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Showing papers in "Bulletin of Engineering Geology and the Environment in 1999"


Journal ArticleDOI
TL;DR: In this paper, the authors present a summary review and a classification of the main approaches that have been developed world-wide for the assessment of hazard and risk of landsliding, and several considerations concerning acceptable risk and risk management are presented.
Abstract: This paper deals with several aspects of the assessment of hazard and risk of landsliding. In recent years the interest in this topic has increased greatly and there are many technical papers dealing with this subject in the literature. This article presents a summary review and a classification of the main approaches that have been developed world-wide. The first step is the subdivision between qualitative and quantitative methods. The first group is mainly based on the site-specific experience of experts with the susceptibility/hazard determined directly in the field or by combining different index maps. The approaches of the second group are formally more rigorous. It is possible to distinguish between statistical analyses (bivariate or multivariate) and deterministic methods that involve the analysis of specific sites or slopes based on geo-engineering models. Such analyses can be deterministic or probabilistic. Among the quantitative methods discussed is the Neural Networks approach which has only recently been applied to engineering geology problems. Finally several considerations concerning the concept of acceptable risk and risk management are presented.

1,227 citations


Journal ArticleDOI
TL;DR: In this paper, the authors evaluated the potential contribution of each tree species to slope stabilisation with reference to existing slope conditions in the mountainous area of Khao Luang, southern Thailand.
Abstract: The mechanical stabilisation of soil slopes by means of tree roots depends largely on the strength properties of the roots and their growth pattern within the soil. In particular areas, the selection of indigenous tree species on the basis of their root properties is an essential part of biotechnical slope protection. In order to determine the effects of tree roots on slope stabilisation in the mountainous area of Khao Luang, southern Thailand, seven tree species were studied. The distribution and penetration of the roots was established and their tensile strength and pull-out resistance determined. The paper evaluates the potential contribution of each of these species to slope stabilisation with reference to existing slope conditions.

179 citations


Journal ArticleDOI
TL;DR: In this paper, the relation between the mechanism of landslides and rainfall is discussed and a formula is suggested which could help in assessing the problems of instability, and an Lf factor, determined mainly from the ratio between the cumulative precipitation and the mean annual rainfall is proposed to indicate the likelihood of occurrence of failure.
Abstract: In the densely populated highland area of Ethiopia, where altitudes exceed 1750 m, the increase in the number and size of landslides during the last 30 years is causing considerable concern among the society. From 1993 to 1998 alone, about 300 lives have been lost, more than 200 houses demolished, greater than 100 km of road damaged and in excess of 500 ha of land devastated. The paper discusses the relation between the mechanism of landslides and rainfall. A formula is suggested which could help in assessing the problems of instability. An Lf factor, determined mainly from the ratio between the cumulative precipitation and the mean annual rainfall, is proposed to indicate the likelihood of occurrence of failure. It is shown that cracks and signs of slope movement are observed when Lf is in the range of 15–30%, while values exceeding 30% indicate a much greater probability of landslide occurrence.

104 citations


Journal ArticleDOI
TL;DR: In this paper, a new method, freeze-cut-drying, is introduced for preparing a soil specimen for microstructural analysis using scanning electron microscopy (SEM), which can preserve the original soil microstructure and minimise flaws such as false voids and erroneous orientations.
Abstract: A new method, freeze-cut-drying, is introduced for preparing a soil specimen for microstructural analysis using scanning electron microscopy (SEM). With this method, moisture in the specimen is removed by freeze-drying and an SEM observation surface is made by cutting the specimen at a temperature below freezing point. Tests on bentonite clay were used to compare the results from this method with those using other existing techniques such as peeling. Image processing was employed to analyse the SEM micrographs quantitatively in terms of distributions of size and orientation of particles and pores in the soil. The results indicate that this method can preserve the original soil microstructure and minimise flaws such as false voids and erroneous orientations which frequently occur in SEM images obtained from specimens prepared by other techniques. This method is particularly suitable for clay soils with high moisture contents and should find wide application in the analysis of soft clays, slurries and marine sediments.

