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By Marco Barla, Mariacristina Bonini, Giovanni Barla

ABSTRACT: The paper describes the characterisation studies of Tectonised Clay Shales at laboratory and in situ scale. The interest relates to tunnelling under squeezing and swelling conditions, in Italy, along the Apennines. The results of monitoring during full face excavation are presented in conjunction with numerical modelling. RESUME: Cet article présente la caractérisation, à l'échelle du laboratoire et in situ, des Argiles Chaotiques. L'attention est portée sur le creusement, dans ces milieux gonflants, des tunnels, dans les zones montagneuses des Appennini, en Italie. Enfin, on présentera les résultats de la modélisation numérique et la comparaison de ces derniers avec les mesures effectuées in situ. KURZFASSUNG: Die Arbeit beschreibt die Charakterisierungsstudien von tektonisierten Schiefertonen, sowohl im Labor als auch vor Ort. Das Interesse gilt dem Tunnelbau unter Quetsch- und Schwellbedingungen in Italien entlang der Apenninen. Die Überwachungsergebnisse des ganzflächigen Ausbruchs werden mit numerischen Modellen präsentiert.

Jan 1, 2003

By R. Strydom, J. H. Selby, J. Slabbert, W. Enslin

Zircon is a naturally occurring silicate of zirconium, which is used in large quantities (~1 million tonnes per annum) for its refractory properties and its extreme chemical inertness. All zircons contain uranium and thorium bound into the crystal lattice, generally at levels up to 500 ppm of uranium plus thorium. This paper focuses on one aspect of the zircon industry—the ability to safely transport large quantities of zircon sand. Currently zircon is not classified as a radioactive material for transport purposes. However, this is because of a factor used in the exemption clauses of the IAEA code on safe transport of radioactive materials. The objective of this study was to determine the validity of this factor, and was submitted as part of an IAEA Coordinated Research Project (CRP). The study is based primarily on measured rather than modelled data and covers the transport of large quantities of zircon from producers in South Africa to customers in Europe. Both occupational exposure of workers and exposure of members of the public have been considered. The transport routes studied cover rail, road, ocean-going ship and inland barge transport of unpackaged bulk products. The study showed that the most exposed member of the public would receive 10µSv/annum,while the most exposed worker would receive 144µSv/annum of exposure. It is concluded that these levels are well below all regulatory limits for such activities involving naturally occurring materials. The study also showed that normal operational exposures are higher than those in accident scenarios, a feature which does not occur with higher activity materials. It is further concluded that the study validates the use of the factor of 10 in TS-R-1, as applied to zircon sand. Additionally it is also concluded that the exemption currently applied to the transportation of bulk zircon sand is valid.

Jan 1, 2003

By Z. Lin, M. Isac, R. I. L. Guthrie

The kinetic and thermodynamic efficiencies of chromium recovery from the slag in an AOD process during the slag de-oxidation period with ferrosilicon is a complex process affected by slag basicity, temperature, the dissolution kinetics of the reducing agents, and intermixing of the slag/metal/alloy addition phases within the vessel. The present work focused on a study and simulation of the fluid dynamics and mixing behaviour of ferrosilicon additions in the AOD process for the production of stainless steel. In order to visualize the mixing behaviour, a two dimensional slice model of an AOD vessel was first built and filled with ZnCl2solution and then covered with silicone oil in order to represent the bulk liquid steel and slag phases, respectively. The injection of argon/oxygen process gases was simulated using air or helium. Particle trajectories and intermixing of the phases was monitored with a high-speed camera. To simulate the 75FeSi additions, glass spheres were used. A three-dimensional version of the AOD model was then constructed in order to confirm the adequacy of the slice model. Similar particle mixing behaviour was observed. Both models demonstrated that the ascending gas/liquid plume created two asymmetric mixing zones: a smaller rapidly re-circulating mixing zone adjacent to the side-wall locating the tuyere(s), and a larger mixing zone in the main part of the vessel. The process efficiency during the reduction period is governed by the thermal behaviour of ferroalloy as well as the mixing efficiency in the main large mixing zone. To enhance the recovery efficiency for chromium, small Fe-Si particles are suggested, given their wide distribution within the slag phase, and their large interfacial areas and rapid melting times for Cr2O3reduction from the slag. Keywords; modelling, ferrosilicon, chromium oxidation, AOD steelmaking.

