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Kinetic Study on the Leaching of Vanadium from LD Converter Slag Using Sulfuric Acid In order to reduce the environmental impact due to land disposal of LD (Linz-Donawitz) converter slag from steelmaking plant and to valorise this waste material, an acid leaching study was carried out to assess the effect of several parameters on the kinetics of vanadium dissolution. The characterisation and morphology of the feed investigated using XRD, XRF. The factors influencing leaching vanadium such as particle size, temperature, slurry density and the concentration of sulfuric acid were investigated and optimised. The maximum vanadium recovery about 95 per cent achieved at 70¦C, S/L: 1/15, acid concentration: 3M and for 150 minutes of leaching time. The dissolution of vanadium in sulfuric acid shows that there are two stages in the kinetics of leaching. At the first 15 minutes, there is a sharp increase in the amount of vanadium extracted and at longer leaching time, the extraction increase slightly. In the present work, the shrinking core model (SCM) was used to describe the acid leaching of vanadium compounds. A summary of the controlling regimes in the SCM are examined below for short time (less than 12 min.) and long time (more than 30 min.) stages. So, it was found that the kinetics of leaching in both stages is controlled by solid product diffusion regime.

Sep 13, 2010

By A Rozendaal

Namakwa Sands, a heavy minerals beneficiation business situated along the west coast of South Africa, is a major producer of titanium slag, pig iron, ceramics quality zircon and rutile concentrate to the international export market. The bulk of the economic mineralisation, which includes zircon, rutile, ilmenite and leucoxene is hosted by a late Cainozoic aeolian succession overlying remnant palaeo-strandline sediments. Relatively younger duricrust layers that cement a significant part of the generally unconsolidated ore compounds the challenging processing character of the primary mineralogy. The complex nature and hardness of the duricrust ore influence their mineability negatively, and can potentially destabilise downstream ore preparation processes. Effectively, up to ten per cent of the entire mineral resource is sterilised as the present infrastructure is not geared to treat the hard-mineralised ore. The metallurgical performance of the primary processing stage, which entails wet density separation, is strongly a function of the quality of the heavy mineral assemblage, liberation state of the economic minerals and slimes content. Elevated concentrations of garnet, a gangue contaminant exhibiting similar physical characteristics as the economic minerals, subtract substantially from the recovery performance of the secondary concentration process, which comprises mainly wet magnetic separation. By contrast, the intrinsic mineral purity of the economic fraction governs its successful recovery to saleable products as stringent product quality specifications apply. Improved mine planning through geometallurgical enhancement of the existing mineral resource model is envisaged to benefit the entire Namakwa SandsÆ mineral beneficiation chain, ultimately aiming to optimise mineral resource utilisation.

Jan 1, 2008

By S. Okubo, K. Fukui

Empirical equations established for estimating the rock strength of the working face based on the cutting forces of a tunnel boring machines (TBM) are further examined and discussed with respect to the dominant factors affecting TBM performance. Constants in the equations are related to TBM-specific parameters such as excavation (tunnel) diameter, cutter diameter, and cutter distance. The relationship between the constants and the TBM specifications is examined in this study on the basis of data collected at ten tunnels, and it is found that the constants are most strongly influenced by the cutter diameter and tunnel diameter. Zur Schätzung der Gesteinsfestigkeit an der Arbeitsfläche ermittelte empirische Gleichungen, die auf den Schneidekräften von Tunnelbohrmaschinen (TBM) beruhen, wurden weiter im Hinblick auf die vorherrschenden, die Leistung der TBM beeinflussenden Faktoren hin untersucht und diskutiert. In der Gleichung enthaltene Konstanten werden zu den TBM-spezifischen Parametern wie Auschachtungs- (Tunnel) Durchmesser, Schneidendurchmesser und Schachtlänge in Beziehung gesetzt. Die Beziehung zwischen diesen Konstanten und den technischen Daten der TBM wird in dieser Studie auf der Basis der bei 10 Tunnelbauten gesammelten Daten untersucht. Dabei wurde gefunden, dass diese Konstanten am stärksten von den Durchmessern der Schneiden und der Tunnel beeinflusst werden. Cette étude examine et discute les équations empiriques permettant d'estimer la résistance de la roche attaquée aux forces de coupe des tunneliers dans le cadre de l'étude des facteurs dominants affectant les performances des tunneliers. Les constantes de ces équations concernent les paramètres spécifiques des tunneliers comme le diamètre d'excavation (du tunnel), le diamètre du couteau et la distance de coupe. Cette étude examine le rapport entre ces constantes et les caractéristiques techniques des tunneliers d'après des données collectées dans dix tunnels et elle conclut que ces constantes sont principalement influencées par le diamètre du couteau et le diamètre du tunnel.

