Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We performed torsional deformation experiments on pre-hydrated fine-grained olivine aggregates using an innovative experimental assembly to investigate water weakening in mantle rocks at high shear strains. San Carlos olivine powder was cold-pressed and then hot-pressed under hydrous conditions, producing aggregates with average grain sizes of 7 or 15 μm. Deformation experiments were performed in a high-resolution gas-medium apparatus equipped with a torsional actuator, under a confining pressure of 300 MPa, a temperature of 1200 °C, and constant shear strain rates ranging from 8 × 10−5 to 1.4 × 10−4 s−1. Maximum shear stresses range from 150 to 195 MPa. These values are 30% lower relative to those determined in previous torsion experiments on dry, fined-grained dunites under similar conditions. Textures and microstructures of the starting and deformed specimens were characterized by scanning and transmission electron microscopy. All deformed aggregates exhibit a shape-preferred orientation marking a foliation and lineation, as well as a reduction in mean grain size from 15 μm down to 3-4 μm due to dynamic recrystallization. Olivine crystallographic fabrics developed rapidly (γ < 0.1), but their strength, characterized by the J-index, is low compared to naturally deformed peridotites or to polycrystalline olivine deformed at similar finite shear strains under dry conditions. The crystallographic fabrics are consistent with deformation by a dislocation accommodated creep mechanism with activation of multiple {0 k l}[1 0 0] systems, among which the (0 1 0)[1 0 0] slip system is dominant, and minor participation of the (0 1 0)[0 0 1] slip system. Transmission electron microscopy confirmed the occurrence of dislocations with [1 0 0] and [0 0 1] Burgers vectors in most grains. Analysis of unpolarized infrared spectra indicates that hydrogen concentration in the olivine lattice is below the saturation level of 18 ppm wt H2O, which is similar to those typically observed in spinel-bearing peridotite xenoliths, and also provide evidence for water-rich inter-granular material trapped in pores and grain boundaries. Seismic properties computed from the CPO observations correspond to those most commonly observed in naturally deformed mantle peridotites with fast P-wave propagation and S-wave polarization subparallel to the shear direction. These torsion experiments on fine-grained olivine polycrystals under hydrous conditions indicate that water weakening under lithospheric conditions is linked to various defects with hydrogen in the olivine structure, as well as with water-derived species in grain boundaries or pores.
ISSN: 0031-9201

hal-00745170
https://hal.archives-ouvertes.fr/hal-00745170
DOI : 10.1016/j.pepi.2012.05.001

Éditeur(s) : HAL CCSD
Résumé : International audience
To determine whether exercise modality affects arterial hypoxemia (EIAH) during training-intensity exercise, 13 triathletes performed 20 min of cycling (C) followed by 20 min of running (R): C-R, and two weeks later, 20 min of R followed by 20 min of C:R-C. Each trial was performed at an intensity slightly above the ventilatory threshold and close to the daily training intensity (75 % of VO2max). Ventilatory data were collected continuously using an automated breath-by-breath system. Partial pressure of oxygen in arterial blood (PaO2) was measured after each C and R segment and arterial oxyhemoglobin saturation (SpO2) was monitored continuously via pulse oximetry. The metabolic rate was similar across modalities and trials, i.e., C-R (53.8 +/- 3.8 vs. 51.1 +/- 5.3 ml.min(-1).kg(-1)) and R-C (52.2 +/- 4.5 vs. 53.2 +/- 4.6 ml.min(-1).kg (-1)). EIAH showed significantly greater severity for R compared to C irrespective of the order (p < 0.05 for both trials). R values of PaO2 (and SpO2) for C-R and R-C were 88.7 +/- 6.0 mm Hg (93.0 +/- 0.6 % SpO2) and 86.6 +/- 7.3 mm Hg (93.5 +/- 0.6 % SpO2) and C values were 93.7 +/- 8.4 mm Hg (95.4 +/- 0.4 % SpO2) and 91.4 +/- 5.4 mm Hg (94.8 +/- 0.3 % SpO2). R ventilatory data described a significantly different breathing pattern than C, with higher respiratory rate (35.9 b.min(-1) vs. 51.1 b.min(-1) for C-R, p < 0.01; and 50.0 b.min(-1) vs. 41.5 b.min(-1) for R-C, p < 0.01) and lower tidal volume (2636 ml vs. 2282 ml for C-R, p < 0.02 and 2272 ml vs. 2472 ml for R-C, p < 0.05). We concluded that EIAH was greater during running than cycling for a similar metabolic rate corresponding to training intensity and that EIAH could thus be considered dependent on exercise modality.
Internation Journal of Sports Medicine

