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In this study, the flotation performances of ethoxycarbonyl thionocarbamate (ECTC), dialkyl thionocarbamate (DATC) and xanthate copper sulfide collectors are compared by the structure-reactivity relationship using generalized perturbation theory and density functional calculation at the B3PW91/6-31G(D) level. The electron-donating power of xanthates is strong and, therefore, xanthates can strongly react with metal cation on the surfaces of copper and iron sulfide minerals through the formation of normal covalent bonds. This explains the poor selectivity of xanthates and also the high pH levels (above 13) required for the flotation separation of copper/iron sulfide minerals. DATCs are more selective for copper sulfide flotation, particularly against gangue iron sulfides. Although less powerful than xanthates, DATCs can perform copper/iron flotation separation at lower operating pH (commonly at pH levels below 11.5). ECTCs use an ethoxycarbonyl replacing an alkyl N-substituent in DATCs. The presence of the ethoxycarbonyl group effectively changes the functional group of collector from -C(=S)NH- to -C(=S)NHC(=O)-. The strong electron-withdrawing ethoxycarbonyl group adjacent to the C=S group decreases the electron density of the sulfur atom, which improves ECTC?s selectivity against iron sulfide minerals at slightly alkaline conditions. The lowest unoccupied molecular orbit (LUMO) of ECTC, which is constituted by the pz-orbit of every atoms in the conjugate -O-C(=O)-N-C(=S)-O- group and which is pleased with accepting richly d-orbital electrons (feedback electrons) from the (t2g)6(eg)3Cu(II) or t6e4Cu(I) configuration of copper cation on the surfaces of copper sulfide minerals, resulted in the formation of dative p-bond. The iron atom, which has a (t2g)6Fe(II) or (t2ga)3(ega)2 Fe(III) configuration on the surfaces of iron sulfide minerals (Fe(III) is the predominant composition at alkaline conditions), has difficulty in offering its d-orbital electrons (feedback electrons) to ECTC?s LUMO. ECTC collectors are powerful for copper sulfide minerals and very selective against iron sulfides, which has been further confirmed by UV spectra and bench-scale and industrial-scale flotation tests.

Jan 1, 2008

By Christopher Haycocks

Self-supporting, open stoping underground mining methods are some of the earliest, starting with the prehistoric flint mines of Europe and the Egyptian gold mines of Nubia in the time of the pharaohs. When the early miner created an opening, it had to be inherently stable and self-supporting to enable him to continue. Therefore, as mining progressed beyond simple gophering, self-supported open stoping methods were devised to meet the needs of individual ore bodies. Timber for support appears in mines as early as 1000 BC, but this was for no more than local ground control. The ingenuity of mining engineers through history has so refined open stoping methods that today they produce more tonnage than any other mining system. Self-supported open stoping finds its application in moderate to strong rocks that exhibit little jointing or fiagmentation. Good back, hanging wall, and footwall conditions that require no more than incidental support are an essential part of these mining methods. Open stoping methods find applications in all inclinations of ore body from flat to vertical, and where ore movement may be either mechanical or under the influence of gravity. Table 18.0.1 demonstrates the range of ore bodies suitable for open stoping, with particular reference to their dip and the deposit thickness. Most of the flat-dipping applications use ore pillars for overall support and ground control that may be recovered under some conditions after completion of normal stoping practices. In steeper ore bodies, rib, crown, and sill pillars used to block out the ore may be recovered subsequent to the completion of stoping. Open stopes are frequently filled to facilitate pillar recovery. Two of the methods, vertical crater retreat (VCR) and shrinkage stoping, utilize fragmented ore for temporary support in the stopes. In these two cases, the stope is not strictly open until after drawdown.

Jan 1, 2008

By Clay Haynes

In 2005, Black & Veatch Corporation began designing a raw water conveyance system for San Luis Obispo County from Lake Nacimiento to the city of San Luis Obispo. The first element of the water transfer system will be a raw water pump station and lake tap. The wet well of the pump station will consist of a concrete lined shaft approximately 180 feet deep constructed in the very incompetent sandstone of the Vacqueros Formation. The lake will be wet tapped at approximately 172 feet below grade using a slurry earth pressure balance tunnel boring machine. The 48 to 72-inch finished diameter microtunnel will be approximately 500 feet in length. Construction is scheduled to begin in the winter of 2007.

