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By L. Y. Sadler

This report summarizes the findings of a 9-yr research program, sponsored by the U.S. Department of Energy and conducted by the Bureau of Mines, to evaluate refractory liner materials for coal gasifier reactors. Commercially available refractories were exposed to coal gasifier reactor environments, reproduced in the laboratory with a high-temperature, high-pressure test facility, followed by extensive postexposure evaluation. Thirty-six castable or gunnable refractories and cements and 24 refractory brick were evaluated. The behavior of castable refractories reinforced with stainless steel fibers was also examined. Gas environments that were evaluated included steam, H2, CO2, CO, and typical high-and low-Btu gas mixtures. Exposure pressures ranged from 100 to 1,000 psig, temperatures from 5000 to 1,1000 C, for periods from 50 h to 2,000 h. In some exposures, sodium and/or potassium hydroxide were introduced in order to simulate a high-alkali environment. It was found that intermediate-and low-alumina refractories produced from domestically available raw materials, rather than high-alumina refractories produced from imported raw materials, gave the best service as liner materials and that alkali attack was probably not a serious problem with most refractories. Based on the results of this program, good choices of refractory liner materials for gasifier reactors can be made.

Jan 1, 1984

Experimental studies on viscosity of titanium bearing slags have been reviewed and the assessed data were used in extending the capability of the structurally related viscosity model for silicate melts, developed by the present authors. Experimental data on ternary and higher order systems containing CaO, MgO, MnO, FeO, Al2O3, TiO2, Ti2O3, SiO2were assessed and used. The newly extended viscosity model represented the viscosity behaviour over broad temperature and composition ranges. The structural role played by TiO2and Ti2O3in silicate network structure is discussed with respect to their effect on viscosity of melts. Keywords: viscosity model, TiOx containing silicate melts, silicate network structure.

Jan 1, 2004

By Boleslaw A. Klosinski

Drilling of a pier hole is accompanied with stress releasing in the surrounding soil and often with loosening of soil at the pier base. In effect the drilled piers are more deformable than driven piles of comparable dimension. The bearing performance of a pier may be considerably improved by properly executed base grouting. Various techniques of base grouting are used; many of them were described by Bruce (1986). The grouting devices are often placed within the pier. Alternatively the soil at or under the base is treated by cement or chemical grout. Preloading of the base subsoil by use of a special grouting cell is considered as the most effective way. Treatment of the ground below pier base with cement or chemical grout may be also useful. It may be performed immediately after the pier construction or during service, as a measure for increasing the pier capacity.

Jan 1, 1995

By Joel Moskowitz

In 1990, the United States General Services Administration (GSA) issued a contract for design and construction of a new federal court building in New York City. Mueser Rutledge Consulting Engineers (MRCE) served as Project Geotechnical Engineers. The project site is in the historic government district at Foley Square. It is surrounded by the New York County Courthouse to the west, an existing federal prison building and federal courthouse across Pearl Street to the south and southwest, an office structure to the north, and a residential tower to the east. The interior of the site was crossed by streets which have now been demapped. As with many urban sites, this site was previously occupied by tenement buildings or industrial structures demolished near the turn of the century. Remains of old building foundations were exposed during construction excavation. In addition, buried fuel oil tanks servicing the adjacent courthouse were removed and the usual assortment of urban utilities had to be relocated for the new building foundations. Ground surface elevations vary from about 4.5 to 6 m above the local Mean High Water Datum Plane.

Jan 1, 1996

By J. M. Benson

Metal powder compaction offers unique advantages in the manufacture of net-shape components using techniques such as laser sintering, conventional press and sintering, metal injection moulding, direct rolling, direct forging, and hot isostatic pressing. If the output from the primary metal production process is in powder form, then considerable cost and energy savings can be realized by direct conversion to semi-finished or final shapes. This possibility exists for titanium and possibly also for Ta, Zr, Hf, and Nb metals. However, these attractive benefits are associated with some significant risks. The high surface-to-volume ratio of powder particles coupled with the reactive nature of these metals means that special care must be taken when handling them. Powder explosions are unfortunately still a regular occurrence internationally and these often result in serious injury and loss of life. Even seemingly 'safe' compounds such as sugar, flour, and grain can be extremely hazardous when handled or milled and dust clouds are produced. In addition, exposure to airborne particles can have adverse effects on the human body, especially when particles are inhaled on a regular basis. Furthermore, the medical consequences of these are not fully understood, especially in the case of nanoparticles. The impact is often not observed immediately and debilitating illnesses may emerge only years or decades later. As far as is known, there are no South African guidelines for handling of metal powders. This paper attempts to provide an awareness of the risks associated with metal powders (including those produced indirectly by other metalworking/finishing operations) as well as some guidelines for their safe handling, based on international best practices.