Jan 1, 2004

By P. S. Pashkovsky, S. N. Smolanov

The essence of the method consists in creation of drop of opposite sign at the isolating stoppings, by which air losses through the accident district change direction of their motion. The period of reversal is selected in that way so that air may not find itself in the zone of burning. The method of fighting the fire considered was repeatedly used in the coal mines of the Ukraine. The theoretical basis of efficiency and two examples of use of this method by fighting the underground fires are adduced in the paper.

Jan 1, 2003

By I. K. Craig, F. R. Camisani-Calzolari

Defects which occur at the surface of a continuously cast slab impede the throughput of final product, because an extra stage in the process is required to grind the defects away before further processing can take place. Defect prediction and the minimization of the occurrence of defects is required. The use of two models to define the defect propagation is explained. Both models are derived using system identification techniques such as auto-regression with exogenous input(ARX). One model is used to determine the effect of manipulated variables such as casting speed and measured disturbances such as mould level on temperatures within the mould. The other isused to determine or indicate the effect of the mould temperatures on the occurrence of defects such as transversal cracks. The latter model can be used to predict when the defects will occur and the former can be used to control the occurrence of the defects. Keywords: continuous casting, surface defect, control system, predictor, system identification, ARX

Jan 1, 2003

By Gift Makusha, Dave Minney

Anglo Coal South Africa mines coal for both the domestic and export market using open cast and strip mining methods. To establish a mine, a process is set in place to gather ever increasing amounts of geological and metallurgical data to confirm a proven reserve. Increasingly, geotechnical data are also included in this process to confirm that reserve is easily and safely mineable. The mine design process is an iterative one using a combination of numerical modelling and empirical data to arrive at a mining layout that is both, practical, productive and safe. In South Africa it is a legal requirement to compile a code of practice to combat rock fall and slope instability accidents and these have to be revised annually, reinforcing the iterative process of continual improvement. To ensure best practise occurs, all Anglo Coal operations are subjected to annual 2nd party audits and ad hoc 3rd party audit by independent consultants. This paper attempts to explain the process described above in a concise, but understandable manner. 1.0 GEOLOGICAL SETTING The Ecca sediments date from the Permian period and the coal deposits were formed in glaciated valleys on a basement of Dolomite, Ryolite or Granophyre rock types. The sediments overlying the coal deposits are typically flat lying and multiple bedded. The sediments consist of mudstones, shales and sandstones and are generally capable of forming stable highwalls given the time that they must stand up for. Anglo Coal extracts coal from the Witbank, Highveld and Vereeniging coalfields. The Witbank coalfields contain five seams numbered from the base upwards, 1 to 5 Seam; Highveld coalfield the 2 and 4 Seam and the Vereening area the seams are described as Top, Middle and Bottom seams. Coal deposited over the basement Dolomite formation display very erratic dips, as contemporaneous subsidence occurred in some instances over sinkholes that were forming, resulting in local thickening of the coal deposit and resulting in strata that dips toward the centre of the sinkhole.

Jan 1, 2006

By P. He

Abstract This paper introduces tested results of rock-socketed pile in Nanjing, Wuhan and Chongqing. From a force- transfer model, a distribution of axial force for pile-body and inlaid resistance for rock-socketed pile was deduced. Comparing the results of test and calculation, it shows that the calculation result coincide with the test result. Keywords rock-socketed pile, load transfer, inlaid resistance, end resistance. Zusammenfassung: dieser text legt eine kuyze Einfuehyung ueber die Erfolge wissenschaftlicher Forschungsarbeit in bezug auf die Grundprinzipien der Mechanik von Belastungsuebermittlung der Einlegesteinpfeilers der Durch Benutzung von Ausgleich/Balance der inneren Kraft und Deformationskoordinierung wird das mechanische Modell der Belastungsuebermittlung des Einlegesteinpfeilers aufgestellt. Vom lebendigen Beispiel wird dia Wellenkraft des Steinpfeilera und die Verteilungskurve Einlegebfestigungskraft ausgelegt, man hat diess bereits mit der tatsaechlichen genessenen Kurve verglichen. Schluesselwoerter: Einlegesteinpfeilers, Belastungsuebermittlung, Einlegebfestigungskraft, Seitenwiderstand. Résumé - Le présent article décrit de façon succincte des résultats de la recherche sur le mécanisme du transfert de chargement du pieu d’ancrage au massif. Une modèle dynamique du transfert de chargement du pieu d’ancrage au massif est ainsi établie avec l’application des conditions de l’équilibre de contraintes internes et de coordination de la déformation. L’expérimentation sur des exemples réels a permis de mettre à jour des courbes de distribution de la force axiale du corps du pieu et de la force d’ancrage avec comparaison aux courbes effectivement mesurées in situ. Mots clés - Pieu d’ancrage au massif, Transfert de chargement, Force d’ancrage, Résistance à la pointe

