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By D. W. Ginsberg, D. Cieplinski

"The lifetime cost of a material handling system, or any mine system, can be reduced through the application of quality engineering. Dynamic simulation is a powerful tool that can be used to enhance the experience and ingenuity of the design team. It cannot only de-bottleneck the system to improve system productivity, but also define critical design criteria to eliminate over-design and reduce capital cost. Eliminating over-design also reduces operating costs by lowering component replacement costs and by ensuring all parts of the system operate at a higher utilization and efficiency. IntroductionA mine owner’s profitability is improved when a mine is developed at the lowest lifetime cost. This cost relates not only to capital and operating costs, but also, to a great extent, on the efficiency and reliability of the operation. These factors are tied directly to the quality of the engineering which depends on the experience of the engineers involved, and their ability to apply known system information in a rational and constructive manner.It is becoming apparent that it is increasingly more difficult to deliver the quality of engineering expected and needed to provide attractive lifetime costs using traditional design methods. Historically, system information has been evaluated based on a limited amount of information to which global rules-of-thumb and the engineer’s personal experience were applied to develop design criteria. However, market forces are dictating that more system parameters be defined and that they be defined more accurately so that the most economical system can be developed. This increase in the volume of information and the need for more accurate predictions is straining, if not already exceeding, the ability of engineers to apply simple global rules of- thumb and to combine all the information in a rational, comprehensive and representative set of design criteria. Furthermore, as proposed system production rates increase beyond established industry practice, the extrapolation of the engineer’s experience becomes more difficult and increases the risk in the proposed design."

Jan 1, 1998

By Denby B, Hollands R. Schofield D

Surface mines are in operation worldwide, the vast majority employ large haul trucks for the transfer of material both to the outside world and around the site. The sheer size of these trucks and the operating conditions means there is a high

Jan 1, 1998

By M. Paventi, M. J. Scoble, B. B. Mohanty

There is no straightforward and systematic method for adequately measuring blast damage in on-going mining operations. This paper considers various techniques available for the measurement of blast damage, making particular reference to recent underground hardrock mine studies. This paper concludes by indicating the importance of understanding and accounting for geology and emphasizes the need for a robust damage-audit procedure.

Jan 1, 1998

By J S. J van Deventer, D C. Shallcross

New developments are taking place in the recovery of gold from leached pulps that are based upon the adsorption of the metal cyanide species onto ion exchange resins. Despite the success of several resin-in-pulp pilot plant operations in the Western World and large-scale plants in the former Soviet Union, the process is yet to gain recognition as a viable alternative to the carbon-in-pulp process. An experimental research program has investigated the use of a variety of different types of resins for the recovery of gold, but to-date no resin studied has the desired properties of high selective loading capacity for gold cyanide and a simple inexpensive elution procedure. In addition very little is known concerning the physical strength of resins and their ability to resist shattering due to osmotic shock during cycles of adsorption and elution. The ability of ion exchange resins to enhance the leaching of refractory and re-adsorbing ores has not been investigated. This paper highlights the necessary factors that need to be addressed before commercialisation of ion exchange technology for gold extraction is feasible.

Jan 1, 1998

For effective backfilling, a system with the 13 features covered under the section: effective backfill systems, is required. Effective backfilling cannot be done with systems that are badly designed, outdated or overextended. But in cases where the requirements for effective backfilling are overlooked, the shortcomings of such systems may wrongly come to be regarded as limitations to the capabilities of backfilling per se. Mining is currently done to depths of 3500 m, and is to go deeper since the gold-bearing reef extends down to 4000 m and 5000 m below surface. Effective backfilling systems will be required at such depths, and with suitable design this can be achieved. Mining the narrow tabular orebody of a typical South African gold mine is described at the start of this paper, then cycloned backfilling is discussed in general, and its effectiveness (most of the fill placed in South Africa is cycloned backfill or ædeslimed tailingsÆ).

Jan 1, 1998

By Dennis C. Martin

Assessment of the potential for mining induced subsidence and determination of ultimate design requirements for a mining operation should be based on a number of assessment approaches. Although the rock mechanics engineer has a variety of limit equilibrium and numerical modeling tools available for assessment and prediction of subsidence effects, empirical approaches based on precedent experience provide a powerful tool for calibration/verification of analytical models and prediction of subsidence. Three separate analyses approaches have been applied to the assessment of potential subsidence for a proposed block caving mine in eastern Canada. The investigations have included an assessment of documented historical information from previous block cave mining at the site, deterministic analyses using limit equilibrium approaches to assess kinematically possible failure mechanisms, and three-dimensional numerical modeling techniques. Analyses results have been used and compared with precedent experience and documentation of subsidence behavior from previous mining to optimize the subsidence predictions for the proposed mine.

