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By Klaus Rieker

Over the last 30 years Wayss & Freytag Ingenieurbau AG has gained a lot of experience in mechanized tunnelling on various major projects. During this period most important developments concerning the machine technology for EPB- and Slurry-Shields have taken place. Since the first application of a hydro shield for the Wilhelmsburg Collector project in Hamburg in the early seventies, several stages of development have led to the current state-of-the-art in mechanized tunnelling. The continuous improvement of TBM techniques allows the execution of high quality tunnelling, particularly with regard to maximum safety and efficiency. The practical experience of the construction companies is of essential importance in order to continue further development and improvement.

Jan 1, 2005

By T. P. Dolley

Domestic production of industrial sand and gravel in 2004 was about 29 Mt (32 million st), a 6-percent increase from 2003. This increase was buoyed by a robust construction sector of the U.S. economy. U.S. apparent consumption was 30.3 Mt (33.3 million st) in 2004, an in-crease from 2003. Imports were about 490 kt (540,000 st) in 2004, an 11-percent increase from 2003. Imports of silica are generally of two types. They include small-quantity shipments of very-high-purity silica or a few large shipments of lower grade silica that were shipped only under special circumstances (such as very low freight rates).

Jan 1, 2005

By J A. Rabe, PAP Fouche, K O?Neill

Two of the most important issues mines have to deal with are tracking the ore mined from pit to plant and to test the efficiency of beneficiation equipment. Kumba Resources and Saco Systems are working together at moment to develop a RFID tracer system to help address these issues. This paper will focus on the tracking of ore from pit to plant. The main advantages for ore tracking is to ensure plant feed blending and dilution according to plan. The RFID tracer system works on the basis of a tracer that physically simulates the ore properties and radio frequency technology that facilitates communication with the tracer and allowing information to be stored on the tracer. This paper tends to indicate the progress on the application of RFID tracer technology in the minerals processing environment as tested at Kumba Resources so far. It is concluded that the system has great potential, but some important problems remain

Jan 1, 2005

By R. J. Durrheim

The seismicity of the Witwatersrand Basin and Bushveld Complex has been analysed, revealing significant differences in source and damage mechanisms. A comparison of mining taking place at similar depths and extraction ratios indicates that the seismic energy release rate is considerably lower in the Bushveld Complex. Technologies introduced in the past decade to manage the risk of rockbursting are reviewed and assessed. These include geophysical methods to detect hazardous structures ahead of mining, new mining layouts and support systems, and the mechanization of in-stope processes. Despite important differences in geology, in situ stress, mining layouts and methods, there are many opportunities for the reciprocal transfer of knowledge, experience and technology between the gold and platinum mining sectors to improve the management of the rockburst risk.

Jan 1, 2005

By R. M. Goktan

Point-attack picks are one of the most widely used tools for the mechanical excavation of rock and coal. In the literature, some practical formulas have been developed to estimate their performances under varying cutting conditions such as the pick geometry, cutting depth and cutting geometry. In this study, it is shown that Evans?s theoretical model, the most cited in the literature, has serious limitations concerning the changes in the cutting geometry. Analysis of the two independent full-scale linear rock cutting experimental data reveals that both his theory and its recent modification can not fully explain the mechanism of rock breakage under asymmetrical attack. The cutting force predictions made by employing such models are shown to be too significantly weak to be of any service in practice. In this study, a semi-empirical approach was followed by means of which cutting forces under varying cutting geometries could be made. By analysing the full-scale rock cutting test data, prediction equations of the peak cutting force and mean cutting force have been developed. Comparisons of laboratory determined and predicted force values indicate that the suggested prediction equations are applicable to quite different rock materialsm which have uniaxial compressive strength in the range of about 30?170MPa, and valid for different cutting geometries. It is also shown by regression analysis that the established prediction equations are statistically significant.

