Search Documents

By Shulin Xu, Moreno Pescara, Nicola Avagnina, Piergiorgio Grasso

The Roreto Tunnel is a shallow, twin-bore, road tunnel on the connection between the A6 and the A21 motorway in NW Italy. The challenges faced the design and construction of this tunnel derive from 1) the presence of groundwater, both phreatic and artesian; 2) excavation in loose and/or little cohesive materials; 3) excavation in cohesive materials containing water-saturated, sand lenses; and 4) surface constraints due to the urban environment. In this paper, these problems are examined and the rationale led to the optimum design choices and construction solutions explained. The experience should be useful to others when tunneling in similar situations.

Jan 1, 2003

The objective of this international conference was to assist the mining and minerals industries in their global transition to sustainable development. The main theme of the meeting, therefore, was the development, monitoring and assessment of sustainable development criteria for mineral operations. Emerging technologies that can assist in the development of criteria and performance measurements were also presented at the meeting. A goal of the conference was also to conclude with a consensus plan and a process, representing a variety of stakeholders, which can provide guidance to the global minerals community on the path to sustainable development. A number of papers were not submitted in time to be included in the printed proceedings. Hence this addendum was compiled and includes last minute paper submissions. The pages of this addendum are numbered consecutively to the main volume of proceedings, so that when a reference is made to a paper, a proper page number may be quoted.

Jan 1, 2003

By Francesco Vegliò, Luigi Toro, Francesca Pagnanelli

Different hydro-metallurgical processes have been studied in order to recover manganese(II) from oxidised minerals such as MnO2. An innovative acid reductive leaching carried out in mild experimental conditions was here considered using agricultural and industrial wastes containing carbohydrates as reducing agents. The leaching process was investigated from a kinetic and equilibrium point of view in order to optimise the experimental conditions, develop a kinetic model and obtain high purity concentrated MnSO4 solutions. To study the leaching kinetic a Shrinking Core Model (SCM) was modified by a variable activation energy term to take into account both the variable reagent concentrations and the reaction rate change with respect to the manganese dioxide conversion. The influence of the particle size in the kinetic model is discussed with the support of SEM analysis before and after leaching. Manganese extraction yield was maximised (170-190 g/L) using appropriate carbohydrates and acid excesses, while impurity concentrations were kept low (Fe<10ppm and Ca<300ppm) pre-treating the ores, using hydro-alcoholic leaching medium and different combinations of down-stream processes. In particular precipitation, solvent extraction and adsorption onto active carbon were tested to eliminate Fe and Ca from MnSO4 solutions.

Jan 1, 2003

By Markus A. Reuter, Joep Verwoerd, Marc J. A. Pijnenborg, Yongxiang Yang

"Incineration is a proven disposal technology for all waste materials with heat release potentials, and provides high degree of toxic destruction and control for a broad range of hazardous materials. In the Netherlands, all the hazardous wastes are processed at AVR-Chemie located at the Rotterdam harbour, through rotary kiln incinerators. The newly enforced regulations from the European Union with stricter emission levels require a better understanding of the incineration process and improved process control. However, the transport phenomena and combustion processes within the kiln system are very complex and not well understood. In order to get better understanding of the incineration process, research has been carried out to study the fluid flow and combustion behaviour of the incineration system. Computational Fluid-dynamics (CFD) was used to simulate the gas flow and waste combustion process, and temperature measurements of the operating rotary kiln incinerator were conducted to validate the CFD model. This paper will present the latest results from the current research project for simulating gas flow and combustion heat transfer for a wide range of hazardous waste streams.The simulation of the waste incineration process was carried out using a general-purpose CFD code Phoenics. The rotary kiln and the secondary combustion chamber (SCC), with a waste processing capacity of 50,000 ton/y and an energy input of 30 – 40 MW, is translated into a CFD model. The model includes a k-e turbulence model and a global gas-phase combustion model (3-gas or 7-gas combustion model). The 3- gas model (Simple Chemically-Reacting System, SCRS) predicts only the thermal effect of the fuel combustion, and only one global fuel is used, therefore, real chemical species are not taken into account. In the 7-gas combustion model, (an Extended SCRS, ESCRS), different forms of waste fed into the incinerator have been modelled into a mixture of a general hydrocarbon fuel C3H4 and other components such as CO, CO2 and H2O. Thus, all the incoming fuel streams with different compositions and calorific values can be properly converted into separate inlets. The combustion of the waste is assumed to take place only in gas phase in two steps: (1) primary combustion of the main fuel component C3H4 to form CO and H2, (2) secondary combustion of CO and H2O to form CO2 and H2O. The rate of each combustion reaction is assumed to be controlled by turbulent mixing of fuel and oxidant (air or oxygen), i.e. the Eddy-Break-up (EBU) model. The resulted temperature field was validated with temperature measurement data, and the simulated temperature distribution from both 3-gas and 7-gas model have reasonable agreement with the measured data."

