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By C. Balci

Specific energy is defined as the amount of work required to break a unit volume of rock and is used to predict the performance of mechanical miners. It is obtained from full-scale rock cutting experiments, which require large block samples, experienced personnel and expensive equipment found in only a few research centres in the world. Estimation of the optimum specific energy, at which a given geological formation is excavated at optimum cutting geometry in the most energy efficient manner, from mechanical rock properties to predict the performance/efficiency of roadheaders is the basic aim of this study. The mechanical rock property tests require only core samples, which are easier to obtain and to test. In this context, full-scale rock cutting tests are performed on 23 different rock, mineral and ore samples including sandstone, claystone, tuffite, chromite, trona and copper collected from some operating mines in Turkey. The optimum specific energy values are obtained for each sample. Physical and mechanical property tests are performed on the core samples obtained from the same samples to determine uniaxial compressive strength, indirect (Brazilian) tensile strength, static and dynamic elasticity moduli, Schmidt hammer rebound values, density, and Cerchar abrasivity index. The relationships between the optimum specific energy and the mechanical rock properties are analysed using statistical methods. The results indicate strong relationships between the optimum specific energy and the mechanical rock properties. The strongest relationships are found by using uniaxial compressive strength and tensile strength. The performance models developed in this study are in good agreement with the empirical models previously developed for roadheaders and can be used reliably for prediction purposes. Keywords: Mechanical excavation, roadheader, performance prediction, rock cutting, optimum specific energy, mechanical properties of rocks.

Jan 1, 2004

By S. Sun

Recent studies on the physico-chemical properties of molten slags and oxide solid solutions of interest is reviewed. The review covers redox and phase equilibria in slags, viscosity, diffusivity, electrical conductivity, kinetics of interfacial reactions between slags and CO-CO2, interfacial properties and phenomena. Some highlights from ongoing work on modelling phase diagrams, component activity, viscosity and electrical conductivity of multi-component slags will be presented and results compared with published experimental data on slags with or without suspended solid phases.

Jan 1, 2004

By T. Watanabe, M. Nakagawa, K. Kimapong

Ultrasonic wave was irradiated on metal surface in water to introduce compressive residual stress. The ultrasonic wave that was oscillated with 19.5 kHz ultrasonic transducer and amplified with a step type horn was irradiated. Slight plastic deformation occurred at the surface region of pure metal such as Cu and compressive residual stress was introduced. It seemed that the plastically deformed depth from the metal surface corresponded approximately to the depth of introduced residual stress. The higher compressive residual stress could be introduced into the surface of Cu-Zn brass and SUS304 stainless steel because work-hardening was simultaneously induced to those alloys. Furthermore, since martensitic transformation was induced by the plastic deformation in the case of SUS304, the compressive residual stress could be introduced more deeply into the surface region. The residual stress of SUS304 reached to the maximum value of 574 MPa by irradiating for 5min.

Jan 1, 2004

By Gerrit V. R. Goodman

A laboratory study assessed the impacts of water spray pressure, face ventilation quantity, and line brattice setback distance on respirable dust and SF6 tracer gas concentrations around a continuous mining machine using a sprayfan or directional spray system. Dust levels were measured at locations representing the mining machine operator and the standard and off-standard shuttle car operators, and in the return airway. The results showed that changes in all three independent variables significantly affected log-transformed dust levels at the three operator sampling locations. Changes in setback distance impacted return airway dust levels. Laboratory testing also identified numerous variable interactions affecting dust levels. Tracer gas levels were measured on the left and right sides of the cutting drum and in the return. Untransformed gas levels around the cutting drum were significantly affected by changes in water pressure, face ventilation quantity, and setback distance. Only a few interactions were identified that significantly affected these concentrations. Gas levels in the return airway were grouped by face ventilation quantity. Return gas levels measured at the low curtain quantity were generally unaffected by changes in water pressure or curtain setback distance. At the high curtain quantity, return airway gas levels were affected by curtain setback distance. A field study was conducted to assess the impact of these parameters in an actual mining operation. These data showed that respirable dust levels may have been impacted by a change in water pressure and, to a lesser extent, by an increase in curtain setback distance. A series of tracer gas pulse tests were also conducted during this study. The results showed that effectiveness of the face ventilation was impacted by changes in curtain flow quantity and setback distance. Laboratory testing supported similar conclusions.