Jan 1, 2003

By V. M. Troughton

Further pile load testing has been carried out at Canary Wharf to compare the performance of base grouted and ungrouted bored piles founded in the Thanet Sand. The testing regime included three preliminary test piles and two working test piles. The results of these tests are summarised in Table 1 below. Two of the preliminary test piles were located only 14m apart to compare the performance of a base grouted and ungrouted pile in similar ground conditions. The load/settlement behaviour of these two preliminary test piles are compared on Figure 1. All the piles were drilled under bentonite with a drilling bucket. In the base grouted piles four grouting tubes were placed with the reinforcement cage to within 500mm of the pile toe. After the pile had been concreted these grouting tubes were then extended to the pile base by drilling and packers were installed. Grout was then injected into the four tubes simultaneously.

Jan 1, 1991

By S. Sakurai

We discuss the mechanical characteristics of underground structures that are subjected to vertical oscillations. Under such circumstances - expected when an earthquake rupture occurs very close to highly developed urban areas - the conventional seismic analysis, which mainly considers horizontal shear oscillations, may not be fully valid. Our analysis, based on the elastic wave theory, shows the effects of vertical disturbances and the generation mechanism of the unique damage patterns observed on the occasion of the 1995 Hyogo-ken Nanbu (Kobe) Earthquake. Wir diskutieren über die mechanischen Eigenschaften der unterirdischen Strukturen, die sich vertikalen Schwingungen aussetzen. Unter solchen Umständen - erwartet, wann ein Erdbebenabbruch sehr nah an hochentwickelten städtischen Bereichen geschieht - kann die herkömmliche seismische Analyse, die sich hauptsächlich horizontale Schubbewegungen überlegt, möglicherweise nicht völlig gültig sein. Unsere Analyse, basiert auf der elastischen Wellentheorie, zeigt die Effekte der vertikalen Bewegungen und den Erzeugungsmechanismus der einzigartigen Beschädigungsmuster, die anläßlich des 1995 Kobe Erdbebens beobachtet wurden. Nous discutons les caractéristiques mécaniques des structures souterraines qui s’exposent aux oscillations verticales. Dans ces conditions - s’attendent quand une rupture de tremblement de terre se produit tout près des secteurs urbains fortement développés - l’analyse séismique conventionnelle, qui considère principalement des oscillations horizontales de cisaillement, peut ne pas être entièrement efficace. Notre analyse, qui est basée sur la théorie des vagues élastiques, montre les effets des mouvements verticaux et le mécanisme de génération des modèles uniques de dommages, que nous avons observés à l’occasion du tremblement de terre 1995 de Kobe.