Jan 1, 2003

By I. R. Muirhead, S. Frimpong

"The mechanization of mining operations in underground coal mines has led to faster cutting rates of coalfaces with increased levels of emission of gaseous and particulate contaminants in the workings. Consequently, the fresh air streams from the main ventilation systems reaching distant workings are often insufficient, ineffective or inadequate and have to be supplemented by auxiliary ventilation systems to create and maintain the required working environments underground. The efficiencies of auxiliary ventilation systems are largely affected by drivers of the system such as the type and capacity of the fan; the type, length, diameter and condition of the ventilation ducting and the distance from the discharge end of the intake ducting to the face. Traditionally, single point measurements of methane gas concentrations using either flame safety lamps or hand-held measuring instruments have been used to assess how safe underground coal workings were. Unfortunately, such occasional measurements of methane gas concentrations do not give an accurate picture of the real gas concentration in the working as they are often taken from the easily accessible locations in working. Continuous monitoring of the methane gas concentration in development headings enables a better assessment of the environmental conditions prevailing there. All variations in the methane concentrations are more easily captured on a continuous monitoring basis than by instantaneous single point measurements. The approach adopted in this work was to continuously monitor the concentration of methane very close to the face and about 60 m outbye in development headings, observe the types of auxiliary ventilation equipment and their sizes being used in the working as well as noting the lengths from the discharge ends of the forcing and exhaust ductings to the face.In this paper, empirical methods are used to calculate the mean efficiencies of the auxiliary ventilation systems in selected development headings in coal mines in North America. This enables the assessment of the effectiveness of the auxiliary ventilation systems and the identification of the system drivers in them. The results show that the efficiencies of the forcing systems ranged from 17.02% to 96.81% while the efficiencies of the overall systems varied from 6.04% to 54.16%. The distance from the discharge end of the intake ducting to the face appeared to be the strongest driver in the performance of the auxiliary ventilation systems studied. It was also noted that when the discharge end of the intake ducting to the face does not exceed 7 m, there were faster purging rates of methane at the face and the efficiencies of the overall auxiliary ventilation system were greater than 50%. These findings are very important in underground coal mining in North America as they will assist to avert calamities, such as the Westray coal mine disaster in 1992 which resulted from the explosion of methane gas, by identifying which components of the ventilation system need special attention to create safe working conditions underground."

Jan 1, 2003

By Jeff Peterson, Alastair Grogan

During the winter of 2001/2002, a number of seismic exploration projects were carried out in the Mackenzie River Delta area of the Northwest Territories, in Canada. The purpose of the seismic projects was to identify potential drilling targets for subsequent drilling programs, using explosives as a seismic source. Recent changes to fisheries regulations meant that blasting under lakes, the Mackenzie River and offshore from the delta, was not allowed to induce water overpressures in excess of 100 kPa in these water bodies, and that a water overpressure monitoring program had to be conducted to confirm that this requirement was being met. This paper describes the water overpressure monitoring program on one of the exploration projects, presents the results of the monitoring, and discusses the challenges of carrying out this work in the middle of an arctic winter.

