complaints received. The New York Trap Rock Corporation operates four stone quarries on or near the Hudson River within 60 miles of New York City. The Company supplies approximately 7,080,000 tons of high grade, crushed and graded aggregate, rip rap and by-products to the New Pork City area annually, This stone is carried to the market by a fleet of company owned deck &cows which are moved by tugs of a subsidiary towing company. Stone from two of the quarries is diabase: and, from the remaining two, dolomite.

Jan 1, 1962

PRESIDENT AND DIRECTOR JOHN R. SUMAN HOUSTON, TEXAS PAST PRESIDENTS AND DIRECTORS DONALD B. GILLIES CLEVELAND, OHIO H.- G. MOULTON NEW YORK, N.Y. TREASURER AND DIRECTOR KARL -EILERS SEA CLIFF, N. Y. VICE-PRESIDENTS AND DIRECTORS W. B. HENRY HOUSTON, TEXAS HENRY KRUMB NEW YORK, N. Y. ERIE V. DAVELER , NEW YORK N Y W. M PEIRCE PALMERTON, PA. PAUL D. MERICA NEW YORK, N. Y. LEROY SALSICH DULUTH, MINN.

Jan 1, 1941

By D Martín, G. Díaz, F. Cubeddu, A. B. Mejias

The Modified ZINCEXTM Process (MZP), developed by Técnicas Reunidas, is an industrially proven flexible process. It can handle a wide range of primary and secondary raw materials, producing SHG zinc. The core of the Modified ZINCEXTM Process is the zinc solvent extraction unit. This unit is an effective barrier for any leachable impurities present in the raw material. As a result of this an ultra-pure zinc solution is always obtained. The high versatility of the process makes the application of the technology in different scenarios possible. MZP can be effectively applied when developing a whole new plant (Skorpion) or adapting its scheme to an existing refinery (Akita), in both cases giving the same results. Flexibility in terms of capacity of the plant is a great advantage of the MZP, there is the possibility to adapt the global process to a wide range of production capacities. Zinc production capacities of over 150 000 t/a may be achieved with a single solvent extraction plant train. The robustness of the Modified ZINCEXTM Process has been recently proven on two new plants currently in operation: Portovesme (Italy) and Horsehead (USA) after start up during 2013. The status of both plants is described in this paper.

Jan 1, 2014

Industrial minerals by definition are minerals used as part of an industrial process and usually are one of a number of components, eg finely ground Limestone is an extender in the manufacture of paint. They are normally non-metallic and non-fuel, but like all generalisations there are a number of exceptions. Take rutile û a source of titanium, a metal and also the raw material in the manufacture of titanium dioxide pigment. Industrial minerals under this general definition include construction and agricultural minerals. They are included in the same grouping, principally because their sources are similar and in many cases the raw material, example limestone, can be multi-functional. Calcium carbonate raw materials such as limestone, are used in a wide range of applications from industry as an inert filler, to agriculture as a 'lime' source and to construction and as an important component in the manufacture of cement. As far as this paper is concerned I will avoid discussing the agricultural or construction applications, including burnt lime production.

Jan 1, 1985

Evaluation of tyre chains has been taking place at King Island Scheelite for several years. Results indicate that tyre life has been greatly improved in all cases. Good cost sav- ings are resulting on small loaders. The worth of chains is difficult to prove on larger loaders under the conditions at King Island Scheelite. However, the dramatic decrease in the number of punctures has convinced the Company that chains are worthwhile on some larger loaders.

Jan 1, 1977

By Steve Bessinger, Steve Signer, James Pile

The San Juan Mine and the National Institute for Occupational Safety and Health conducted a study to measure how development mining affected bolt loads. Twelve fully grouted, instrumented roof bolts were installed at two three-way intersections as part of the standard bolting pattern. Newly developed miniature data acquisition systems (MIDAS) were used to measure bolt load changes during initial face advance and cross-cut breakthrough. The effects of cut placement and depth on roof bolt loads were studied. This test showed how bolt loads increased at five positions along the bolt length during initial mining. Both entry advance and cross-cut breakthrough produced a similar percentage of increase in bolt loads. Geologic differences between the test sites were probably responsible for the differences in amounts of bolt loading. The test site with more top coal and a higher rock quality designation (RQD) had lower bolt loads.