Jan 1, 2005

By E. V. Lilford

Valuators of mineral properties are faced with a range of valuation methodologies, the most important of which are grouped under the headings of the market approach, the cost approach and the income approach. The way in which value is defined and the detail of the different valuation methodologies is examined here. This paper aims at documenting the variety of valuation procedures and applying each method to a variety of gold projects and comparing the outcomes. Any decision to apply a valuation technique will depend principally on the stage to which the project has been developed. The valuation approach to a greenfield project will be substantially different from that applied to a well-drilled, extensively explored mineral property. Furthermore, a valuation exercise may produce different outcomes for the same gold project depending on which method is applied. In order to investigate the variability in valuation methods and to explore the outcomes of different approaches, a series of five gold projects was analysed. The projects differ in regard to levels of capital application, infrastructural setting, depth below surface, in situ grade, and the stage of development, and were valued using the different methods. The most critical aspect of any valuation is the capacity of the valuer to identify the salient issues and ensure that they are incorporated into the valuation. The danger of simply applying ?black box? solutions to valuation problems without a full understanding of the parameters and the areas of uncertainty is emphasized. The importance of the valuator?s experience, insights into best practice and the ability to recognize and submit to the requirements of compliance within the minerals industry is among the most important characteristics of a valuer.

Jan 1, 2005

By Richard Frentress, Dave Donelon, Robert Henderson, Mike Warnert

"The Round Mountain gold mine is an open-pit mining operation located 97 kilometres north of Tonopah in Nye County, Nevada. Gold has been produced from the property since 1906.Gold is currently recovered using a combination of four independent processing operations. These include a 10,000 ton per day mill, a 30,000 ton per day, crushed ore heap leach, a 150,000 ton per day, run-of-mine ore heap leach and a small high-grade gravity concentration circuit. In 2002, Round Mountain Gold Corporation produced 755,494 troy ounces of gold at a total direct operating cost of US$2.14 per ton ($193/oz).This paper presents a summary of the Round Mountain operations and discusses some of the processing innovations that have enabled the mine to profitably recover gold from a large low-grade ore body.INTRODUCTIONRound Mountain Gold Corporation is a 50/50 joint venture between Kinross Gold Corporation and Barrick Gold Corporation. Kinross acquired its ownership interest in the Round Mountain mine upon completion of combination with Echo Bay on January 31, 2003. The joint venture partners continue to support an aggressive exploration program in the vicinity of the mine in order to add reserves and extend the mine life.The Round Mountain mine currently operates a conventional open pit that is approximately 8,200 feet long, 4,900 feet wide and 980 feet deep. Mining is conducted on 34-metre benches by electric shovels and front-end loaders paired with 150, 190 and 240-ton haul trucks. Blasthole samples are collected and assayed and provide the control for ore segregation. Based upon these assays, blasted pit rock is determined to be run-of-mine Dedicated Pad ore, crushed Reusable Pad ore, high-grade ore or waste.Gold is recovered using a combination of four independent processing operations. These include run-of-mine ore heap leaching (Dedicated Pad), crushed ore heap leaching (Reusable Pad), milling and the gravity concentration circuit. Non-mineralised rock is delivered directly to the waste dumps. Low-grade ore is trucked directly to the Dedicated Pad and medium-grade ore is crushed and placed on the Reusable Pad. High-grade ore is handled in one of three ways: 1) leached on the Reusable Pad and offloaded to the mill; 2) sent directly to the gravity plant with tails reporting to the mill; or 3) sent directly to the mill or mill stockpile. The gold particle size distribution of highgrade ore determines the processing method."

Jan 1, 2005

By M. Kumral

Raw material fed into a processing or refining plant is required to be uniform in composition for several reasons. When the mined ore is highly variable in quality the only way to ensure consistency is to homogenize the ore prior to the process. The problem is more complicated in the case of multiple ore sources. The idea behind the research is that theoretical blending ratios can serve not only to meet predefined specific criteria but also to reduce grade fluctuations of variables under consideration. In this paper, the problem is formulated as a quadratic programming problem, whose objective function is in quadratic form and constraints are linear. A case study was conducted on a data set from an iron orebody to demonstrate the technique. The objective was to minimize the blend variability in terms of each variable (in this study, iron, silica, alumina and lime) grade of ores extracted in three different production faces. The stockpile capacity, lower and upper limits of each variable satisfying operational requirements and non-negativity were constrained to the model. A modified simplex method developed by Wolfe was used for solving the blending and homogenization problem. The promising results can be used as apart of the stacking and reclaiming design. Keywords: blending and homogenization problem, quadratic programming, Wolfe method.