Jan 1, 2004

By S. Sun

The equilibrium distribution of Cu, Fe and Ni between Cu-Ni-Fe mattes and Pt alloy was measured as functions of the sulphur partial pressure (pS2), oxygen partial pressure (pO2),temperature and Fe content of the matte. The distribution ratios of Cu, Fe and Ni between matte and alloy were independent of oxygen pressure when the pS2was fixed at 2.5x10-5atm and pO2was varied between 10-15and 10-12atm. The distribution ratio of Cu, Fe and Ni increased as the sulphur partial pressure increased. The Cu and Ni distribution ratios decreased with increasing temperature and the Fe distribution ratio increased slightly over the temperature range of1350?1500°C. For mattes where the proportions of Cu and Ni were kept constant, the distribution ratio of Cu increased as the Fe content in the matte increased. The Fe and Ni distribution appeared to be independent of the iron content in the matte and had a value of 1.2 and 1.6 respectively. The activity of Cu, Fe, Ni in the matte was calculated using a regular solution model for solid Pt-Fe-Ni-Cu alloy. The activity coefficient of Cu, Fe and Ni decreased as pO2and pS2increased.The activity coefficients also appeared to be independent of the Fe content and temperature over the range of 36 to 54 wt% iron and 1350 to 1500°C respectively. Keywords: activity, alloy, matte, thermodynamics

Jan 1, 2004

By M Pizey, C Ross

Rehabilitation approaches, methods and outcomes have changed markedly over the last 100 years, and especially over the last 20 years. Alluvial gold dredges have moved from creating a legacy of boulder fields and ponds to radiata pine plantations and highly productive dairy pastures. The rehabilitated farmland has reduced flood risk, improved drainage and efficient paddock design. The next challenge is to include areas of environmental diversity in these projects, for example, shelter belts, patches of native trees, and wetlands that were part of the original landscape.   West Coast coal mines have also come from a legacy of leaving it to nature to rehabilitate damage by mining to establishing native ecosystems or plantation forests. Developments in techniques at Stockton Mine are used to illustrate the changes in approach to rehabilitation of native forest and tussock heathland ecosystems. The proposed Cypress Mine will adopt a full range of avoidance, remediation through rehabilitation, and off-site mitigation techniques in a æthree-prongedÆ approach.   We propose a coordinated extractive industry approach to mitigate for the impacts of mining on native ecosystems and achieve nationally important conservation benefits that individual projects cannot afford. This approach is particularly beneficial in New Zealand, as our native ecosystems must be actively managed to conserve native plants and animals. Currently, some important species and ecosystems are not being actively managed for conservation.

Jan 1, 2004

A physical modelling study has been carried out to simulate the slag-metal dispersion induced by a high-strength bottom gas injection. Water and kerosene were utilized to simulate metal and slag respectively. A water model of CLU (Creusot-Loire Uddeholm) vessel was used with three different nozzle orientations, namely, off-centre, triangular off-centre and centre. The gas flow rates changed from 0.00599m3/sec to 0.01081m3/sec. Height of heavy and light phases was kept fixed at 0.23 m and 0.02 m respectively. The dispersed phase holdup was determined at various axial and radial distances, gas flow rates, and tuyere configurations. The observations revealed that at a fixed gas injection rate, as the vertical distance increased in the centerline, straight off-centre orientation resulted in greater dispersed phase hold up values than those of the centre configuration and the triangular off-centre orientation. The dispersed phase holdup was found to increase with gas injection rate and decreased with axial distance. The variation of the dispersed phase hold up with the dimensionless axial distance and the gas injection rate was correlated by using the Modified Froude Number. The experimental values of the dispersed phase holdup were found to be in good agreement with the correlated values obtained from the modelling equations. The findings of the present study may be utilized in the ferroalloy refining vessels in terms of designing tuyere locations for optimum processing conditions.

