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By G. D. Naugle, L. C. Atkinson

Introduction Deep open-pit mines invariably affect the local and regional hydrologic systems. Pit dewatering, occurring during mining operations, puts an obvious hydrologic stress on these hydrologic systems. However, post-mining hydrologic impacts resulting from the pit refilling with groundwater following the cessation of mining activity can also be significant. The prediction of the rate at which the post-mining pit will fill with groundwater is a critical aspect of assessing the long-term hydrologic impacts. Numerical groundwater flow modeling provides a method for predicting the groundwater refilling rate of the pit. The rate at which pit "lakes" fill depends on several factors: •the rate and duration of pit dewatering; •the depth and size of the ultimate pit and •the pre-mining hydrologic regime. These factors can be incorporated into a detailed numerical groundwater flow model that can then be used to assess the effects of dewatering and post-mining recovery on the local and regional hydrologic systems. A sufficiently detailed, numerical groundwater model provides the oportunity to: •account for complex geology near the pit; •assess the impact of active pit dewatering and •predict the long-term impacts of post-mining groundwater flow into the pit. A detailed groundwater model incorporating these items has been developed and applied at an operating open-pit mine. Developed by Durbin and O'Brien (1987), the three-dimensional, finite-element, groundwater flow model was used to represent the hydrologic system of an approximately 253-km2 (98-sq mile) area surrounding the pit. Historical groundwater elevation data, stream flows and meteorologic, geologic and geophysical data were used to establish the dimensions and initial conditions for the model. Steady-state conditions, representing the pre-mining local and regional hydrologic systems, were simulated using the initial conditions incorporated into the groundwater model. The groundwater model was then utilized to simulate various dewatering programs, to predict the filling rate and the groundwater depth in the ultimate pit once mining activities are complete and to assess the long-term impacts on the regional groundwater flow system. Development of pit lake model Groundwater modeling efforts were completed in two phases. The first focused on pit dewatering activities, while the second phase concentrated on the post-mining effects on the hydrologic system. The final estimates of groundwater elevations calculated during the pit dewatering simulations were used in predicting the post-mining recovery of the hydrologic system. The groundwater model was also modified prior to the second phase to account for the volume of rock removed during mining activities. To account for the actual volume of rock mined, the geometry of the post-dewatering model grid was modified to approximate the final pit geometry. The depth and width of the ultimate pit were divided into eight idealized stages that represented significant changes in the bench geometries. These eight stages were then introduced sequentially into the model according to the predicted water elevations within the pit. In this way, changes in the volume and depth of water within the pit were accounted for through time. Once the ultimate pit geometry was accounted for in the model, it was necessary to assign new hydraulic characteristics to those parts of the model grid (elements) that represented excavated rock. The solution of the numerical model requires that finite hydraulic conductivity values be assigned to the portion of the groundwater model that represents excavated rock. Therefore, the calculated groundwater elevations differ, somewhat, between the edges and the center of the open pit. These model-calculated water elevations at the edge and in the middle of the open pit represent the elevation of water that would occur in the pit lake. To minimize the error in the estimated level of water within the pit lake, the hydraulic conductivity was increased to a value that would: •minimize the predicted difference between the groundwater elevations across the open pit and •produce a numerically stable solution. Specific storage is the hydrologic parameter that accounts for the water produced by compaction of the aquifer matrix. To predict the groundwater volume that would flow into the ultimate pit, this parameter was assigned a value equivalent to the compressibility of water. This value of specific storage reflects the post-mining groundwater storage occurring as an open body of water. Additionally, a specific yield of 1.0 was assigned to the pit elements to represent the 100% porosity of the open pit. In

Jan 1, 1994

By Jim Sundal

Primary steel manufacturers using electric arc furnaces generate one of the largest hazardous waste streams nationwide. The waste stream, known as electric arc furnace dust, is a listed hazardous waste with the designation K061. Oregon Steel Mills, Inc., (OSM) of Portland, Oregon, has implemented a process known as Glassificationn, which uses KO61 as an ingredient in an onsite recycling process. Because OSM was able to demonstrate that the Glassificationm recycling process beneficially uses all toxic constituents in the electric arc furnace dust and that the recycling process produces marketable products, the process is not subject to Resource Conservation and Recovery Act (RCRA) permit requirements. The marketable products manufactured using Glassificationn include roofing granules, ceramic glazes and colorants, abrasive blasting media and, more recently, synthetic slag fluidizers. The purpose of this paper is to identify the regulatory issues for recycling hazardous waste and demonstrate that OSM glass frit is effective as a slag fluidizer in primary steel manufacturing.

