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"A method is described for determining the viability of hard rock orebody extraction by block caving. Using a very limited amount of geotechnical data, the procedure enhances Laubscher’s empirical stability graph method by using the complex structural modelling system (ChaSM) to assess cavability and block cave tonnages.IntroductionIn considering the selection of suitable mining methods, block caving has gained popularity over other extraction systems in recent years (Butcher, 1999). This has been ascribed to the fact that block caving is the lowest cost per ton mining method, with orebodies that were in the past considered unsuitable for caving, now being successfully mined. However, even though all orebodies will cave, a problem exists in the evaluation of economic viability — it is necessary to be able to predict both when the orebody will cave and what will be the sizes of the initial ore fragments (and the associated tonnages) that report to the drawpoints. This problem is compounded by the fact that, during the scoping study phase of a project, only limited geotechnical data may exist on which to base an assessment of whether block caving is viable or not. Empirical and numerical methods of cavability assessment do not account for the full effects of geological discontinuity trace lengths, nor for the stress regime. Those require significant geotechnical data to be available. The result is that uncertainty may exist as to whether block caving is an economic option. This uncertainty is complicated by the fact that limited experience exists with the caving of more competent orebodies.This paper describes a method for assessing cavability, and for predicting the size of initial ore fragments and the tonnages reporting to block cave drawpoints, using only the level of data normally available during a scoping study. Fragment size and tonnages are assessed by identifying potentially unstable blocks and wedges in the undercut back using statistical joint data. The effects of lateral confining stresses are accounted for by comparing the in situ stress orientations with the joint orientations. To evaluate the accuracy of the method, a back analysis exercise was conducted to predict cavability and initial tonnage for a mine in which the actual behaviour is known. The method is then applied to cavability and tonnage predictions for a hard rock orebody."

Jan 1, 2002

The integration of mining and mineral processing technologies into new advanced mining systems is considered to offer several benefits, including selective mining, reduction in waste, increased productivity, flexibility, and improved resource utilization. This paper focuses on underground hardrock mining and the integration of pre-concentration technologies into future mining systems as representing realistic, shorter-term integration options. Control of fragmentation to optimize grinding, pre-concentration of ores, in situ leaching, and modular mining/mineral processing systems are possible with existing technology. Current research is directed toward development of integrated underground systems that minimize surface activity and minimize or eliminate surface waste disposal. Results from a simulation model of an integrated underground pre-concentration system are presented.

Jan 1, 2002

A standard practice of auditing mill designs has developed in the mining industry. The purported aim of this task is to ensure that the mill being offered conforms to the design specification, thus reducing the purchaserÆs risk. However, careful examination of the auditing methods used in the past shows that this is not the case. In some cases, what auditors have been providing is effectively a quality assurance check of the input data, not a full independent audit of the vendorÆs design. It will be shown that these past auditing methods have contributed to the stagnation of mill specification development. This lack of specification improvement combined with the current trend towards increased allowable fatigue stress ranges can result in an increase in risk for the purchaser.

Jan 1, 2002

MIM Holdings Limited has acquired a reputation for the successful application of R&D to develop break-through technologies for the mining industry. The Isa Process tank-house technology has been licensed to copper refineries throughout the world, and almost 40 per cent of the worldÆs copper is refined using this technology. Isasmelt copper and lead smelting technology is either in use, or is currently being installed, by eight companies in eight countries around the world. Jameson Cell technology is widely used in the coal mining industry and increasingly in the base-metal industry. The IsaMills developed at Mount Isa and McArthur River made it possible to develop the McArthur River and George Fisher orebodies. This paper will address the need for innovation and then discuss the development of the IsaMill and Isasmelt technologies. It will conclude with some comments about why MIM has been so successful in developing such technologies.

Jan 1, 2002

The gold salting fraud at Busang on the island of Kalimantan, Indonesia was exposed in early 1997 and resulted from the independent drilling, sampling and assaying of PT Freeport Indonesia which reported assays from the South East Zone with negligible concentrations of gold. Since then, a number of legal actions directed at former Bre-X directors, consulting firms and financial or broking institutions are at various stages and are based on numerous allegations surrounding the supposed existence of obvious and numerous warning signs or æred flagsÆ. These include: the absence of references to visible gold in the drill logs; the alluvial nature of the gold grains; the high gravity recoveries; the invalid comparison with Kelian; the absence of outside scrutiny and the lack of external review/audit and surface depletion of gold. The focus on the red flags has been at the expense of the numerous positive indications or ægreen flagsÆ. These include the morphology and chemistry of the gold grains, the gravity testwork, the amalgamation results, the role of external consultants, the results of a review by one of North AmericaÆs leading minerals auditing groups, the behaviour of the gold at surface and the presence of references to visible gold in the drill logs. The flawed nature of the discussion of the technical facts surrounding Busang has prevented a meaningful and informed discussion about what actually happened and has, therefore, prevented the formulation of meaningful remedies for the future.

