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By T. G. Carter

Support system design for tunnels and underground excavations has for many years relied heavily on the use of rock mass classification systems and the Hoek-Brown failure criterion as a means for characterizing rock mass behaviour. Because of their development, both the GSI system and the Hoek-Brown criterion admirably characterize most ?normal? rockmasses from the viewpoint of their behaviour for rock excavations. They, however, run into difficulties when applied at the two ends of the rock competence scale. This is largely because block size and incipient strength are such that rockmass behaviour in these domains tends not to be controlled by interblock shear strength but rather by material strength. At the low end of the rock competence scale (UCSi <<15 MPa and GSI generally <30) discontinuities play less of a role and rock mass strength tends to matrix strength. Similarly, at the high end of the scale (GSI >>65, mi>>15), because discontinuities are now widely spaced, block size becomes so significant that again, intact material behaviour rather than the fracturing becomes the dominant factor controlling rock mass strength. In this paper several case examples are presented to illustrate the application of the high-end (spalling) and low-end (weak ground) transition Hoek-Brown relationships proposed by Carter, Diederichs and Carvalho (2007) as a basis for better defining rockmass behaviour at the extreme ends of the rock competence scale.

Jan 1, 2008

By J Steyn

Block Cave mining is one method used to extract ore from underground diamond mines as well as other massive orebodies such as copper. This necessitates the excavation of many kilometers of tunnel within the ore body. The integrity of these excavations needs to be maintained over a number of years. Most Kimberlites and weak orebodies are extremely susceptible to degradation when exposed to moisture and the atmosphere. It is therefore essential that some form of weathering protection is applied as soon as possible after exposure. Conventional methods of weathering protection such as shotcrete do not easily fit in with the production schedule, hence the need for a more efficient system that could be applied immediately after exposure and serve as a temporary support or even as a permanent support medium. The main advantages of thin sprayed liners (TSL) compared to shotcrete are the ease of application, speed of application, early strength, much reduced transportation of material, less labour intensive and cost effectiveness. Several Thin Sprayed Liners suitable for various mining environments and geotechnical conditions are available and could be well suited as additional support the undercut level development in a block cave where this may be required. TSL offer a cost effective support solution as an alternative to shotcrete in areas where the building of a support structure is not a requirement.

Jan 1, 2008

By J. A. Organiscak

Enclosed cabs are a primary means of reducing the silica dust exposure of equipment operators at surface mines. The National Institute for Occupational Safety and Health (NIOSH) has investigated various factor effects on enclosed cab air filtration system performance. Factors experimen­tally investigated were intake filter efficiency, intake air leakage, intake filter loading (filter flow resistance), recirculation filter use and wind velocity effects on cab penetra­tion (inside to outside cab concentration ratio). Adding an intake pressurizer fan to the filtration system was also investigated. Results indicate that the intake filter efficiency and recirculation filter were the two most influential factors on cab penetration .Use of a recirculation filter significantly reduced cab penetration over the intake air filter by itself due to the multiplicable filtration of the cab interior air. Cab penetration was also affected to a lesser extent by intake filter loading and air leakage. Adding an intake pressurizer fan notably increased intake airflow and cab pressure while providing only minor changes to cab penetration.

Jan 1, 2008

By M. Sokoto, H. Hata, K. Nishina, K. Haiki

Fluoride ions in zinc electrolyte cause corrosion to aluminum cathode plates at zinc electrowinning process, so we have developed an iron compound as a fluoride ion adsorbent used in zinc sulfate solution. The iron compound is synthesized from FeC13 solution with a small amount of sulfate ion by neutralizing reaction with Na2CO3 solution. The fluoride ions adsorbed on the surface of the iron compound are desorbed in alkaline solution and the iron compound can be reuse as a fluoride ion adsorbent. Moreover, if adsorption capacity of the iron compound decreases, it can be dissolved in HCl solution and re-synthesized.