Jan 1, 2008

By Antonio de Lucas, Juan Francisco Rodríguez, Ignacio Gracia, Mª Teresa García

"The amount of waste of Polystyrene (PS) foams is increasing in last years due to their use in insulation, protecting and, storing many different food products. Conventional methods of recycling such as crushing and shrinking by heated air or frictional heat have the disadvantages of molecular degradation, resulting in a reduction of the quality of the recycled polymer. Dissolution and shrinking with suitable solvents is one of the cheapest and more efficient ways of polystyrene recycling but in the process of the solvent recovery by distillation a certain degree of molecular degradation is produced. In this way, CO2 supercritical technology appears as an interesting alternative for the elimination of solvent. This work proposes a global process to polystyrene recycling in two steps: a polystyrene dissolution with a suitable “green” solvent followed by its elimination by supercritical tecnologhy. In order to develop a “green process” the constituents of essential oils, limonene, terpinene, cymene, and phellandrene, are selected as the most appropriated solvents. Introduction In the last years, disposal of the non-biodegradable plastic wastes has been recognized as a serious environmental problem. Recycling these wastes has great interest in order to prevent the environmental pollution and to preserve natural sources (1, 2, 3). Since the Polystyrene foams (PS) is one of the most used foam in isolation, protecting and food storage most of recycling work is concerned with this polyolefin (4). The two main alternatives for treating polymer wastes are energy recycling, where wastes are incinerated, and mechanical recycling (5). Environmental argumentations such as toxic emissions are building up a public resistance against incineration process (6). Mechanical recycling is a popular recovery path for manufacturers and is carried out on single-polymer waste streams. Any way, the market for recycled products can only be found if the quality is close to that of the original. Unfortunately the process of classification and further recovery of these wastes makes them often more expensive than virgin plastic (7, 8). Solvent extraction is one of the cheapest and more efficient ways for PS recycling. If it is done in house of waste producers the separation between plastics could be easy and effective and the transport costs would be eliminated."

Jan 1, 2008

By Scott M. Doehla

A proposed rehabilitation of a 200,000 sf, 75-foot high steel-frame building at the former U.S. Navy Yard in Brooklyn, New York required the review of existing foundation data and an investigation of the foundations with respect to their condition. The building was constructed in stages between 1856 and 1933, including several expansions and interior equipment with isolated foundations. The building has clear spans on the order of 50 feet and at one time supported cranes allowing transport of heavy equipment through the building. The proposed rehabilitation is to include a food manufacturing center and office space having multiple stories. Original construction drawings, available from the Brooklyn Navy Yard Development Corporation?s drawing archive, were reviewed to determine the foundation system supporting the structure. The original drawings provide a window into the methods utilized during late 19th and early 20th century pile foundation construction. The review revealed that the building is supported by pile foundations ranging from timber to concrete-filled steel pipe (depending on the year of construction). Annotations including pile driving records were available on some drawings indicating the design and as-built capacity (using the ENR formula for driving resistance). An investigation consisting of test borings was performed to identify the subsurface conditions underlying the building for evaluating theoretical capacity of the piles. A test pit investigation was performed against existing columns within the structure to expose the piles and pile caps for inspection pertaining to pile condition. The test pit investigation revealed methods utilized during original construction to integrate new columns with existing floor slabs, the use of below-grade brick arches to support a floor slab, and the condition of timber piles which were likely installed up to 120 years ago. The observations made within the test pits were compared with original drawings to evaluate the accuracy of these drawings.