Jan 1, 1994

By Russell J. Foster

Public awareness of, and involvement in, recycling has increased significantly in recent years. Nevertheless, recycling is generally perceived as a new development, and is familiar only in the context of municipal solid waste management. The actual magnitude and scope of metals recycling in the United States have gone virtually unnoticed. Over time, both the quantitative and qualitative aspects of secondary metals recovery and reuse have changed substantially, while the attendant regulations have become increasingly stringent. This U.S. Bureau of Mines report examines trends and developments in major metal demand and recycling, and analyzes the possible impacts of regulations with regard to recycling activities.

Jan 1, 1994

By M. Polat

Variations in flotation rate by particle size and specific gravity have been investigated for three different bituminous coals. The flotation rates for various components were determined by separating the products of bulk flotation into size-specific gravity fractions. The effects of feed size and reagent addition on the flotation response of individual size-specific gravity fractions were evaluated.

Jan 1, 1994

By Elliot Schwartz, Julian Szekely

"In this paper we describe an experiment that was recently performed on the IML-2 Space Shuttle mission in which the thermophysical properties of molten metals were measured using electromagnetic levitation. In the planning of these experiments calculations had to be performed to predict the levitation and stirring forces, heating rates, sample deformation, and internal flows within the sample. These predictive calculations were essential for both the planning of the experiments and for the re-planning of experimental runs during the actual Space Shuttle mission.Introduction""Materials Processing in the Computer Age"" involves the use of mathematical modeling to obtain a quantitative understanding of the phenomena that govern materials processing operations. Microgravity, or space shuttle experimentation represents a specific case in point here; the very high cost of the space shuttle flights, the very limited flight opportunities that are available, and the tight resources aboard a shuttle clearly mandate that these experiments be very precisely planned and that all possible opportunities for mathematical modeling be fully exploited.The purpose of this paper is to present the results of calculations performed for the planning of a space shuttle experiment involving electromagnetic levitation and wherever possible present a comparison of the computational predictions with both experimental measurements and asymptotic analyses. Finally we shall seek to discuss the practical implications of both the computational methodologies and the potential experimental findings."

Jan 1, 1994

By Norman L. Kotraba

Zia Metallurgical Processes, Inc. has developed and patented a steelmaking process capable of converting iron bearing metallurgical wastes into high quality steel products. The process utilizes a proprietary design rotary hearth furnace to convert iron bearing wastes, pelletized with coal, or other forms of carbon, into direct reduced iron (DRI). This DRI is fed, hot, from the rotary hearth furnace into a Zia All Purpose Vessel (ZAV) where it is smelted and refined into high quality steel. A specially designed turret with three independent arms, each supporting a separate ZAV, comprises the heart of the meltshop. No overhead cranes are required to transport molten metal from the smelting/refining operation to the ladle metallurgy station to the caster to an inspection station and back to the smelting/refining point. The molten steel is contained in the ZAV throughout the operations eliminating the possibility of steel con¬tamination by non-metallic inclusions occasioned by the exposure to ambient air during metal transfer into ladles. The result is the creation of very clean steel that can be alloyed to produce virtually any desired grade from stainless steel to common structural steel.

Jan 1, 1994

By R. G. Hilton

This paper deals with application of Super Detox? stabilization technology to the treatment of electric arc furnace dust (US-EPA listed hazardous waste KO61 ). The process has been used on approximately 170,000 tons of electric arc furnace dust. In addition to the nearly four years of commercial experience at Sterling, Illinois, the process is now being permitted for application at two other locations. The process was originally developed by the Bethlehem Steel Corporation and then further improved by Conversion Systems, Inc. (Bethlehem Steel's Licensee). The treatment process offers many unique bases for its selection, including: A) Low cost compared to the treatment alternatives; B) Lowest available TCLP leachate levels for any process treating K061. Many other processes leave some residue that represents a disposal requirement, although often not addressed; C) Produces minimized final waste disposed, including the fact that the total volume of dust generated and less than the volume occupied by the residue slag from HTMR; and, D) Opportunities for the beneficial utilization of part or all of the waste stream through the development of chemical and physical characteristics. Each of these aspects will be specifically discussed in the paper, including that status of the operations now under permit.

Jan 1, 1994

The Ok Tedi open pit mine will have final wall heights in excess of 750m. The behaviour of these excavated slopes will be influenced by the presence of numerous defects. This paper discusses the identification of possible failure mechanisms within the pit walls based on mapped fault and joint data. Results from analyses using these data have formed the basis for the ultimate pit design.