Jan 1, 2008

By P Fuller, A R. Penney

Re-commencement of mining in the Western Zone of Beaconsfield Gold Mine following a seismically-induced rockfall fatality in April 2006 required a change of mining method involving drilling and blasting from specially developed drives in the footwall of the orebody. Broken ore is mucked remotely from ore drives on each level. Support in the footwall drives is required to maintain stability during their development and as stopes are retreated, which increases induced stresses and further seismic events are triggered. The paper outlines the challenges involved and methods used to select the footwall drive support to handle both static and dynamic load demand. The importance of load development in the support system, its displacement capacity, the compatibility of support elements and energy absorption capacity of the support system are highlighted. It is usual in any support selection process to ensure that capacity exceeds demand to create a factor of safety. In this case the demands on the system relate to load, displacement and energy absorption and the support system capacity for each must ensure that appropriate factors of safety for each are achieved. The paper shows how these factors are not independent and that selecting a high factor of safety for load can lead to compatibility problems with support elements in the support system.

Jan 1, 2008

By J. J. Sammarco

Light emitting diodes (LEDs) are emerging as viable replacements for incandescent-based cap lamps used in mining. The photometric and energy characteristics of these light sources differ in important ways. The present paper describes the performance of LED and incandescent sources in cap lamps in terms of correlated color temperature, color rendering, light output, electric power, ambient temperature and airflow, and light source aging. Importantly, these characteristics can influence a miner?s ability to spot mining hazards thus impacting safety. Secondly, some of these characteristics interact with the operating life of the cap lamp?s battery power, such that differences between LED and incandescent sources can be magnified toward the end of a 10­hour battery discharge cycle. Empirically, we have determined that after 8 hours at an ambient temperature of 25 °C, the average light output of an incandescent cap lamp can decrease to about 69% of its initial value when powered by a lead-acid battery and it can decrease to about 65% of its initial value when powered by a nickel-hydride battery. An LED-based cap lamp using a constant current drive circuit can maintain about 96% of its initial value when powered by a nickel-hydride battery. Real-world tests addressing the effects of ambient temperature and airflow on the light output of an LED and incandescent cap lamp were conducted in the NIOSH Safety Research Coal Mine (SRCM). The LED cap lamp yielded a vertical average illuminance improvement of approximately 9.5% and the INC cap lamp yielded a vertical average illuminance degradation o f approximately 4%. The differences between LED and incandescent cap lamps were further quantified by the calculation of ?mesopic luminance? data that indicated for the same photopic luminance (i.e., as measured using a conventional light meter) the LED cap lamp could be up to 38 % more efficient than the incandescent cap lamp with a lead-acid battery at the end of the 10-hour driving cycle. Lastly, accelerated life tests were used to empirically determine light output depreciation as the incandescent light source age approached its useful life. There was about a 35% decrease in light output. This is quite considerable, especially given that the light output will decrease an additional 30% to 45% over the period of a 10-hour shift. The implications of the differences between LED and incandescent sources are discussed. This information is crucial in determining how visual performance could be affected for real-world conditions where batteries discharge during the work shift and as the light source ages. To date, only idealized conditions have been used for LED and incandescent cap lamp visual performance research.

Jan 1, 2008

By W Zirima

A detailed, mine scale non-linear numerical model of Rosebery mine has been built for the purpose of simulating life-of-mine global deformations. The model was calibrated using observations of displacement and damage, and was then used to investigate the correlation between dissipated plastic energy (DPE) and seismic event occurrence. The study is unique because the seismic data was collected over a relatively short period using a temporary portable seismic system. It is the intent to undertake significantly more work, but the analysis of limited data shows that a very good, non-linear relation between DPE and event probability is present. The observed correlation is consistent with measurements from other mines where more data was available. With more data, the strength of the correlation will allow the DPE analysis to be used during the design and sequencing phase of planning to better design the mine to minimise seismic hazards.