Jan 1, 2005

By L Maw

New ZealandÆs largest gold producersÆ OceanaGold Macraes Mine is characterised by a large tonnage and relatively low grade operation. To survive in diminishing real gold prices, the operation must focus on a culture of continuous improvement. This paper presents the outcome of a supplier sponsored continuous improvement project known as the Orica Advanced Mining Services project.   In March 2004 OceanaGold (then GRD Macraes) entered into an Advanced Mining Services (AMS) project with Orica Mining Services. The motivating factor behind OceanaGoldÆs need to improve bulk waste productivity and SAG mill throughput was the planned increase in production from five million to 5.4 million tonnes per annum. A stripping ratio of ten to one meant that optimisation of the drill, blast and production functions was paramount.   The primary focus of the project was to optimise the drill and blast parameters to suit the variable rock conditions throughout the mines main operating pit (Frasers Pit). Fragmentation of the ore for presentation at the SAG mill, and cost reduction on the mining of bulk waste movement, were the primary objectives. A number of additional initiatives complimenting the interface between drill, blast and ore production were also established. These included; +        reduced ore loss through delineation of ore boundaries to allow for blast movement; +        established blasting parameters for variable geological conditions, resulting in improved fragmentation; and +        improved asset utilisation by establishing a blasting regime that angled grade control holes to be used as blastholes in the stockworks area.   A year into the project, the philosophy of continuous improvement is now in-grained at the Macraes minesite. As the project continues, the focus is on the further refining of those procedures established, to ensure a continued focus on lower unit mining production costs.

Jan 1, 2005

By V. Kamavaram

Keywords: Recycling, Aluminum Metal Matrix Composite, Ionic Liquids, BMIC Recycling of aluminum metal matrix composites (MMC) via electrolysis in ionic liquids at near room temperature was investigated. The electrolytic melt comprised of 1-butyl-3-methylimidazolium chloride (BMIC) and anhydrous AlCl3. Impure aluminum composite (Duralcan MMC Al-380, 20 vol % SiC) was electrochemically dissolved at the anode and pure aluminum (>98%) was deposited on a copper cathode. The deposits were characterized by scanning electron microscope, X-ray diffractrometer, and mass spectrometer. The influence of various process parameters such as concentration of electrolyte, and applied cell voltage on the recycling process was studied. The recycling process yielded current densities in the range of 200-500 A/m2, and cathode current efficiency of about 85%. The results indicated that impurities such as Cu, Si, Ni, Fe, Mg, Mn, and SiC particles were removed as anode residue. Energy consumption of about 3.7-6.3 kWh/kg-Al was obtained at a cell voltage of 1.0-2.0 V and cell temperature of 100 ± 5°C. Low energy consumption and no emission of pollutants are the two main advantages of this process compared to present recycling processes.

Jan 1, 2005

By Kerry Gee, Gary Colgan, James Fricke

Introduction Elevated zinc concentrations are observed in groundwater within alluvium adjacent to Silver Creek east of Park City, Utah. The study area is located in a small valley one and one-half miles northeast of Park City, Utah in Summit County, Utah (Figure 1). Although surface water concentrations in Silver Creek are typically less than 1 mg/l, groundwater concentrations have been measured as high as 85 mg/l in a near neutral pH environment. The elevated zinc concentrations in groundwater result from several factors including: (1) dissolution of zinc from tailings exposed at the surface and within the alluvium, (2) oxidizing conditions created by surface/ground-water exchange, and (3) ideal geochemical conditions for the dissolution of zinc-containing minerals. These ideal conditions include readily soluble minerals, available anions for complexation, and lack of available surface adsorption sites.

Jan 1, 2005

By K. Viking

This article deals with some of the civil engineering related problems to be encountered when offshore wind energy projects transform from prototype offshore wind energy converter farms, developed and installed during the 1990's, to commercial farms that's currently planned to be built. The offshore wind energy converter (OWEC) installations encounter a wide range of problems, only partial of these are geotechnical. In Europe both onshore and offshore wind farms have, from a historical point of view, usually been founded by using the monopole technique, installed with traditional impact hammers, or by using gravitational foundations. However, the rapid development of bigger turbines and larger wind farms, together with increasing considerations of fatigue aspects, has lead to financial benefits of developing and exploring other foundation techniques. This paper reviews some Scandinavian experiences regarding critical components of the design phase in relation to connecting the superstructure to the ground, and some of the main considerations of how the loads applied to the structure are transferred to the surrounding soil. Keywords: Offshore Wind Turbines, Wind Farms, Foundation, Pile, Gravity Structures

