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By Jessie L. Bonner, W. Stephen Blomberg, Mark Leidig, Heather Hooper

Understanding the effects of the bench on ground motion can improve the design of cast blasts and achieve improved blast efficiency while remaining below vibration requirements. A new dataset recorded in September 2003 from a coal mine in Arizona has allowed us to examine the excitation of short-period Rayleigh-type surface waves from four simultaneously-detonated explosions in and below a topographic bench of a mine. The explosions were recorded on a network of over 150 seismic sensors, providing an extensive understanding of the ground motion radiation patterns from these explosions. We detonated two separate explosions (~3 tons and ~1.5 tons ANFO) in the deepest pit of the mine, thus the explosions were shot to solid rock. Within 25 meters of these two explosions, we detonated two additional explosions of similar explosive yields in a bench, thus these explosions were shot to the free face. Radiation patterns and spectral ratios from the explosions show increased amplitudes (by a factor of 1.5 to 2) at azimuths behind the bench relative to the amplitudes in front of the bench. We compared these findings to seismic observations from two ~1.5 million pound cast blasts at the same mine and found similar radiation patterns. Modeling of these blasts shows that the variations in ground motion are caused by the topographic bench as a result of 1) horizontal spalling of the rock falling into the pit and 2) non- linear scattering near the free- face. We also note that shooting to a buffer (previously blasted rock) causes the azimuthal variations to be significantly reduced.

Jan 1, 2005

By P. M. Soupios

There is an increasing requirement for geophysical surveys carried out during geotechnical investigations to provide direct information about rock quality or other geotechnical parameters. With the paucity of information to correlate geophysical results with actual rock properties, this is still difficult to achieve and additional research effort needs to be performed to address this issue. Nowadays, several researchers have been described detailed studies which designed specifically to investigate this matter. Generally, geophysical techniques which are used to estimate seismic velocities in the subsurface focus on the low strain levels that are not large enough to induce significant nonlinear, nonelastic stress-strain behavior (Luna and Jadi, 2000), which is normally evaluated when addressing liquefaction potential of soils in the shallow subsurface. Soil parameters relevant to seismic ground response (Rechtien, 1996) are density, relative density and void ratio, permeability, shear modulus, water saturation, soil fabric and stress history. Detailed characterization of elastic properties near a major construction site (e.g. a bridge) is useful for near field dynamic analysis of soil-structure interaction (SSI) effects. The coupled effect of the bridge foundation (piles, piers or abutments) and the soil immediately surrounding these substructure elements is essential for dynamic SSI analysis of these critical bridge structures. This paper presents a geophysical investigation performed along the under construction highway of Egnatia Odos, approximately 13 km west from the town of Xanthi in N. Greece. Twelve geotechnical boreholes, drilled at the maximum depth of 75 m, approximately located 20 m from the Nestos River. The objective of the survey was to obtain the high-resolution compressional and shear wave velocities of the shallow subsurface for computation of elastic engineering properties of the unconsolidated material interposed between the investigated boreholes. Joint interpretation of borehole logs and velocity images obtained by P- and S-wave traveltime inversions outlined shallow geological anomalies.

Jan 1, 2005

By A. J. Makoka, B. C. Qi

Reliable monitoring of corrosion is vitally important in the combat against corrosion and over the last two decades the interpretation of electrochemical noise has received considerable attention as a means to discriminate between different types of corrosion. To this end, many different analytical methods have been proposed, such as power spectral density analysis and analysis via various other stochastic criteria. However, although many corrosion systems are nonlinear and therefore not readily interpretable by the abovementioned analytical approaches, few studies in the analysis of electrochemical noise to date have exploited advances made in the analysis of nonlinear systems. In this paper, the use of phase space methods to analyze and detect change in corrosion systems via electrochemical noise is considered. In particular, the electrochemical noise data are used to reconstruct trajectories in the so-called phase space of the system and changes in the topology of these trajectories or attractors as represented by correlation dimension curves are consequently interpreted as an indication of change in the dynamics of the system.