Jan 1, 2003

By K. C. Mills, R. Thackray

A test has been devised that can predict accurately the % crystallinity developed in a slag film formed between the steel strand and the mould. The % crystallinity in the test samples was determined and compared with that for slag films formed in the mould when casting with that flux. There was good agreement between the % crystallinity in the test samples and the slag films. It was found that additions of TiO2and ZrO2had little effect on the amount of crystalline phase formed, but additions of CaO caused a dramatic increase in the amount of crystalline phase formed. Various parameters (which can be calculated from chemical composition of the flux) have been plotted against % crystallinty in the test samples. It was found that the modified (NBO/T) ratio provided the best relation with % crystallinity for the various parameters tested. There commended relation is % crystallinity=141.1(NBO/T)-284.0. Keywords: continuous casting, mould flux, slag film, crystallinity, chemical composition

Jan 1, 2004

By S. E. Olsen, M. Tangstad, G. Tranell, K. Berg, S. Gaal

In this study, the reduction behaviours of MnO and SiO2containing slags by solid carbonaceous materials was investigated in both small and larger-scale laboratory experiments. Five types of carbonaceous material were investigated: 2 graphites, industrial coke, anthracite and eucalyptus charcoal. The effects of the reductant type/properties on the reduction kinetics, metal composition and metal yield, have been quantified. Results show that the reduction rate is highly dependant on the type of carbon used. It was found that the reductant type significantly influenced the SiO2reduction while it did not seem to have a large effect on the MnO reduction. This may be due to the different CO2and SiO reactivities of the materials.

Jan 1, 2004

By J. Drzewiecki, J. Kabiesz

Coal mining using longwall methods of mining can lead to intense disturbances of undermined roof strata. The disturbances may extend beyond the extraction area and the resulted rock mass deformations will appear differentiated. In the case of stiff and undermined roof strata, the energy stored in these rock masses may be frequently dissipated in the form of high-energy seismic tremors. Such events can occur if these strata should fail or „free themselves” either from the constrainment of rock environment or from adjacent strata. It has also been found that the amount of the stored energy closely depends on the size and/or slenderness of these strata. Thus, it would be possible to apply specific preventive measures to reduce the energy of mining – induced seismic tremors. The methods are based on artificial disintegration of the structure of energy – storing strata. One of the most efficient methods is a method of directional hydraulic fracturing, which is regarded as an alternative solution from the traditional blasting and hydraulic methods.

Jan 1, 2003

The distribution of chrome spinels in a magnetically fractionated ilmenite concentrate sourced from the Murray Basin was characterized by XRF assaying, quantitative electron microprobeanalysis, grain mapping, automated mineral phase clustering, and modal analysis. At least 14 distinct chrome spinel types were present in the concentrate. There is considerable variation in the amount of each chrome spinel type present, although a high-Mg, high-Al phase makes up close to 45 per cent of the total spinel population. Magnetic fractionation results showed significant variation in the composition and relative abundance of spinels reporting to each fraction. Low magnetic field strength fractions (ie. high susceptibility grains) were dominated by chrome spinels that are mid-range in Al and Cr. These spinels have the highest magnetite, ulvospinel and Fe(Al,Cr)2O4components. In comparison, the high field strength fractions (i.e. low susceptibility grains) have the majority of the grains with high-Al contents indicating a higher proportion of Mg(Al,Cr)2O4component. Spinels high in a (Al,Cr)2.67O4non-stoichiometriccomponent are absent at low field strengths but tend to be concentrated in the high field strength, non-magnetic fractions. Intermediate field strength fractions tend to exhibit a broad spread in spinel compositional types. A mild roast treatment of the sample had no clear effect on the distribution of chrome spinels between different magnetic fractions, but it did cause a change in the magnetic properties of the accompanying ilmenite grains. The effect of more extreme roasting conditions on the magnetic properties of the chrome spinels is to be determined.