Jan 1, 2008

By Jurgen te Kook

State-of-the-art for subsidence calculation are stochastical models. Although these models were successfully used all over the world they have their limitations due to the fact that they are not based on mechanical laws. For example the models did not take the rock mass structure and the rock mass characteristics into account. Therefore in a research program the skills of geomechanical numerical models for subsidence calculation were investigated. A case study shows that numerical models which are in principle based on the elastic theory are suitable for subsidence prediction. Due to the principles of these models the results are not sufficient in the case of multiple seam extraction. More extended geomechanical numerical models like FLAC and UDEC were investigated in further steps of the research work. Up to now large area geomechanical models require unrealistic long calculation times if the level of detail is similar to that of small scale calculations. Due to this it was necessary to implement a simplified description of the rock mass structure and characteristics. Different case studies show that this approach is successfull for subsidence calculation by numerical geomechanical models even for multiple seam extraction.

Jan 1, 2008

By F. Raupp-Pereira, G. G. Cunto, J. A. Junkes, D. Hotza, V. P. Della

"The present work investigated the valorization of wastes as alternative raw materials for ceramic industries. Different industrial wastes based on the SiO2-Al2O3-CaO system and classified as non-hazardous were selected: sludge from varvite cutting process, sludge from gneiss breaks processes, sludge from filtration/clarification of potable water and a clay classified also as waste. All as-received residues were characterized by X-ray fluorescence, differential thermal analysis, thermogravimetry and particle size distribution. The applicability of these materials in ceramic formulations was then evaluated. The formulated mixtures were subjected to forming by pressing and extrusion followed by thermal treatment. After optimization of the processing conditions, the properties of the samples sintered at different temperatures were also evaluated. The waste materials studied proved to be alternative raw materials to natural mineral resources for the ceramic industry.IntroductionOne of the most important problems that have accompanied the humanity in recent decades is the environment’s degradation. In the same context, the natural resources exploration and technological development are phenomena which, if aren’t controlled, can cause ecological disequilibrium with unpredictable consequences [1]. It is in this perspective that recycling of various wastes assumes relevant importance.The recycling, understood here as the waste process reuse, is a common practice in the First World countries, where the raw materials have strategic aspects and the disposal techniques of solid wastes have considerable economic costs. In Brazil, the ecological conscience begins to be aroused due to, in the last ten years, the implementation of stricter laws for environmental control, in general, and licensing of waste generating from industrial activities, in special. The terms “residue” or “waste” are normally used to describe what remains of a production process; when an application for this material is not found. When wastes or residues are susceptible to be incorporated as raw materials or energy sources in a new material production, they can be understood as by-products [2].The valorization of industrial wastes is important, due to the need to pollute less and give an ecologically correct destination for wastes. The waste recycling, independent of its kind, presents several advantages in relation to using primary natural resources, such as reduction in the volume of raw materials extraction, lower energy consumption, lower levels of pollutant emissions and improvement of the health and safety of the population. The most visible advantage of recycling is the preservation of natural resources, extending its life and reducing the destruction of landscape and ecosystems [3]."

Jan 1, 2008

By Asok Kumar Das

"In steel making ferroalloys occupies a commanding role for production of varied quality of steel. Ferroalloys enable alloying elements such as chromium, silicon, manganese, vanadium etc to be safely and economically introduced into metallurgical processes thus giving certain desirable properties of the alloyed metal. Their importance grew with the progress of the steel metallurgy which implied more diversified alloying elements, in better controlled quantities, in purer steel. The ferroalloy industry became a key supplier to the steel industry. Production of ferroalloys generally involves the use of Electric Arc furnace(EAF) into which raw materials(e.g. various metal ores, quartz, coke, lime etc ) with relatively fluctuating physical compositions are loaded. Due to this, one of the major environmental impacts of producing ferroalloys is the emission of dust and fume from the smelting process. INTRODUCTIONFerro Alloys are essential ingredients used for refining, de-oxidation, desulphurization and alloying addition in the production of different types of steel and hence Ferro Alloy industry forms a back bone of iron and steel in the world. Indian ferro alloy industry is more than 45 years old. It produces most of the bulk ferro alloys and a large number of special ferro alloys. The present installed capacity of the Indian ferro alloy industry is sufficient to meet the requirement of existing level of indigenous steel production of about 46 million tonnes. Revised National Steel Policy – 2008 envisages production of more than 100 million tonnes of steel by the year 2011-12, at proportionate annual growth rate per annum. The focus of the policy is to achieve global competitiveness not only in terms of cost, quality and product-mix but also in terms of global benchmarks of efficiency and productivity. In order to achieve the objectives of National Steel Policy and also to meet the requirement of ferro alloys, the Indian Ferro Alloy Industry has to gear up in terms of enhancement in production capacity, sourcing of raw materials, up gradation of technology, improvement in productivity, automation / mechanization, customer satisfaction etc."