54 citations


Journal ArticleDOI
TL;DR: In this article, the authors discuss the mechanism of dynamic disturbance and its contribution to rock burst using numerical simulation based on an example from a hydropower station in China, and demonstrate that the accumulation of elastic strain energy in the rock is the main internal cause of rock burst.
Abstract: The accumulation of elastic strain energy in the rock is the main internal cause of rock burst. However, dynamic disturbance is an important external factor, frequently triggering this phenomenon. The paper discusses the mechanism of dynamic disturbance and its contribution to rock burst using numerical simulation based on an example from a hydropower station in China.

53 citations


Journal ArticleDOI
TL;DR: In this article, the impoundment of 49 dams in the Niger catchment area with a combined reservoir capacity of 36 million m3 has a direct impact on the Niger Delta, resulting from the reduction in flow and sediment delivered to the coast.
Abstract: The Niger Delta has a fragile coastline in which the river hydraulic forces are in dynamic equilibrium with coastal processes. The impoundment of 49 dams in the Niger catchment area with a combined reservoir capacity of 36 million m3 has a direct impact on the Niger Delta, resulting from the reduction in flow and sediment delivered to the coast. The delta has experienced shifts in the ecological equilibrium manifested as adjustments to the coastline geometry, lower flood water levels and upstream migration of tidal influences. Although the effects of upstream dams are cumulative, the large capacity dams have the most immediate impact. The construction of the dams results in a sudden drop in water level which is followed by a gradual recovery. Data from the Niger Delta suggests that although some rivers recover part of their flow, levels are still below those which existed prior to the construction of the Kainji Dam.

48 citations


Journal ArticleDOI
TL;DR: Abandoned mine works are a potential cause of ground subsidence and hence are of major concern where development or re-development is to take place as mentioned in this paper, however, information necessary to locate potential hazards may be available but occurs in numerous scattered locations and it may require considerable time to access the data.
Abstract: Abandoned mine works are a potential cause of ground subsidence and hence are of major concern where development or re-development is to take place. In the United Kingdom, information necessary to locate potential hazards may be available but occurs in numerous scattered locations and it may require considerable time to access the data. In recent years thematic geological maps have been produced for some of the British coal field areas. The paper describes the historical evolution of the mining system, emphasising the pillar workings which began in the sixteenth century. Methods of investigation such as downhole hammer and geophysics are briefly mentioned and the importance of zoning the land discussed. Stabilisation measures may involve occupying the workings with hydraulically-emplaced fill or cheap bulk grout. In areas of less risk, special foundation structures may be used.

31 citations


Journal ArticleDOI
TL;DR: In this article, the legal difficulties of proving the cause and occurrence of a landslide are explored through three legal case studies involving damage, or potential damage, resulting from landslide movements, and the legal definition of a "landslide" suitable for legal purposes is examined and the various causes of landslides are briefly reviewed.
Abstract: Ground movements of many types can be responsible for socio-economic losses that lead to construction or insurance claims or even legal proceedings. Should the ground movements be the result of landslide movements, proving the cause or even the occurrence of the landslide may often be the main area of dispute. In this paper the definition of a 'landslide' suitable for legal purposes is examined and the various causes of landslides are briefly reviewed. The legal difficulties of proving the cause and occurrence of a landslide are then explored through three legal case studies involving damage, or potential damage, resulting from landslide movements.

25 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a model of glissement de terrain observees dans l'agglomeration de Constantine comme temoins d'une activite neotectonique.
Abstract: L'etude presentee se compose de deux parties. La premiere explique certaines formes de glissement de terrain observees dans l'agglomeration de Constantine comme temoins d'une activite neotectonique. La seconde partie presente quelques caracteristiques geotechniques, des formations geologiques instables, obtenues par differents moyens: les essais de laboratoire, les essais in-situ, les correlations.