Jan 1, 1994

By C. E. Jordan

The U.S. Bureau of Mines investigated flotation hydrodynamics to improve the recovery of coarse phosphate. Fluid velocity profile measurements were used to characterize the hydrodynamics within commercial phosphate flotation cells and laboratory flotation cells. The effects of agitation, aeration, and pH on coarse phosphate recovery were measured in the laboratory flotation cells and correlated with the hydrodynamics measurements. Test results revealed that the agitation energy and aeration level had a significant effect upon flotation response. By optimizing these two parameters, 92 pct of the phosphate was recovered in a rougher flotation concentrate grading 28 pct P2O5?

Jan 1, 1994

By P. S. Hettinger

Land Application Discharge (LAD) is a useful method of disposing of waste water from mining operations and in certain climatic regimes, stormwater runoff. LAD systems function under the premise that metals, salts and nutrients in water are dispersed over a large area and are effectively assimilated into the soil profile. Depending on the soil structure, migration or mobilization of dissolved metals through the soil profile can be Substantially reduced. Land application of treated effluent from sewage lagoons or waste water plants was probably the first general use of land applied water. LAD has gained popularity with the mining industry as a means of disposing of waste water and process water. In addition, large volumes of snow meltwater and stormwater are often placed in storage in Montana during spring, and Land Application Discharge has shown to be an effective method for disposing of stormwater during the dry, summer season. LAD can also provide an alternative to recycling or treating waste water at on-site waste water treatment plant&. Application of stormwater or process water can result in little or no change to the background concentrations of metals in baseline water quality samples. One cautionary note about LAD: high salt concentrations and pH values are associated with process water from heap-leach facilities and are known to cause burning of local vegetation. Some pre-treatment of process water may be necessary to prevent such environmental problems.

Jan 1, 1994

By Ross R. Bhappu

Anticipating a major power cost increase in 1990, Cyprus Copper Company decided to modernize the Miami Smelter at a cost of $92.5 million. The modernization project included the addition of an Isasmelt vessel for use as the primary copper smelter and the modification of the existing electric furnace to a slaglmatte separating vessel. The project was completed in June of 1992 and is currently operating at close to its design capacity. This paper provides a summary of the decision making process, a description of the project, a summary of start-up problems and solutions and the current status of the smelter operation.

Jan 1, 1994

By Anupam Madhukar

The essence of an atomistic unified kinetic model of strained thin film growth and defect initiation is presented along with a comparison of its consequences obtained from computer simulations with experiments. Within the competing kinetics of a strain dependent activated incorporation of atoms and an asymmetry between upwards and downwards inter-layer migration, the model provides a consistent description of 2D versus 3D morphology evolution accompanied by the appearance of surface vacancies and steps at no energy cost. The correlated migration of these precursor defects offers an atomistic mechanism for the emergence of surface half-loops from the growth front (thus accounting for configurational and thermal entropy) governed by activation energies closer to their correlated motion under the evolving strain fields and thus substantially less than those calculated with respect to the perfect crystal as the reference state. The essential mechano-chemical nature of the problem is compared and contrasted with the historical literature of such phenomenon as precipitation hardening and sintering in metallic and ceramic composites.

Jan 1, 1994

By Dale W. Collins

The disposal of arsenic from copper operations possess various health, environmental and processing problems. There are basically two areas of concern. The first being the disposal or treatment of smelter flue dusts and the second the removal of arsenic from refinery electrolytes. A number of treatment options have been proposed including the addition of soluble arsenic wastes to copper heap and dump leaching solutions. This approach will allow arsenic to be reintroduced to the ore via Solvent Extraction (SX) raffinate associated with hydrometallurgical operations. Knowledge of the attenuation behavior and mechanism during leaching is important in determining the long term stability of arsenic and the success of this approach. Parameters, such as uptake capacity, pH, particle size and solution chemistry have been investigated. Arsenic attenuation has been examined using column leaching with experiments employing both continuous flow and pulsed additions of As(V). In the initial stages of leaching, the attenuation of arsenic appears to depend on the pH and iron concentration in the effluent. Arsenic stability in the copper oxide ore has been examined with rinses of progressively lower pH.

Jan 1, 1994

By H. EI-shall

In this paper, the results of a fundamental study involving zeta potential and turbidity determinations of solid suspensions are discussed. Illustrations of how these results are utilized to design field applications of solid grade polymers to clarify mine drainage water are presented. Other applications in different industries are also reported. The operational and economical advantages are examined.