Jan 1, 2005

By M. van Schoor

The bulk of the world?s platinum production originates from the Merensky and UG2 reefs within the Bushveld Complex, South Africa. Both the Merensky and UG2 reefs are disrupted by faults, dykes, potholes and iron-rich ultramafic pegmatite bodies (IRUPs)?features that impact negatively on production, planning and safety. It is therefore advantageous to know of their presence and geometry ahead of mining. To date, no geophysical technique has been successfully applied to the routine mapping of mine-scale potholes and IRUPs. These disruptive features may vary from a few metres to several tens of metres in diameter. In this paper the applicability of in-mine electrical resistance tomography (ERT) to map potholes and other disruptions to the continuity of the Merensky and UG2 reefs ahead of mining is demonstrated using two case studies.

Jan 1, 2005

By Luciano R. G. Santos

Keywords: biosorption, cadmium, copper, biomass, spent zeolite. The majority of the industrial activities produce some kind of solid wastes. In this work two industrial residues (spent zeolite and wood sawdust) were chemically modified to increase their heavy metals sorption capacities. Manilkara longifolia (a Brazilian plant known as parajú) sawdust was first treated with NaOH and modified with different citric acid concentrations (0.6-1.2 mol/L) at 120°C, for 90 min. Infrared spectroscopy confirmed the presence of carboxylate groups in the wood structure as result of their mixing. Similarly, spent zeolites were also submitted to a chemical treatment (NaOH) to remove carbon deposited during oil cracking and to recover its sorption capacity. Batch experiments carried out at ambient temperature showed that both materials present sorption capacity for copper and cadmium comparable to weak acid ion exchange resins. A maximum of 78 mg-Cd/g and 59.7 mg-Cu/g as well as 29.9 mg-Cd/g and 14.6 mg-Cu/g were observed for the sawdust and the zeolite, respectively. The results were modeled according to the Freundlich and Langmuir equilibrium isotherms and compared with results of other studies.

Jan 1, 2005

By Michael Kelly

Inertial navigation technology has, for the first time, allowed the position of a longwall shearer to be mapped in three dimensions. Following the success of the technology in highwall mining and successful trials on a longwall face, the Australian Coal Association Research Program (ACARP) commissioned a three year "Landmark" project that aimed to advance longwall automation to the level of "on-face observation" by the end of 2004. This project has been completed with the following successful technical outcomes: Automatic face alignment was achieved, using an inertial navigation-based sensor on the shearer, to accurately measure face geometry and feedback signals used to move OEM (Original Equipment Manufacturer) roof supports. Operational on-line measurement of creep with creep information incorporated into face alignment corrections. Inertial Navigation System (INS)-based enhanced horizon control was bench-tested. Operational broadband communications system to shearer using wireless Ethernet on a commercial-product basis. Acquisition of located coal-face features for use in thermal infrared-based horizon control. Automated Longwall Information System (LIS) developed which integrates information from multiple systems and sensors and provides high quality visualisation and control interfaces. Automatic roadway and face convergence monitoring tools successfully tested. Condition monitoring tools developed and demonstrated for improved face reliability. This paper summarises the outcomes of the project and describes the work being undertaken for the 2 year Landmark Extension project approved in April 2005. Consistent with the conference theme, the paper focuses on the ground control aspects of the project.

Jan 1, 2005

By S. Hamilton

Borates are essential to life, and to many products that are essential to an acceptable standard of living. They occur naturally in seawater at an average concentration of five milligrams of boron per liter. Fresh water lakes, rivers, streams and ground water generally have concentrations of about one milligram boron per liter. Borates are also present in soil at concentrations ranging from 0.1 to three milligrams of boron per kilogram. Because most of that boron is locked into insoluble minerals, clay or organic matter, boron deficiency is more widespread than boron enrichment. Borates evaporate into the atmosphere from seawater, rain, snow and hot springs. In rain and snow, natural boron concentrations range from 0.002 and 0.1 milligrams boron per liter. All told, boron moves through the atmosphere at a rate of 5 Mt to 7 Mt/a (5.5 million to 7.7 million stpy).