By A G. Thompson, E Villaescusa, D Howard

The Western Australian School of Mines (WASM) has developed a facility for the static testing of full-scale ground support elements (Morton et al, 2007). The test facility consists of several stiff steel frames used to support the sample and a screw feed jack is used to load the sample. A large-scale punch test method has been developed to load various shotcrete configurations. The shotcrete is sprayed on to a rock substrate containing a centrally located circular disc. The rock and shotcrete sample is placed on to the sample frame and restrained on all sides. The circular disc is displaced at a constant rate by the screw feed jack which in turn loads the sample. Instrumentation measures the displacement and the load being applied to the sample through the loading disc. The testing method is described in detail and the results from the testing program are presented. The results show that it is possible through laboratory testing to simulate some of the mechanisms of shotcrete support reactions better than conventional beam and panel tests.

Jan 1, 2008

By J. Perlacia

"As the bulk handling sector continues its transformation to Industry 4.0, the mining industry, and its harsh working and environmental conditions, provides a perfect spot to study the feasibility of remote analysis and maintenance of the components used for bulk handling. The most important and expensive tools have been adapted to the digital era in recent years, from remotely controlled haul trucks to monitored conveyor belts.However, the big items of the installations rely on smaller parts that have been leftaside, mainly due to the difficultyof adapting them to the Internet ofThings (IoT).The paradigmatic example is the lack of monitored rollers, while all the other components of the conveyorbelt installations (the belt itself, motors, drums, etc.) were monitored some time ago. The main problem is that a failure of a single roller can cause the stoppage of the entire conveyor, due to possible damage to the belt. Thus, the implementation of an integral monitoring system of all the components of the conveyor is a must.The research and development department of ULMA Conveyor Components has been working since early 2012 on the development of monitored rollers, testing all the problems until their final installation in different demanding conditions, from the extreme heat in Australia to the freezing cold of Norway. All the tests have been done under actual working conditions, in real installations and have provided valuable knowledge in the identification of problems, their solutions and the final advantages of a roller monitoring system.Background and current stateThe malfunction of a single roller in certain conveyor belts can force the standstill of the entire installation until its replacement, due to the risk of greater and more expensive failures, such as a rip in the belt. In the case of a bulk handling installation, where a continuous supply of material is necessary, an unexpected stop of one hour could result in huge economic losses."