Jan 1, 2012

Neither the copper orebodies nor the zinc-lead-silver orebodies at Mount Isa were formed syntectonically as has been claimed for the last 20 and 10 years respectively. Both orebody types were cogenetic, coeval, and formed early during the sedimentation and diagenesis of the host formation. The copper orebodies are interpreted as having formed diagenetically at hand specimen scale, syngenetically at formation scale. The zinc-lead-silver orebodies are interpreted as having formed primarily by sedimentary means at both hand specimen and formation scales.

Jan 1, 2000

By David R. Beadman

The Fleming method is widely used for the analysis and prediction of single pile behaviour under maintained loading. The method does not distinguish between bored and driven piles. Driven piling avoids the need to dispose of spoil from the pile installation and is therefore becoming increasingly attractive. This paper considers the theoretical effects of the possible preload at the base of a driven pile after installation, using the hyperbolic functions as defined by Fleming. The Fleming method is reviewed and the equations and analyses are adapted, using spreadsheets, to allow for a possible preload. The simplifying assumption of the effect of the elastic compression of the pile is also reviewed and a more analytical method adopted to assess the elastic compression. Some driven pile test data is analysed to consider the possible effects of the preload on the performance of a driven pile and to test the theoretical relationships that are developed in the paper.

Jan 1, 2006

By Behrouz Tehrani

The size, complex issues, and requirements to construct large number of tunnels, for a single project, expeditiously, and without exceeding the overall project budget, a program Construction Management (CM) team is highly recommended to be selected early during design process to provide guidance/direction relative to contract packaging and scheduling. This paper is not focused on the project itself, however, the emphasis is on experiences gained from the project. Wishing that some of the strategies described in this paper will be of value to owners of underground project.

Jan 1, 2008

By M. Reuter, U. Boin

The target of the current metallurgical industry is to recycle and utilize all their by-products, so as to close the sustainable production loop. Slags are the important wastes and by-products of metallurgical industry, which have been treated, recycled and used worldwide. The present paper summarizes the current status of utilization of the various slags from ferrous and non-ferrous metal production, as well as waste incineration, and recycling of salt fluxes in secondary metal production. In addition, the environmental issues of the metallurgical slags are addressed. The metallurgical oxide slags have stone-like properties and, thus, their major applications are in civil engineering field. The slags should be recycled, modified and processed in a proper way, by taking the environmental impact into consideration. With the treatment of salt slags for melting aluminium scraps, as an example, the recycling and elution properties of the salt slags are discussed. Our research indicates that the viscosity of the salt flux is increased with addition of non-metallic components, that a certain percentage of fines remain in suspension, which determines the viscosity, affecting the settling of heavier materials. High slag viscosity will lead to more fine aluminium metal entrapped in the salt slag (may also be seen as a high temperature slurry), and thus increase the load of salt slag recycling. Keywords: recycling, environment, metallurgy, slags, fluxes, salts.

Jan 1, 2004

By Paul Staples, Chris Morley

"The development of the Cerro Verde, Amplats Mogalakwena and Boddington projects over the last few years has helped to establish the use of high pressure grinding rolls (HPGR) in comminution circuit designs in large-scale hard-rock applications. The increasing acceptance of this innovative and sometimes controversial technology has had the natural effect of prompting many other new projects to examine HPGR as an alternative to the established, usually SAG-based, comminution circuit design approach.At the current stage of development of the technology, HPGR-based circuit capital costs are generally higher than for the equivalent SAG-based circuit, so that HPGR must offer sufficient operating cost benefits to offset the additional capital costs over an acceptable pay-back period. It is usually necessary to undertake comprehensive project-specific trade-off studies to quantify this effect.This paper describes the processes involved in the execution of a typical SAG-HPGR trade-off study, from the preliminary assessment of ore characteristics and project criteria, through testwork, circuit modelling, equipment selection and cost estimates, to a project-economics comparative assessment of the options. The trade-off study determines both the technical feasibility of the respective technologies and their commercial viability in the given project setting.The paper concludes with a cautionary note to the effect that, while HPGR has many potential benefits, it is not a panacea, and that, for some ore types and project conditions, the more established conventional technologies are often more appropriate."