Jan 1, 2002

By Harovel G. Wheat

It has been shown that the incorporation of fly ash into concrete as a replacement for part of the cement can be beneficial. In some cases, the strength of the concrete can be increased and the permeability can be decreased. This latter property can lead to a reduction in the migration and/or penetration of aggressive species into reinforced concrete. Some of these species, such as chlorides from deicing salts or marine environments, can subsequently result in accelerated corrosion of the steel reinforcement, a loss of the protection provided by the passive film on steel, and a loss of structural integrity of the concrete. Care has to be taken so that the appropriate compositions of the components of the fly ash are utilized in order to ensure maximum benefit to the concrete structures. This will be discussed as it relates to fly ash generation and treatment.

Jan 1, 2002

By Karl A. Gschneidner

The magnetocaloric effect has been known for 120 years and has been utilized for cooling about 70 years. But in the last four years significant advances have been made to show that magnetic refrigeration is a viable and competitive cooling technology. Most of the work has focused on reciprocating devices, but rotary apparati are being developed. To date the magnetocaloric properties have been characterized for more than 200 materials. The magnetocaloric effect behaviors have been classified into three types of behaviors. The most common one is found in magnetic materials which exhibit a second order magnetic phase transition. Magnetic materials which exhibit a first order magnetic phase transition account for the second group of materials. Materials which exhibit multi-magnetic phase transitions make up the third group. The best candidate materials for magnetic cooling over the range from -4 to -1 350 K are also presented.

Jan 1, 2002

About 90 per cent of the pre-mining BIF-hosted iron ore resource of the Hamersley Province of Western Australia is of the Phanerozoic supergene martite-goethite type. The remaining ten per cent formed as supergene deposits at ~2000 ¦ 200 Ma, and were later modified by burial to form the Proterozoic martite-microplaty hematite ores. The supergene-metamorphic segment of this general unified model has been challenged by three recently published hypogene-based genetic models for the hematite ores, all requiring meteoric oxidation to produce the ore. The most recent and detailed, by Taylor et al (2001), is based on data from the small Southern Batter and North deposits of the Mount Tom Price mine. The authors proposed that during Stage 1 æoverpressured bicarbonate-saturated basin brines from the dolomite aquifer of the Wittenoom FormationÆ at 150 - 250¦C, dissolved free silica from BIF to produce a stratigraphically thinned, magnetite-carbonate-silicate-apatite rock. In Stage 2, meteoric oxidation of siderite to secondary microplaty hematite + ankerite, and magnetite to martite, at unspecified elevated temperatures and pressures, was followed by carbonate leaching (Stage 3). Finally, during Stage 4, weathering with removal of apatite, produced the typical low-phosphorus, porous martite-microplaty hematite ores of the Tom Price-Whaleback type. However, evidence of both microplaty hematite and martite reduced to magnetite, and of infill silica, apatite, and ferroan chlorite, with late-stage pyrite, in the pore space of martite-microplaty hematite ore, shows that the hydrothermal activity at Mount Tom Price is a post-ore event. Neither pyrite nor ferroan chlorite could resist the oxidation required to form hematite ore. Recrystallisation of microplaty hematite in these infilled zones to a typically coarser form than present in most of the normal ores, is a further supporting factor. A more credible, post-ore alternative to the hypogene genetic model is suggested here. Re-exposure to leaching by ground water of the metamorphosed ore deposits in the Phanerozoic resulted in the partial removal of remnant goethite. Localised modifications in the porous BIF/ore contact zones were driven by exothermic oxygen/pyrite/carbon reactions in the footwall Mt McRae Shale. Cool descending oxygenated meteoric water in the permeable ore horizons, acted as one limb of a thermal convective cell. In the other limb, heated reducing solutions rose through the permeable contact zones, to produce the observed localised modifications of BIF and ore. Expelled silica from the carbonatised BIF invaded adjacent porous ore to form erratic silicified ore zones, and to produce the local quartz vein systems found in the associated overlying BIF.