Jan 1, 2008

By G. Konstantopoulou

Environmental degradation due to abandoned quarries is an international problem, more intense when these sites are found in urban or suburban zones, in environmentally sensitive areas or are visible from sites of special interest. Rehabilitation solutions applied worldwide, range from simple relief restoration and planting to more sophisticated site exploitation in order to serve specific social needs. The elaboration of rational rehabilitation plans for every site presupposes deep knowledge and comparative evaluation of all the parameters of the problem. In this paper, a methodological approach of rehabilitation solutions for abandoned quarry sites is elaborated, based on domestic and international experience and practice. Solutions are grouped in eight main categories. In every category the framework of prerequisites and confinements (environmental, technical, social, economic, legal) for their application in Greek quarry site is investigated. A comparative assessment of alternative restoration solutions is introduced, using tools supplied by environmental economics, cost-benefit analysis, G.I.S. and multi-criteria analysis and follows in two stages: 1) Establishment of a set of criteria aiming at a priority list for a number of quarry sites located in a geographical or administrative district. 2) Assessment of alternative solutions for every single quarry from the previous priority list for the selection of the most adequate using technical, economical, social and environmental criteria.

Jan 1, 2008

By William A. Hustrulid

The subject of surface mine development is large. This section covers the fundamental concepts involved in both the open pit mining of thick or steeply dipping deposits as well as the strip mining of thin, shallow, and relatively flat-lying seams or beds. Design involves the marrying of geometries, ore and waste characteristics, equipment, and economics so that the desired result is achieved. Generally, there are many possible combinations from which to choose. For example, extraction over a short time period requires one strategy while quite another is applied for longer times. Variations in supply and demand require some flexibility of operation. Customer requirements impose certain constraints regarding the set of possible designs. Over recent years, planning and operating considerations for surface mining imposed by environmental requirements have increased markedly. There have, at the same time, been enormous advances made in the design aids available to the mine planner. Computer simulation of the various options, whether it be for mine design or equipment selection, provides detailed information for decision making in real time. A significant challenge to the engineer/planner is how to best use the aids avail-able. Because of the widespread use of commercially available and in-house computer software by industry, this section does not deal with the details of planning (for basic coverage of mine development, see Section 7). Rather, some of the basic concepts are stressed. The principles involved in equipment sizing and selection are discussed. A highly important but sometimes over-looked aspect of planning, haul road design, is also covered. For surface mining operations of the future, in-pit crushing and conveying will become even more important. Some of the considerations for application evaluation are included. The section concludes with some future concepts for surface mining.

Jan 1, 2008

By M Sandy, P Bamford

The Challenger Gold deposit was discovered in 1995 by Dominion Mining Ltd in a remote western area of the Gawler Craton in South Australia. Mine development commenced in 2002 with initial production from an open pit supplemented by ore from a very small adjacent auxiliary pit. Development of the underground mine commenced in 2004. The orebody plunge of just less than 30 degrees requires careful attention to mine design. Production from the M1 orebody, with less than 800 ounces per vertical metre (ovm) and very limited æsurgeÆ capacity, requires careful scheduling and implementation to ensure continuity of ore feed for milling. Initial production results from underground stopes included more dilution than anticipated. The narrow, high-grade zones proved to have much more complex geometry than early interpretations had indicated. Greatly improved understanding of the mineralisation controls resulted in important changes being made to the underground mine design and method. Coupled with careful control of development and drilling and blasting practices, this resulted in an immediate reduction in dilution and high recoveries of the resource. The benefits of these changes flowed through in the 2005/06 financial year, resulting in a 150 per cent increase in gold production to 108 080 oz and a sharp reduction in cash operating costs to A$280/oz. This was followed in 2006/07 with production of 108 91 oz of gold at an operating cost of $309/oz and in 2007/08 with 109 326 oz of gold at $367/oz. Production to June 2008 has been mainly from the M1 orebody, with the lowest stoping to date on the 580 m Level (615 m below surface) above development mining on the 520 Level. The rate of vertical advance of mining this orebody has averaged 150 vertical metres per year. The increased current combined JORC compliant resource and reserve position of over one million ounces, now includes the M2 and M3 orebodies with a current total average gold inventory up to 1400 - 1500 ovm. Exploration has intersected other shoots and all shoots are open at depth. The adjacent M2 and M3 orebodies are being developed for stoping. The narrow width of these zones from 1 m up to 4 m will require continued focus on ore zone definition, accurate development and careful drill and blast practice. In addition, to minimise cost increases in the current period of rapidly escalating labour, equipment, consumables and energy costs, high productivities will need to be maintained to allow the established rapid mining advance to continue at low unit costs.