hal-00720806
https://hal.univ-antilles.fr/hal-00720806
https://hal.univ-antilles.fr/hal-00720806/document
https://hal.univ-antilles.fr/hal-00720806/file/sm290.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Recent geochemical work shows that subduction-zone serpentinites are repositories for fluid-mobile elements absorbed during interaction with sediment-derived fluids. Unraveling the geochemical fingerprint of these rocks helps to define timing of tectonic accretion of sediments along the subduction interface and the role of serpentinite in element recycling to volcanic arcs. Here we present the trace element and isotopic composition (B–O–H, Sr, Pb) of high-pressure serpentinites from the Voltri Massif (Ligurian Western Alps, Italy), to discuss their role as incompatible element carriers and their contribution to recycling of sediment-derived components in subduction zones.The serpentinites presented here record metamorphic olivine growth during eclogite-facies metamorphism and show undeformed and mylonitic textures. Field relations show that undeformed rocks are enclosed in deformed ones and that no metasedimentary rocks are present nearby. Undeformed serpentinite has very high δ11BSRM951 (from +26‰ to +30‰), low Sr and Pb isotope ratios (87Sr/86Sr = 0.7053–0.7069; 206Pb/204Pb = 18.131–18.205) and low As and Sb contents (0.1 and 0.01 μg/g, respectively). Oxygen and hydrogen isotope compositions are +4.5‰ and −67‰, respectively. In contrast, mylonitic serpentinite shows lower δ11B (from +22‰ to +17‰), significant enrichment in radiogenic Sr and Pb isotopes (87Sr/86Sr up to 0.7105; 206Pb/204Pb up to 18.725), and enrichment in As and Sb (1.3 and 0.39 μg/g, respectively). δ18O of the mylonitic serpentinites reaches values of +5.9‰, whereas δD is comparable with that of undeformed rocks (approximately −70‰). In mylonitic serpentinites, the B and Sr isotopic values and the fluid-mobile element (FME) concentrations are near those for the Voltri metasedimentary rocks (calc- and mica-schists). Pb systematics also reveal influx of a crust-derived component.Our dataset shows that undeformed serpentinite still preserves an oceanic geochemical fingerprint, whereas mylonitic serpentinite is reset in its concentrations of FME and its B, Sr and Pb isotope compositions, due to interaction with sediment- and crust-derived fluids. The environment of this interaction is either compatible with (i) an outer-rise zone setting, with percolation of seawater-derived fluids enriched in sedimentary components into bending-related fault structures, or with (ii) subduction channel domains, where ascending sediment-derived slab fluids infiltrate slices of former oceanic serpentinite accreted to the plate interface domain. Influx of sediment-derived subduction fluids along major deformation zones in serpentinite modifies the element budget of the rocks, with important implications for element recycling and the tectonic history of serpentinite. The B, Sr and Pb isotopic systematics, coupled with FME concentration in serpentinites are particularly helpful geochemical tracers of interaction between different reservoirs in subduction-interface environments, and are more sensitive than the traditionally applied stable oxygen and hydrogen isotope compositions.
ISSN: 0016-7037

hal-01419940
https://hal.archives-ouvertes.fr/hal-01419940
DOI : 10.1016/j.gca.2016.06.034

Éditeur(s) : Springer
Résumé : The French Atlantic coast contains large highly productive intertidal mudflats that are colonised by juveniles of numerous flatfish species, including the common sole (Solea solea, L.). These ecosystems are also heavily exploited by the shellfish farming industry. Intensive bivalve culture is associated with substantial biodeposition (1-6 t-dw ha(-1) day(-1)), which directly or indirectly contributes to increase exopolysaccharide (EPS) concentrations at the interface between water column and seabed. EPS are long-chain molecules organised into colloids, which influence rheological properties of water, particularly viscosity. Increased water viscosity had consequences for ventilatory activity of juvenile flatfish, whereby the minimal pressure required to ventilate the medium increases directly with EPS concentration. Moreover, the critical EPS concentration ([EPS](crit)) at which water was no longer able to flow through the branchial basket ranged from almost nil to over 30 mg l(-1), depending on species and size. [EPS](crit) was lower in small individuals and individuals from species with high metabolic rates (turbot and plaice). These differences may depend upon gill and bucco-branchial cavity morphometrics. The ventilatory workload of sole increased with viscosity to a maximum at 2 mg EPS l(-1). Viscosity might, therefore, be a limiting factor for flatfish post larvae, which colonise the intertidal mudflats, depending upon their size and species. EPS concentrations in the field can reach 15 mg l(-1). A selective effect is conceivable but remains to be estimated in the field.
Marine Biology (0025-3162) (Springer), 2007-09 , Vol. 152 , N. 4 , P. 803-814

Droits : 2007 Springer
http://archimer.ifremer.fr/doc/2007/publication-2801.pdf
DOI:10.1007/s00227-007-0731-z
http://archimer.ifremer.fr/doc/00000/2801/