Jan 1, 2002

The Pongkor Gold Mine employs 678 staff. The mine is owned by the Indonesian state company PT Antam Tbk and is located 100 kilometres south west of Jakarta, in Java, Indonesia. Mine and infrastructure development started in 1992 following intensive geological exploration over 15 years. First gold production was in June 1994. The mine comprises three main orebodies: Ciguha, which is nearly mined out, dips at 75¦ from surface to 150 m. Kubang Cicau, dipping at 80¦ from surface to 230 m, and averages 3.5 metres thick at a grade of 10 g/t Au and 128 g/t Ag; and Ciurug, dipping at 60¦ from surface to 300 m and averages eight metres thick at a grade of 14 g/t Au and 172 g/t Ag. Present global ore reserves are 4.6 million tons at a grade of 12.3 g/t Au and 133.6 g/t Ag. Exploration is continuing for new veins. Initial mining was by manual cut and hydraulic fill at Ciguha, followed by Kubang Cicau. In 1996, it was proposed to convert Ciurug to a mechanised cut and fill operation. Two single boom jumbos and three load-haul-dumps (LHDs) were purchased with the assistance of a gold loan from NM Rothschild and Sons. Implementation of this upgrade was delayed by both a national economic crisis and an invasion of the concession by illegal miners. It was not until May 1999 that raise bore vent rises and access drift infrastructure commenced. Major underground development started in 2000 and is continuing. Production cut and waste fill stoping started in July 2001. The change from manual to mechanised methods has required a total change in work practices and attitudes. However, the process has resulted in a production increase from 600 tpd to 1200 tpd. A three-month compliance test (a condition of the financing loan) was successfully completed, from July to September 2001, with an average production of 700 tpd at Ciurug and 500 tpd from Kubang Cicau.

Jan 1, 2002

By S O. Hille

Modern remote mining operations in Australia are more commonly trending towards fly-in/fly-out (FIFO) sites. This trend is driven by numerous factors including increased business centralisation, reduction in operating costs, and a desire to live in coastal cities that offer closer family networks and a greater diversity of facilities. Consequently, the resource development industry has had to adapt. When WMCÆs Mount Keith Nickel Operation commenced operations in 1994, it was developed as FIFO for its entire workforce. Since then, there have been several permutations of rosters within a 21 day compressed work cycle including the 14/7 cycle. This paper discusses a case study of the change in management process to the 9/5 work cycle focusing on minimising fatigue in the workplace. It includes the discussion of the business case, employee reaction and the practical application. The impact of the best practice change after 18 months is discussed.

Jan 1, 2002

By M Boyd

The University of Wollongong was named University of the Year 2000, for its work in preparing students for the e-world. Computer facilitated learning is being introduced into subjects throughout the engineering course. First year mining engineering students are introduced to computers, e-communication, using the UniversityÆs web based information system, and web based subject delivery. Mining engineering students in the mid-years of the course use programming languages and numerical computation software such as MATLAB, while students in the final years use a range of commercially available professional engineering software such as TALPAC. Most of these subjects are offered as part of the UniversityÆs Learning Online program, co-ordinated by its Centre for Educational Development and Interactive Resources (CEDIR). Learning Online subjects are delivered using the Web Course Tools (WebCT) environment. WebCT allows all resources to be accessed through the web, allows email communication between lecturer and student, and allows discussion groups for the exchange of ideas. Students can submit their assignments through WebCT and receive immediate feedback. This paper describes how WebCT has been used to deliver a first year engineering computing subject, mid-year numerical computation subjects, a mining economics subject and mine planning subjects.

Jan 1, 2002

By D Kahler

Modern gold production from the Gympie Goldfield commenced in 1995 with the first production from the Monkland Mine. The primary ore target was the 2.5 m wide Inglewood Fault ore zone, which was initially mined using traditional narrow-vein shrink stoping. This manuallyintensive mining method allowed the mine to re-open with minimal capital cost, however the trade off was low productivity and high operating costs. As the mine has developed, access through 100-year-old, timber-lined, small shafts, and the high cost of delineating reserves, has restricted modernisation of the operations. In early-2000 a stockwork lode was discovered adjacent to the existing workings with an economic width of 40 m. In order to maximise the benefit of such an orebody, mining needed to be approached in a new way. This paper summarises the many changes implemented at the Monkland Mine, including the necessary cultural change, implementing long-hole stoping, de-bottlenecking and the application of mechanisation. The result has been a significant improvement in safety performance, higher productivity and a more secure future for all those involved in the project.