Jan 1, 2003

By Doug Halbe

?Many are called, but few are chosen.? The biblical adage applies not only to life, but also to hydrometallurgical processes. There have been, in the past, many outstanding successes with new processes ? and also some dismal failures. What are the odds of success for a new process? When there have been problems, why? What can you do to make sure these problems don?t occur with your process? What effect will a slow startup have on project economics? How do financial institutions ? the people who loan your company money for the project ? feel about new processes and why? Is it possible to predict or estimate the time required to reach design parameters?and if so, how do you sell this estimate to management ? and financial institutions? Probably most important ? when do you start thinking about the answers to these questions?

Jan 1, 2003

By K. G. Lomberg

The integration of various highly sophisticated IT applications has been implemented at Bafokeng Rasimone Platinum Mine, a new platinum mine in the Anglo Platinum Group. This system is required to assist with compiling the necessary geological and grade information together with safety, environmental, ventilation, rock engineering and logistical constraints, to allow the design of the appropriate mining layout, to schedule this design, provide the necessary output for technical review and costing as well as budgeting to allow medium- and long-term business planning. In addition the production management and short-term planning needs must be met. This includes the plotting of all underground and surface infrastructure and excavations, giving the necessary mining and best cut instructions, daily production management, ore reserve and grade management as well as assisting with budgetary management. In addition all safety, health, environment and risk assessment requirements and legal requirements have to be met. The system at Bafokeng Rasimone Platinum Mine has met these criteria. Keywords: Platinum, Bushveld Complex, Mine Planning, Production Management

Jan 1, 2003

TasmaniaÆs mineral endowment has resulted in 600 abandoned mines. Commonly occurring sulfide minerals such as pyrite and pyrrhotite can generate acid drainage and also mobilise heavy metals. Due to the StateÆs steep topography and high rainfall the risk to water quality in the receiving environments is significant. Surface waters impacted by abandoned mine sites typically showed high sulfate and metal distribution at pH range of 2.0 to 5.0. The impacted waters generally showed metal distribution in the high acid/extreme metal to low acid/low metal range. A similar trend was shown by sulfate distribution. Elevated levels of metals and sulfate downstream from several abandoned mine sites indicated that active sulfide oxidation is occurring and these sites may be potential point sources of metal pollution in the receiving environment. High correlation between metal and sulfate distribution suggests that sulfate distribution in surface waters may be used as a cost-effective investigation tool for preliminary assessment of acid drainage.

Jan 1, 2003

Vibrations are of concern not only for the safety of surface structures but also for the stability of underground openings. A number of parameters affect the intensity of vibration in underground openings due to blasting in adjacent opencast mine viz. total explosive weight detonated in a round, maximum explosive weight per delay, propagating media, depth of cover, RMR of the roof rock, age of the underground openings etc. Although a few researchers have tried to study the impact of parameters stated above, the impact of initiation sequences on generation of vibration in underground openings due to opencast blasting has yet remained untouched. A study was planned to evaluate the impact of initiation sequences on the magnitude of vibration in underground openings due to blasting in opencast mine. Nine production blasts with top and bottom initiations were performed at Samleshwari opencast project in India and eighteen vibration data were monitored in the roof of Hingir Rampur underground colliery in both the initiation sequences. The result indicated that the vibration produced in the underground openings from bottom initiation was lower than that of top initiation.

Jan 1, 2003

By Paul Sterk

In underground mining a great deal of time, money, effort, and resources have been used in the effort to minimize blast-induced damage. This damage occurs to the back, ribs, and pillars when the energy of the explosive is released back into the rock due to over confinement or the overloading of explosives in the perimeter holes. This damage can result in roof falls, dilution of ore, excessive rock bolting, scaling, screening, shot-creteing and other safety and support issues.

Jan 1, 2003

By James A. Finch, Linda Restrepo, Mitra Mirnezami, Amy Buchanan, Maryam Hashemi

Settling rate studies on slurries from Cu/Zn flotation plants occasionally reveals two aggregation maxima at pH 8-10 and 10-12 (Figure 1). From measurements on sphalerite and silica suspensions the double maxima could be replicated. These maxima correspond to the effects of Zn and Mg ions. The aggregation mechanism of both ions is related to the formation of the corresponding hydroxide precipitate. A combination of chemical and electrostatic bridging by the hydroxides is considered to be the aggregation mechanism.