Jan 1, 2008

By B. Nebreda, I. Vegas, R. Vigil, O. Rodríguez, M. I. Sánchez de Rojas, M. Frías, R. García, J. Urreta

"This paper shows the possibility of reutilize paper sludge waste as supplementary cementing material for the cement manufacture. This industrial waste consists essentially of a mixture of organic matter (30%) and inorganic compound, such as calcite and clay minerals. The raw paper sludge does not present pozzolanic properties, but once calcined at 650ºC during 2 hours, exhibits high pozzolanic activity, similar to silica fume at 28 days, as a consequence of the transformation of kaolinite into metakaolinite. Calcined paper sludge was used as partial Portland cement replacements of 0, 5, 10 and 20%. Enhancement in compressive strength was appreciably obtained for 10 and 20% substitution levels from 7 days on. Furthermore, calcined paper sludge slightly reduces the initial and final setting times of cement paste. Introduction Natural pozzolanic materials have been ordinary used in different aspects of construction, mainly for their influence on the microstructure and durability of blended cement matrixes [1, 2]. Due to the regulations of environmental protection, many researches are focusing on the possibility of obtaining pozzolanic materials from industrial wastes and not from natural materials (ceramic wastes, silica fume (SF), activated clays) [3–5]. One of the most used pozzolanic products is the metakaolin (MK) obtained from the activation of natural clay (kaolinite). The positive effect that MK has on blended cement performances [6,7] and also the influence that curing temperature and matrix nature have on the reaction kinetics and stability of hydrated phases produced during the pozzolanic reaction, according to the studies carried out by Frías et al. [8,9] are well known. However, there is a worldwide trend towards the use of recycled products in cement industry. In this line, some authors have reported an alternative way of obtaining MK from waste paper sludge [10-14]. The raw paper sludge (PS), once calcined under controlled conditions (700-800ºC), produces a MK with pozzolanic properties [15-20]. The present research is part of an experimental study about alternative source for MK from the Spanish paper recycling industry and its use as supplementary cementing material. This contribution pays special attention to the option of reducing activation temperature below 700ºC. This fact has a positive effect in reducing the energy consumption, as well as in reducing environmental impacts associated with decarbonation of calcite. The chemical and mineralogical characteristics of raw paper sludge and derived calcined product are described. In addition, the influence and behavior on blended cement properties (setting times and mechanical properties) are also discussed."

Jan 1, 2008

By Eric J. Pederson

The down hole hammer is widely used in specialty geotechnical construction. The common uses include tie-back anchor installation, micropile installation, and general soil/bedrock drilling operations. Veit used these techniques to develop a cost effective way of installing the foundation system for University of Minnesota Football Stadium. The soils present at the site of the stadium contained layers of concentrated cobbles and boulders. The geotechnical engineer recommended a driven pile system, and the base bid outlined in the project documents consisted of an H-Pile using a 14x73 pile section. Veit submitted an innovative alternate consisting of using a rotary percussion system to install a 12? O.D. pile. This paper will show that this pile type and installation method was the correct choice for the project. The design criteria for the compression, uplift, and lateral capacities and deflections were met, while eliminating pile damage. The method resulted in a significant cost savings to the University and maintained the project schedule.

Jan 1, 2008

By Burrows. A.