Jan 1, 2003

By G F. Brent, R D. Hart, C Carr, F Felipe

In underground operations, where copper, gold and other metals are mined, the open stopes can be backfilled to stabilise surrounding workings. This fill may consist of tailings from the processing plant, usually mixed in slurry with a binder such as ordinary Portland cement (OPC). Extensive use is made of tailings in OPC-based paste fill, cemented hydraulic fill or cemented aggregate fill applications. A large underground operation such as the Mount Isa Copper Operations utilises over three million tonnes of backfill per annum. Geopolymers offer an alternative binder system with significant environmental advantages over OPC. Geopolymers are formed by polymerisation of aluminosilicate precursors in an alkali medium. They generally form products with superior strength characteristics as well as increased resistance to degradation, particularly under acidic conditions. Geopolymers have lower carbon dioxide emissions associated with their manufacture than OPC and offer further potential advantages, such as the use of less water and more waste materials. The application of geopolymers to weak material systems such as mine backfill has not been widely studied. The aims of this investigation were to assess a range of Australian mine process wastes for suitability as feedstocks in fill applications and to construct a range of these cemented minefills using a geopolymer binder. The physicochemical characteristics of each of the wastes are discussed as well as how they ultimately contribute to the geopolymer cement through direct replacement of OPC. Results from various tests on the candidate geopolymer fill formulations are presented and the potential of such fill formulations to replace OPC in mine backfilling operations is highlighted. The significant potential contribution to reducing greenhouse gas emissions from the use of geopolymer-based mine backfill across the industry is noted. Conversion of a single mine, such as the Mount Isa Copper Operations, is shown to match the reductions in greenhouse gas emissions due to the current total installed photovoltaic electricity generation capacity of Australia. A similar examination of wastes available to a gold mine could potentially yield new binders for use in established or new fill systems.

Jan 1, 2007

By A. Moergeli

The Swiss are building the world’s longest tunnel, the 57-Kilometer (35-mile) long Gotthard Base Tunnel. Lot 252, Tunnel Amsteg: Two Hard Rock Tunnel Boring Machines (TBM) crossed hydro-thermally decomposed granite. While the East TBM advanced slowly but steadily, the West one got stuck for five months and had to be recovered by special means and methods. Both TBMs have finished their more than 11-Kilometer (7 miles) long drives successfully. Lot 360, Tunnel Sedrun: For the first time in tunneling, roadway support machines are used through most challenging, squeezing geology. They constantly advance in full face mode for about one Tunnelmeter/24 hours.

Jan 1, 2007

By M. Perolo, A. Contini, E. Ramelli, G. Borgonovo, L. Locatelli

This paper presents the ground settlement monitoring system used during the construction of two tunnels bored by two EPB TBMs, beneath the existing and active railway embankment in Bologna (Italy). The tunnels run close to large buildings and beneath bridges and other infrastructure. Data are collected from remote total stations and from electro levels installed directly on the railway tracks. The automated monitoring system acquires and analyses data then sounds an alarm in the event that there is a problem. Alarms are sent out in case of excessive tilt or settlement. Data is provided through a dedicated web application for multiple-party access, to gather, manage and store monitoring data.

Jan 1, 2007

By Luo Yang

A one-dimensional wave equation based algorithm for estimation of shaft and toe resistance of driven piles using High Strain Testing (HST) data is presented. The pile is represented by a uniform elastic bar, while the soil around the pile is assumed as a homogenized isotropic medium, and Smith model is adopted to represent soil-pile interaction in the wave equation analysis. In most cases, the displacement of pile particles along pile shaft is greater than recoverable soil deformation (i.e., soil quake in Smith model). Therefore, static shaft resistance could be reasonably assumed to be totally mobilized during pile driving. Smith damping factor is used to account for combined dynamic and rate effect. Force and velocity time histories measured at the pile head are used as input boundary conditions in an analytical solution of the one-dimensional wave equation. As a result, two unknown parameters, static shaft resistance and Smith damping factor, can be incorporated into the one-dimensional wave equation and determined analytically for the time duration prior to the first downward wave reaching the pile toe. Then, soil resistance and Smith damping factor at pile toe can be further determined. The advantage of the proposed analysis technique is that the Smith damping factor and the static soil resistance can be directly determined based on the closed-form solution of the one-dimensional wave equation, which is computationally efficient. Numerical examples are given to illustrate the use of the proposed method to determine the pertinent Smith model constants and the static resistances.