Jan 1, 2004

By A B. Richards

Effective control of blast vibration and flyrock requires that significant factors be identified and quantified, that the blast be designed to ensure both blasting efficiency and compliance with applicable limits, and that the blast design be effectively implemented by field personnel. Significant factors contributing to ground vibration and airblast are: charge mass; distance and direction relative to the blast; drilling design: burden, spacing; stemming height and material type; hole diameter and depth; and initiation sequence and direction.In addition, airblast may be strongly influenced by shielding and meteorological conditions. Ground vibration is also influenced by the transmission characteristics of the ground and soil. Flyrock throw is determined by charge mass, burden, stemming height, blasthole diameter and depth. The contribution of each of the factors has been quantified and models developed to enable the environmental outcomes of blast design to be predicted. Environmental blast design is necessary to ensure compliance with regulatory limits and the implementation of æsafeÆ exclusion zones for flyrock clearance. This paper discusses the models used for environmental blast design and demonstrates the often significant effects that lapse during implementation of the design can have on predicted outcomes. In practice, drillers and shotfirers are sometimes confronted with situations that require modifications to the blast design to cope with the real site situation. Methods are presented that may be used by drillers and shotfirers to evaluate the effect of these modifications, the tolerances that must be reached during their work practice and checking procedures, and the consequences of their actions.

Jan 1, 2004

We had a cold, gray winter here in Kansas City and I spent a lot of time watching out my den window at the squirrels and birds trying to get by in the lousy weather. I remember too well working in the cold, loading shots. I was frostbitten several times since I couldn’t tie in MS connectors with gloves on. Those old connectors had a piece of detonating cord on either end of a metal tube that held the delay and you tied them to the trunk lines with square knots. Doing this on a “warm” day in Alaska or Montana shooting ditch for a pipeline could be a frosty experience. Also remember how hard it was to connect up electric caps (detonators to you new guys) in the cold. Now I don’t want you to feel sorry for me ‘cause I suspect most of you younger fellows have also paid your dues in the cold and for that matter in the heat too. Wowee, the heat at the bottom of a Chicago dolomite quarry in August was enough to fry the brains of all that were there. Maybe that’s why the third deck of my brains doesn’t exist.

Jan 1, 2004

By W. W. Rudolph, L. N. Trevani, P. R. Tremaine

UV-visible spectroscopy, Raman spectroscopy, and vibrating tube densimetry have been used in our laboratory to determine equilibrium constants of aqueous species at temperatures as high as 325 °C. The UV-visible and Raman spectra of solutions containing metal complexes and ionized acids or bases can be used to yield formation constants by applying curve fitting methods to resolve the contribution of each species. Colorimetric pH indicators identified by Johnston and coworkers at the University of Texas (Austin) provide an alternative means of determining ionization constants and the pH of complex mixtures. High precision density measurements over the same range yield standard partial molar volumes, which are key parameters for "equations of state" for aqueous species. Examples are given for the copper-ammonia system, simple carboxylic acids, and the iron-sulphate system.

Jan 1, 2004

By Li. Jiarong, Zuojian Liang, Qingyan Xu, Baicheng Liu, Shizhong Liu, Hailong Yuan

Single crystal solidification of turbine blades is a key technology for the production of reliable and high efficiency gas turbines. The solidification process of single crystal investment castings causes a number of problems that have to be solved such as the increase of casting defects and complexity of production process. Computer modeling and simulation is helpful to predict the defects and improve the process design. In the paper, a mathematical model for three dimensional simulation of solidification and single crystal growth of investment castings was developed based on CA, mechanism of crystal growth and basic transfer equations such as heat, mass transfer equations. Many factors including constitutional undercooling, curvature undercooling and anisotropy, which had vital influences on microstructure evolution, were considered in the model. Temperature, crystal growth interface and structure defects of investment castings of single crystal superalloy were investigated at withdrawal rates of 4.5mm/min and 7mm/min. Simulated results showed that microstructure evolution and structure defects were predicted reasonably and calculated results were coincident with experimental ones. The study indicated that three dimensional solidification simulation technique is a powerful tool for understanding the fundamental of solidification and the formation of structure defects in single crystal investment castings and finally for optimizing process design.