Temperature profiles in the lead smelter sinter bed at Xstrata Zinc Mount Isa sinter plant have been measured using a wireless temperature probe. Corresponding sinter samples have been collected for characterization. The sinter peak bed temperatures were found to be in the range of 1000 - 1200 °C. Microstructures and softening temperatures of these sinters have been characterised. Strong correlations have been observed between peak bed temperature and peak hood temperature, and between mean sinter softening temperature and peak bed temperature. It was found that higher peak bed temperature results in higher sinter softening temperature. For the feed material used in the trials, to obtain sinters with mean softening temperatures above 1050 °C, peak bed temperatures above 1130 °C are required. There appears to be a direct correlation between granule size distribution in the feed and peak bed temperature attained. High peak bed temperatures are observed in sinters with narrow granule size distribution.

Jan 1, 2008

By Günther M. Volkmann

Continuous developments in tunneling require knowledge transfer between designers and suppliers to optimize the application of support systems. This collaboration allows the designer access to the latest research results, technical innovations, and support specific measurement techniques as well as the supplier?s experiences on recent projects. Project specific requirements determine the information that can be used to increase support system efficiency, advance rate, degree of safety, or decrease costs. This cooperative effort results in not only an unambiguous tender document, but also an optimized design with reduced risk that is coordinated with safe and high performance construction techniques. This paper will address the benefits of an early collaboration to both the design and the specifications in the tender document by using the A3 Hindhead project (UK) as an example.

Jan 1, 2008

By Afrodite Ntziouni, Vassilia Kasselouri – Rigopoulou, Athanasia Kyritsi, Konstantinos N. Pistiolas, Stamatia Gavela, Konstantinos Kordatos, Lazaros Iliadis

"The present study deals with the production and characterization of rice husk ash (RHA) and its use in the synthesis of zeolite of type ZSM-5. Rice husk was combusted in various temperatures with aim to find the suitable conditions for the production of amorphous silica. The resulted amorphous silica ash was then utilized as a starting material for the synthesis of ZSM-5 zeolite using the low temperature and atmospheric pressure process. The method led successfully to the synthesis of highly siliceous zeolite of type ZSM-5. The produced material was characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM).IntroductionRice husk is a major by-product of the rice-milling industries and it is usually used as a fuel for steam generation due to its high calorific power. During its combustion, rice husk ash (RHA) is produced. Knowing that the annual rice world production is over 615 million tons (2005), thus resulting in a potential production of more than 22 million tons of RHA [1], it can be understood that the RHA disposal is a crucial issue towards the environmental protection. However, due to the high silica content, RHA can be used as an alternative cheap source of silica for many uses, including as filler in polymers [2], concrete [3] and synthesis of zeolites [4-7].The burning of rice husk in air results in the formation of RHA with content in SiO2 that varies from 87 to 97% depending on the burning conditions, the rice variety, the climate and the geographic area [8]. Some small amounts of inorganic impurities are always present in the ash along with unburned carbon. The unburned carbon can be removed from the ash by further heating treatments in high temperatures, but this usually leads to the crystallization of the amorphous silica to cristobalite and/or tridymite [9]. The crystallization of the contained silica of the ash is also occurred when the burning conditions of husk are uncontrolled [10]. This crystallization is a disadvantage towards the preparation of silicon based materials, because the silica ash is rendered inactive in its crystalline form [11]."

Jan 1, 2008

By Daniel Adolfsson, Ryan Robinson, Fenwei Su, Jelena Blagojevic

"Cold bonded briquetting of steel plant by-products has proven to be a viable recycling alternative concerning technology, economy and environment in both the traditional blast furnace route and the direct reduction process. A critical parameter in cold bonded briquettes is the type and amount of binder used during production. The binder material must meet certain quality requirements concerning low and high temperature strength, chemistry and economy. Currently, SSAB Tunnplåt uses ordinary Portland cement (OPC) as binder in their cold bonded briquettes. In order to improve binder quality and possibly decrease OPC dependency, a binder feasibility study has been conducted concerning an internal by-product, ladle slag, as a supplement and/or partial substitute for OPC. Several characterization techniques have been used to study the behaviour of ladle slag, these include: XRD, XRF, SEM, glass content analysis, calorimetric analysis, particle size distribution and thermochemical stability considerations concerning the CaO-Al2O3-SiO2 system.IntroductionRecently, a project was initiated at SSAB Tunnplåt AB, in Sweden, which aimed at reducing the amount of ordinary Portland cement (OPC) as hydraulic binder in cold bonded briquettes by partly replacing it with ladle slag. OPC is traditionally used within civil engineering, and widely accepted as a hydraulic binder in a number of different applications. OPC consists of four major crystalline phases, i.e. C3S, C2S, C3A and C4AF. Tricalcium aluminate as well as the ferrite phase in OPC reacts very quickly with water, for this reason gypsum is added to the clinker in order to retard these reactions. The fact that gypsum is present in the system limits the recycling of briquettes to the BOF, since the presence of gypsum during steelmaking results in a significant amount of sulphur emissions. The latter along with the expense that follows, makes it worthwhile to consider alternatives for OPC as binder in cold bonded briquettes."