Jan 1, 2003

By Y. Shiraishi, Y. Sakurai

A new method, the gliding cylinder method, was proposed as a wide range viscometer for the measurements of molten salts, slags, and glasses. The method consists of two coaxial cylinders, cylindrical bob and a vessel containing a liquid sample. There is a narrow gap between bob and vessel. When the vessel moves against the bob, the generated force on the bob consists of three types of resistance: (1) Stokes’s resistance on the bob, (2) a capillary flow resistance though an annular gap between vessel and bob, and (3) lubricating resistance in a gap. The last two can be calculated on a theoretical basis but the first cannot be estimated by a simple calculation since a wall effect did not calculate easily. However, it can be assumed that the generated force depends on both the viscosity of a liquid and velocity of the vessel. Thus, the relation between viscosity and a force at desired velocity of the vessel was measured using several standard reference materials including glycerol aqueous solutions and standard reference oils. The results depended on the magnitude of the gap between the bob and the vessel. For the wider gap, it was shown that the viscosity is a linear function of a gradient of force with respect to a vessel velocity. In contrast, if the gap is small, the viscosity depends on the gradient (of force with respect to velocity). This implies that the non-linear phenomena would occur in Stokes resistance. Though detailed analysis is in a further investigation, a calibration method can be applied to determine the viscosity by this method, because good correlation was obtained among these quantities. Viscosity of molten salts, such as NaNO3and ZnCl2was measured by this method as high temperature demonstration. Keywords: viscometer, viscosity, sphere pull-up method, fused salts, molten slags, glass melts

Jan 1, 2004

By R. W. Ottermann, N. D. L. Burger, A. J. von Wielligh, P. R. de Wet, J. L. Steyn

A low noise blast hole drilling system was developed to limit the risk of noise induced hearing impairment in mining operations. Noise induced hearing loss has been identified as a major occupational health risk in SA mines. The noise generated by pneumatic percussion drills is a major contributor to such noise induced hearing. This motivated the South African Safety in Mines Research Advisory Committee (SIMRAC) to commission the development of a low noise rock drill system. The system had to be designed, manufactured, tested and demonstrated in a simulated underground mining environment. The specification required noise levels below 90 dBA. Other important design considerations were ease of manual transport, setting up and operation. The primary design concept was to encapsulate a standard Seco S215 pneumatic rock drill in a composite material tube. The tube is pushed onto the rock face by a pneumatic cylinder and is sealed at the rock face by an elastic seal. The drill is pulled towards the rock face by a rope and pulley mechanism fitted inside the tube. This mechanism is powered by a second pneumatic cylinder. The actions of moving and setting the drill require two persons. However, the team can carry out the drilling function itself on several drills simultaneously because of the self-thrusting design. The drill is supported by two camlocks. The exhaust (air containing dust, water, rock shavings, oil and grease) is removed from the encapsulating tubes via exhaust tube to the end of the stope. In this way exhaust noise and air pollutants are disposed of away from personnel. Tests were conducted in a test stope. Noise levels of under 90 dBA were achieved, thereby attaining the primary design specification. This was achieved without materially compromising ease of handling. Penetration rate was somewhat improved compared to that of the standard drill, so that productivity could be maintained. Keywords: Drill, rock drill, quiet, noise, mine, underground.