Jan 1, 2005

By C Hall, J L. Mauk

New 40Ar/39Ar dates of vein and wall rock adularia from seven epithermal deposits and one porphyry copper prospect help constrain the ages of mineralisation in the Hauraki Goldfield. Vein adularia from the Paritu region yielded a single 40Ar/39Ar plateau date of 16.315 ¦ 0.066 Ma. Five 40Ar/39Ar plateau dates of three samples of vein adularia from the Opitonui deposit overlap within error to yield a preferred age of 13.149 ¦ 0.016 Ma. Two samples of vein adularia from the Night Reef at the Broken Hills deposit yield exceptionally flat 40Ar/39Ar plateaus, and all dates overlap within error to provide an age of 7.121 ¦ 0.010 Ma. Two 40Ar/39Ar plateau dates of one sample of vein adularia from the Wharekirauponga deposit overlap within error to provide an age of 6.318 ¦ 0.061 Ma. Four 40Ar/39Ar plateau dates of three samples of vein adularia from the Maratoto deposit overlap within error to provide an age of 6.411 ¦ 0.022 Ma. Two samples of adularia from altered wall rock at the Sovereign deposit yield three 40Ar/39Ar plateau dates that range from 6.547 ¦ 0.021 to 6.806 ¦ 0.028 Ma. This suggests that mineralisation formed around 6.6 Ma, but the results are complicated because the adularia contains minor illite that post-dates adularia formation. Results from the Karangahake deposit are complex. Two samples of vein adularia yield three 40Ar/39Ar plateau dates that range from 6.116 ¦ 0.116 to 6.901 ¦ 0.101 Ma, whereas one sample of wall rock adularia that contains minor late illite yields two 40Ar/39Ar plateau dates that overlap within error to provide a date of 5.734 ¦ 0.041. The range of dates indicates that more work is necessary to understand the history of mineralisation at this deposit. Two samples of vein adularia from the Tui deposit yield four 40Ar/39Ar plateau dates that overlap within error to provide an age of 5.714 ¦ 0.017 Ma. These results confirm previous work that indicates that the ages of epithermal deposits young southward in the Hauraki Goldfield. These results are also consistent with previously postulated different ages for deposits hosted in Kuaotunu Subgroup rocks in the northern goldfield (>10 Ma), and deposits hosted in Waiwawa Subgroup rocks in the southern goldfield (7.1 to 5.7 Ma).

Jan 1, 2005

I once read an æarticleÆ in FHM Magazine entitled æThe Coolest Jobs There Ever WasÆ. It was about a group of guys who were pursuing careers that any person on the planet would just kill for. I distinctly remember drooling over the pages, thinking how much I would love to be Michael SchumacherÆs Chief Engineer at Ferrari, or the Principal Designer and Tester for one of the big Dutch rollercoaster companies. From that moment on, I decided that I wanted a career that was cool enough to make it into the pages of that article. Throughout my time at university, I always had that article in the back of my mind. As a result I constantly wondered about what sort of job I could end up with once I left university. More importantly, I wondered if FHM would be banging down my door to put me in the magazine! After a long and stressful job hunting process (in between completing a thesis and studying for exams) I finally managed to land myself a job with Orica Mining Services. I can honestly say I didnÆt know what to expect when I first joined Orica. Most of my friends ended up working for big mining companies, while I was offered a position with one of the biggest suppliers to these mining companies. However, I had a feeling when I was discussing the role with my future supervisor during the interview process that the job was going to be awesome. I have now spent a year working for Orica and I absolutely love it! While I feel that my job is worthy of being in that FHM article, unfortunately, I donÆt think I am going to get my opportunity to be in the magazine. Apparently I donÆt look too good in a bikini! However, I would love to have the opportunity to discuss the journey that I have taken so far û from my time as an environmental science graduate, then moving on to mining engineering, to now, being part of the Orica Mining Services Graduate Program. My suggestion is to use this paper as a resource. I have learnt during my time at university, as well as my time in the workforce, that the best people you can learn from are your peers. Take what you feel is relevant from the paper; hopefully it will help guide you in shaping your own career.

Jan 1, 2005

By Dave Capstick, Ken Garner, Jim Porter

Technologies and systems used in the management of energy consumption in the mining and metal processing industry are well understood and documented from the supply side of the business. It is our contention that in many instances, through a more complete understanding of the demand side of the business, based on the detail of the operations plan, will provide greater lead time in terms of the design, implementation and utilisation of power supply infrastructure. Thus, optimal management of demand in a proactive manner, based on production requirements, will ensure both security of supply as well as continuity of operations. This paper describes the technology and methodology that is being developed to enable the above statement to be achieved. We use a case study to demonstrate the ability of the tools and methodology and conclude by outlining the business benefits achievable as well as the future developments emanating from this initiative.