Jan 1, 2008

By Pekka Parvinen, Saija Luukkanen, Pentti Pirkonen, Väinö Hintikka, Hannu Sekki

In the study was developed a new method for the treatment soils contaminated by polychlorinated dibenzodioxin and dibenzofuran. The method is based on attrition of soil so that the contaminants absorbed on the particle surfaces are liberated with the fine fraction formed in the attrition process. Same the attrition process produces active surface which can absorb the free contaminants. Before starting the remediation process must be decided the limit value under which the residual concentration must lie. Then in the laboratory is performed an experiment in the base of which is determined the grain size level; material under which much be removed together with the contaminant. In the real sample has been found that after the attrition the limit value 0.5 ng/g (I-TEQ) is obtained when the fine under 0.1mm fraction (20% of the original soils amount) is removed together with the contaminants 96% (original level 10 ng/g; 100%).

Jan 1, 2008

By Hebi Yin

A two-dimensional finite element solidification model was developed to simulate the transport phenomena occurring during laser deposition of AISI 410 stainless steel during the Laser Engineered Net Shaping (LENS®) process. The molten pool geometry and the distribution of temperature, solute concentration and velocity were calculated during deposition of a thin wall plate. An analysis of the simulations results revealed the importance of heat transfer by both conduction and convection as well as the roles of the driving forces for convection in the molten pool. The heat transfer and the flow pattern in the molten pool are considerably dependent on the travel speed of the laser beam. For the alloy and process parameters in the simulations, no significant macrosegregation was observed. The temperature-dependent properties and thermodynamic variables involved in solidification modeling were calculated using Thermo-Calc software. The results of this work contribute to the current understanding of transport phenomena in the molten pool of laser deposition processes.

Jan 1, 2008

By Yinlun Huang, Cristina Piluso

"Industrial sustainability looks to improve material and energy efficiencies, product quality and variety, and productivity within an industrial zone, thus pursuing the long-term sustainable development of the region. This paper introduces a systems-based modeling methodology, which provides industrial leaders with the ability to evaluate future production options to determine the path with the highest positive impact on both their own sustainability and the sustainability of the overall industrial zone. A comprehensive study on sustainable development of an auto-manufacturing focused industrial zone under uncertainty is illustrated. Introduction Sustainable development refers to a continuous process of improvements that must be followed in order to achieve a state of sustainability. In its most general form, a widely accepted definition of sustainable development was identified in the Brundtland Report as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” [1]. Sustainability will occur when the material and social conditions can be maintained or improved for human health and the environment over time without exceeding the ecological capabilities that support them [2]. An industrial zone is defined as a geographic area comprised of a network of industrial sectors, each composed of a number of entities. Such a zone is highly integrated and complex, and contains numerous uncertainties due to each industry’s extreme dependencies on its suppliers and customers throughout the product supply chain. In the context of an industrial zone, sustainable development refers to the continuous process of advancements in the zone, and the entities that comprise it, creating more value, wealth, and profits (economically viable dimension), providing environmentally benign products with less raw material consumption and waste generation (environmentally compatible dimension), and collaboration and a direct relationship among all involved in the supply chain, i.e. the corporations, employees, suppliers, investors, communities, customers, etc. (socially responsible dimension). These are the triple bottom lines of industrial sustainability. In order for economic, environmental, and social sustainability improvements to be successfully implemented within an industrial zone, the industrial decision makers must possess system-wide analysis abilities. The analysis of the sustainable development of an industrial zone involves decisions at the local, regional, or national levels, which are complex and involves handling of ill-defined parameters with a high degree of uncertainty due to the imperfect understanding of the underlying issues [3]. This work focuses strictly on the uncertainties in future zone planning and a method and a scenario based approach that can be used to evaluate the sustainable development of an industrial zone among these uncertainties."