Jan 1, 2010

By Jamal Rostami, Richard Kastner, Ahmad Ramezanzadeh

Improving the accuracy of the performance prediction models for hard rock Tunnel Boring Machines (TBMs) is important in estimation of the schedule and cost of tunnelling in related projects. The effects of rock mass on performance of TBMs has been studied extensively, yet due to the complex nature of the process, impact of many parameters influencing machine advance rate are not very clear and there is still room for improvements. More accurate estimates can be obtained by better understanding of operating parameters in various geological conditions and can lead to matching machine specifications with job conditions, optimizing machine performance, and avoiding long delays and downtime for increased productivity. This paper will offer review of two case histories including Queens Water tunnel in New York and KCRC project in Hong Kong. The analysis of the available field data, including the geological back mapping and results of laboratory testing of rock mechanical properties, machine operational parameters and achieved rate of penetration will be presented. This includes statistical analysis of available field data to provide a better understanding of the influence of rock mass properties on performance of hard rock TBMs as well as related formulas to improve performance estimates.

Jan 1, 2005

By John W. M. Lambert

This paper describes the execution and the results of a new method to seal off leaks in water retaining constructions. The new method, called BioSealing is based on activating the bacteries, present in soil and groundwater. The method was tested under field conditions in 2004 and applied at the HSL aqueduct of the 'Ringvaart Haarlemmermeer' in 2005.

Jan 1, 2006

By James W. Marold

Tunnel and shaft plugs have been designed to assist in construction of new and rehabilitation of existing tunnels and shafts. Tunnel plugs have been used to provide construction access for side by side tunnels, separation of raw and treated water, and to allow operation of one tunnel during construction of a nearby tunnel. Shaft plugs have been used to seal up surface openings to tunnels and to prevent seepage of water to the surface through adjacent tunnels or shafts. The design construction details of tunnel and shaft plugs are provided. Typical examples of tunnel and shaft plugs are provided.

Jan 1, 2008

By R Sridhar, M Fe, W G. Bacon

The problems of magnetite build-up have plagued the non-ferrous pyrometallurgical industry for many years. To better understand these problems, a study was undertaken to determine the thermodynamic variables that affect the behaviour of magnetite under different smelting conditions. Equilibration studies were performed in the nickel smelting systems of matte-gas and matte-slag(silica saturation)-gas. The relationship of thermodynamic variables such as temperature, sulphur and oxygen partial pressure and matte grade on iron and magnetite activities were calculated and the significance on smelting parameters such as metal losses and partition coefficients were defined. The experimental data from this study were employed to develop practical methods which could be used to control the build up of magnetite, as well as to obtain additional metallurgical benefits. In general, a lower sulphur partial pressure and higher temperature operation was shown to enhance the metallurgical benefits of nickel smelting by decreasing the magnetite activity. Operating in this manner can also have added benefits such as higher metal recoveries, more efficient vessel utilisation and efficiency and lower smelter emissions at equivalent or higher primary furnace matte grades.

Jan 1, 2000

By J S. J van Deventer

Geopolymerisation is a new technology that processes and transforms aluminosilicate minerals into mechanically strong and chemically stable products. In this investigation, minerals such as fly ash and kaolinite were used as the solid raw materials for geopolymerisation. Inorganic salts were added to the geopolymeric pastes to simulate ionic contamination during processing for building and construction applications. The resultant products were examined and characterised physically. It was found that the early strength development of geopolymeric pastes could be changed according to the nature as well as the extent of the contamination. At a small dosage, the effect of the contamination on the early geopolymeric system depended heavily on the nature of the artificial surfaces that were created in the geopolymeric solution through the addition of the chemical additives. For example, the samples containing MgCl2 and Mg(NO3)2 had shown the same yield stress developments due to the similar surfaces that were formed. The cations of these salts were expected to hydrolyse and form magnesium hydroxide precipitates immediately after the addition to the early geopolymeric systems. The calcium cations of CaCl2 also precipitated upon addition, but the nature of the surfaces of these hydroxides was quite different to those of the magnesium hydroxides and gave rise to different yield stress development. The samples that contained the insoluble salts (in water) demonstrated different yield stress development when compared to each other because of the different nature of the additive surfaces that were exposed to the geopolymeric solution. These results suggested that heterogeneous nucleation could be responsible for the change of the rheological behaviour upon inorganic salt addition. When the extent of the ionic contamination was large, the anions released from the insoluble salts (in water) changed the nature as well as the concentration of the geopolymeric solution and the setting processes were retarded. Oxides, in general, behaved very differently from other salts, indicating the uniqueness of the oxygen anions in a system rich in hydroxyl and silicate anions. The inorganic salt contamination in geopolymers did not show any significant signs of structural change according to the XRD diffractograms collected. The seven-day compressive strength was not lowered by the inorganic salt contamination and it could sometimes be beneficial to the product performance, for example, an increase of 20 MPa was induced by the addition of calcium oxide. Inorganic salts as chemical additives have demonstrated the potential to modify setting times of geopolymers without sacrificing much of the productsÆ strength and integrity.