Jan 1, 2006

By A Querzoli, B Williams

In late 2014 the Flinders Power Management Team was executing business improvement plans to ensure continued electricity generation until 2028 and beyond. Six months later, in June 2015, the Board announced the closure of the Flinders Power South Australian business, including the Leigh Creek Coal Mine, the Northern and Playford Power Stations located at Port Augusta and the 250km railway line. The announcement was preceded by a brief period of internal planning. A date was soon set for ceasing coal mining operations, being November 2015. The mine is unique in many ways. Located approximately 550km north of Adelaide the site has over 100 years of history and was formerly operated by the South Australian Government. Privatisation in 2000 saw the mine continue operation under Perpetual Leases from the South Australian Government. The leases included exemptions from multiple sections of the Mining Act 1971, obliging primary regulation under the Mines and Works Inspection Act 1920. The coal, being a low rank sub-bituminous brown coal, is prone to self-heating and spontaneous combustion. The mine and company town Leigh Creek were the economic and cultural heartbeat of the community. Facilities at the mine were shared by the community and vice versa. While many mines across Australia and the world enter periods of care and maintenance, few have been actively closed to the point of relinquishment (Bennett and Lacy, 2016). A swift decision to close, followed by a short mining operations shutdown period, presented significant technical and regulatory challenges for both the mine operator and for Regulators. The subsequent joint risk mapping process employed by Flinders Power and South Australian Mining Regulators was a unique real-world example of collaborative mine closure planning and execution. Lessons learnt are valuable for all mines, production facilities and for Regulators, even for those who may wrongly assume that closure is many years away. CITATION:Williams, B and Querzoli, A, 2018. Risk management for minesite closure planning and execution – start now! Lessons from the closure of the Leigh Creek Coalfield, South Australia, in Proceedings Life-of-Mine 2018, pp 68–72 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By D. Knuutila, G. Goyette, James A. Finch, G. Bartolacci, A. Fortin, Chi Ho Lau, A. Lockhart

"In a COREM-McGill collaborative research and development project, gas dispersion parameters and froth properties were manipulated in a copper flotation plant to study interactions between the collection and the cleaning zones. In this paper, specific work on developing some relationships between operating conditions and froth stability in a rougher column flotation cell of 125 m3 is reported. Froth stability, measured by image analysis, was related to the following process conditions for specific flotation machines in an industrial case study: Gas flow rate, collector dosage, pH, frother type and dosage. Across the range examined, froth stability was improved through a decrease in gas flow rate and/or increasing frother dosage. Metallurgical results (grade and recovery) showed that both gold and copper were dependent on froth stability.INTRODUCTIONMcGill and COREM have over the past two years collaborated in a research and development project to merge gas dispersion parameters, frother analysis (McGill technology), and froth properties (COREM’s imaging system) to study the interactions between the collection zone (pulp) and the cleaning zone (froth). The main goal is to increase knowledge of flotation cell hydrodynamics since it is known to govern the metallurgical performance of the flotation process (Power et al., 2000). In this paper, specific work on developing some relationships between operating conditions and froth stability in a copper flotation circuit is reported.The objective of this work is to study gas dispersion in a large volume flotation column (hydrodynamics) and to measure its impact on the froth. By froth imaging, it is possible to diagnose operational problems on the basis of froth characteristics (Bartolacci et al., 2005a) and consequently, to propose ways of improving process performance by froth analysis (Bartolacci et al., 2005b).Another approach to froth characterization is investigated in this paper. In the same flotation column, a froth stability apparatus (column) was included (Triffet and Cillers, 2004). The mechanical froth stability apparatus is used to link “hard” froth characteristic measurements to “soft” froth characteristic measurements (those obtained by imaging)."

Jan 1, 2008

By JO Choi

Jet-grouting method is a useful technique to reinforce foundations on relatively soft or vulnerable soil layers such as fractured zone and stratum with cavities. Although jet-grouting has been widely applied to various field works, a reliable design standard has not been established yet. A number of model tests were performed to investigate end bearing behaviors of piles reinforced by jet-grouting. It was concluded that end bearing capacity was increased in proportion to uniaxial compressive strength of grout column. Based on the test results, the design criteria for the end bearing capacity were suggested.