Jan 1, 1998

By Emil B. Milosavljevic

Problems associated with distillation and other classical methods for analyzing operationally defined cyanide (CATC, WAD, Total and Free Cyanide) will be discussed. These methods often achieve incomplete, species dependent cyanide recoveries and suffer from serious interferences. Depending on the relative concentrations of interferents and other matrix constituents, underestimation (ultimately Type II errors probability of not detecting a constituent when it is actually present) or overestimation (ultimately Type I errors -probability of deciding a constituent is present when it is actually absent) of the cyanide levels present in a ,given sample may occur, causing in the first case false security and in the second case, excessive cyanide treatment costs. Mahy, if not all, enumerated problems can be solved by using novel flow injection (FI) gas-diffusion amperometric methods. A modification of the recently approved FI ligand exchange (FIILE) method for determination of available cyanide (USEPA Method OIA-'l677) that obviates sulfide interference will be discussed. Eight laboratory round-robin data obtained for the FI UV -digestion (FIIUV) method that determines total cyanide (Proposed Method OIA-1678) will also be presented. In addition, some methods for cyanide speciation will be presented. Finally, research needed for developing reliable methods for determination of operationally defined cyanide in solid samples will be summarized.

Jan 1, 1998

By S. Ozbilen, B. Erdogan, M. Erdogan

To study by thermal analyses the response of precipitation hardenable alloys of Al-Cu-Mg and Al-Li-Cu-Mg system to natural and artificial ageing, a series of ternary and quaternary Al-alloys with nominal compositions of Al-l.13wt%Cu-0:65wt%Mg (alloy-I), Al-1.15wt%Cu-0.57wt%Mg-0.07wt%Li (alloy-2), Al-l.19wt%Cu-0.56wt%Mg-0.75wt%Li (alloy-3), Al-2.0lwt%Cu-0.89wt%Mg (alloy-4), Al-2.14wt%Cu"0.56wt%Mg-0.07wt%Li (alloy-5) were used in the present investigation. Samples in the form of rolled sheets are subjected to water quenching at 25EC after solution treatment at 530EC for 20 min. Alloys were aged naturally at room temperature (25EC) up to 2 months and artificially at 190EC up to 2 days. By using differential scanning calorimetry (DSC) in the temperature range of25-300EC, differential thermal analysis (DTA) in the temperature range of25-600EC together with Vicker's hardness measurements, the response to natural and artificial ageing of the alloys used in the present study were investigated. It was observed that in these alloys, GPB(Cu, Mg) zones [Guinier-Preston zones with Cu and Mg] do form during water quenching at 20EC following solutionizing heat treatment. Natural ageing of the same alloys causes formation of more GPB(Cu, Mg) zones, which results in hardening in the alloys. Artificial ageing at 190EC up to l day results in GPB zone dissolution causing preliminary decrease in hardness values while two days of artificial ageing in the alloys cause S' (Al2CuMg) precipitation confirmed by DSC/DTA analyses resulting in an increase in hardness values. Li addition up to 0.75wt% helps T1 (Al2CuLi) and T 2 (Al6CuLi3) phase formation together with S' precipitation as DSC/DTA analyses show after the same heat treatment.

Jan 1, 1998

By Dan Eyde

Low levels of thallium were detected in the mine water drainages, and process water discharges of western mining and smelting operations. This required remediation under state regulatory standards, which allow discharges of no more than .0017 ppm thallium in mine water discharges. Influent streams containing thallium can be mitigated to state discharge standards after a single pass through the series of fluidized upflow columns. Test work to determine the optimal flow rates used pilot scale systems at two separate locations treating 5 - 25 gpm of effluent. The test system at the gold mine mimics the full-scale system, which will be based on the existing upflow carbon tanks that have been converted to zeolite columns. The system installed at ASARCO's East Helena smelter has a far more complex influent stream with a high loading of competing cations. Nevertheless the columns filled with CABSORB® are successfully mitigating the thallium contamination. CABSORB® ZS500RW is a product based on the sodium analog of the zeolite mineral chabazite named herschelite.