Jan 1, 2000

By S. Fletcher, C. Calle, K. Constanti-Carey, R. Ruzbacky, M. D. Horne

Laboratory test-work has established that two classes of redox catalysts based on anthraquinone and bipyridinium derivatives are effective in accelerating the rate of removal of metallic iron from reduced ilmenite (RI) in the aeration step of the Becher process. Two water-soluble anthraquinone derivatives are efficient: 9,10-anthraquinone-2,6-disulfonicacid, disodium salt (catalyst AQ-2,6) and 9,10-anthraquinone-2-sulfonic acid, monosodium salt(catalyst AQ-2). When 0.2 per cent w/v of either was added during aeration the rate of metalliciron removal was accelerated by two to three times. Furthermore, the addition of either compound resulted in magnetite (Fe3O4), the iron oxide phase preferred in commercial practice, being formed. However, both AQ-2,6 and AQ-2 were rapidly lost from solution during aeration although their catalytic activities persisted even when their concentrations in solution were low(<0.05 per cent w/v). The negatively charged anthraquinones were lost from solution most probably by adsorption onto the magnetite that has a net positive charge at the pH values encountered during aeration. To address this problem, the catalytic activities of positively charged bipryridinium derivatives were tested. Two water-soluble bipyridinium compounds, paraquat (1,1’-dimethyl-4,4’-bipyridinium dichloride) and diquat (6,7 dihydrodipyrido [1,2-a:2’,1’-c] pyrazinediiumdibromide), were found to significantly accelerate the rate of removal of metallic iron from reduced ilmenite, and both gave magnetite as the oxide product in the laboratory tests. Moreover, recycle tests showed they were not lost from solution as quickly as were the anthraquinone derivatives. Results in larger scale plant laboratory reactors also showed a significant increase in aerationrates when diquat was added and magnetite was again the oxide formed. However, the oxygensupply to the reactors was insufficient to achieve the maximum effect of the catalysts on theaeration rates. The limited supply of oxygen in a full scale aerator may prevent the application ofthe catalysts in a commercial Becher operation. Keywords: Becher process, aeration, anthraquinone, bipyridinium, redox catalyst, reduced ilmenite

Jan 1, 2003

By Simon St J Tose

The objective of this paper and presentation is to review the different criteria and methodology used by AEL and other organisations to create a pre-split design which delivers a stable highwall for the life of that part of the mining operation. It will look at the need to adapt and change the way, size and direction of the production blasts as the mining phase approaches the highwall position for which a pre-split has been created. Key Words: Pre-split: Design; Highwall; Perimeter

Jan 1, 2006

Historically, mine ventilation practices as it was referred to then and which was enforced by legislation of those days, focused primarily on the conditions in the working place and little attention given to actual exposures of workers to contaminants in the working environments. With the advent of the Leon Commission of Inquiry into Safety and Health in the South African Mining industry in 1994, findings in the report indicated that more attention should be given to occupational health of workers. The upshot of this report resulted in the promulgation of the new Mine Health and Safety Act (MHSA) with certain sections of it devoted to all the aspects of occupational medicine and occupational hygiene. This paper describes the present situation with regards to statistics on occupational hygiene performance and compensation paid out to persons who have contracted occupational diseases, as well as the way forward in terms of legislation implemented in September 2002 on the chronic and acute issues affecting the mining industry in SA.

Jan 1, 2003

By G. X. Zeng

A calculation programme of finite element method has been developed in order to study the behavior of excavation with sheet piling in soft clay. Based on a series of isotropically consolidated-undrained tests (CIU) on Hangzhou clay a linear relationship between the normalized initial tangent modulus number, E1, and stress-path parameter, a, is found for four different stress paths, and stress-path dependent modulus equations derived. Meanwhile, several influence factors, such as embedment depth and stiffness of the wall and soil conditions, were taken into consideration in the programme. Some valuable conclusions were obtained. Finally, a case history was studied by the proposed method of calculation. The result of calculation and the field observation are in good agreement.

Jan 1, 2010

By Frank P. Frandina

The Heartland Corridor Clearance Improvement Project is part of a regional Public-Private initiative to allow double stack container trains a direct route from the Port of Norfolk through Virginia, West Virginia, Eastern Kentucky and into Central Ohio. The project involves clearance improvements to twenty-eight tunnels, twenty-one of which require structural modification. With construction of the first Package of tunnels just underway at press time, this paper summarizes the program implementation from design through the initial stages of construction.

Jan 1, 2008