Jan 1, 2005

By Mark Dangerfield

[Power-Point Presentation]

Jan 1, 2005

One of the most important factors leading to the success of a cement plant is its location. A multicriteria decision-making method is used to rank alternative plant locations. The set of criteria is established and corresponding criteria should be established for each case study, although this multicriteria decision-making approach has broader applicability. In this paper, the analytic hierarchy process (AHP) with 5 criteria is used to develop a location evaluation hierarchy for an alumina?cement plant in East Azerbaijan province of Iran. Five alternatives for the plant location are evaluated. The main criteria are transportation, water supply, power supply, fuel supply and land. Other criteria have the same importance as these five alternatives. The alternatives are ranked by a multicriteria method and the best site is proposed. Keywords: plant location; multicriteria decision-making

Jan 1, 2005

By G Tsatouhas, R Newell, K Y. Wong

A sulfide ion selective electrode was used to control sulfidiser addition in the flotation testing of a synthetic and a naturally occurring ore containing malachite in order to compare the behaviour of sodium sulfide and calcium polysulfide. Both slug and controlled potential sulfidisation methods of addition were used. Under defined optimum CPS conditions, calcium polysulfide was a more effective sulfidising agent than sodium sulfide on the basis of both capital and operating costs. Surface and solution studies were used to compare the mechanism of each sulfidiser. For calcium polysulfide, XPS showed that polysulfide ions are adsorbed, whereas for sodium sulfide it is the hydrosulfide ions that are adsorbed on the mineral surface. For calcium polysulfide, the CuSx layer was believed to form on the malachite surface, which promoted the flotation of the malachite, by xanthate. Studies of surface morphology of the sulfidised malachite showed that a fairly uniform sulfidised layer is formed with both reagents. The use of sodium sulfide resulted in a thinner initial sulfidised layer compared to polysulfide at equivalent initial sulfur concentration.

Jan 1, 2005

By G. Aggistalis, N. Kazilis, C. Rawlings, N. Rachaniotis, S. Raptopoulos, M. Knights, R. Game

The Egnatia Odos (Odos meaning road) is one of Greece’s largest ever highway construction projects and one of Europe’s most important. The Highway will assist in the connection of the Greek Ionian/Adriatic Coast with Turkey and the Black Sea reviving an historic Roman alignment “Via Egnatia” connecting Rome to Constantinople (now Istanbul). There are 74 twin tunnels (60 bored and 14 cut-and-cover) with lengths ranging from 160 m (175 yd) to 4,600 m (5,031 yd) and 100 m (109 yd) to 270 m (295 yd),respectively. The complex geology and resulting physical geography have had a major influence on both the design and construction of these tunnels. This paper describes the management, design and construction challenges of these numerous tunnels.

Jan 1, 2005

By Robert Harris, David Duncan

The Samira Hill gold mine represents the first commercial gold project for the landlocked country of Niger in West Africa. It began production in October 2004 as the result of over 10 years of exploration and development work. There were several administrative, social and technical challenges that had to be overcome to realize the successful development of the project. The Samira mine is located on the geological structure known as the ‘Samira Horizon’ which is developing as a promising district for additional discoveries and other mine developments.

Jan 1, 2005

By Christoph Broeckmann, Andrew Gardula

"The adoption of high-pressure grinding throughout the cement industry has yielded enormous savings in energy and wear material costs. There are also a number of installations, which are applied in iron ore and kimberlite processing operations. High pressure grinding offers the same potential for energy and media savings, as well as opportunities for improved, downstream metallurgical performance, in hard rock mineral processing. This paper focuses on developments in machine design and wear surface engineering for high-pressure grinding of the hard rock ores in the mineral processing industry.INTRODUCTIONIn the early eighties 3.4 % of the world electric energy was consumed for crushing and grinding operations of minerals and 0.6 % in the ore dressing industry. During that time using a laboratory press Prof. Schönert found that interparticle comminution at high pressure requires remarkably less energy as conventional grinding technologies. In grinding of cement clinker he expected energy savings between 33 and 50 % compared to ball mills [1]. Piston presses are limited in throughput. Thus, the principle of interparticle comminution was adapted by the use of high pressure grinding rolls (HPGR) to a continuous plant process. Figure 1 shows the main components of a roller press: The roller nip of width s is formed between the floating roller (1) and the fixed roller (2). The diameter of the rolls will be denoted with D, the width with B. The total press force F can be adjusted using a hydraulic system with two or four pistons (3). In order to compare machines with different roll geometries the specific pressing force p is introduced:"