Éditeur(s) : HAL CCSD SAGE Publications
Résumé : International audience
The distribution of redox-sensitive elements (V, U, Mo, Mn) was studied in a sedimentary archive of the Pierre-Blanche lagoon encompassing 3500 years of sedimentation. Between 240 and 255 cm (i.e. between 0 and 350 cal. ad) in the core, there was a dark layer with no mollusc shells. Enrichments of V, U and Mo and depletion of Mn were observed in this layer compared with overlying and underlying sediments. This was attributed to the occurrence of anoxia in bottom water or at the sediment/water interface during the Roman period. This episode was concomitant with the formation of a sandy barrier, which now isolates the lagoon from the sea. Our results suggest that the isolation of the lagoon, which was deeper in the period concerned than at present, favoured stagnation of the water. Combined with the excess nutrient inputs because of human activities in Lattara harbour, stagnation may have caused anoxia in bottom water at least in some parts of the Palavasian lagoon system. Bottom conditions nevertheless remained sufficiently reducing for the accumulation of U and Mo to persist until around 800 cal. ad. Although the lagoon has been hyper-eutrophic since at least the middle of the 20th century and although anoxia occurs frequently in summer, redox proxies show no evidence for their occurrence. The shallow water and associated resuspension and reoxidation events explain the lack of V, Mo and U enrichment in recent sediments.
ISSN: 0959-6836

hal-01062151
https://hal.archives-ouvertes.fr/hal-01062151

Éditeur(s) : HAL CCSD Société Géologique de France
Résumé : Based on a High-Resolution 3D seismic block acquired in the Gulf of Lion in 2004–2005 we investigated fluid pipes and pockmarks on the top of the interfluve between the Hérault canyon and the Bourcart canyon both created by turbidity currents and gravity flows from the shelf to the deep basin in the north-western Mediterranean Sea. Combining the geometry of the potential fluid pipes with the induced deformation of surrounding sediments leads then to the ability to differentiate between potential fluid sources (root vs source) and to better estimate the triggering mechanisms (allochtonous vs. autochtonous cause). We linked together a set of derived attributes, such as Chaos and RMS amplitude, to a 3D description of pipes along which fluids may migrate. As previously shown in other basins, the induced deformation, creating cone in cone or V-shaped structures, may develop in response to the fluid pipe propagation in unconsolidated sediments in the near surface. The level at the top of a cone structure is diachronous. It means that stratigraphic levels over this surface are deformed at the end of the migration. They collapse forming a depression called a pockmark. These pipes are the result of repeated cycles of fluid expulsion that might be correlated with rapid sea-level rise instead of sediment loading. The most recent event (MIS 2.2 stage) has led to the formation of a pockmark on the modern seafloor. It has been used as a reference for calculating the effect of a rapid sea-level rise on fluid expulsion. As all physical and geometrical parameters are constrained, we were able to define that a + 34 m of sea level rise may account for triggering fluid expulsion from a very shallow silty-sandy layer at 9 m below seafloor since the last glacial stage. This value is consistent with a sea level rise of about 102 m during this period. This study shows that the episodic nature of fluid release resulted from hydromechanical processes during sea-level rise due to the interactivity between high pressure regimes and principal in situ stresses.
ISSN: 0037-9409

hal-01667241
https://hal.archives-ouvertes.fr/hal-01667241
DOI : 10.1051/bsgf/2017190

Éditeur(s) : HAL CCSD Université des Antilles
Résumé : International audience
Loin d’apparaître comme de simples interfaces, les littoraux de la Caraïbe sont constituésd’enclaves fonctionnelles qui se juxtaposent donnant une mosaïque créole polyéthnique(mosaïque raciale), aux fractures sociales et spatiales marquées (mosaïque sociale et spatiale).Dans ces îles paysannes qui traditionnellement tournent le dos à la mer, la plage a longtempsété perçue par les populations littorales et les pêcheurs comme une continuité de l’île de laplantation pour y habiter et y pêcher. Une marge ouverte à tous dont la population rurale seméfiait pour ne l’aborder que quelques heures dans l’année à Pâques ou à la Pentecôte.2 Tout au long du XX siècle, une véritable subversion du regard s’opère par les classesdominantes, bourgeoises et touristes qui investissent les plages, souvent celles qui n’étaientguère fréquentées. Quitter la plage peu à peu investie par les touristes pour les fonds blancsou la Baignoire de Joséphine constitue une nouvelle marque, une volonté de maintenir unehiérarchie sociale par la distance.3 Depuis quelques années, les plages deviennent des lieux d’hybridation entre les populationslocales et les touristes. Avec la tertiairisation des sociétés, les populations antillaises desclasses moyennes et défavorisées découvrent les plages qui occupent une place importantedans la culture (publicité, télé…) des jeunes générations. Les plages sont investies etdeviennent peu à peu des espaces conviviaux.4 La ségrégation sociospatiale demeure cependant dans les pratiques, les temps et même lesespaces occupés. Si certains îlets et fonds blancs, comme les plages s’ouvrent au plus grandnombre, la piscine privée, le yacht, l’îlet privé, l’enclave protégée permettent toujours deconserver distance et discrétion. De même la capacité financière nécessaire à la pratique decertains sports nautiques permet cette démarcation. Ainsi, touristes, Métropolitains et Antillaisdes classes moyennes ou appartenant à la bourgeoisie, se côtoient et se croisent mais nepratiquent pas forcément la même plage.
ISSN: 1779-0980

hal-01202979
https://hal.archives-ouvertes.fr/hal-01202979
https://hal.archives-ouvertes.fr/hal-01202979/document
https://hal.archives-ouvertes.fr/hal-01202979/file/etudescaribeennes-693-4-la-plage-reflet-des-fractures-sociales-et-ethniques-aux-antilles.pdf
DOI : 10.4000/etudescaribeennes.693