Jan 1, 2008

Most of the Ta-Nb ores in China occur in altered granites, and Ta-Nb minerals occur in these granites as accessory minerals. This type of Ta-Nb ores are characterised by whole mineralised granite mass, large reserves, low grade of tantalum and niobium, less economic minerals, complex mineralogy, difficulty in separation and concentration of Ta-Nb minerals and high operating cost of ore dressing. The Ta-Nb ore presented in this paper is a low-grade Ta-Nb ore occurring in altered granite in Jiangxi province. It has large reserves, with the grade of Ta2O5 0.013 per cent and Nb2O5 0.023 per cent. The process mineralogy study carried out by the authors determined ore mineralogy and ascertained occurrence of Nb and Ta and their mineral processing characteristics. The results are used as the guide for developing the optimum mineral processing flow sheet. The results also indicated that this type of Ta-Nb ore contains a high content of Li, K and Na, a low content of deleterious impurity Fe, and the tailings can be used as feed for glass and ceramic materials. This study provided important mineralogy information for exploiting and utilising low-grade Ta-Nb ore resources, developing a mineral processing flow sheet and further utilising the tailings.

Jan 1, 2008

By I. Ocak

The modulus of elasticity of rock material (Ei) is an important rock property that is used as an input parameter in the design stage of engineering projects such as dam and tunnel constructions, mining excavations, and so forth. However, determination of the modulus of elasticity is sometimes difficult to obtain by laboratory tests because high-quality cores are required. For this reason, empirical methods for predicting the modulus of elasticity of rock material have been popular research topics in recently published literature. In this study, the relationships between the uniaxial compressive strength (UCS), unit weight (?) and modulus of elasticity for different types of rocks were analysed by using 177 data obtained from laboratory tests carried out on cores obtained from drill holes within the area of the Kadiköy-Kartal Metro line (Istanbul, Turkey). Keywords: Kadikoy?Kartal Metro, uniaxial compressive strength, unit weight, estimating the modulus of elasticity.

Jan 1, 2008

By N J. Beukes, J Gutzmer, C Reinke, M Bau

In this study the light sparse phase search (SPL_Lt) mode on the Mineral Liberation Analyser (MLA) was successfully used to identify and quantify the abundance of rare earth element (REE) phosphates in Precambrian iron formations. Monazite (light REE phosphate) and xenotime (Y and heavy REE phosphate) are identified and data from the MLA combined with the mineral chemistry of the two minerals are used to calculate and model the expected REE concentration and distribution in these two REE phosphates. The REE phosphates account for up to 31 per cent of the REEs in the banded iron formations (BIFs) and excellent correspondence is observed between the modelled REE patterns and the whole rock geochemical data available for the same samples. Except for quantifying the mineral weights, the sparse phase search also allows for the localisation of REE phosphate grains and the observation of their association with other minerals using backscatter electron (BSE) imaging. These observations are used to conclude that the REE phosphates were most likely of diagenetic origin, with REEs and phosphate remobilised from primary chemical precipitates. It is demonstrated that automated mineralogical techniques can be used to qualitatively and quantitatively describe the influence of a rockÆs trace mineralogy on its geochemistry.