Jan 1, 2003

By M. Kuchta, A. Newman

LKAB’s Kiruna Mine, located above the Arctic Circle in northern Sweden, is the second-largest underground mine in the world today. The orebody is a world-class high-grade magnetite deposit, from which three raw ore products are extracted. We use mixed integer programming to determine a production schedule, i.e., which production blocks to mine, and when to start mining them, so as to minimize deviation from planned production quantities while adhering to the operational constraints of the mine. The resulting model contains thousands of binary variables and a commensurate number of constraints, precluding us from obtaining a schedule in a reasonable amount of time. We describe a method that builds on prior, related work, to expedite solution time. Keywords: underground mining, production planning, optimization, integer programming

Jan 1, 2003

By M. Arlandi, J. C. Monge

In this paper, the finite element method is used to obtain deformations of a rock tunnel. More than 3,000 numerical simulations and calculations were carried out. The analysis of this results has allowed to achieve mathematical formulations and graphs, to obtain in advance support monitored displacements in tunnelling construction, so they can be predicted before excavation and supporting woks. The application of the presented formulations and charts will aid engineers to control tunnel monitoring, reducing decision time when problems occur. The analysis is limited to cases involving elastic behaviour of the terrain for tunnels of average to good quality in rock, and to excavation sections of average or smaller dimensions for road tunnels. The results show that, in all cases, mathematical expressions to obtain induced displacements around tunnel excavations, have similar pattern than Kirsch (1898) expressions for circular excavations. As corollary of the achieved results, a method to estimate in situ natural geostress ratio K0=sh/sv , by means of convergence measurements, is presented. In diesem Beitrag wurden die Verschiebungen eines Tunnels durch die Methode de Finiten Elemente berechnet. Mehr als 3000 numerische Simulationen und Berechnungen wurden ausgeführt. Die Analyse dieser Resultate hat es ermöglicht, mathematische Formeln und Grafiken zu entwickeln, die zur Voraussage der Verschiebungen in Tunnel dienen, auch unter Betrachtung der verschiedenartigen Abstützungen. So können die Verschiebungen vor den Erdarbeiten und dem Bau der Abstützung abgeschätzt werden. Die abgeleiteten Formeln und Grafiken werden vor allem einen grossen Dienst für Ingenieure bei der Mithilfe zu zeitsparenden Entscheidungen im Tunnelbau und bei der Tunnelkontrolle leisten. Die analysierten Fälle sind auf eine elastische Modellierung des Baugrunds beschränkt, sowie auf eine mittlere bis gute Qualität des Felsens und auf die Aushebung von Abtragungsabschnitten mittlerer oder geringer Grösse für den Strassenverkehr. Die Resultate zeigen, dass in allen Fällen die hergeleiteten Formeln zur Berechnung der durch den Tunnelbau verursachten Verschiebungen um den Tunnel die gleiche mathematische Struktur haben wie diejenigen von Kirsch (1898) für kreisförmigen Bodenaushub. Als Korollarium der ausgeführten Berechnungen wird eine Methode zur Abschätzung der vorherrschenden in situ Geospannungs-Verhälniss K0=sh/sv angegeben, die von den Messungen der Verschiebungen im Tunnel ausgeht. Dans cet article, la méthode des éléments finis est utilisée pour obtenir les déformations d’un tunnel creusé dans la roche. Plus de 3000 simulations numériques et calculs ont été effectuées. L’analyse de ces résultats a permis de définir des modèles mathématiques et des abaques afin de prédire, avant l’excavation et les travaux de soutènement, les déplacements auscultés pendant la construction du tunnel. L’application de ces modèles et abaques permettra donc aux ingénieurs de contrôler les déplacements durant l’auscultation du tunnel et de réduire le temps de décision lorsque des problèmes surviennent. L’analyse est limitée au cas du comportement élastique du terrain pour des tunnels creusés dans de la roche de moyenne a bonne qualité, et à de sections d’excavation de petites à moyennes dimensions pour des tunnels routiers. Les résultats montrent que, dans tous les cas, les expressions mathématiques permettant d’obtenir les déplacements induits autour des excavations de tunnel, présentent des similitudes avec celles de Kirsch (1898) pour des excavations circulaires. Comme corollaire aux résultats obtenus, une méthode pour estimer le rapport des

Jan 1, 2003

By S. J. Thomas, P. A. Lilly, J. A. L. Napier

An industry research project has been established to examine the issue of rock mass failure in large open pit slopes. The approach began with numerically modelling failure at the laboratory scale with a displacement discontinuity program. The interim results from the program suggest the output failure mode is dependent upon the input parameter cohesion weakening. Es wurde ein Forschungsproject mit unterstützung von Bergbauindustrie bearbeitet. Die Zielsetzung der vorliegenden Arbeit war die Analysierung des Böschungsgefähr im größen Festgesteinstagebauen. Das Verfahren besteht aus der numerischer Modelierung mit Ansatz einen sonderen Rechnerprogram. Die erste Ergebnis zeigt, daß die Aufgabe am Angabendaten (cohesion) abhängig sein wird. Un project de recherche industriel fût conduit avec le but d’examiner les éboulements de roche dans les mines a ciel ouvert. La premiere étape a été de modelliser numériquement les éboulements dans un laboratoire en utilisant un programme de déplacement discontinu. Les resultants préliminaires du programme indiquent que la prédiction des ébouliements est directement reliée à la magnitude de la cohesion.