Jan 1, 2003

By F. F. Roberto, E. Kirby, A. R. Marchbank

The application of biologically assisted methods for metal extraction in the mining industry has a long history, but development of modern techniques has been relatively slow. There is, however, a resurgence of interest in the industry with the recent development of methods to successfully treat base metals concentrates. Two major pilot plant programs for treatment of chalcopyrite concentrates have been initiated in the past year and results from one are beginning to be released. This paper provides an overview of methods that have been applied in the past, from the earliest deliberate applications of the technology, through the copper and uranium heap and dump leach applications, the more highly engineered agitated tank leach gold applications and the developments currently taking place in the industry.

Jan 1, 2003

By Kang N. Zhong, Hui H. Luo, Yi H. Wei, Yu L. Wang

"More than 85% of phosphorous reserves in China occur as middle-low grade phosphate of sedimentary origin. The main gangues are dolomite, quartz, silicates, and clays. The characteristics of minerals are finely disseminated. Flotation results have shown that the floatability of apatite of this kind of ore is much worse than that of igneous and metasedimentary origin because of its high specific surface area. Although some effective depressants, such as naphthalene sulfonate and phenanthrene sulfonate, are used to decrease the MgO content in the P2O5 concentrate, its presence is still high (about 2%) in the Chinese concentrates. Meanwhile, the wastewater may cause some environmental problems. Batch flotation results and measurements of specific surface area and CO3 2- have revealed that there is a relationship between the floatability of apatite and the surface area.A two-stage flotation flowsheet, which includes a combination of direct and reverse flotation, was developed for beneficiating sedimentary phosphate ores. The direct flotation was conducted in an alkaline medium and most of the apatite and carbonate minerals floated leaving quartz and siliceous gangue in the sink. In the reverse flotation circuit, the floated product was further beneficiated in an acidic medium to eliminate the carbonate as a float product. Apart from the high quality of concentrate, the two-stage flotation also facilitated the treatment and the recycling of wastewater. A wastewater recycling procedure was developed and tested in a continuous flotation process. The key factor was the careful selection of effective and non-toxic reagents."

Jan 1, 2003

By H. Ozturk

In this paper, the computer program ‘SHAFT’ developed for estimation of support requirements for circular mine shafts is introduced. Theory of support design is based on the analytical solutions of circular excavations under non-hydrostatic loading (Detourney and St. John1), and Lame’s thick-wall cylinder theory (Timoshenko6). For rock mass strength property determination Hoek-Brown failure criterion (Hoek et al.2) is used. Mainly two types of support, concrete and steel are taken into consideration as a support member. Program is written in Quick Basic language. Input parameters of the program are shaft radius, number of zones having the same properties along the shaft depth, and depth, unit weight, horizontal to vertical stress ratio, GSI, and uniaxial compressive strength of intact rock of each zone, and compressive strength and safety factor of support member. Output of the program is the graphical representation of shaft with the required support member and thickness throughout the depth of the shaft.

Jan 1, 2003

By Torn H. Okabe

A fundamental study was conducted with the purpose of establishing an environmentally sound recovery process for recycling of valuable metals, by combining scraps containing such metals. As an example, direct extraction and recovery of neodymium (Nd) in magnet scraps was investigated by utilizing liquid metal as an extraction medium. It was found that liquid magnesium (Mg) is a suitable extraction medium and can extract Nd from iron alloys with high efficiency at around I 100 K. The newly developed extraction apparatus for Nd is a mechanically simple and static device without moving parts, where the Mg extraction medium circulates due to differences in the temperature inside the reaction vessel. This developed device can simultaneously accomplish continuous extraction of metal Nd from scraps, re-extraction of Mg from Mg-Nd alloy and the eventual recovery of pure Mg. As a result, metal Nd with 98 % purity was directly recovered from magnet scraps under certain conditions. It was also shown that the extraction agent Mg could be reused. The results of this investigation show the possibility of establishing a new process for the direct extraction of Nd in pure metal form without oxidization.

Jan 1, 2003

By Jiann-Yang Hwang

A study on microwave assisted chalcocite leaching was carried out with a microwave hydrothermal reactor. The leaching was conducted with thick mineral slurries (50-100 g/l). The leaching media is a mixed solution of CuCL2 and NaCL The investigation included the effect of leaching temperature, quantities of the minerals per unit slurry volume as well as the initial concentration of cupric ions were investigated. The results were discussed and compared with that using conventional leaching method.