22 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe a set of nombreux depots de laves torrentielles, preleves dans 11 bassins versants des Alpes francaises, nous a permis de definir de two families of laves.
Abstract: L'etude detaillee de nombreux depots de laves torrentielles, preleves dans 11 bassins versants des Alpes francaises, nous a permis de definir deux familles de laves, les laves a matrice cohesive et les laves a matrice granulaire (materiau ecretea 20 mm). Leur typologie est precisee par des criteres granulometriques discriminants relatifs aux fractions 20 a 200 μm. Lorsque les zones sources sont clairement identifiables, l'etude des echantillons preleves dans ces zones montre que les materiaux mobilises presentent des caracteristiques granulometriques et geotechniques proches de celles des laves torrentielles qu'ils ont generees. Ainsi, les depots de laves torrentielles portent la signature de la zone source principale, tant au niveau granulometrique, que petrophysique et geotechnique, et rendent compte d'un faible tri granulometrique pendant la propagation de la lave torrentielle. De plus, ces etudes mettent en exergue l'importance des caracteristiques des materiaux potentiellement mobilisables, et notamment du critere granulometrique, sur les conditions du declenchement des laves torrentielles.

15 citations


Journal ArticleDOI
TL;DR: In this article, the developpement des ravins in the bassin of Oued Maiez situe in Tunisie Centrale has been investigated, and it has been shown that the nature lithologique des differentes unites geologiques and superficielles identifiees comme relativement homogenes dans le bassin versant is determinant din le developement of ravins.
Abstract: L'erosion ravinante reduit de plus en plus les terres cultivables en Tunisie Centrale en les transformant en badland. Le developpement des ravins est variable dans l'espace et dans le temps suite a la variabilite des parametres physiques et naturels qui regissent l'accroissement des ravins. Nous nous sommes proposes dans cette recherche d'etudier l'effet des formations lithologiques sur le developpement des ravins dans le bassin versant de 1500 ha d'Oued Maiez situe en Tunisie Centrale. Les cartes du reseau hydrographique de 1963 et 1989 ont eteetablies a partir des photographies aeriennes au 1/12,500 non redressees. La prospection du terrain nous a permis de constater que la nature lithologique des differentes unites geologiques et superficielles identifiees comme relativement homogenes dans le bassin versant est un facteur determinant dans le developpement des ravins. Ainsi, les argiles gypseuses de la formation Cherichera (Lutetien-Priabonien) presentent un chevelu de ravins dense alors que les sables fins de l'Oligocene inferieur sont incises par des ravins en forme de gorges etroites dont la profondeur depasse souvent les 5 m (Fig. 7). Nous avons alors etabli un leve cartographique detaille au 1/12,500 de ces differentes unites qui sont au nombre de 8.

Journal ArticleDOI
TL;DR: In the Fej Hcine mining area of north-west Tunisia, the Medjerda River and its principal tributary, El Melah, are polluted by heavy metals and arsenic as discussed by the authors.
Abstract: In the Fej Hcine mining area of north-west Tunisia, the Medjerda River and its principal tributary, El Melah, are polluted by heavy metals and arsenic. The geochemical studies undertaken have indicated pronounced falls in the concentrations of metals since the mining activities ceased, although the river sediments still contain higher levels than the local host rocks, particularly arsenic and zinc. At the Tunisia/Algeria border, arsenic concentrations in the Medjerda waters can exceed 1 mg/l. Leaching tests on samples of ore, flotation tailings and an arseniferous mass indicate that whilst Zn, Pb, Cu and Cd concentrations do not exceed 1 mg/l in the leachate solutions, arsenic levels reach 5, 344 and 9,400 mg/l respectively. The study has shown that the pollution originates not only from the mining activities but also from the mineral occurrences present in the mining district and from another source within Algeria.