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
[1] The Pyrenees, north of the North Pyrenean fault, display a complex structure involving a succession of peridotite massifs, basement massifs, and mid-Cretaceous to Late Cretaceous basins located in a narrow domain, which was affected by a mid-Cretaceous, preorogenic, high-temperature, low-pressure metamorphism. The Late Cretaceous basins were interpreted either as pull-apart basins formed during transcurrent motion of Iberia relative to Eurasia or as remnants of a larger extensional basin. Recent models support that peridotite massifs result from the exhumation of the mantle during this preorogenic event. The northern boundary of the Agly basement massif shows evidence of ductile deformation of the basal formations of the Agly sedimentary cover. Macroscopic and microscopic kinematics indicators consistent with asymmetry of crystallographic fabrics suggest normal sense of shear and thus suggest detachment, at least partial, of the Mesozoic cover from its basement. Triassic to Early Cretaceous limestones are mylonitic and consistently shows a foliation, a NS- to NE-trending lineation, shear criteria suggesting top-to-the-north shearing and locally boudinage. At the microscopic scale, mylonites are characterized by a very fine grain size, frequently <10 µm. They contain larger, partially recrystallized calcite parent grains and undeformed quartz grains with calcite fringes crystallized in pressure shadows. In these mylonites, calcite systematically shows a weak but well-defined crystallographic-preferred orientations, suggesting HT dislocation creep combined to diffusion creep and possibly grain boundary sliding in the finest fraction of the mylonites. Paleotemperatures determined using Raman spectrometry suggest synkinematic temperature conditions in the range 340-390°C, in good agreement with observed microstructures and calcite CPO. The mylonitic fabric in Mesozoic limestones is folded by EW-trending Pyrenean folds north of the Agly basement massif, attesting that this fabric formed before the Pyrenean orogeny. These data consistently support preorogenic extension under medium-temperature conditions of the northern Agly massif and likely of the massif itself. Since simultaneously (~100 Ma) a mid-Cretaceous basin opened south of the basement massif, we suggest a model of preorogenic exhumation of the Agly massif in response to the regional extension associated to the rotation of Iberia. This model may explain the exhumation of the North Pyrenean massifs during a single preorogenic event that allowed the opening of extensional basins and the exhumation of the lithospheric mantle. All these structures being subsequently reworked during the Pyrenean orogeny.
ISSN: 0278-7407

hal-00852833
https://hal.archives-ouvertes.fr/hal-00852833
DOI : 10.1002/tect.20015

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A set of four reactive flow-through experiments at temperature T = 100 degrees C and total pressure P=12 MPa was performed in limestone reservoir samples. By using various ranging from 0.7 to 10 MPa, these experiments mimic mass transfers occurring (1) near the injection well, where the brine is almost saturated with CO2 (i.e. P-CO2 approximate to P), and (2) at increasing distances from the injection well, where the fluid displays lower values and higher divalent cation concentrations due rock dissolution along the fluid pathway. Results for P-CO2 = 10 MPa show non-uniform dissolution features associated with transport-controlled mass transfer, while reaction-controlled uniform dissolution is observed for P-CO2 = 2.5 MPa. The experiment with P-CO2 = 6 MPa allows investigating in detail the transition from transport-to reaction-controlled dissolution. Conversely, the experiment reproducing conditions far from the injection well (P-CO2 = 0.7 MPa), shows a decrease of porosity triggered by the precipitation of Mg-rich calcite. For all the dissolution experiments, the time-resolved porosity phi(t) can be modeled by a simple non-linear equation including parameters that characterise the dissolution regime triggered by the reactivity of the inlet fluid (measured by the Damkohler number, Da). Furthermore, all dissolution experiments display power scaling between permeability (k) and porosity (phi) with distinctly different scaling exponents characterising the reactivity of the fluid percolating the sample, independently from the decrease with time of the reactive surface area. It is shown also that dissolution at moderate positive values of Da seems the most efficient to increase permeability and promote a rapid spreading of the reaction front, while inducing minimal modification of the porosity in the vicinity of the CO2 injection well. These results can be used to parameterize the k-phi function for modeling the earliest dissolution processes occurring in the vicinity of the reaction front.
ISSN: 0009-2541

hal-00445277
https://hal.archives-ouvertes.fr/hal-00445277
DOI : 10.1016/j.chemgeo.2009.03.028

Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy B - Oxford Open Option A Oxford University Press (OUP)
Résumé : International audience
Peridotites exhumed in the footwall of axial detachment faults at slow-spreading ridges are highly serpentinized. Most mid-ocean ridge detachment settings are magmatically active and hydrous fluid circulation in and near the fault has been shown to be influenced by the presence of melt or magmatic lithologies. Our working area along the Southwest Indian Ridge (62–65°E) is nearly amagmatic and represents an end-member to study the hydrous alteration of exhumed peridotites without these magmatic influences. We use an integrated petrological approach combining microstructural, mineralogical and chemical observations to unravel the sequence of serpentinization in 272 dredged samples of variably serpentinized peridotites and to document the circulation of serpentinizing fluids in and near the exhumation faults. We find that serpentine recrystallization and veins overprint the initial serpentinite mesh texture in ∼25% of the samples. Oxygen isotope data suggest that this sequence developed at relatively high temperatures (271–336°C) and under increasing fluid–rock ratios, from near stoichiometry for mesh texture formation to >10 during recrystallization. Increasing fluid supersaturation relative to serpentine favors the replacement of mesh texture lizardite by chrysotile and polygonal or polyhedral serpentine. We attribute local recrystallization into antigorite to moderate Si-metasomatism, possibly following pyroxene serpentinization. We do not observe the more pronounced Si-metasomatism leading to talc replacing serpentine that is reported for the more magmatically active Mid-Atlantic Ridge detachment settings and is attributed to prior leaching of magmatic rocks. Scales of preferential fluid pathways in our samples evolved from pervasive and close-spaced (<500 µm) microfractures during the formation of the initial serpentine mesh texture, to centimeter-thick planar domains of enhanced fluid flux, spaced at ∼10 cm intervals and probably grouped in corridors that may be up to ∼100 m across. Serpentine minerals are enriched in some fluid-mobile elements (Cl, B, U) relative to the peridotite protolith, and several elements (Al, Fe, Si, Cu, As, Sb, REE) are redistributed at the millimeter to decimeter scale. Serpentinizing fluids were seawater-derived, probably mildly alkaline (small to no europium anomalies), reducing and H2-enriched (formation of magnetite). These fluids may have been similar to, though warmer than, those venting at the ultramafic-hosted Lost City hydrothermal fluid (30°N, Mid-Atlantic Ridge).
ISSN: 0022-3530

hal-01174047
https://hal.archives-ouvertes.fr/hal-01174047
DOI : 10.1093/petrology/egv014

Éditeur(s) : EDP Sciences
Résumé : We present results obtained from a pristine site of French Guiana (South America), at the Pic Matecho, a region far from gold mining activity. This area contains a small permanent lake, a rare situation in French Guiana. Tree canopy, soils and Lake Matecho sediments were analysed in total Hg and Pb-210. The annual deposit of litterfall is estimated at 40 mug (Hg)/m(2)/y. The top sediment content of 0.2 mug (Hg)/g indicates a large contribution of the atmospheric deposit. In sediment, the decrease of total Hg with depth is neither due to local human influence, nor to increase of atmospheric background during this century. It is attributed to remineralization of organic matter in the upper part of the sediment : the majority of the total Hg deposited at the water/sediment interface is not permanently trapped in the sediment but remobilized in water. Interpretation of the historical sediment profile suggests a constant deposit rate over the last millennium.
Journal De Physique Iv (1155-4339) (EDP Sciences), 2003-05 , Vol. 107 , P. 859-862

Droits : 2003 EDP Sciences
http://archimer.ifremer.fr/doc/00000/10630/9348.pdf
DOI:10.1051/jp4:20030433
http://archimer.ifremer.fr/doc/00000/10630/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
New outcrops in the Sinis peninsula (Sardinia, Italy) allow a detailed description of the Messinian erosion surface. The correlation between outcrops, industrial seismic data and data collected offshore Oristano from a recent cruise permits reconstruction of the geometry of this surface from presently emerged interfluves to the deep canyons offshore, with: - onshore: an eroded karstic plateau presently cropping out over a 20 km × 5 km area. Well-preserved karst structures occur locally and can form several metres high reliefs. The southernmost edge of the plateau is limited by a cliff. The karstic plateau and the cliff are sealed by transgressive deposits of Pliocene age; - offshore, an interfluve zone with a mostly flat and low-angle dipping plateau, westward dissected by paleovalleys which were identified down to a depth of 2000 m. In the Oristano Gulf, Messinian paleovalleys were also identified. The Capo San Marco paleocliff was probably located on the edge of a canyon. Onshore, only one major erosion surface was identified, located at the top the Messinian sequence. Offshore, this surface extends down to the abyssal plain. The surface was emplaced above deposits related to the Terminal Carbonate Complex. This indicates that the marginal evaporites are older than the major drawdown of the Mediterranean sea-level. The major drawdown is related to the deposition of the deep evaporites.
ISSN: 0037-0738

hal-00407864
https://hal.archives-ouvertes.fr/hal-00407864
DOI : 10.1016/j.sedgeo.2008.06.005