Jan 1, 2003

By T. E. Wilson

The length of Alaska&apos;s coastline, combined with the presence of a significant number of fjords, encourages consideration of marine disposal of mine tailings. However, the decision-making process is complex because various factors govern the viability of the submarine tailings disposal (STD) option. An expert system, called the Submarine Tailings Disposal Expert System (STADES), was developed to help mining project planners explore the feasibility of STD. A review of the existing literature, supplemented by engineering recommendations, on the various aspects of the marine disposal of tailings formed the knowledge base for the expert system. The shell used to develop the expert system was LEVELS.

Jan 1, 2003

By Zhang Chuanfu

The fibrous nickel oxide powder was prepared by the method of chemical precipitation and pyrolysis, that is, the NiO precursor was firstly precipitated from nickel ions solution with addition of oxalate salt and then the final NiO powder was obtained by pyrolysis of the prucursor. The effects of the pH, reaction temperature, reactant concentration, addition of surfactant on the morphology of the precursor particles were investigated. The influences of the various conditions, including the temperature and time, the air flow and the speed of the temperature increase on the morphology, average size and specific surface area of the NiO particles were also addressed. The fibrous NiO particles with IOO~ 120 in axis/diameter ratio and 5.5 m2/g of the specific surface area may be produced under certain operation conditions by this process.

Jan 1, 2003

By L H. Chapman, I J. Kelso, N H. S Oliver

Utilisation of modern 3D visualisation tools, can improve our ability to correlate between different datasets, and thus to produce more accurate geological models. Here, we present an application of such techniques to the Century Zinc Deposit, northwestern Queensland, Australia. This stratiform orebody is the second largest Zn resource in the world (167.5 Mt at 8.2 per cent Zn, 1.2 per cent Pb, and 33 g/t Ag). It is hosted in the Page Creek Syncline affecting Mesoproterozoic shales and siltstones of the Wide Supersequence of the Isa Superbasin. As in other deposits, (eg McArthur River, Lady Loretta, George Fisher and Dugald River), the mineralised sequence is bound by an important regional structure, the Termite Range Fault, which partly intersects the deposit along its Eastern side. This fault is thought have been active during sedimentation and probably also during mineralisation of the lowest part of the Wide Supersequence. The anastomosing geometry of this fault system and crosscutting relationships with other NE trending structures indicate that it was reactivated several times from Mesoproterozoic to at least late Devonian times (>1000 million years in total); as a result, the ore sequence is subdivided into several fault blocks.Using two different computer modeling packages (GOCAD and 3ds max), we have reconstructed and restored the stratigraphic horizon with the highest Zn content, realised a series of isopach maps for each mine scale stratigraphic unit, plotted the three-dimensional distribution of Zn, Pb, Ag, Fe and SiO2, and have begun to evaluate the degree of correlation between thickness changes and sulphide zoning. With this approach it is possible to better understand the timing of mineralisation from a genetic perspective, because the origins of the orebody are controversial. Three-dimensional reconstruction is a vital tool for identification of syn-sedimentary and post-sedimentary fault activity. In conjunction with sulphide precipitation, these are factors that greatly influence the stratigraphic thickness distribution. Post-sedimentary deformation can be recognised directly by core logging and pit mapping, but the effect of tectonic movements during sedimentation (growth faults in particular), that represents a substantial variable when we attempt to reconstruct basin evolution, is difficult to evaluate without this methodology. The 3D models improve our understanding of the local basin architecture, identifying similar grade characteristics at different structural levels and thus suggesting that much faulting and folding are post-mineralisation events. In addition, we identified several growth faults adjacent to thickened layers, representing two possible sedimentary depocentres. These thicker domains apparently relate to the highest Pb content. If further analysis of rocks, thickness and grade distributions support this preliminary correlation, then a syn-sedimentary model for mineralisation might be applied, and would contrast with the sub-surface model for mineralisation of Broadbent et al (1998).

Jan 1, 2003