Jan 1, 1998

By E. Fockedey

he destruction of free cyanide on a Co3O4 doped carbon felt was studied. The experiments were done with an eiectrochemical filter press cell on dilute alkaline solutions containing 250 mg/l NaCN. No chloride ions were added to the solutions. The cobalt oxide protects the felt against corrosion and has a catalytic effect on the degradation of the cyanide. This kind of electrode allows working with current density as high as 1200 Aim without any visible degradation of the felt. The most interesting results were obtained with a current density of 400 Aim' at which the cyanide concentration can be lowered to 5 mg/l with a current efficiency of more than 70 % and a specific energy consumption of about 10 kWh/ kg CN.

Jan 1, 1998

By Roy A. Imbsen

Following the 1989 Loma Prieta earthquake, California Department of Transportation (Caltrans) expedited an effort to evaluate and retrofit important state-owned toll bridges to en­hance performance of the state's transportation systems during and after major (credible) earthquake events. Imbsen and Associates, Inc. (IAI) along with their sub-consultants, were awarded a contract to conduct seismic evaluation and to develop retrofit design for Benicia-Martinez Toll structure, to meet a "Serviceable" performance requirement after the event of a "Safety Evaluation Earthquake." This paper describes the design and construction specifications for the deep foundations supporting the main spans of the Benicia-Martinez Bridge. Benicia-Martinez Toll Structure (George Miller Bridge), a high-level deck-type welded truss bridge with welded girder approach spans, carries Interstate Route I-680 over the easterly end of Carquinez Strait near San Francisco, CA. The nearly 5000 ft long main truss structure consists of ten spans, ranging from 330' to 528' in length, supported on cellular reinforced con­crete pier structures. Foundation systems across the waterway, consist of cellular reinforced concrete footings, supported by groups of 6' diameter, concrete filled, steel caissons, resting on 5' deep rock sockets, at depths of 50' to 150' below the water level. Seismic evaluation of the existing foundation systems accounted for spatially varying ground motion along the length of the structure, variability of foundation material strength (i.e. at bed-rock), variation and effects of scour depth on the performance of the foundations, and dy­namic soil-structure interaction. Performance of caissons beyond their elastic strength, as well as their effects on the behavior of the foundations and substructures were evaluated and considered in establishing foundation vulnerabilities. Several retrofit strategies were considered leading to a final retrofit strategy to strengthen end connections of existing caissons, as well addition of new caissons to provide adequate lateral force resistance for the foundations. Final design package includes specifications as well as construction methods and requirements for existing and new caissons, under traffic, and pile load testing procedures for design loads of up to 12500 kips per caisson.

Jan 1, 1998

By G. Wendel

Uranium is a naturally occurring radioactive material in the earth?s crust. Geological processes have resulted in concentration of uranium into ore mined for its gold content in South Africa. This uranium is present in the form of discrete particles of uranium minerals, generally oxides, which are normally insoluble. Chemical and physical processes during gold mining and extraction, particularly when carried out in conjunction with uranium extraction and sulphuric acid manufacture, act on the uranium minerals and the radioactive decay products of uranium. This may result insignificant accumulations of radioactive materials in certain parts of the process. There are a number of naturally occurring radioactive materials in the earth?s crust, such as Uranium-235, Thorium-232, andPotassium-40. This paper focuses on Uranium-238, together with its decay products, and how they affect the gold mines. Water plays a significant role in the redistribution of radionuclides, both as a physical transport medium, and as a solvent in which chemical reactions take place.