Jan 1, 2008

By S Larbi-Bram, F Shi, E Manlapig

Mining companies have recognised that characterisation of particle breakage plays an essential role in the design and optimisation of comminution circuits. Recently the JKMRC comminution research team has developed a new breakage model incorporating the effect of particle size, and a new breakage characterisation testing device, called the JK Rotary Breakage Tester (JKRBT), which allows rapid testing of particle breakage under high energy single impact and low energy repetitive impact conditions. The latter is believed to be the dominant breakage mechanism in AG/SAG mills. Existing devices, such as the JKMRC Drop Weight Tester, are not suitable for performing repetitive impacts since they are too time consuming. Positive feedback received from mining company sponsors to the new technology has prompted the JKMRC to further validate the device and the model through a formalised experimental test program on professionally designed and manufactured JKRBT machines. The first JKRBT was installed at the Anglo Research laboratory in Johannesburg in March 2007 and four more major mining companies will participate in the project in 2008, with commercial release expected in early 2009. The JKRBT has the potential to revolutionise ore testing, with applications in laboratory impact breakage characterisation of rock samples, drill cores, coal and other materials. It also stands poised to significantly advance the process control of comminution circuits since it is readily adaptable to on-line ore hardness measurement. Can any mine afford to miss out on this technology?

Jan 1, 2008

By Liu Wei-feng

In this paper, the practice of separating precious metals from base metals in gold-antimony alloy by selective chlorination leaching under controlling potential in China has been introduced in detail. The precious metals and the base metals can be separated completely when the complex gold-antimony alloy is treated by this process. The impurity metals were removed effectively since the leaching efficiencies of copper, nickel and antimony are over 99%, with direct recovery of gold being 99.83% that is about 20% higher than that of the original process and silver, antimony, copper and nickel are also recovered effectively. The gold grade of the resulting crude gold powder can reach to 94%.The new process has been applied in the treatment of gold-antimony alloy for two years, and many former procedures have been cancelled, such as electrolysis, Anode slime leaching by nitric acid, smelting in crucible and blowing in muffle. The new process is more shorten, lower cost and friendly to the circumstance comparing to the original process.

Jan 1, 2008

By C Caris, K Fowle, M Schmid, E van Wyk, D Schofield, A Squelch, M S. Kizil

This paper has been written collaboratively by members of the International Mining VR Group. It is the first of a series of papers. Mining in the 21st century is a high technology industry that strives to reduce risk and improve safety through the use of improved processes and procedures. This risk reduction process is aligned with the innovative use of technologies often developed for other industries. Computer-based visualisation systems and their content are such innovative technologies, in particular the use of virtual environment systems and mixed reality. A primary objective of developing virtual environment systems and the mixed reality content displayed in them for the mining industry is to allow mine workers and operators to practice mine processes and demonstrate competency in tasks that will be encountered in day-to-day mining operations at mine sites. It is anticipated that providing easy access to virtual environment systems will facilitate the avoidance of high-risk situations through improved knowledge, skills, understanding and decision making. Via virtual environment systems mine workers will also be able to practice infrequent or emergency events and maintain preparedness for such events. Day-to-day mining practices can also be evaluated. The rapid pace of technology innovation and the decreasing cost of simulation hardware and software present a plethora of technology to the uninitiated. This can be confusing. In this paper taxonomy is presented that classifies hardware, what it can display and also content that can be included or displayed on the various computer-based visualisation systems. The taxonomy provides insight into where technology can and may be implemented in the future as virtual environments are a dynamic and evolving technology. The taxonomy should also assist in the decision making process when scoping or selecting technology for a particular purpose.

Jan 1, 2008

By Fred Fuchs

"Most deep foundation work is either unseen by the general public or viewed as an inconvenience in their daily lives. Hurricane Katrina changed that perspective for everyone in New Orleans — and many other people in the U.S. and abroad. The public and the government of south Louisiana, and the U.S. Army Corps of Engineers (USACE), all needed to restore trust in the system that protects their property and, more importantly, their lives. While much has been written about the failures of government agencies, in this case incredible solutions were devised and implemented despite daunting schedules and arduous conditions. These solutions were achieved through collaboration, and through the efforts of USACE, where the goal was to fi nd the most expeditious and effective design/build solutions. This disaster thrust the pile driving industry into the national spotlight. Boh Bros. Construction Co., L.L.C., along with numerous local and national heavy construction companies, subcontractors, material suppliers and government agencies, take pride in the milestones reached after Hurricane Katrina.The majority of New Orleans’ population lives below sea level. Historically, the city has been protected by a fl ood control system consisting of earthen levees and I-walls (steel sheet pile topped by vertical concrete wall). Rainwater is pumped out of the city over this protection system and into canals that feed into Lake Pontchartrain. On August 29, 2005, when Hurricane Katrina made landfall just east of the city, the levee system experienced a major failure of several I-walls lining the outfall canals, causing flooding of 74% of the east bank of the city. The counterclockwise rotation of the wind pushed the lake water onto the south shore, raising the level of water more than 10 ft (3 m). A failure of 450 ft (137 m) of floodwall lining the east side of the 17th Street Canal caused extensive damage. This breach prevented the use of the pump stations that outfall into the 3-mile (4.8 km) long 17th Street Canal."