Jan 1, 2006

By Jeramy B. Decker, Paul H. Madsen

"During the excavation of the north bound tunnel of the Devil’s Slide Tunnel project, deformation (convergence) was measured after passing through Fault Zone B. The tunnel convergence was not symmetrical, but was larger on the left side of the profile. It was determined that a shear zone nearly parallel with the tunnel drive was contributing to the uneven deformation. This paper will discuss how it was determined that the shear zone existed and how multi-point borehole Extensometers (MPBX) were used to verify that a significant amount of the deformation was occurring due to movement along the shear zone as the excavation was advanced. In addition, performance of the shotcrete liner in the area of the convergence will be examined. Finally, the paper will consider the means and methods that were utilized to ultimately control and stabilize the deformation. INTRODUCTION The Devil’s Slide Tunnel Project consisted of excavating two 1,250 meter tunnels each with a profile of 80 m2 utilizing the New Austrian Tunneling Method (NATM) or otherwise known as the Sequential Excavation Method (SEM). The tunnels are part of the California Coastal Highway south of Pacifica, CA, a suburb of San Francisco. The tunnels were opened to traffic in March of 2013. Geological Setting The tunnels run north-south through the San Pedro Mountain ridge, which is part of the Santa Cruz Mountains. The tunnel lies within the San Andreas Fault system and is 7.2 km west of the surface trace of the San Andreas Fault and 2.8 km east of the surface trace of the San Gregorio Fault. The 10 km strip between these two faults is referred to as the La Honda structural and terrain block (Decker et al. 2010; Amini et al. 2005; Earth Mechanics Inc. 2003). Locally, the tunnel passes through three blocks representing different geological conditions: South Block, Central Block, and North Block (Figure 1) (Decker et al. 2010; HNTB Corporation et al. 2005). The South Block consists of Mesozoic aged granodiorite and quartz diorite. The South Block also contains many local shear zones and a low angle thrust fault (Fault A). The South Block ends at Fault B, which is the southern border of the Central Block."

Jan 1, 2016

By Jean-Louis Briaud

The following is a summary of a very recent report prepared at Texas A&M University for the National Cooperative Highway Research Program and entitled "Downdrag on Bitumen Coated Piles". Anytime the soil settles more than the pile, downdrag or negative skin friction will develop. The load in the pile increases with depth up to a certain point and then decreases down to the pile point. This phenomenon has been quoted as being the number one culprit for deep foundation failures. In Chapter 1, an introduction to downdrag is given. The most common criterion for downdrag is to consider it in design as soon as the settlement of the soil surface after pile driving exceeds 0.5 in. Coating piles with bitumen is an effective way of reducing downdrag forces and therefore allows to use smaller piles for the same load. This results in cost savings. Coating piles with bitumen increase the cost of piles by about 33% and therefore the decision to use bitumen is generally based on economic considerations.

Jan 1, 1989

By Glen D. Frank, Jeremy P. Theys, Mina M. Shinouda, Gary W. Gilbert

PURPOSE OF THE PROJECT The Big Walnut Augmentation Rickenbacker Interceptor project began in 1995with the preparation of the Scope of Services for the design of the Rickenbacker Interceptor, with service to and around the Rickenbacker Air Force base. The air base was soon to be placed under civilian control through a Port Authority, with an expected influx of businesses and services, requiring increased sanitary service capability. Due to political differences regarding annexation and other issues, the project was placed on hold. In mid 1996 the Scope of Services was rewritten with more emphasis on a tunneling option, but still only addressing the air base and surrounding tributary are a sanitary service requirements. The consultant selection process began in late 1996 with the Request for Statements of Qualifications issued in December. Three firms were selected to furnish proposals based on the revised Scope of Services that now included requirements for hydraulic modeling of the service areas and the Big Walnut Outfall (BWO) and an expanded soil investigation requirement. All three firms were requested to make presentations to the selection committee, with the committee selecting URS Greiner for further consideration and negotiation. A contract was entered into in August of 1997with URS Greiner. The major sub-consultants were Lachel and Associates, Inc., H.R.Gray and Associates and Solar Testing Laboratories, Inc. The project began with geological investigations, preliminary soil borings, well investigations, tributary area evaluations, hydraulic modeling of the BWO system and research into other projects planned for the Rickenbacker airport and surrounding area. The hydraulic modeling of the BWO and the proposed Rickenbacker Interceptor confirmed that the BWO suffered wet weather surcharging and would require augmentation to properly convey the future flows to the Southerly Wastewater Treatment Plant(SWWTP). The project scope expanded to include evaluation of both the Rickenbacker Interceptor and the Big Walnut Augmentation projects. Both projects previously identified in the Capital Improvements Program. The work on the expanded scope for the Big Walnut Augmentation and the Rickenbacker Interceptor began with the evaluation of a parallel 2.75 meter (108") diameter augmentation sewer from SWWTP to S.R. 317and Parsons Avenue, then continuing east along S.R. 317 as the Rickenbacker Interceptor. The parallel 2.75 meter (108") sewer had been planned for in the design of