Jan 1, 1994

By P. A. Hendricks

The surface coal mining industry in the United States employs over 50,000 people and is responsible for 60% of domestic coal production. This represents a very significant contribution to our national economy and an important source of highly skilled and well paying jobs. The U.S. Bureau of Mines (USBM) has targeted surface mining as an important research priority to reduce the social and economic costs associated with surface mining injuries and fatalities. USBM safety research focuses on the development of technologies that can enhance productivity and reduce mining costs through a reduction in the number and severity of mining accidents. This report summarizes a number of completed and ongoing research programs that address a broad range of surface mining safety problems. Research methods are described, and research products which are suitable for industry implementation are highlighted.

Jan 1, 1994

By L. M. . Chia

The successful treatment of waste materials to recover metals with acceptable purity is often hampered by the presence of undesirable impurities. The problem is further complicated by the need to insure that any residues or solutions generated are environmentally acceptable. Hydrometallurgical processes involving leaching- solvent extraction-electrowinning offer some attractive features which address many of these problems. However, in certain instances trace impurities that contaminate the organics are difficult to chemically strip and interfere with the overall process efficiency. A new processing scheme has been developed which appears to provide some attractive alternatives for impurity removal from organics. It has been shown that many ionic impurities can be electrochemically removed from the organic by spontaneous direct reduction using solid metals. A variety of metal ion impurities have been removed from selected common organic extractants such as D2EHPA and TBP using different metals as the reducing agents. The results and probable mechanisms involved in the reactions are discussed.

Jan 1, 1994

By J. A. Porter

This paper uses project examples, primarily associated with large iron ore mines in Brazil, to demonstrate opportunities for the mining industry to go beyond traditional compliance and impact mitigation to proactively operate within the ethics of environmental and economic sustainability.

Jan 1, 1994

By A. L. Garassino

Dans cet article on parle sortout de l'approche de calcule pour les pieux charges horizontalement avec particuliere reference aux curbes p-y et è une solution semi-empirique qui prende en consideration les variations typiques du module du sol avec la deformation obtenue par les données expérimentales. 1. INTRODUCTION The analysis of the piles under lateral loads depends very strictly from the pile stiffness and geometry, from the soil type and from the strain field. Different approaches were adopted in solving the problem. Some Authors developed methods for estimating the ultimate lateral resistance of piles and pile groups by conventional static approaches, as the Brom's widely known (1964) or by the plane strain solution developed by Davis (1961) or by empirical engineering con­siderations l

Jan 1, 1994

By W. C. Lacy

It is the responsibility of educators to look ahead and prepare young engineers and scientists to cope with industrial and social problems of the future. We are faced with a review of history as well as prophesy of the future. The mining industry exists in a "bubble" with little interaction or communication with the outside. This isolation must be broken down if the industry is to survive in the U.S. and Canada. The ability to communicate with the general public and public officials is essential. Many changes are occurring that will require readjustments in technology and staffing. Aging population will result in raising retirement and increasing available workforce. This may force shorter working weeks to supply additional jobs. Environmental concerns will likely direct more attention not only to these concerns during mining, but to planning for post-mining land usage. Retraining and up-dating educational programs are required to cope with these changes.

Jan 1, 1994

By Michael K. Watkeys, Charlesworth. E. GUY, Jacobus E. Potgieter, Anhaeusser. Carl R., Roger L. Gibson, Alexander F. M. Kisters

Abstract - Intrusive features of cupriferous noritoids from the deeply eroded Proterozoic granite-gneiss terrane of the Okiep Copper District in South Africa illustrate the emplacement of basic magmas into a mid- to lower-crustal environment. The small, easterly trending intermediate to basic intrusions of the so-called Koperberg Suite display a wide variety of geometries, occurrence and emplacement modes, including dike-, sill- and plug-like bodies. Coeval granulite-facies metamorphism, partial melting and ductile deformation of country rock gneisses during intrusion of the basic magmas led to emplacement and dilation processes of the intrusions which differ significantly from those described for dikes and sills at shallow crustal levels. Regional tectonic stresses are largely negligible due to very low differential stress (?1 - ?3) during deformation and intrusion, which permits emplacement at high angles to the principal compressive stress and which follows favorably inclined structural anisotropies. Dilation of the basic intrusions is largely determined by compositional differences of host rocks and occurs by thermal erosion, i.e., assimilation of wall rock gneisses. Low length-to-width ratios of basic to ultrabasic dikes and predominantly diaper -like outlines of mesocratic bodies are indicative of low viscosity contrasts between the mafic magmas and high-grade metamorphic host-rock gneisses. Buoyancy-controlled ascent of the basic to intermediate intrusions is expressed by a broad compositional zoning of basic bodies with respect to the granite-gneiss stratigraphy. Various intrusion modes within the stratigraphic column of the granite-gneiss sequence reflect a lithological and structural stratification of the seemingly homogeneous granite-gneiss terrane.

Jan 1, 1994