Jan 1, 2002

By Alicia E. Ares

316 L Stainless Steel samples were solidified directionally under conditions which produced the columnar to equiaxed transition. The position of the transition was located in each sample and the distance from the bottom of the ingot was measured. During solidification the distribution of temperatures were measured by means of thermocouples located strategically. From the measured temperatures the following parameters were derived; the local temperature gradient, the cooling rate and the velocities of the liquid and solidus fronts. Comparing the location of the transition and the values of these parameters it was found that the temperature gradient reaches negative values of as low as -13.44 "C/cm, and velocities of the fronts of around 0.1 cm/s. Also, a supercooling of 5.81°C were measured which was associated with the supercooling for the nucleation and growth of the equiaxed grains ahead of the columnar front. In addition the primary and secondary dendritic spacing was measured in both regions. The spacing was compared with the predictions from available models. The results are presented and discussed in the frame of the results obtained for other alloys

Jan 1, 2002

By T. R. Ellis

"The valuation of mineral properties in the U.S. is only partially regulated. The regulations which have jurisdiction or impact appear to have such mainly as a consequence of unintended fallout, since the regulations were designed for other purposes. Court case history can also be important. The combined results are a mixture of bad and good, with important lessons to be learned.Since 1981, the Securities and ExchangeCommission has prohibited U.S. listed companies from reporting quantitative estimates of mineralization and the value of mineralization, other than proven and probable reserves. This results in the minerals appraiser (valuator) working with a shortage of data in his everyday work, both on the subject property and in sales analysis.Between 1989 and 1995, all 50 states and essentially all federal agencies adopted the Uniform Standards of Professional Appraisal Practice (USPAP) for real property appraisals (valuations). The major national appraisal societies also require their members to abide by USPAP. A significant portion of minerals appraisals must now follow these standards. This paper will discuss the content of USPAP. It provides a very good framework for the valuation of a minerals property or a mine, both as real property and as a business. However, the credentialing standards for real property appraisers are now prohibitive for minerals appraisers."

Jan 1, 2002

By G. Shore

"The development of a DC resistivity instrumentation system for data acquisition in extreme topography yielded an unexpected bonus in the quality and information content of the type of raw data gathered. Not only were traditionally too-rough areas being investigated systematically for the first time, the unique high-density, multi-directional raw data were providing the opportunity to greatly expand the range of conductive and resistive signatures that could be accurately recognized. Using a true 3-D inversion algorithm, 3-D earth resistivity imagery began to show distinctive anomaly patterns for hydrothermal mineralization at the seldom-visited resistive end of the spectrum, successfully imaging epithermal gold systems in conditions that had defied conventional ground and airborne geophysics for years.The traditional mode of designing a resistivity survey to test a specific target concept was shown to be an unnecessary limitation on exploration thinking when a single sweep acquisition of dense, multi-directional 3-D raw data could effectively provide the all-targets “shotgun” coverage that would take 10 or 12 conventional surveys to duplicate. Exploration planning has the opportunity to move from single steps of trial and error geophysical testing to a mode of mapping everything at the outset, and then sorting out what might be of exploration interest in the results. Survey parameterization becomes the non-technical process of marking an outline on a map and declaring “survey here.” Operational and interpretational reasons for not testing where the exploration interest lies have all but disappeared. With any-terrain capabilities and unprecedented raw data density and overlap to support interpretation of complex conditions, that outline can be drawn through extreme rough terrain, including lakes, cliffs, industrial facilities, and grounded installations to test for generally unknown sub-surface features of potential interest.As more is learned about the larger-scale signatures of ore settings and the district-scale geo-electric imprint of hydrothermal processes on lithology, it appears that the only thing certain about ore signatures is their uncertainty. This is not bad news. New opportunities abound as the advanced 3-D technology allows a first effective look at the previously unexplorable rough terrain or complicated settings, and a second look at areas where older results may now be known to be non-definitive."