Jan 1, 2004

In September 2003, a test was conducted to see if a115-mm- (4.5-in.-) diam Mocap Vari-Stem blasthole plug could improve the pattern of explosives using different top stemming material. The test took place at the J.S. Faulkroad and Sonsstone quarry in McCalisterville, PA. The test consisted of a production stone blast. Half of the holes were stemmed with standard crushed stone. Two-thirds of the remaining half were stemmed with Vari-Stem plugs and crushed stone. And the remaining one-third of the second 50 percent was stemmed with Vari-Stem plugs and only drill cuttings.

Jan 1, 2004

By D. Ouellet, G. Gagnon, B. Simser, V. Falmagne

The mining sequence at Noranda’s Bell- Allard mine calls for two mining fronts retreating toward a central pillar known as the Retreat Zone between pyramids A and C. It is clear from numerical modelling and rock mass characterization that the induced stress level in the pillar will exceed the rock mass capacity. A mining plan was developed including the redimensioning of stopes in the Retreat Zone, additional ground support and instrumentation in order to ensure the safety of the workforce and to maximize ore recovery while minimizing production delays. The mining strategy consists in allowing the rock mass to fracture and fail progressively while maintaining control of the existing openings with the appropriate support. A systematic analysis of rockbursting and caving hazards was conducted for all accesses and stopes in order to plan ground support and instrumentation needs.

Jan 1, 2004

By P. Mpofu

In this work, the modification of interfacial chemistry of colloidally stable kaolinite clay dispersion has been carried out to improve its flocculation performance and dewatering behaviour. Synergistic action between dispersion pH, hydrolyzable metal ion and high molecular weight polymeric flocculant structure type (anionic polyacrylamide-acrylate copolymer (PAM) and non-ionic polyethylene oxide (PEO)) was found to play a pivotal role in inter-particle bridging, the enhancement of the settling rate and extent of consolidation of the pulps. Flocculation with PEO led to higher settlings rates in acidic than alkaline pH, whilst for PAM, the maximum dewatering rate was achieved in the neutral pH range 6 - 7.5. Upon shear, the PEO flocculated pulps showed dramatic improvement in consolidation to 40 wt%, the extent of which was greater at lower than high pH values. For PAM-based pulps were however, not shear-responsive, lower sediment solid contents of 15 - 23 wt% was observed between pH 3 and 11. Hydrolysable metal ions, Mn(II) and Ca(II), used respectively at pH 7.5 and 10.5 in conjunction with PAM and PEO, significantly enhanced the settling rates and consolidation of the pulps. The findings exemplify the strong links existing between pH-mediated particle surface chemistry. polymer structure-conformation, inter-particle bridging and dewaterability of kaolinite dispersions.

Jan 1, 2004

By Jaco J. van Vuuren

Modikwa Platinum Mine, in the Eastern Bushveld of South Africa's Limpopo Province, is a new operation employing a hybrid mining method where mechanised methods are used for the main developments and the narrow, 60cm reef is conventionally stoped using a down-dip conventional mining method. Throughout the mine, the hanging wall immediately above the reef comprises 3 jointed and laminated layers of varying thickness, commonly known as the triplets, below a non-cohesive leuconorite parting plane. At North shaft, using pre-stressed standing support and mechanically anchored rockbolts, it was found difficult and hazardous to hold all three triplets in the hanging wall, however bringing them down caused a significant increase in dilution and therefore cost of mining. A novel solution was conceived whereby two of the triplets are kept up using short, stiff resin anchored rockbolts installed systematically within 0.5 m of the face. This resulted in both safety and productivity benefits. The rockbolts create a stable and safe hanging wall and allow the mine to extract UG2 reef more economically. New drilling equipment, developed locally from available drilling technology, can be operated from a safe position, and in situ tests and measurements are made to confirm effective support. The technology and underlying concepts were successfully tested in a trial stope prior to rolling out the new support system across all the stopes at North Shaft. This has involved an extensive training programme to ensure that the rockbolt system is installed correctly and that the conditions are appropriate for this technology. The paper describes the motivation behind the project, the underlying technology and its application to Modikwa, and the benefits now being realised.