Jan 1, 2008

By J Elsen, R Snellings, K Van Balen

This research concerns the mineralogical study of the physico-chemical reactions taking place at the pozzolan-binder interface. Lime binder/ pozzolan mixtures have been prepared for different natural zeolites. Analcime, phillipsite, chabazite, erionite, mordenite and clinoptilolite were mixed with portlandite and water, after which the progress in the reaction was quantitatively determined by thermogravimetrical analyses from three to 180 days. A first and important step was the thorough characterisation of the raw materials by quantitative X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope energy- dispersive X-ray (SEM-EDX) measurements of the zeolite minerals, Brunauer-Emmet-Teller (BET) specific surface area measurements, grain-size analyses and cation exchange capacity measurements. Beside these zeolite samples with varying Si/Al ratios, two clinoptilolite samples exchanged to the calcium, potassium and sodium form were studied and the difference in their short- and long-term reactivity was assessed. Also the difference in reactivity between identical clinoptilolite samples ground to different grain sizes, obviously having different specific surface areas, was determined experimentally. The results indicate that the external surface area only influences the short-term reactivity, whereas the cation content has effect on both long- and short-term. Na-exchanged samples combine clearly more portlandite in the first few days, whereas the reaction slows down afterwards compared to K- and Ca-exchanged samples. The early reactivity of the unexchanged zeolite samples could be explained by these two parameters, but their long-term reactivity seemed to be related to their Si/Al ratio. Samples with zeolites rich in Si reacted faster then their Al-rich counterparts.

Jan 1, 2008

By D Sinclair

Sustainability will become a more stringent issue in mine planning over the next 40 years. The evidence of this is apparent in State and Commonwealth government policies now emerging in respect to water, green house gases, waste and other process emissions. The mining industry has developed policies such as æEnduring ValueÆ, which go some way towards establishing a framework within which mining can continue to be an underpinning strength within the Australian economy. However, the demands of new policies are directed at extending sustainability in ways that will change the way in which projects are implemented. This paper examines the nature of new policies aimed at water, energy and emissions, considering examples of where mining practices have or may change in order to meet new objectives in resource efficiency. Important issues will, as always, be the international price competitiveness of the mineral resources being produced but, where this is now devolved around mining and processing costs, these costs may in the future be strongly correlated to the nature and cost of local energy resources compared with those in Australia, the ability to mitigate and minimise water resource use and environmental impacts deriving from emissions and the veracity of competitor nations in meeting the same standards of performance in resource efficiency usage and in emissions control. As these systems bed down internationally mining in Australia will need to concentrate, amongst other things, on finding higher grade orebodies and on better technologies to release the value of lower grade ores. For our mining industry to remain strong, greater expenditure will need to be focused on these objectives. Finally, it will be important for the industry to remain vigilant and proactive in directing government policy development to ensure that practical objectives in mining are not curtailed unnecessarily through ignorance of mining market precepts developed over the centuries of mining operations.

Jan 1, 2008

By Trevor Rangasamy

Technically based guidelines for managing rock related risks associated with strip mines in South African collieries are currently vague and are to a large extent based on experience and trial and error. To date, no mine specific or universal design charts exist within the South African industry. Quantification is done on a reactive basis i.e. following reported instabilities. The conditions under which, proactive tools to manage instabilities would be practically applicable are: The design of simple easy to use charts. Designing the charts for a target audience that is primarily production management. Well organized, logical set-up of the charts that will allow for easy future refinements. Allowing for variations in rock and soil properties within the charts that would account for colliery specific and region specific variability. The factors selected for in depth investigation that were deemed to have either individually or in combination, a primary influence on the stability of strip mines are (in no order of priority): Appropriate batter angles for ?soft? materials. Surcharge loading (spoils, dumps, topographical highs) on the highwall side. Influence of the thickness of stratification on stability. Influence of moisture content on stability. Influence of the changes to the coal seam dip angle on stability. Influence of persistent ?strip long axis? parallel faults/joints on stability. Spoil stability for variations in material type. This paper provides details of the work undertaken, using principally numerical modelling techniques, to produce design charts that will allow for proactive management of rock-related instabilities on strip mines.

Jan 1, 2008