Résumé : L’objet de cette thèse est l’étude des comportements mécanique et à la corrosion d’un nouveau système de fondation, dit pieux SPIRMEC, adapté aux structures légères. Le travail s’est focalisé sur deux grands aspects. Le premier aspect concerne l’analyse du comportement sous chargement axiale des pieux SPIRMEC sur la base de l’expérimentation et de la modélisation numérique dans un sol mou non cohésif. Quant au deuxième aspect, il traite du problème de la corrosion de l’acier constituant le pieu dans un environnement tropical humide. Le comportement des pieux SPIRMEC sous une charge axiale de traction, dans un sol fin non cohésif, a montré le développement d’une surface cylindrique de rupture. Celle-ci ne dépend pas de la configuration géométrique des pieux tel que : l’espacement S, le diamètre d’hélice Dh et le diamètre du tube d. En adoptant ce critère de rupture et à l’aide d’une analyse statistique des données, nous avons proposé quatre méthodes analytiques de prédiction de la capacité portante des pieux SPIRMEC à partir des essais in-situ et au laboratoire qui sont: •Méthode CPT basée sur la résistance de pointe pénétromètrique (essai CPT), •Méthode MPT basée sur la pression limite pressiomètrique (essai MPT), •Méthode du couple d’installation, •Méthode analytique basée sur les paramètres de cisaillement de sol notamment l’angle de frottement interne (essais triaxial et boîte de cisaillement). Ces méthodes tiennent compte de la géométrie du pieu, du procédé de mise en oeuvre et de la compacité du sol. L’analyse de performance des méthodes proposées a montré que les méthodes analytique et CPT représentent mieux le comportement des pieux testés. La modélisation numérique du comportement des pieux SPIRMEC sous charge axiale de traction a été également étudiée à l’aide du code de calcul Plaxis 2D. Un modèle axisymétrique a été adopté pour modéliser la géométrie de la structure. Le modèle de comportement hardening soil a été retenu pour modéliser le comportement élastoplastiq des couches de sol. Un modèle élastique linéaire a été retenu pour le pieu. Quant au comportement de l’interface sol-structure, il a été pris en compte par un modèle élastoplastique basé sur les critères de Mohr-Coulomb. L’expansion du sol résultant de l’installation des pieux a été approchée par une cavité cylindrique. Cette dernière a été modélisée par des déformations volumiques anisotropes. Nous avons constaté, qu’appliquer une déformation volumique de l’ordre de 40% permet une bonne concordance entre les résultats numériques et expérimentaux. L’étude paramétrique nous a également permis de constater l’existence d’une variation linéaire entre la capacité portante et l’espacement S. Le comportement de l’acier galvanisé dans le sol a été également étudié au moyen de trois approches: électrochimique, visuelles grâce au microscope électronique et gravimétrique. Les tests électrochimiques de corrosion du zinc ont été réalisés dans la solution de sol artificielle pour deux périodes bien distinctes : saison des pluies et après 8 mois de contact sol-pieu. Une forte dépendance est constatée de la vitesse de corrosion de zinc au pH et à la conductivité de la solution. La vitesse de corrosion est plus importante en saison des pluies qu’après 8 mois de contact de pieu avec le sol. Les fortes concentrations en sulfates semblent augmenter la vitesse de corrosion. Les analyses menées au MEB montrent que la zone de fluctuation de nappe et en surface externe (sol/air) sont les zones les plus corrodées. La comparaison entre les différentes techniques d’évaluation de la vitesse de corrosion a montré que l’eau de nappe peut être utilisée comme un milieu représentatif du profil chimique d’un sol non cohésif et légèrement granulaire.
The purpose of this thesis is to study the both behaviors mechanical and of the corrosion of a new foundation system, called spirec piles, for lightweight structures. The work was based on two main aspects. The first aspect concerns the analysis of behavior of the spirmec piles under axial loading on the basis of experimental and numerical modeling in a non-cohesive soft soil. On the second aspect, it addresses the problem of corrosion of steel forming the pile in a humid tropical environment. The behavior of the tested piles under axial traction load, in a non-cohesive soil, showed the development of a cylindrical surface of failure. This does not depend on the geometrical configuration of the tested piles such that: the spacing s, the helix diameter dh and the diameter of the shaft. By adopting this failure criterion and using statistical data analysis, we proposed four analytical methods for predicting the bearing capacity of the piles from in-situ and laboratory tests, which are: cpt method based on tip resistance penetrometer (cpt test), mpt method based on pressuremeter limit pressure (test mpt), method of installation torque and analytical method based on the shear parameters of soil (triaxial tests and shear box). These methods take into account the geometry of the pile, the method and implementation of soil compaction. Performance analysis of the proposed methods showed that the analytical methods and cpt represent better the behavior of piles tested. An axisymmetric condition was assumed to model this geometry in two-dimensional space. In this study, we proposed to model the pipe screw pile with plates elements available in plaxis 2d. The helixes were modeled as circular disks. Interface elements were incorporated along the pile to simulate the soil-pile interaction. Hardening soil model was chosen to describe the soil with drained behavior was assigned for all layers. Linear elastic for pile and elastic plastic model based on the mohr-coulomb criterion was used to describe the interface behavior. The lateral expansion generated by the pile shaft was modeled by anisotropic volumetric strains (ɛxx=ɛzz, ɛyy=0). The pile behavior under tensile loading at different volumetric strains, it is clear that the best fit was obtained at volumetric strain of 40%. The parametric study also allowed us to establish the existence of a linear variation between the bearing capacity and spacings. The behavior of the galvanized steel in the ground has also been studied using three approaches such as: electrochemical, microscopic imaging and gravimetrically. Electrochemical tests of the corrosion of the zinc have been made in artificial soil solution into two periods, the rainy season and after eight months of contact soil-pile. Is a strong dependence of the observed corrosion rate of the zinc at the ph and conductivity of the solution. The corrosion rate is higher in the rainy season compared to eight months of contact of the pile with soil. High sulfate concentrations increase the rate of corrosion. The meb analysis shows that the fluctuation zone of the water table is the most corroded area. Comparison between the different methods of evaluating the corrosion rate showed that the ground water may be used as a representative profile of the chemical environment of a non-cohesive soil and slightly granular.