Jan 1, 1998

By A. Wahib Khair

"This article first describes the impact of respirable dust on the health of miners in underground coal mines in the United States of America. Second, it identifies the major sources of dust generation, namely cutting tools in the road headings. Two surveys associated with cutting tools were made to determine the useful life of these cutting tools, and to determine the effect of cutting tool wear on productivity of the continuous miners. Third, this article presents the results of a series of experiments carried out in the Rock Mechanics Laboratories at West Virginia University in order to study: 3.1 the effect of cutting tool rate of wear on respirable dust generation, 3.1.1 the effects of rock materials on tool wear and respirable dust generation, 3.1.2 the effect of cutting tool geometric parameters on respirable dust generation, and 3.1.3 the effect of tip materials used in the cutting tool on respirable dust generation. Recommendations in regard to cutting tool design are also presented in this paper.Silica and coal dust are the two major elements affecting the health of underground miners. According to Lemen [1] approximately 1,500 men died due to breathing in silica dust in 1936 while tunneling through a mountain of mostly silica, near the town of Gauley Bridge, West Virginia. Coal dust resulting in lung diseases in one of the major health hazards in underground coal mines. The impact of black lung on miners, coal workers' pneumoconioisis (CWP), has ranged from 16,000 to 23,000 each year since 1982 [1].The trend for conventional mining to continuous machine cutting of coal, using more productive machinery, is inexorable. Intolerable level of dust generated at the face is an indication of inefficient coal/rock cutting by these machines. The federal goverment of the United States paid about 11.7 billion dollars in workmen's compensation to more than 470,000 miners with CWP [2]. Bieniawski and Zipf [3] reported that annual benefit payments were about 2 billion dollars. The enactment of the Health and Safety Act in 1969 in the United States triggered the initial investigation into coal cutting mechanisms and cutting tool designs.The surveys concerning the utilization of cutting bits and performance of continuous miners in underground coal mines were made in order to have first hand information about bit consumption and coal produ¬ction.Three types of used bits, commonly utilized cutting tools on continuous miners, were collected from different coal mines. The used bits were grouped into symmetrically and asymmetrically worn bits. Distribution analysis for weight loss and conical height loss was done. Details of the results are presented elsewhere [4], here the results are summarized briefly. The analysis shows that approximately 50% of the collected bits have worn asymmetrically, which shows that many bits do not rotate properly during cutting. Analysis of the distribution of bit wear showed that the degree of bit wear varied from one type to another and with mining conditions. On average, the weight loss of the used bits was 4% to 7% with a maximum of 31%. Correspondingly, the loss of the conical height was observed to vary between 11% and 23% with a maximum of 71%. Figure 1 shows typical data associated with some of the used bits."

Jan 1, 1998

By N. Kanari

Chalcopyrite concentrates and their pure constituents were chlorinated by C12+N2 between 25 °C and 750 °C. The reaction products were analyzed by SEM, XRD and chemical analysis. The effect of gas flow rate and chlorine content of the gas mixture on the reaction rate were investigated. At room temperature, these solids start to react with chlorine giving metal and sulfur chlorides. Complete reaction is achieved at about 300 °C and the iron and sulfur chlorides were fully volatilized. The chlorination residue is composed of valuable metals' chlorides. A simplified flow - sheet for the treatment of chalcopyrite concentrates by chlorine was suggested.

Jan 1, 1998

By G. D. Mcdowell, L. B. Cochrane, B. D. Thompson

"Abstract - Exploration for deep underground copper and nickel sulfide deposits in the Sudbury mining camp is carried out with surface drilling. More detailed drilling, with an advanced underground exploration program, may be necessary to establish an accurate interpretation of the deposit geology and upgrade the resource estimate to the measured category for reserve estimation and feasibility assessment. Resource evaluation is a lengthy and costly process that could result in a decision not to proceed with the project. For projects that proceed to production, significant reductions in the operating and capital costs could be achieved with a more accurate interpretative model of the deposit geology and mineralization. Quality control procedures to ensure the integrity of the drilling data and interpretation guidelines are essential steps in the development of a deposit model. The use of block modeling techniques and the application of geostatistics for resource estimation further improve the quality of the resource model.Significant improvements to the interpretive models can also be achieved by incorporating additional information from geophysical measurements to validate and constrain the geological interpretation. The geophysical models must be consistent with known geological environments and oreforming processes, which has required the concurrent development of comparative models from exploited deposits. These geophysical techniques can also provide key geotechnical information required for the optimum design of the mining method and mining sequence. The objective of this program is to improve the accuracy of the deposit model and the quality of the resource and reserve estimates in order to optimize capital investments and reduce the development and operating costs of underground mining projects. Several of these techniques are currently being tested at INCO Limited’s Sudbury operations. The results from those tests are presented and their applications are discussed within the framework of resource/reserve classification systems and project evaluation objectives."