Nov 1, 2019

By Giovanni Barla, Stefan H. Boshkov

This paper examines the application of gelatin mixture models to the study of factors such as gravity effects, tectonic and residual stresses, anisotropy, physical nonlinearity, time-dependent behavior of the rock mass and connectedness of the geologic space. The technique of calibrating gelatin mixtures proposed by Richards and Mark in 1966 is applied to the particular problem considered. Similitude relationships between model and prototype are discussed with reference to the constitutive equations describing the physical behavior of the rock mass. The interaction between two openings in a linearly elastic medium, under conditions of plane strain, is used as an illustrative example with the view to describing the history of stress and deformation changes on the rock medium and lining around a slusher drift while undercuts are made in block caving. The prediction of the displacement, stress field and mode of fracture associated with a given rock structure, its initial stress field, and its physical properties is essential to rock mechanics and ground control. The basic approach is to assume the rock mass to behave as a continuous, homogeneous, and isotropic medium. The classical theory of elasticity is the simplest theory based on such a concept. Specification of the elastic constants, the initial state of stress in the ground, and the boundary conditions on stress and displacement allows one to predict stress and displacement within the body. Subsequently, provided that a criterion which governs rock fracture under various stress conditions has been established, a stability analysis of the rock structure can be performed. A natural extension of the present knowledge consists of removing some of the simplifying assumptions which characterize the analytical solutions based on the classical theory of elasticity. Complex geometry, the significance of tectonic and residual stresses, anisotropy, physical nonlinearity, time-dependent behavior of the rock mass and connectedness of the geologic space are some of the important factors which are neglected in the classical approach. A better insight into the real problem can be attained with either the finite element method of stress analysis or an experimental technique. The former has already been applied with success on several occasion 1-4 and is destined to render great service in the field of rock mechanics and ground control. The latter, which will be considered in this paper, has been used extensively in applications too numerous to be enumerated. Experimental technique involves either prototype testing, if the area to be studied is accessible, or model testing. Two- and three-dimensional photo-elastic analyses are very convenient means of obtaining the stress distribution in models of complex geometry. In general, such analyses are confined to studies of stress fields around openings which are sufficiently far removed from the surface boundary so that the stresses in their neighborhood are practically equal to those produced by an initial uniform stress field; i.e., so that gravitational effects are negligible. There are, however, many rock structures where these effects must be taken into account to attain a more realistic representation of the problem. Surface and near surface rock structures, systems of openings interacting with one another, and structural components loaded only by their own weight are some of the obvious examples. This paper was written to show how factors neglected in the usual analysis based on the classical theory of elasticity, can be taken into account when gelatin mixture models are used inconjunction with photoelastic methods. The interaction between two openings in a linearly elastic medium, under conditions of plane strain, is used as an illustrative example, with a view to describing the history of stress and deformation changes on the rock medium and lining around a slusher drift while undercuts are made in block caving. The birefringence of gelatin mixtures has been known for some time. A series of experiments were carried out by Rossi in 1910,5 but after that very

Jan 1, 1970

By Raquel Costa, Aldino Campos, Frederico Carvalho Dias, Pedro Madureira, Patrícia Conceição, Ana Filipa Marques, Andreia Afonso, Maria Ana Martins, António Calado, Luísa Pinto Ribeiro

Since its formation in 2004, the Task Group for the Extension of the Continental Shelf (EMEPC) has been collecting hydrographic, geological and geophysical data to support the extension of the continental shelf beyond 200 NM. In 2008, the EMEPC acquired a 6,000 m rated ROV named "Luso" and has been cooperating with several national and international institutions to increase and improve its operational capabilities to conduct research on deep-sea minerals. The Portuguese continental shelf corresponds to a broad area of the seafloor encompassing different physiographic domains: the mid-Atlantic ridge system, abyssal plains and numerous seamounts. From 2008 to the present, the mid- Atlantic ridge and seamounts have been the most visited sites with the ROV "Luso". Several hydrothermal vent sites are known to occur along the mid-Atlantic ridge to the south of the Azores archipelago and mostly within the Portuguese EEZ. Vent fields were also discovered in the extended continental shelf, namely the Rainbow and the Moytirra sites located to south and to the north of the Azores archipelago, respectively. The most studied seamounts correspond to those forming the Great Meteor chain and the Madeira- Tore rise. All these visited sites are related either with the occurrence of polymetallic sulphides or cobalt rich Fe-Mn crusts and the opportunities to further pursue their exploration will be discussed.

Sep 1, 2014

With significant increase in steel output in the world the price of iron ores has been soaring recently. Especially, there is a strong demand for iron ores in China, leading to more attentions paid to developing low grade iron ores. In this paper mineralogy of nm-of-mine hematite ore was deter-mined, and coal-based direct reduction-magnetic concentration was successfully developed to beneficiate low grade hematite ore. Mineralogy analysis indicates that this hematite ore is a super fine refractory ore, with the main valuable mineral hematite being closely associated with quartz and distributing uniformly and mostly occurring within the size of 3~5J.lITI,leading to being difficult to beneficiate due to super fine hematite and only grading 28.83% Fetotal. This hematite ore failed to be effectively upgraded by traditional processes in trial tests, such as reverse flotation, gravity concentration, and magnetic separation, or the integration of the above processes. In contrast with adoption of the coal-based direct reduction-magnetic separation process, concentrate was produced with high iron grade and metallization degree in the present work, which provides a theoretical basis for utilization of low grade iron ores. By optimization of direct reduction conditions, such as reduction temperatures, duration and mass ratio of reductant coal to iron ore, the reduced ore with 93.72% metallization degree was prepared, and then three-stage grinding-magnetic separation of the reduced ore were conducted, the final concentrate was manufactured, assaying 69.54% Fetotal and 98.01 % metallization degree, and with low content of impurities. This iron concentrate with high metallization degree produced by this process is a superior burden for converter instead of blast furnace. This process is enviromnent friendly by directly making iron using coal and iron ores instead of coke, resulting in less emissions and low production cost.