http://www.theses.fr/2014AGUY0790/document

Éditeur(s) : HAL CCSD
Résumé : International audience
The advent of pen-based interfaces has led to the development of many applications concerning the analysis of a drawn shape. But a drawing is not only a shape. It is also all the gestures which constitutes the drawing activity, as well as their planning. Pen-based interfaces give us the possibility to analyze this dimension of sketching. We call this kind of analysis: procedural analysis. In this article, we will show how to identify the privileged drawing procedures of users by identifying a constant pattern despite a huge within-drawer variability in drawing procedures. After stating how to extract this constant pattern, we shall show how we can use those results into a drawing-based user identification method.
ICFHR 2012 - International Conference on Frontiers in Handwriting Recognition
Bari, Italy

hal-00708708
https://hal.inria.fr/hal-00708708

Éditeur(s) : HAL CCSD Oxford University Press
Résumé : International audience
The BioMart Community Portal (www.biomart.org) is a community-driven effort to provide a unified interface to biomedical databases that are distributed worldwide. The portal provides access to numerous database projects supported by 30 scientific organizations. It includes over 800 different biological datasets spanning genomics, proteomics, model organisms, cancer data, ontology information and more. All resources available through the portal are independently administered and funded by their host organizations. The BioMart data federation technology provides a unified interface to all the available data. The latest version of the portal comes with many new databases that have been created by our ever-growing community. It also comes with better support and extensibility for data analysis and visualization tools. A new addition to our toolbox, the enrichment analysis tool is now accessible through graphical and web service interface. The BioMart community portal averages over one million requests per day. Building on this level of service and the wealth of information that has become available, the BioMart Community Portal has introduced a new, more scalable and cheaper alternative to the large data stores maintained by specialized organizations.
ISSN: 0305-1048

hal-01146849
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01146849
DOI : 10.1093/nar/gkv350
PUBMED : 25897122

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The upward oil migration in a transparent and rough fracture containing a liquid of higher density is studied experimentally using a light transmission technique. The aperture heterogeneity is also measured by light transmission. The injection of oil in a fracture containing a heavier fluid produces a gravitational fingering instability. Depending on the injection velocity (capillary number, Ca) and the density difference between the two fluids (Bond number, Bo), different patterns are observed during the oil displacements. The width of the finger and its velocity are measured as a function of Bo and Ca. A stability analysis of the interface, based on a generalised Darcy equation in a two-dimensional fracture, allows an accurate description of the experimental results. The order of magnitude of the finger width and its velocity are in good agreement with the calculations, with small disparities due to various unknown fluid flow parameters: capillary pressure, finger thickness in the gap of the fracture, finger tortuosity and oil velocity field into the finger. The theoretical approach allows constructing a (Ca, Bo) phase diagram of stability of the interface.
ISSN: 0169-3913

hal-00429329
https://hal.archives-ouvertes.fr/hal-00429329
DOI : 10.1007/s11242-009-9340-2

Résumé : Le Laboratoire Côtier de La Tremblade est implanté géographiquement dans le premier bassin ostréicole d'Europe (30 000 tonnes produites et 60 000 tonnes commercialisées chaque année). L'ostréiculture est une activité économique très importante en terme d'emplis, qui doit cohabiter sur un même littoral avec le tourisme et l'agriculture générant parfois des conflits d'usages (gestion de l'eau, qualité de l'eau). Les avis donnés à l'Administration ou aux collectivités locales s'appuient sur les résultats de la surveillance ou ceux émanant des études spécifiques comme les études microbiologiques locales. Les activités, les responsabilités de chacun dans le cadre ce de mandat, figurent dans le Manuel Qualité du Laboratoire. Enfin, l'assistance technique à la profession conchylicole, en matière environnementale ou de préparation à la mise en marché des coquillages revêt des formes multiples : formations données, distribution de fiches pratiques, fourniture de renseignements, interface entre professionnels et laboratoires de recherche, études spécifiques.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00074/18538/16085.pdf
http://archimer.ifremer.fr/doc/00074/18538/