Jan 1, 1998

By Rubén Alvarado

The markets and environmental protection rules are more and more exacting, both of which have determined that copper smelters should look for technological development and global management to ensure their viability and competitivity in the short and long term. The main facilities of the present and future Smelting-Converting Process at Codelco's Caletones Smelter, is based on Teniente Converter reactors with a high operational availability that have reached concentrate processing capacities near 2,000 tpd. These reactors are in operation in most of the smelters in Chile as well as in Zambia, Peru, Mexico and, in ?the near future, in Thailand. Since 1993, the Smelting-Converting process of the Caletones Smelter of Codelco-Chile has been based on one Reverberatory furnace, two Teniente Converters and four Peirce-Smith Converters. These facilities, together with the operation of two Fluidized Bed Dryers, three Slag Cleaning Furnaces, and two Oxygen Plants have allowed the smelter to reach concentrate smelting capacities and copper productions of 1,215 kt/year and 360 kt/year, respectively. This transitional operating scheme, combining together traditional and advanced technological equipment, needs further modernization to successfully face the modern world challenges, especially with relation to the environmental commitment, production costs and wide satisfaction of customers. For this reason, for the period 1997-2000, a Modernization Plan has been worked out. This plan considers an increase of the present throughput, which will permit a significant increase in productivity, as well as finding a definitive solution for meeting the environmental regulations. Among these projects, we can point out the definitive shut down of the Reverberatory Furnace, which is a contaminating piece of equipment of low energetic efficiency. Additionally, it considers the installation of two new Slag Cleaning Furnaces, one additional Oxygen Plant, and the incorporation of two new Sulphuric Acid Plants with a production capacity of 4,500 T/D, that will recover over 92% of the sulphur content, of process off-gases.

Jan 1, 1998

By K Kuganathan

This paper describes a new methodology that can be applied to compare several bench extraction strategies requiring backfill. The method is applicable at the planning or operational stages and can be used to maintain dilution within design parameters and improve the overall economics of bench stoping operations. The parameters influencing bench performance have been empirically rated based on economical, geomechanical, operational and backfill properties. Four different extraction strategies have been considered and rated from most preferred to less preferred using an integrated approach to bench extraction.

Jan 1, 1998

By Cocker J, Urosevic M

Seismic methods have become common for the detection of low-throw faults ahead of underground coal mining. Surface seismic methods cannot theoretically be used where dykes occur, because seismic waves transmit from the surface down to the seams, and reflect back to the surface. Consequently, where sub-vertical structure such as dykes occurs, the surface seismic method fails.The ability of seismic methods to image dykes depends on the geometry used, the dyke thickness and the seismic wave propagation mode in relation to dyke composition and internal structure. Surface seismic methods find it difficult to distinguish between faults/fractures and very thin dykes (1-2m in thickness) when the dyke's thickness is less than the seismic wavelength. Consequently, borehole seismic methods have to be used to detect the presence of such thin dykes.

Jan 1, 1998

By Keith Heasley

As part of the initial investigation and validation of a new boundary-clement formulation for stress modeling in coal mines. the underground stresses and displacements at two multiple-seam coal mines with unique stress problems are modeled and predicted. The new program, LAMODEL, calculates stresses and displacements at the seam level and at requested locations in the overburden or at the surface. Both linear elastic and non-linear seam materials can he used: and surface effects, multiple seams, and multiple mining steps can be simulated. In order to most efficiently use LAMODEL for accurate stress prediction, the program is first calibrated to the site-specific geo-mechanics based on previously observed stress conditions at the mine. For this calibration process. a previously mined area is "stress mapped" by quantifying the observed pillar and strata behavior using a numerical rating system. Then, the site-specific mechanical properties in the model are adjusted to provide the best correlation between the predicted stresses and the observed underground stress rating. Once calibrated, the model is then used to predict future stress problems abead of mining. At the two case study mines, the calibrated models showed good correlation with the observed stresses, and also accurately predicted upcoming high stress areas for preventive action by the mines.

Jan 1, 1998

By S. O. Yuan, R. L. Grayson

As a followup to a USBM-sponsored research project, the authors utilized the knowledge-base structure and system concepts from a Sun Sparcstation-based worker-scheduling system of the mine-management support system to develop a PC-based application. The new software adopts the nested-window concept to facilitate data collection and modification on personnel, including their availability and work priorities during a shift. The system can optimally allocate manpower on a work shift and can delineate supervisory training responsibilities. The various components of the software, including enhancements made to the original system, are described in detail.

Jan 1, 1998