Jan 1, 2014

By Dolea Gabriel Gheorghe

In the present paperwork is proposed an economical-mathematical model (fuzzy) that aims optimize the technological variants of the mechanized coal face. By fuzzification, the issues to solve become more flexible and allow the decision maker to acquire more variants for the functions objectively established. The description of technological solutions is carried out by a set of controllable variables of "category" type by which the type of the machinery is defined within the frame of the actual geological & mining conditions. In the paperwork are used concepts of "successions graph" and "matrix of compatibilities"; with their help a methodology to choose between different technological variants of coalfaces is proposed. It treats the problem of developing the functions that express the membership degree in vague concept. In the end it is presented an assessment procedure for the technological variants of mechanized coal face.

Oct 1, 2009

By Gawen Jenkin

The extraction of metals from ores is often an energy-intensive process, requiring either smelting or leaching at high temperature, or the use of large quantities of strong acids or bases that require energy to produce. These processes often produce wastes, in gaseous, liquid or solid form, which require treatment before they can be safely disposed, and this waste treatment requires further energy. Thus there is a need to develop more energy-efficient and environmentally-compatible methods. In this sense, the paper point out that ionic liquids are one such method, and that they can be used to selectively dissolve and recover native gold and tellurium, sulphides and tellurides.

Oct 21, 2015

By R Kahnt, S Jahn, D Baacke, M Eckart

Relocation into the Lichtenberg open pit mine of about 110 million m3 of sulfide-bearing and ARD-generating waste rock piled up on the surface is the most important and cost-intensive single surface restoration project conducted by WISMUT GmbH at the former Ronneburg uranium mining site. The waste rock comprises for the most part Palaeozoic shales, limestones and diabases with pyrite contents of up to seven per cent. Waste pile relocation began in 1992 and is scheduled to be completed by 2007. The approach used for relocation has been extensively described elsewhere (Jakubick et al, 1997; Hockley et al, 1997; Chapman et al, 1998; Paul, 2003). Following completion of the backfill that will be up to 60 m above the initial ground level, a dry cover will be placed on top of the backfilled mine wastes. The area to be covered amounts to about 220 ha. Design planning for the final cover placement of which is to begin in 2004 had to be based on a comprehensive cost-benefit analysis over and above compliance with legal requirements. The crucial question to be answered in this respect was to determine û in addition to the expenditure required to ensure reuse, radiation protection and soil protection û the extent to which additional time, effort and money were justified in order to minimise contaminant release from the unsaturated portion of the backfilled pit contributing to total releases into the ground water and possibly achieve savings in long-term operating costs for the on-site water treatment plant. Optimisation was based on contaminant balance modelling for the entire site reproducing dominant physical and geochemical processes. Among the specifics underlying the cover design is that contaminant release from the backfilled open pit must not be considered independently of that from the adjacent flooded underground mine and that a major part of the backfilled open pit will also be submerged. Following weighing of cover-related short- and long-term costs it was found that higher construction costs for the various cover options will not be offset by cost savings in the long-term water treatment. As a consequence of pit flooding, even a costly multiple cover including an impermeable layer will only insignificantly impact on concentrations and loads at ground water spill over points. As a result of comprehensive studies and investigations, a combined cover of cohesive soil material from on-site excavation overlain by a 0.4 m thick storage layer to restore natural soil functions for revegetation was derived and submitted for approval. Together with hydraulic measures, this approach is to meet any requirement in terms of radiology, water protection, stability, erosion protection, and reuse.

Jan 1, 2003