Éditeur(s) : HAL CCSD
Résumé : International audience
In this paper, we describe a blood alcohol content estimation prototype based on a comportment analysis performed by artificial neural networks. We asked to subjects that had drunk alcohol to play a video-game after having measured their blood alcohol content with a breathalyser. A racing game was modified so that it could provide various data related to the use of the controls by the player. Using the collected data, we trained our neural network in order to be able to determine whether or not the subject had exceeded a blood alcohol content threshold. We also succeeded in estimating this blood alcohol content with a mean error of 0.1g/l. We could perform those estimations independently of the track played among the two ones used. It was also performed in "real time", e.g., using only the data collected within the last 10 seconds of playing.
Proceedings of the 2011 International Conference on Advances in Computer-Human Interactions
Gosier, Guadeloupe

Droits : info:eu-repo/semantics/OpenAccess
hal-00849971
https://hal.archives-ouvertes.fr/hal-00849971
https://hal.archives-ouvertes.fr/hal-00849971/document
https://hal.archives-ouvertes.fr/hal-00849971/file/article.pdf

Éditeur(s) : HAL CCSD
Résumé : International audience
This study investigated the possibility of there being differences in respiratory muscle strength and endurance in elite and competition triathletes who have similar maximal oxygen uptakes (V_O2max) and ventilatory thresholds (Thvent). Five internationally-ranked elite, [mean (SD) age 23.8 (1.4) years] and six nationallyand regionally-ranked competition [age 21.1 (1.1) years] male triathletes performed two successive trials: first an incremental cycle test to assess V_O2max and Thvent and second 20 min of cycling followed by 20 min of running (C-R) at intensities higher than 85% V_O2max. Cardioventilatory data were collected every minute during the two trials, using an automated breath-by-breath system. Maximal expiratory and inspiratory (PImax) strength were assessed before and 10 min after C-R from the functional residual capacity. Respiratory muscle endurance was assessed 1 day before and 30 min after C-R by measuring the time limit (tlim). The results showed firstly that during C-R, the competition triathletes had significantly (P<0.05) higher minute ventilation [mean (SEM) 107.4 (3.1) compared to 99.8 (3.7) lÆmin-1], breathing frequency [44.4 (2.0) compared to 40.2 (3.4) Æmin-1] and heart rate [166 (3) compared to 159 (4) beatsÆmin-1] and secondly that after C-R, they had significantly lower PImax [127.1 (4.2) compared to 130.7 (3.0) cmH2O] and tlim [2:35 (0:29) compared to 4:12 (0:20) min] than the elite triathletes. We conclude that, despite similar V_O2max and Thvent, the competition triathletes showed less extensive adaptive mechanisms, including those in the respiratory muscles, than did the elite triathletes. This led to higher ventilation, which appeared to be the cause of the faster development of fatigue in the inspiratory muscles in this group.
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY

hal-00720562
https://hal.univ-antilles.fr/hal-00720562
https://hal.univ-antilles.fr/hal-00720562/document
https://hal.univ-antilles.fr/hal-00720562/file/BoussanaEJAP02_2_.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We explore the relations between deformation, annealing, and melt percolation during rifting and the effect of these processes on seismic anisotropy by analyzing the microstructures and crystal preferred orientations (CPO) in a suite of mantle xenoliths from Mega, in the southern end of the Ethiopian rift. Previous geochemical studies on these xenoliths showed evidence for interactions with variable melt types and volumes during the rifting process. The peridotites have dominantly coarse-porphyroclastic microstructures, but coarse granular or partially recrystallized microstructures also occur. The olivine CPO, characterized by orthorhombic to fiber-[100] patterns and moderate intensities, the common occurrence of (100) tilt walls, and the predominance of <0vw> rotation axes accommodating low angle misorientations in olivine support deformation by dislocation creep with dominant activation of the [100](010) system. Annealing (static recrystallization) of variable intensity followed this deformation. Modal enrichment in pyroxenes in > 60% of the studied peridotites corroborates extensive, but spatially heterogeneous reactive melt percolation leading to refertilization of the lithospheric mantle beneath the southern Ethiopian rift. The common interstitial shapes of the pyroxenes and lack of correlation between the pyroxenes and the olivine CPOs in many samples suggest that part of the refertilization is post-kinematic. However, there is no simple relation between reactive melt percolation and annealing of the olivine deformation microstructure. Comparison with data from other xenolith localities points to changes in the metasomatic imprint in the lithospheric mantle along the East African rift system correlated with the evolution in the rift maturity. Seismic properties averaged over all samples show typical lithospheric mantle patterns with fast propagation of P- and polarization of the fast S-waves parallel to the lineation. The anisotropy is moderate (< 6% for P-waves and < 4% for S-waves), implying that aligned melt must contribute to the strong seismic anisotropy measured in the Main Ethiopian rift, north of Mega.
ISSN: 0040-1951

hal-01355918
https://hal.archives-ouvertes.fr/hal-01355918
DOI : 10.1016/j.tecto.2016.05.027