Jan 1, 2002

By Brent Blanchard

The use of explosives to safely fell structures can be traced back over 300 years. Since then, dozens of chemists, inventors, blasters and demolition experts worldwide have played prominent roles in the evolution of what has become the modern-day explosive demolition industry. In America, one of the earliest applications of explosive demolition occurred in response to the great fires of San Francisco, where homes and businesses were blasted with gunpowder in a desperate attempt to create firewalls. Later in the 19th century, inventions such as nitroglycerine, dynamite and blasting caps made structural blasting a safe, efficient alternative to conventional demolition methods. The 20th century brought the first experiments in shaped charge technology, and this, combined with developments in portable seismology and non-electric delay systems, allowed an ever-expanding variety of structures to be explosively felled by demolition experts throughout the country. The 1950s and .60s brought a new wave of commercial structural-blasting entrepreneurs (several of whom are still active today), and their efforts towards improving adjacent-structure protection and public relations beget the felling of large commercial buildings in dense urban environments. By the late 1980s, publicity-driven motives were gaining greater influence in the decision to .implode. various structures, and the transformation of blasting operations into promotional spectator events played a role in several injuries and fatalities. Since that time, however, a renewed sense of responsibility practiced by most blasting firms and project officials has resulted in the safe, successful completion of hundreds of recent endeavors. In sum, what appears today as an efficient, economical - and visually spectacular - way to demolish structures has its roots in developments of the past several centuries

Jan 1, 2002

A mini- or micro-machine is a small electro- mechanical device. There are several existing applications of micro-sensors such as the accelerometers used in automobile airbags or the force sensors and grippers used at the ends of micro-surgery tools. Potential applications of existing mini- and micro-technologies are possible and could be used to improve the control and efficiency of fragmentation, heap leaching and other mining and mineral processing operations. A more radical proposition is to devise mass-produced, possibly disposable, minimachines that would operate in large groups. These would be the basis of highly selective, efficient, flexible, and clean mining and mineral processing methods. The paper is intended to promote discussion of how innovative applications of mini-technologies can be used to improve and radically change current mining and mineral processing methods.

Jan 1, 2002

By Kenneth N. Ham

Hydrometallurgy covers a wide spectrum of areas and its knowledge base is enlarged and enhanced by contributions from many other fields. Dissolution of metals and alloys in aqueous media will be used to illustrate how rich the field of metal extraction can be. Comprehensive understanding of the fundamentals of metal and alloy dissolution in aqueous systems requires creative application of thermodynamic principles, solutions chemistry, ligand complexation theory, electrochemistry, transport phenomena and heterogeneous kinetics. In addition, recent developments in instrumentation in the fields of interfacial phenomena and corrosion have tremendously advanced the field of metal extraction in aqueous system. The close relationship between metal extraction in aqueous systems and various physicochemical phenomena occurring in corrosion and interfacial systems will be discussed and illustrated with examples.

Jan 1, 2002

By M. Peshko, J. C. Gingerich, L. W. Matthews

"Noranda has successfully developed and implemented two leading-edge mineral exploration technologies — hyperspectral remote sensing and 3-D seismic surveying. Airborne hyperspectral imaging provides detailed geological and mineralogical mapping capability at both a regional and project scale that facilitates improved selection of prospective terrain and an accelerated exploration cycle. Noranda, in partnership with Falconbridge, has licensed the exclusive use of the Earth Search Sciences Inc. (ESSI) Probe-1 hyperspectral scanners (128- channel, 0.43 µm to 2.5 µm spectral range) that are capable of mapping in excess of 3500 km2 per day at 10 m pixel resolution. The technology has been successfully deployed on four continents over a broad range of terrain from desert to boreal forest and the high Arctic.To augment the company’s deep search initiatives, Noranda has successfully modified and implemented existing 3-D seismic technology to help targeting massive sulphides located at depths ranging from 500 m to 2000 m. In the fall of 1998 and early 1999, Noranda completed an 18 km2, 3-D seismic program in eastern Canada by successfully drill testing acoustic impedance anomalies locating massive sulphides at depths in excess of 1100 m."

Jan 1, 2002

No one process, product or effect of the minerals sector can be viewed in isolation when addressing sustainable development. Meaningful assessments of the minerals sector require that its processes and production are drawn together in a generic framework that gives a holistic view of its performance and progress. Lifecycle Assessment is increasingly accepted as an appropriate means of constructing such a framework. It is a step beyond using the simplistic concept of the triple bottom line of social, environmental and economic performance to drive and communicate sustainable development. However, fundamental questions need to be raised about the scope and purpose of lifecycle assessment, such as what effects and performances should be assessed, for whom should they be assessed, and what performance indicators should be used and how should they be selected. The principles of eco-efficiency, industrial ecology, The Natural Step (TNS) and other pertinent philosophies and initiatives driving mineral sector sustainable development are outlined to support a lifecycle stewardship vision for the minerals sector. Articulating this vision through a holistic lifecycle indicator system showing inputs and outputs, natural partnerships, effects on community, environment and economy facilitates recognition of problems, opportunities and partnerships that can be usefully pursued.

Jan 1, 2002