Jan 1, 2003

By P. Goosen, A. Paterson, E. Paulsen

Ticor South Africa is currently involved in the mining and processing of a heavy mineral oredeposit at Hillendale Mine on the KwaZulu-Natal north coast. The orebody is characterized by a high ultra fine fraction (-45µm) that has a variable rheological behaviour when subjected to shear and hydration. Experience at Hillendale has shown that the ultra fine mineral tailings are sensitive to shear history in terms of shear intensity and shear duration as well as hydration history. This phenomenon expresses itself right through the primary beneficiation process influencing the mineral separation, but is especially prevalent on the residue disposal i.e. slurry transport and deposition on the tailings impoundment. Tube viscometer test work was conducted on the flocculated fine tailings that indicated that there was a change in rheology as a result of shear. This paper presents the results of the on-site test work conducted at the mine to measure the rheology at various stages in the process.

Jan 1, 2003

By A. Bouvard, N. Hoteit, E. Boidy, F. Pellet

In the context of the construction of an Underground Research Laboratory devoted to the feasibility studies of radioactive waste deposits, it appears of the utmost importance to study the long-term behaviour of rock, over a long time period. In this paper, some results of tests performed on the argillite from the Meuse-Haute-Marne site test in Eastern France are presented. Then a numerical simulation of one of this test using the viscoplastic damaging constitutive law proposed by Lemaitre is presented. Finally, this law is used to simulate numerically the behaviour of the rock at the wall of a circular tunnel in order to determine the extension and the change along the time of the Excavated Damaged Zone (EDZ). Advantages and limitations of the model are discussed. Dans le cadre de la réalisation d’un laboratoire de recherche souterrain conçu pour étudier la faisabilité d’installations de stockage de déchets radioactifs, il apparaît fondamental de caractériser non seulement le comportement viscoplastique à très long terme des matériaux mais aussi les phénomènes d’endommagement consécutif à la redistribution de contraintes provoquées par l’excavation des cavités. On présente ici les résultats d’essais réalisés sur les argilites du site de Meuse/Haute-Marne et destinés à caractériser leur comportement visco-endommageable. Il est ensuite procédé à une application de la loi viscoplastique endommageable de Lemaitre pour simuler l'un de ces tests. Les apports et les limites d'un tel modèle sont mis en évidence par des simulations numériques du comportement de la roche au pourtour d'une galerie circulaire permettant de suivre l’évolution au cours du temps de la zone endommagée (EDZ) à la paroi . Im Rahmen des Baus eines unterirdischen Forschungslabors für die Untersuchung der Machbarkeit von Deponien für radioaktive Abfälle erweist es sich als äußerst wichtig, das langfristige Verhalten von Gestein über einen langen Zeitraum zu untersuchen. Im vorliegenden Artikel werden einige Ergebnisse von Untersuchungen vorgestellt, die mit Tonschiefer aus der Meuse-Haute-Marne in Frankreich durchgeführt wurden. Anschließend wird eine numerische Simulation der Untersuchungen unter Verwendung des von Lemaitre vorgeschlagenen viskoplastischen Verformungsgesetzes vorgestellt. Schließlich wird dieses Gesetz auf die numerische Simulation eines Kreistunnels angewandt, um die Ausdehnung und die zeitliche Entwicklung der Auflockerungszone (EDZ) zu bestimmen. Es werden die Vorteile und Grenzen des Modells diskutiert.