Jan 1, 2007

By T. Nishimura, H. Kiyama, K. Wakimoto

Discussion on the load bearing capacity of ground and the stability of tunnel is presented. We derive a simplified solution of a circular lined-tunnel in an elastic ground. The solution results in a better understanding of characteristic curves. Use of DEM allows us to consider effects of possible yield of the overstressed zone around the tunnel and inherent discontinuity of ground on the curves. Diskussion auf der Last Tragfähigkeit Bodens und die Stabilität des Tunnels wird dargestellt. Wir leiten eine vereinfachte Lösung eines kreisförmigen Ausbautunnels in einem elastischen Boden ab. Die Lösung ergibt ein besseres Verständnis der Kennlinien. Um Gebrauch DEM erlaubt uns, zu betrachten Effekte des möglichen Ergebnisses der überbetonten Zone den Tunnel und zugehörige Unstimmigkeit des Bodens auf den Kurven. La discussion sur la portance de charge de la terre et de la stabilité du tunnel est présentée. Nous dérivons une solution simplifiée d'un revêtement-tunnel circulaire dans une terre élastique. La solution a comme conséquence une meilleure compréhension des courbes caractéristiques. L'utilisation de DEM nous permet de considérer des effets du rendement possible de la zone surchargée autour du tunnel et de la discontinuité inhérente de la terre sur les courbes.

Jan 1, 2003

By T. H. Eyde

Worldwide production of natural zeolites during 2001 was estimated to be about 3.5 Mt (3.85million st). Construction and agriculture continued to be the major consumers. Estimated production in North America during 2001, including the United States, Canada and Mexico, was about 40 kt (44,000 st). In the United States and Canada, the zeolitic tuffs are ground, extruded or modified for use as adsorbents, desiccants, ion-exchange media and carriers. In Mexico and the rest of the world, the zeolitic tuffs are cut into dimension stone that is used in construction. Zeolitic tuffs are usually composed of the minerals clinoptilolite, mordenite or both. They occur in a variety of colors and are easy to cut and shape. And they have low thermal conductivity. This construction application is classified with dimension stone rather than with chemical and agricultural uses.