Journal ArticleDOI
TL;DR: In this article, the authors describe the results of a study on the stress-strain time dependent (creep) behaviour of silicate-Hardener 600B grouted Leighton Buzzard sand specimens when subjected to incremental loading at certain time intervals.
Abstract: This paper describes the results of a study on the stress-strain time dependent (creep) behaviour of silicate-Hardener 600B grouted Leighton Buzzard sand specimens when subjected to incremental loading at certain time intervals. Unconfined and confined multi-stage creep tests were conducted on sand specimens injected with different silicate content grouts which cover the range generally used in engineering practice. The laboratory results showed that creep movements increase with the increase in stress ratio causing a rise in strain rate which ultimately leads to creep rupture (complete failure). However, an increase in the stress ratio does not affect the linear relationship between logarithm of strain rate and the logarithm of time suggesting that the three parameter phenomenological relationship of Singh and Mitchell (1968) may be suitable to describe the multi-stage creep behaviour of silicate-Hardener 600B grouted sand.

Journal ArticleDOI
TL;DR: In this paper, the importance of the particle size distribution (grading) of a gravel material for unsealed roads has been recognized and various parameters have been devised to allow interpretation of grading curves in terms of a single parameter for ease of application, control and comparison.
Abstract: The importance of the particle size distribution (grading) of a gravel material for unsealed roads has long been recognized. Various parameters have been devised to allow interpretation of grading curves in terms of a single parameter for ease of application, control and comparison. It is shown that there are significant correlations between many of the better known parameters, although it is also clear from the scatter of the data that the parameters probably indicate slightly different properties. The investigation has shown that a new parameter, the grading coefficient, is a good indicator of the grading and can be used interchangeably with many other parameters. In general terms the grading coefficient is approximately half the percentage gravel in a material and grading coefficients of 16 and 34 are roughly equivalent to grading moduli of 1.5 and 2.6, respectively.

Journal ArticleDOI
TL;DR: In this article, les nombreuses mesures disponibles ont pu etre modelisees par un mecanisme de deformation particulier, sans surface de rupture predefinie par the structure geologique.
Abstract: Le versant sud du Mont Sec (Sechilienne, France), compose de micaschistes, est l'objet d'un mouvement gravitaire tres etudie depuis 1985, puisqu'il represente un risque majeur pour la vallee de la Romanche, en amont de Grenoble. Les nombreuses mesures disponibles ont pu etre modelisees par un mecanisme de deformation particulier, sans surface de rupture predefinie par la structure geologique. L'observation geomorphologique et structurale du versant sud, gneissique, de la Toura (Saint-Christophe-en-Oisans, France) a revele de si nombreuses similitudes avec le cas de Sechilienne que le mecanisme propose parait ici aussi adequat. Le poli glaciaire observe sur les contrepentes permet de faire remonter le debut des mouvements aux interstades glaciaires du Wurm. La poursuite des etudes sur ce site faiblement actif ou les conditions d'observation sont excellentes pourra apporter des eclairages utiles pour la maitrise de mouvements de versants plus sensibles comme celui de Sechilienne. Plus largement, ce phenomene semble pouvoir concerner de nombreux versants des socles metamorphiques alpins.

Journal ArticleDOI
TL;DR: In this paper, the authors propose an analysis critique en insistant sur l'influence des methodes d'interpretation employees, and s'appuie pour les interpreter sur des modelisations simplifiees prenant en compte la topographie et la tectonique.
Abstract: Dans le cadre de la conception d'un futur grand tunnel a travers les Alpes, des mesures de contraintes naturelles ont ete faites dans 13 forages profonds, dans des contextes geologiques et topographiques varies. L'article en propose une analyse critique en insistant sur l'influence des methodes d'interpretation employees, et s'appuie pour les interpreter sur des modelisations simplifiees prenant en compte la topographie et la tectonique. Malgre la dispersion des resultats, trois grands types d'etats de contraintes se degagent. A proximite de la vallee de l'Arc, les contraintes horizontales sont fortement anisotropes, orientees suivant la vallee et les contraintes verticales sont fortes, ce qui traduit un effet topographique classique. Sous deux vallons du massif d'Ambin, les contraintes horizontales sont anisotropes et superieures aux verticales. Enfin, sous la retombee orientale de ce massif, on trouve plutot un etat de contraintes de "type K0". Tous ces resultats sont en bonne concordance avec les modelisations presentees, a l'exception des faibles contraintes verticales du massif d'Ambin.