Jan 1, 2005

By V. K. Banakar

The occurrence of hydrogenous ferromanganese encrustations (Fe-Mn crusts) on the Cretaceous age Afanasiy-Nikitin Seamounts (ANS) in the eastern Equatorial Indian Ocean (EEIO) was first reported by Banakar et al. (1997, Marine Geology). The major element composition of the samples from the upper flank of the ANS (~1650 m water depth) indicated enrichment of Co up to 0.9 % (Parthiban and Banakar, 1999, Indian Mineralogist). Subsequently a project supported by the Department of Ocean Development to explore the ANS for Co-enriched Fe-Mn crusts was launched in 2002 by the National Institute of Oceanography. Sampling at regular depth intervals along two transects on the slopes of the northern elevated region of the ANS was carried out. The Fe-Mn oxide deposition is evident on almost all types of substrates viz., basalts, conglomerate limestone, fossil corals etc., and the thickness of the oxide layer varies from a patina to 7 cm. The Fe-Mn crust growth is evident only above a water depth of 3200 m, below which semi-lithified carbonate ooze is dominant. The ANS Fe-Mn crusts from all the water depths exhibit Mn/Fe < 1.5 suggesting pure hydrogenetic accumulation of metal-hydroxides. Bulk sample Ce-contents for a few selected depth-representative samples are remarkably high, up to 3700 ppm with an average of ~2500 ppm. The positive Ce-anomaly decreases from ~8 at 1600 m depth to ~1.6 at 3200 m depth, which is in contrast to the modern dissolved oxygen depth-profile in the region. This observation suggests that major time-period of the Fe-Mn crust accretion history is dominated by ambient waters with lower-oxygen at deeper depths than at the intermediate depths. This in turn probably suggests a major reorganization in the deep-intermediate hydrography of the region in the past.

Jan 1, 2005

By R. L. Virta

Twenty-three companies mined kaolin in nine States in 2004. Production was estimated to be 7.6 Mt (8.3 million st) valued at $912 million, based on preliminary data. This was a slight decrease from 7.68 Mt (8.46 million st) valued at $939 million in 2003.Georgia was the leading producer state with an estimated 6.5 Mt (7.1 million st) in production. It was followed, in decreasing order of tonnage, by South Carolina, Alabama, California, Texas, Arkansas, Nevada, Florida and North Carolina. Georgia accounted for nearly the entire domestic water-washed, delaminated, and pigment-grade calcined kaolin production. Consumption Sales to the paper industry accounted for 49 percent of domestic sales and 64 percent of total sales. Other major markets for domestic sales were refractory products (10 percent), paint (5 percent), fiberglass (4 percent), catalysts (3 percent) and rubber (2 percent).Paper coating and filler markets accounted for about 87percent of export sales of kaolin.

Jan 1, 2005

By Gregg S. Hill, Bert J. Huls

"This paper on coarse particle recovery (CPR) summarizes a process to capture coarse particles that are not recoverable by regular flotation. Several porphyry copper operations in the world operate analogous circuits that recover non-floated copper from tailings; however, the case presented here is unique in that extensive underlying test work has allowed us to elucidate some fundamental principles behind recovery enhancement. This paper discusses an overview of the flow sheet that is proposed to Minera Escondida Ltda., the nature of copper in the feed to the CPR circuit, and the various unit operations within the recovery circuit. Details of the technology behind each unit operation will be presented in later publications.INTRODUCTIONSince 1996 BHPBilliton and MEL (Minera Escondida Ltda.) have developed a process to recover copper from coarse particles in the rougher tailings. Copper recovery from fresh tailings is not new. Several operations in Chile, such as Chuquicamata, El Teniente (AMEC, 2003), Mantos Blancos and others have operated various forms of tailings circuits. Both Chuquicamata and El Teniente practice cascade flotation scalping off froth containing fine copper particles after allowing sufficient retention time, air inducement and, sometimes, additional reagent addition. Chuquicamata tailings are not segregated but floated in sequential cascade and conventional large cell arrangements. At the Valle Central operation of El Teniente a coarse fraction of mill tailings is ground and floated, with the rejects recombined with fine tailings and subjected to cascade flotation through a sequence of concrete launders as the tailings flow towards their final deposition area. Mantos Blancos cyclone the rougher tailings and blend the underflow with scavenger concentrate from elsewhere in the principal circuit prior to flotation in Wemco Cells. Kemess in BC, Canada operates a 160 m3 Outokumpu cell to reduce the tailings sulfur content (Rasmussen, et.al, 2004)."

Jan 1, 2005

By C. Scheffer

This paper describes a model that can simulate the behaviour of a pneumatic intensifier that is generally referred to as an ?air pump? (AP). The AP is used in many South African underground mines, and utilizes compressed air with pressures between 0.3?0.6 MPa to pump water up to pressures of 12?18 MPa. The high pressure water is used in numerous underground mines to pressurize props and roof bolts that act as safety and roof support devices. The simulation model reproduces the intensifier&apos;s operation under various conditions and therefore can be used to investigate the AP&apos;s sensitivity towards environmental conditions, design parameters (such as spring stiffness, plunger diameter, nozzle diameter etc.) and operating conditions. Model validation by comparison with laboratory experiments showed good correlation. The model can subsequently be used to investigate design changes aimed at improving the AP&apos;s performance and reliability over a wider range of operating conditions.