Jan 1, 2002

By J. -H. Wu, S. Nishiyama, Y. Ohnishi

The behaviors and stress distributions of the inclined jointed rock masses with different dip angles obtained from DDA are compared to the results of laboratory tests. By calculating the block stress distributions, it is confirmed that DDA can reproduce the arching around the trap door when lowering the trap door. The shapes of arching change with the angles of inclined layers. In addition, the earth pressures acting on the trap door shows non-symmetrical distributions when the layers are not horizontal. The stress concentration occurs in one side of the rock masses close to the trap door. Furthermore, the surface settlements are also related to the inclined angle, and the loosening zone in rock masses can be different from Terzghi’s theory [1]. Since, simulations have good agreements with the laboratory test , it demonstrates the applicability of DDA to explain the mechanical behaviors of tunnel, such as arching phenomenon, non-symmetrical earth pressure distributions acting on the trap door, and the surface settlement profile in the jointed rock masses. Dans cet article est décrite l’étude numérique du perçage d’un tunnel dans un massif de couches rocheuses jointes inclinées. La simulation à l’aide de l’Analyse de Déformation Discontinue (DDA), en faisant varier l’angle d’inclinaison des couches de roche, nous apporte des résultats en termes de distributions de contraintes et de comportement des couches, résultats qui sont ensuite comparés avec des résultats de tests en laboratoire. Les résultats confirment le fait que la DDA est capable de reproduire le phénomène d’arcage autour de la trappe lorsque la trappe s’abaisse. Les formes d’arcage varient selon l’angle d’inclinaison des couches de roche. Par ailleurs, lorsque les couches ne sont pas horizontales, la distribution de pression agissant sur la trappe est assymmétrique. La concentration de contraintes se produit du coté proche de la trappe. De plus, les tassements de surface dépendent eux aussi de l’angle d’inclinaison. En conséquence, les résultats de simulation sont en accord avec les tests en laboratoire, ce qui prouve que la DDA permet d’expliquer des comportements mécaniques du tunnel tels que l’arcage, les distributions assymmétiques de pression du sol sur la trappe, ainsi que le profil du tassement de surface dans la masse de roches jointes. Dieser Beitrag beschreibt eine numerische Studie über Tunnel im geklüftetem Fels. Das Verhalten und die Druckverteilungen in den unterschiedlich geneigten und geklüfteten Felsenmassen wird mit Hilfe des Discontinuous Deformation Analysis Programms (DDA) simuliert, und mit Laborversuchen verglichen. Die Resultate bestätigen, dass DDA der Gewölbewirkung im „Trapdoor“ Experiment gut reproduzieren kann. Die Form des Gewölbes, ändert sich mit unterschiedlichen Neigungswinkeln der Schichten. Bei geneigten Schichten entstehen unsymmetrische Druckverteilungen. Auch die Oberflächenabsenkung ist von dem Neigungswinkel abhängig. Die gute Übereinstimmung der Simulationen mit den Laborversuchen zeigt, dass die DDA-Methode gut geeignet ist, um das mechanische Verhalten von Tunneln, wie z.B. den Effekt der Gewölbewirkung, die unsymmetrischen Druckverteilungen bei geneigten Schichten, oder die Oberflächenabsenkung in geklüfteten Felsenmassen, zu erklären.

Jan 1, 2003

By k. Osei-Boakye

This paper presents the calibration of a real-time aerosol monitor, the TSI DustTrak?, to the NIOSH 5040 method being used by the Mine Safety and Health Administration (MSHA) for compliance enforcement evaluation. The standard NIOSH 5040 instrument for compliance evaluation of diesel particulate matter (DPM) has an inherent time lag of up to two weeks for laboratory processing of sample results. Therefore, providing the underground mines with a means of quantifying DPM conditions in real-time, will enable them to efficiently and effectively manage DPM levels to ensure compliance with the regulated limit.

Jan 1, 2009

By N. P. Widodo

The ventilation measurements by tracer gas method at Pongkor gold mine show that effective diffusion coefficient, E, at straight airways indicated a similar range of measured one by the laboratory experiments which can be estimated by Taylor equation. On the other hand, E of the curved airways in the mine was estimated as larger than that of the straight ones (1.5 to 32 times than that obtained by the Taylor equation and these have been compared with the data measured in Kushiro coal mine, Japan). The curved mine airways, with small curvature against airway radius and complex velocity profile, possibly give concentration ? time curves with long tailings, thus those airway conditions could make larger E. Laboratory experiments of gas diffusion by a pulsed injection of small amount gas, into straight and curved airways, have been conducted in order to investigate a range of E in mine airways. The plots of E against Reynolds number show that the present laboratory results of straight-long airways are almost close to one calculated by Taylor equation. On the other hand, the values of E measured at curved single-direction airways were smaller than that of the straight airways, which may be due to effects by secondary vortexes flow in the curved airways.

Jan 1, 2009