Journal ArticleDOI
TL;DR: In this article, a plastic waterproof diaphragm inert to percolation products has been installed to protect ground water against pollution hazards resulting from the disposal of industrial wastes in a deserted clay quarry to collect iron manufacturing-derived special wastes.
Abstract: The use of a deserted clay quarry to collect iron manufacturing-derived special wastes has been carefully assessed with a view to protecting ground water resources. The shallower ground water is of low quantity and poor quality. It is encompassed by a calcarenite aquifer, the bottom of which consists of clays. A limited calcarenite layer is found below, transgressively lying over the main Apulian carbonate shelf. The aquifer carbonate rocks enclose large ground water resources which ultimately flows into the Ionian Sea. A plastic waterproof diaphragm inert to percolation products has been installed to protect ground water against pollution hazards resulting from the disposal of industrial wastes. The dump is actually located in the vicinity of major industrial plants, the basements of which corresponds to the shallow aquifer. Both the basements and the railway cuttings greatly affect the ground water flow. Hydrogeological applied numerical calculation techniques have been used to evaluate the impact of a drainage trench on the ground water flow together with any noticeable influence of the latter on construction works and industrial plants in place.

Journal ArticleDOI
TL;DR: In this article, an approche pseudo-statique de la stabilite des talus de la mine d'Afsin elbistan (Turquie) is presented.
Abstract: Le but de ce travail a ete d'effectuer une analyse de la stabilite des talus de la mine d'Afsin-Elbistan (Turquie) en prenant en compte le contexte sismique de la mine par une approche pseudo-statique qui a ete developpee en complement de l'etude statique presentee dans un article precedent.


Journal ArticleDOI
TL;DR: The results were compared with ASTM and British Standard specifications as discussed by the authors, showing that the aggregates were generally within the acceptable limits for use in concrete although there were relatively high values of chloride, sulphate and total dissolved salts in the fine aggregates in Wadis Alaf, Hwarah, Alaf and Faydah.
Abstract: Natural coarse and fine aggregates which accumulated along six selected wadis in the region of Makkah were assessed both qualitatively and quantitatively. The six wadis were Numan, Al-Yamanyah, Al-Shamyah, Hwarah, Alaf and Faydah. More than 440 aggregate samples were collected and their physical, mechanical and chemical properties determined. Petrographic studies on the gravel samples were undertaken to characterise the aggregate types. The results were compared with ASTM and British Standard specifications. The aggregates were generally within the acceptable limits for use in concrete although there were the relatively high values of chloride, sulphate and total dissolved salts in the fine aggregates in Wadis Alaf, Hwarah and Faydah. Nine fine aggregate samples representing upstream, midstream and downstream deposits from these saline wadis were washed in distilled waters after which the aggregates were within the acceptable limits for structural concrete. There were indications of material which could cause alkali-silica in the coarse aggregate at Wadi Faydah. The study proved reserves of 12.5 million m3 of coarse aggregate and 23 million m3 of fine aggregate.

Journal ArticleDOI
TL;DR: Ceci as discussed by the authors explique par les dragages recents dans le chenal externe de l'estuaire de la Loire which ont modifie la propagation de la maree dans ce site, ce qui a conduit a une correction officielle de -0,40 m for le zero des cotes marines.
Abstract: Des mesures des niveaux de basses mers realisees par les autorites portuaires dans l'estuaire de la Loire montrent qu'entre 1969 et 1993 ce niveau est descendu d'une facon significative. Ceci s'explique par les dragages recents dans le chenal externe de l'estuaire qui ont modifie la propagation de la maree dans ce site, ce qui a conduit a une correction officielle de –0,40 m pour le zero des cotes marines.