Jan 1, 2003

By Ch. Schroeder, F. Collin, R. Charlier, Y. J. Cui

The paper proposes two numerical models ot the mechanical behaviour of chalk. First, an elasto-plastic constitutive law reproduces the different plastic mechanisms of the chalk and the influence of pore fluids by introducing the concept of suction. Secondly, a model able to reproduce time dependence behaviour. Eventually, the paper gives a simulation of an academic reservoir during depletion and waterflooding phase. Der Artikel stellt zwei numerische Modelle des mechanischen Verhaltens der Kreide vor. Das erste ist ein elasto-plastisches Modell, das verschiedene plastische Mechanismen der Kreide und den Einfluss von Porenflüssigkeit, unter dem Begriff der Suktion, reproduziert. Das zweite Modell berücksichtigt darüberhinaus das zeitabhängige Verhalten. Schliesslich zeigt die Veröffentlichung eine Simulation einer theoretischen Lagerstätte während der Entleerung und der Wasserinjektion. L'article propose deux modèles numériques du comportement mécanique de la craie. Le premier est une loi élasto-plastique qui reproduit les différents mécanismes plastiques de la craie et l'influence du fluide interstitiel par l'introduction de la notion de succion. Le second est un modèle prenant en compte les effets différés. Enfin, l'article présente une simulation d'un réservoir académique durant les phases de déplétion et d'injection d'eau.

Jan 1, 2003

By N. Gatelier, T. You, J. C. Kandel

ABSTRACT: Underground hydrocarbons storage is a very specific domain for the designer. He is usually free to adjust the section, shape and layout to cope with the geological and geotechnical conditions. This paper presents a panorama of the geotechnical design of mined underground storage caverns, then lists a number of uncommon features encountered in a storage excavated in Sydney, Australia, the Elgas LPG project that had to face major non-isotropic conditions with numerous local variations, impacting on the achievement of the design profiles. Changes in geotechnical design methodology and practice are examined through this project, now in operation, which will have lasted altogether almost ten years. KEY WORDS: underground storage, geotechnical engineering, stability, methodology, design. ZUSAMMENFASSUNG: Die untertaegige Speicherung von Kohlenwasserstoffen unterliegt in der Planung sehr spezifischen Bedingungen. Der planende Ingenieur hat bei der Dimensionierung und Formgebung der Speicherhohlraeume gewisse Freiheiten, muss jedoch vorgefundene geologische und geotechnische Bedingungen beruecksichtigen. Der vorliegende Beitrag gibt zunaechst einen allgemeinen Ueberblick ueber die geotechnische Planung von bergmaennisch aufgefahrenen Speicherhhohlraeumen. Darueber hinaus werden Besonderheiten betrachtet, mit denen das Elgas LPG-Speicherprojekt in einer bergmaennisch aufgefahrenen Kaverne in Sydney, Australien konfrontiert war. Hierbei ging es um die Beruecksichtigung anisotroper Bedingungen mit zusaetzlichen Heterogenitaeten im Gestein und den daraus erwachsenden Schwierigkeiten, die geplante Hohlraumform zu verwirklichen. Ueber einen Zeitraum von fast 10 Jahren, in denen das jetzt in Betrieb befindliche Projekt unterschiedliche Betriebsphasen durchlaufen hat, wurden verschiedene geotechnische Entwurfsverfahren auf ihre Anwendbarkeit geprueft. SCHLUESSELWOERTER: Untergrundspeicherung, Geotechnik, Stabilitaet, Entwurfsverfahren, Planung. RESUME : Le stockage souterrain d’hydrocarbures est un domaine très spécifique pour le concepteur, car celui-ci dispose d'une large liberté pour adapter les sections, les formes et les implantations aux conditions géologiques et géotechniques de l’environnement choisi. Après un panorama de la conception géotechnique des stockages souterrains d’hydrocarbures par la méthode dite des cavités minées, l’accent sera mis sur un certain nombre de particularités rencontrées lors du projet de stockage de GPL de Elgas à Sydney en Australie, creusé dans de très fortes conditions d’anisotropie du massif rocheux, avec de nombreuses variations locales et toutes les implications que cela peut avoir sur le maintien des formes. L’évolution des approches méthodologiques géotechniques durant la dizaine d'années de développement de ce projet depuis les premières études jusqu'à l'exploitation actuelle est également présentée. MOTS-CLEFS : stockage souterrain, géotechnique, stabilité, méthode, conception.

Jan 1, 2003