Jan 1, 2005

By Georgene Renner, William R. Yernberg, Steve Kral

ABB offers complete electrical revamps of mining shovels with ac or dc drives, drive control, frequency converters with insular gate bi-polar transistor technology, intelligent control packages and visualization. Many of the world’s shovel excavators and draglines (walking excavators) were built in the1980s. After 15 to 20 years of round-the clock operation in openpit mines, these machines start to feel their age. Electrical parts are particularly vulnerable. Their performance deteriorates and availability and productivity fall. Even with regular ser-vice and maintenance, a machine of this age will accumulate 400 hours of unscheduled downtime a year. The need for a replacement becomes pressing, but the expense is often prohibitive.

Jan 1, 2005

By Eric M. Hill, Daniel E. Walsh, Hsing K. Lin, John T. Hollow

The Fort Knox Mine is located in Alaska’s interior where the average ambient air temperatures range from -24°C in January to 16°C in July. The mill processes a free milling gold ore utilizing both a gravity recovery circuit and conventional cyanide leach/carbon-in-pulp circuits. Plant slurry temperature cycles seasonally and allows for a unique opportunity to measure the impact temperature has on gold leach kinetics, carbon adsorption efficiency and cyanide destruction reactions. Mathematical models have been developed to accurately predict actual mill performance. This paper describes the development of the models and presents data that allow for a better understanding of the impact of circuit operating temperature on process efficiencies.

Jan 1, 2005

By A. W. Bester

Paper written on project work carried out in partial fulfilment of B. Eng. (Mining Eng.) Cullinan Diamond Mine currently handles 3.2 million tons of run of ore per annum. This is done by means of an underground train system, which is located at 763 metre level. Four trains, one in each quarter of the pipe, collect ore from passes and transport it to centrally located tips in the north and south of the pipe. The ore is then split into coarse and fine fractions. The coarse fraction proceeds to the primary crushers in the north and south. Historically, mining has been performed in such a manner that an equal amount of ore has reported to each quarter of the pipe. However, the tonnage profile of the mine will change such that the ore will no longer be split equally. For approximately five years the majority of ore will report to the east and thereafter most of the ore will report to the western portion of the mine. This will continue for the remainder of the current infrastructure level?s operational life. Coupled with this is the fact that the mine is aiming to increase its annual production to 3.8 million tons. The result is that the current ground handling system cannot accommodate the additional tons and therefore alternative ground handling options have been investigated. The continued existence of Cullinan Diamond Mine relies on finding a system that can economically handle the additional tonnage. Three options were investigated. Firstly, a train option, which would be an upgrade of the current system, was investigated. Two truck options were also investigated, the first of which was a conventional truck option. The second truck option was more interesting and involved an unfamiliar Combi truck system. The truck options were investigated primarily due to the fact that the block height of the BA West (a new production block) can be increased by 15 meters if a truck option is decided upon. This would create a significant increase in revenue for the BA West project. Each of the options was assessed in terms of its physical and financial feasibility. In terms of the physical constraints, it was found that all three systems could work. Detailed financial analysis indicated that either of the two truck options would be a suitable solution. However, due to the limited information regarding the Combi truck option, it should be further investigated. This applies particularly to the actual running and maintenance costs for the equipment.

Jan 1, 2005

By H. Antrekowitsch

The decreasing quality of the input materials in copper recycling leads to a higher content of impurities in the anode copper. An improvement of the pyrometallurgical refining process is therefore necessary to produce high quality anodes for the copper refining electrolysis. The behaviour of the most important accompanying elements (e.g. nickel, tin, lead, zinc etc.) at different reaction conditions has to be investigated in order to improve the metal/slag reactions as well as the vaporisation by selective oxidation in the anode furnace. Therefore the thermodynamic conditions like reaction order and the activity coefficients at the copper refining process have to be known for the optimisation of this technique. Additionally the interaction between different elements has been investigated as a function of the temperature, the content of the elements and the slag composition especially for nickel. These investigations were done at the Christian Doppler Laboratory for Secondary Metallurgy of Nonferrous Metals.

Jan 1, 2005