Journal ArticleDOI
TL;DR: In this paper, le taux de depollution chute immediatement, la cause en etant l'introduction d'une heterogeneite de stratification, par exemple la superposition de deux couches dargile legerement differentes, toutes deux polluees de maniere identique.
Abstract: Des etudes experimentales de depollution par methode electrocinetique de sols contamines nous ont revele que d'excellents resultats peuvent etre obtenus avec des sols argileux homogenes et pollues par du Cd, tant lors d'essais en cellules qu'en s'assujettissant de l'effet d'echelle lors d'essais pilotes conduits sur plus de 3 tonnes de materiaux. Par contre l'introduction d'une discontinuite de stratification, par exemple la superposition de deux couches d'argile legerement differentes, toutes deux polluees de maniere identique, nous montre que le taux de depollution chute immediatement, la cause en etant l'introduction d'une heterogeneite de stratification.

Journal ArticleDOI
TL;DR: In this article, the authors propose a modele continué du processus de sedimentation-consolidation base sur les equations de conservation de deux phases compressible, which permits d'envisager la prise en compte de phenomenes negliges jusqu'alors: fluage, floculation, ecoulements non-darciens, etc.
Abstract: L'etude de la sedimentation et de la consolidation des sediments cohesifs presente un grand interet scientifique par son aspect interdisciplinaire, a la frontiere hydraulique-geotechnique et en raison de l'importance de ses applications a la gestion des zones cotieres. Nous proposons d'associer les points de vue hydraulique et geotechnique en vue d'etablir un modele continu du processus de sedimentation-consolidation base sur les equations de conservation de deux phases compressibles. Ce modele, general et evolutif, permet d'envisager la prise en compte de phenomenes negliges jusqu'alors: fluage, floculation, ecoulements non-darciens, ... Il constitue donc un element fondamental pour une modelisation globale et precise de la dynamique sedimentaire en estuaire.

Journal ArticleDOI
TL;DR: In this paper, the authors discussed the method of evaluating the shear strength of a rock mass for the Baoquan Pumped Storage Power Station project and compared the results obtained by the center point of group and least squares methods.
Abstract: This paper discusses the method of evaluating the shear strength of a rock mass for the Baoquan Pumped Storage Power Station project. Formulae are presented from which numerical characteristics of the shear strength can be derived. The results are compared with those obtained by the centre point of group and least squares methods. The random-fuzzy method is shown to be the more realistic and appropriate approach, allowing for fluctuations of the parameters and corresponding well with the test values.

Journal ArticleDOI
TL;DR: In this paper, three typical cases of deep-seated weathering of graphitic phyllites are presented, where plagioclases and sericite have been transformed to kaolinite whilst pyrite and graphite have remained stable.
Abstract: The zone between lateritic profiles and deep-seated fresh bedrock does not appear to be well documented. This zone is important for engineering geology, both for the design of foundations and the availability of construction materials. Three typical cases of deep-seated weathering beneath laterites are presented. The first describes anaerobic weathering of graphitic phyllites where plagioclases and sericite have been transformed to kaolinite whilst pyrite and graphite have remained stable. The second considers a rock surface in a mature lateritic peneplain dropping away from a riverbank rather than rising from it. The final example presented is where a thick quartz vein was to be quarried for aggregates and dam material, but it was found that long-term weathering had destroyed the grain bonds, resulting in a rock having the engineering properties of a weak sandstone rather than a quartzite.