Jan 1, 2008

By James W. Evans, Brian R. Wildey

"Carbon has been the principal reducing agent in producing metals for centuries. Carbon is an inexpensive reducing agent, but also an effective one, as any undergraduate who knows her Ellingham diagrams is aware. Even in the production of aluminum, an electrolytic process, carbon consumed at the anodes serves to reduce the voltage of the Hall-Héroult cell. The interest in reducing the amount of anthropogenic CO2 has led to this examination of whether a switch to hydrogen as a major reductant is feasible and economic. The main source of hydrogen is natural gas and its production entails the generation of CO2; however, that CO2 is more easily captured than, say, the CO2 leaving an iron blast furnace. Calculations and speculations lead to conclusions about whether there is significant benefit to be obtained from such a radical change in our way of producing metals and the approximate cost of such change.IntroductionThe 1991 paper by Forrest and Szekely1 was one of the first to examine the impact of CO2 emissions from the primary metals industries on global climate change. These authors compared data from 1968 and 1985 and reported a drop in carbon emissions from 115.8 million tons to 65.6Mt over this period, the latter figure representing approximately 1% of the world’s greenhouse gas emissions. Much of this reduction was due to a drop in steel output (with carbon emissions increasing within the aluminum and copper industries in this period) but some were due to technological changes such as increased use of continuous casting. A more recent paper on CO2 emissions, focused on the steel industry in Japan, is that of Ariyama and Sato2. These authors report CO2 emissions of 182.4Mt from the Japanese steel, industry in 2003, down from 194.8Mt in 1990. The former represents 14% of the GHG emissions for Japan in 2003. Much of this emission is from ironmaking and the authors break these emissions down into"

Jan 1, 2008

It is almost eight years to the day when we launched the original SAMREC Code in March 2000. Since that date I think the SA minerals industry has matured beyond recognition in its approach to reserve and resource reporting, and I believe we can be justifiably proud of that progress. Many of those companies that have led the way in reporting standards are listed on our sponsors list. We thank them for their sponsorship but even more for their considerable support in all aspects of the SAMCODE organization. Matt Mullins, my co-speaker here today, has been instrumental in the revision of the SAMREC Code over a long period of time and also took up the reigns with the SAMVAL Code after the retirement of Rob Croll. I would like to formally thank Matt for his immense contribution in producing the two Codes; he can take great pride in the final product and fully deserves the many accolades that we have already received from our international counterparts. He has done all this whilst still maintaining a very demanding day job at BHPBilliton. Matt will be the first to admit that he has received tremendous support from more than 100 people who participated in the various working groups, many of whom are employed by our sponsors. There are obviously too many to mention by name but they deserve a big vote of thanks for their personal contributions. In addition to launching the two Codes we are also launching our ?branding? initiative with our own SAMCODE logo and the SAMCODE website: www.samcode.co.za. All the slides used in the presentation today will be on the website later today as will a newsletter which will serve as a media release.

Jan 1, 2008

By J. J. Carlson

Studies were carried out to determine whether filtration rate changes observed in an iron ore concentrator were due to variations in particle shape. It was confirmed that ores mined from different locations differed in filtration rates by as much as 60%. However, when image analysis was used to quantify the shapes of the individual particles in the filtration feed, it was found that the particle shapes showed almost no variation, and the shapes did not correlate with the filtration rate. It was also determined that the filtration rate variations were not caused by changes in particle size distribution. These results suggest that the differences in filtration rate are due to factors other than size and shape, such as surface chemistry.

Jan 1, 2008