Jan 1, 2005

By J McQuie

The concentrator at WMCÆs Leinster Nickel Operation has operated with flash flotation in the grinding circuit since the early 1990s. There has always been a positive correlation between flash flotation Ni recovery and overall Ni recovery û however this relationship could be explained by differences in the ore, rather than by the action of the Flash flotation cell in reducing overgrinding of Ni. In July 2003, refurbishment within the plant made it necessary to operate the concentrator for a period with the flash flotation cells off. The resulting data set provided evidence that flash flotation in the grinding circuit changes the size distribution of Ni to reduce the amount of slow-floating fine (-7 ¦m) Ni produced. Ni recoveries in the finer size fractions were similar with flash flotation on or off û but because less fine Ni is produced when the flash flotation cells are operated, overall Ni recovery improved.

Jan 1, 2005

By R. T. Jones

The largest known platinum group metal (PGM) deposit in the world is the Bushveld Complex in South Africa, with the Great Dyke in Zimbabwe also being one of the biggest. It is therefore not surprising that the majority (just over 5 million troy ounces or 156 metric tons per annum) of the world&apos;s platinum is produced in Southern Africa. Primary smelting of ore concentrates is carried out in that region by five companies, namely Anglo Platinum, Impala Platinum, Lonmin Platinum, Northam Platinum, all of South Africa, and Makwiro Platinum in Zimbabwe. The only other primary smelter of platinum group metals is Stillwater Mining of Montana, USA, although very significant quantities of PGMs are produced as co-products by Norilsk Nickel of Russia. Smaller (but still significant) quantities of PGMs are produced by Falconbridge and Inco of Canada, also as co-products from nickel sulphide smelting. There are many similarities between PGM smelting and nickel sulphide smelting, and the range of technologies in use includes six-in-line rectangular electric furnaces, three-electrode circular AC furnaces, Peirce-Smith converters, and Anglo&apos;s ACP (based on Ausmelt technology). PGMs are also recovered from residue materials using DC arc furnace technology.

Jan 1, 2005

By C. I. Garcia, G. Zhou, W. Gao, A. J. DeArdo

The development of X-100 and X-120 linepipe steels was investigated using a series of low-carbon Mo-Nb-B steels. The laboratory steels were vacuum melted and processed using advanced thermomechanical processing (TMP) philosophies. Prior to the laboratory hot-rolling experiments, the grain coarsening temperature, the conventional T95 and T5 start-stop recrystallization temperatures and the transformation behavior of y were studied using a computer-controlled high temperature deformation MTS-458 and a Theta-IV High Speed dilatometer systems. The results from these experiments provided the guidelines for the design of the laboratory hot-rolling TMP processing experiments. The mechanical properties of the experimental steels showed yield strengths in the range 700-850 MPa and CVN impact properties of over 80 J at -20°C. The best balance of mechanical properties was obtained by using CCR+DQ+Tempering treatments. The major microstructural features responsible for the observed mechanical properties in order of importance were: a) substructural refinement associated with lower bainite, b) dislocation strengthening, c) fine recrystallized ferrite, and d) small amounts of retained austenite. Fine Nb(C,N) precipitates formed in ferrite were observed, however their contribution to the strength was minimum. Most of the Nb(C,N) precipitation took place in austenite. This precipitation was used to exert microstructural control of austenite during hot rolling. The physical metallurgy and optimum TMP to achieve the mechanical properties are detailed in this paper.

Jan 1, 2005

By C. Maree

Paper written on project work carried out in partial fulfilment of B. Eng (Chem. Eng.) This paper describes the development and use of a process simulator to optimize gypsum recovery at Afmine, a small plant near Yzerfontein on the South African West Coast. The simulator consisted of models of the major plant equipment, viz. hydrocyclones, surge bins, settling tanks, a primary sieve and a dewatering screen. Experimental data suggested that the equipment could be modelled satisfactorily from data published in the open literature. Simulation studies have indicated that gypsum losses on the plant could be reduced substantially by means of some relatively minor modifications to the plant layout. Moreover, sensitivity analyses of the plant have indicated that optimization of the settling tanks should receive priority over the other process units.

Jan 1, 2005