Journal ArticleDOI
TL;DR: The authors presented an etude comparative des caracteristiques residuelles obtenues a l'aide de l'appareil de cisaillement annulaire and de la boite de cis-aillement alterne.
Abstract: Cet article presente une etude comparative des caracteristiques residuelles obtenues a l'aide de l'appareil de cisaillement annulaire et de la boite de cisaillement alterne. Les echantillons de sols etudies proviennent du site instable de Bouchegouf (Algerie). Des correlations entre les differents parametres pouvant influer sur ces caracteristiques residuelles ont ete faites. Il a ete, notamment, montre que les resultats obtenus a l'aide de l'appareil de Bromhead sur des echantillons remanies sont tres voisins de ceux obtenus a l'aide du cisaillement alterne sur des echantillons intacts quand la fraction argileuse est importante.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the chemistry of the interstitial waters affects the plasticity index of the studied soils and as a consequence, the standard van der Merwe swelling potential chart and the Seed activity chart which are based on the Plasticity Index do not provide an accurate assessment of swell potential.
Abstract: Research on varve clays and Miocene clays in the Warsaw area has shown that the chemistry of the interstitial waters affects the plasticity index of the studied soils. As a consequence, the standard van der Merwe swelling potential chart and the Seed activity chart which are based on the plasticity index do not provide an accurate assessment of swell potential.

Journal ArticleDOI
TL;DR: A partir de l'exemple concret d'un grand ouvrage, la presente communication propose de montrer comment les resultats de la recherche menee sur le transfert dans les matrices cimentaires, ont pu etre appliques a la fois au suivi d'one chantier and a prediction of the duree de vie des betons mis en place.
Abstract: A partir de l'exemple concret d'un grand ouvrage, la presente communication propose de montrer comment les resultats de la recherche menee sur le transfert dans les matrices cimentaires, ont pu etre appliques a la fois au suivi d'un chantier et a la prediction de la duree de vie des betons mis en place. Cette demarche unique, menee en collaboration etroite avec le maitre d'œuvre, est basee sur un concept nouveau de Betons a Haute Durabilite. L'ouvrage dont il s'agit est le Pont Vasco de Gama sur le Tage a Lisbonne. Ce pont, long de plus de 17 km, construit en zone maritime sur l'estuaire du fleuve et dont la mise en service a eu lieu en Avril 1998, est l'un des plus importants jamais construits en Europe a ce jour. Une garantie de duree de vie de 120 ans, sans entretien majeur, a ete exigee par le maitre d'ouvrage. Independamment des criteres de durabilite relatifs aux constituants du beton (granulats non reactifs au sens de l'alcali-reaction, nature des ciments et formulations adaptees a l'environnement direct des differentes parties de l'ouvrage), le critere de duree de vie retenu est une concentration limite en chlorures au niveau des armatures de 0.4% par rapport a la masse de ciment. Cette valeur determine le seuil d'initiation de la corrosion des aciers. Les indicateurs de durabilite retenus sont d'une part, un coefficient de diffusion apparent des ions chlore inferieur a 1×10–12 m2 s–1 determine par la methode TANG Luping et, d'autre part, une permeabilitea l'oxygene inferieure a 1×10–17 m2. Ces indicateurs majeurs ont ete completes par des mesures de porosite accessible a l'eau, des tests de resistance a la penetration des chlorures, des essais de migration des ions chlore et des examens approfondis de la microstructure des betons. Les differentes mesures ont ete effectuees sur des betons de laboratoire, des betons de chantier et des betons carottes dans des parties d'ouvrage exposees depuis 1995. Les coefficients de diffusion des ions chlore mesures ou calcules a partir des profils de concentration en chlorures dans les betons d'ouvrage ont ete introduits dans un modele predictif faisant appel a la methode des elements finis prenant en compte les interactions des ions avec la matrice cimentaire et l'evolution du coefficient de diffusion dans le temps. Les differentes simulations effectuees, affinees au fur et a mesure des controles et confrontees a la realite de l'ouvrage, tendent a confirmer la validite du modele predictif utilise et la pertinence des formulations choisies. Celles-ci, mecaniquement equivalentes a celles de Betons a Hautes Performances, possedent des caracteristiques de microstructure, de diffusivite et de permeabilite repondant aux exigences de durabilite de l'ouvrage.