Jan 1, 2004

By B. D. Pandey, D. Bagchi, Premchand

During the separation and recovery of metals from the ammoniacal leach liquor of Indian Ocean nodules by solvent extraction-electrowinning (SX-EW) in close-loop operation, the copper electrolyte containing ~40g/L Cu, 20 g/L Ni and 180 g/L sulphuric acid is bled-off to control the impurities. The recovery of copper and nickel as powders has been examined from the copper bleed solution following partial decopperisation, crystallization of mixed sulphate of the two metals and aqueous hydrogen reduction. From the dissolved sulphate solution containing 17.68 g/L Cu, 18.83 g/L Ni and 0.03 g/L Fe, the copper powder was precipitated at initial hydrogen pressure of 26 bar in an autoclave in 90 min at 140 °C. The residual copper from the spent solution was removed as sulphide and nickel powder was then recovered (99%) in two stages from a solution of pH 4.5 at 40 bar pressure and 190 °C. However, 98% nickel recovery in one stage was achieved when hydrogen reduction was carried out from an ammoniacal solution in the pH range 9-11. Copper and nickel powders were produced from the bleed solution with acceptable purity and specifications suitable for P/M applications.

Jan 1, 2004

By J. Kerr

The first stage of the development of a new modified 201-type low nickel austenitic stainless steel is described in this paper. The alloy is intended for use as a structural alloy, and so requires a yield strength >400MPa as well as acceptable weldability and toughness. The low nickel content will give a lower material cost in comparison to more conventional austenitic grades, and the processing route is required to be similar to that of Type 304 to keep the processing cost low. The base alloy was designed using empirical methods developed for stainless steel, and the properties of the base alloy were verified using a range of small-scale melts. The base alloy had a 0.2% proof strength of ~320-400MPa, and so it is planned to use V additions of ~0.15% to bring about precipitation strengthening in the hot rolled condition, so raising the alloy?s proof strength above the 400MPa minimum.

Jan 1, 2004

By Chuck Edwards

Whatever your opinion of the validity of the scientific case for global warming, or of the wisdom of the Kyoto Protocol, it would seem judicious to err on the side of caution and try to sensibly minimize global climate change. To this end, we should take prudent steps to minimize our emission of greenhouse gases. Cameco is the world's leading supplier of uranium for use as fuel in nuclear power plants. Cameco’s uranium production fuels nuclear power plants in 16 countries. Nuclear power plants generate clean electricity without greenhouse gas emissions. This presentation describes the role that uranium and nuclear power can have in meeting the growing demand for electricity and at the same time combating global climate change.

Jan 1, 2004

By Masaki Kitazume

Deep mixing method, in-situ admixture stabilization technique, has been developed and adopted for on land and marine construction works in Japan. The geotechnical design procedure of the method has been standardized in Ministry of Land, Infrastructure and Transport Government of Japan for port and harbor facilities, which includes the block type and wall type improved grounds for foundation stability, settlement reduction purpose. This procedure is based on the allowable stress concept, in which the induced stresses within the improved ground are confirmed to be lower than the allowable strength in the internal stability calculation. This procedure has been cited by several organizations to establish their standards. The Ministry has a plan to introduce a reliability based design for marine construction works in 2006, in which the design procedure on DM improved ground will also be modified to the reliability based. In the new design procedure, the average and variation of soil parameters and external loads are incorporated by partial safety factors to investigate the stability of improved ground. According to the plan, the author has been studied the design procedure and the magnitude of partial safety factors, and has established a preliminary draft of the standard. This draft will be brushed up through comparing the current design procedure. In this article, the design concept and design procedure of the method are briefly described.

Jan 1, 2004

By S. A. Shuey, P. Taylor

The recycling of electronic waste (e-waste) tends to be a rather complex undertaking when considering the intimate bonding of materials in the average printed circuit board. The development of a recycling process is further complicated when considering the wide variety of products being generated under the heading of “electronics” as well as the constant change in materials of construction coupled with the speed at which electronics are changing. CSM researchers have undertaken a survey of the current state of pyrometallurgical processing of e-waste. This base-line will set the stage for the development of new recycling technology at CSM.

Jan 1, 2004