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Use of bi-modulus geosynthetics for the reinforcement of cohesive landfills on cavities
No full textInternational audienceThe results of an experimental campaign of reinforcement of thin cohesive soil embankments in the case of cavity collapse are presented. In particular, the aim is to test the effectiveness of a new type of bi-stiffness geosynthetic. A coupled DEM-FEM numerical model is validated based on these results and allows a better understanding of the soil- geosynthetic interaction phenomena mobilized during the collapse. Comparison between the numerical and experimental results obtained with the two types of reinforcement (mono-stiffness and reversed bi-modulus) make it possible to underline the interest of the innovative product developed
Caractérisation expérimentale et numérique du massif rocheux imprimé en 3D pour la modélisation physique à grande échelle
No full textThis thesis contributes to developing an experimental device for physically modeling reduced-scale fractured rock masses subjected to underground excavation (mines, quarries, tunnels, boreholes). The approach uses 3D printing technology to create sand-based specimens with controlled mechanical properties and morphology, explicitly incorporating rock joints. The thesis consists of the mechanical characterization of the printed sand material, an experimental campaign to characterize the shear behavior of printed discontinuities and cylindrical specimens containing discontinuities, the development of a stress and strain monitoring strategy in the printed sand material, and a preliminary test in the final Dimitri device. The characterization of the printed sand material proves particularly valuable for studying non-resistant porous analogues of natural rocks, characterized by anisotropy (orthotropy) and exhibiting a brittle-ductile transition behavior. Direct shear tests are conducted on rough joints modeled as 3D-printed fractal objects in the second part. Subsequently, cylindrical specimens containing three configurations of real geometry discontinuities (rough joints with rock bridges) are manufactured and tested under uniaxial compression. This represents the first attempt at an explicitly discontinuous reduced-scale model containing joints with controlled mechanical behavior. The results highlight the influence of discontinuities on the overall behavior of a rock mass. This experimental study is complemented by a numerical study using the UDEC software, employing Voronoi tessellation to reproduce the behavior of the analogue material and utilize it in the numerical modeling of the prototype modeled by physical modeling.Cette thèse est une contribution au développement d'un dispositif expérimental de modélisation physique à l'échelle réduite de massifs rocheux fracturés aléatoirement faisant l'objet d'une excavation souterraine (mines, carrières, tunnels, forages). Ce travail consiste à utiliser la technique d'impression 3D combinant du sable et un liant phénolique, pour introduire explicitement des joints rocheux à propriétés mécaniques et morphologie contrôlés. La démarche de la thèse consiste en une caractérisation du comportement mécanique du sable imprimé, une campagne expérimentale de caractérisation du comportement mécanique au cisaillement de discontinuités imprimées et d'éprouvettes cylindriques incluant des discontinuités, le développement d'une stratégie de suivi de l'état de contrainte et de déformation dans le matériau sable imprimé et l'élaboration d'un test préliminaire dans le dispositif final Dimitri. La caractérisation du matériau sable imprimé se révèle être particulièrement intéressant pour étudier des analogues de roches naturels non résistante poreux, anisotrope (orthotrope), et caractérisée par un comportement de transition fragile-ductile. En second partie des essais de cisaillement direct sont réalisé sur des joints rugueux assimilés à un objet fractal imprimé en 3D. Dans un second temps, des éprouvettes cylindriques contenant trois configurations de discontinuités à géométrie réel (rugueuse + ponts rocheux) sont fabriquées et testées sous compression uni-axiale. Il s'agit d'une première tentative d'un modèle réduit explicitement discontinu et contenant des joints ayant un comportement mécanique contrôlé. Les résultats permettent de mettre l'accent sur l'influence des discontinuités sur le comportement global d'un massif rocheux. Cette étude expérimentale est complétée par une étude numérique dans le logiciel UDEC, utilisant la technique de Voronoi tessellation, dans le but de reproduire le comportement du matériau analogue, et de l'utiliser dans la modélisation numérique du prototype modélisé par la modélisation physique
Development of a methodology to study the induced effects of PM from the railway environment on lung cells
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TOXinTRANSPORT : project about toxicological, chemical and physical characterizations of particles in the cabin air of TRANSPORT in movement
No full textInternational audienceTOXinTRANSPORT is an exploratory project that aims to characterize the physicochemical and toxicological properties of particles in transport environments. Particles were analysed in an Underground Railway Station (URS) and in Railway Rolling Stock (RRS). Results show that most particles are composed of iron oxide. URS results show relative value stability among the week of most measured variables. RRS results show significant difference between the days of the week which is likely related to rolling stock conditions such as air conditioning. In-vitro results show influence of particles on metabolization. One of the Oxidative Potential (OP) test sensitive to metals shows high values in both environments compared to urban ambient air measures already done due to higher metals concentrations in the air in those underground environment. Principal component analyses show that some metals such as iron can be related to cellular inflammation
Incorporation of Fast-Elimination Chemicals in Hair Is Governed by Pharmacokinetics–Implications for Exposure Assessment
No full textInternational audienceMechanisms governing chemicals' incorporation in hair are incompletely understood, and gaps remain to link the concentration of chemicals in hair to level of exposure and internal dose present in the body. This study assesses the relevance of hair analysis for the biomonitoring of exposure to fast-elimination compounds and investigates the role of pharmacokinetics (PK) in their incorporation in hair. Rats were administered with pesticides, bisphenols, phthalates, and DINCH over 2 months. Hairs were analyzed for 28 chemicals/metabolites to investigate correlations between their concentration in hair and the dose administered to the animals. Urine collected over 24 h after gavage was used to determine chemicals' PK and to investigate their influence on incorporation into hair by means of linear mixed models (LMMs). Eighteen chemicals presented a significant correlation between concentration in hair and level of exposure. In models combining all chemicals, agreement between concentration in hair predicted by LMM and experimental values was moderate (R2 = 0.19) but significantly increased when PK were included in the models (R2 = 0.37), and even more when chemical families were considered separately (e.g., R2 = 0.98 for pesticides). This study shows that pharmacokinetics mediate incorporation of chemicals in hair and suggests the relevance of hair for assessing exposure to fast-elimination chemicals
Impacts of Long-Term Exposure to Ocean Acidification and Warming on Three-Spined Stickleback (Gasterosteus aculeatus) Growth and Reproduction
No full textInternational audienceThe warming and acidification of surface waters as predicted by the IPCC leads aquatic species to face major multifaceted changes in their environment. Although teleosts have efficient regulatory systems to cope with these changes, such changes clearly have the potential to impact their physiological functions. Hence, it is crucial to estimate the ability of teleost fishes to cope with multi-stresses to predict how they will deal with future environments. In this context, we investigated the joint effect of warming and acidification on three-spined stickleback (Gasterosteus aculeatus) from the juvenile stage to adulthood, focusing on parameters linked to growth, sexual maturation, and reproduction. Juvenile sticklebacks were split in 2 climate scenarios: a “Current” scenario corresponding to the current seasonal physico-chemical parameters of the water of the “Rade de Brest” in France, and a “RCP8.5” scenario with a warming of 3 °C and an acidification of 0.4 pH units. After 7 months, fish in the RCP8.5 scenario reached the same size and mass as those in the Current scenario, but they needed greater amounts of food to reach satiety. Furthermore, the mortality rate over the experiment was higher in the RCP8.5 scenario. Muscle lipid content, an indicator of energy reserves, was lower in females in the RCP8.5 scenario, suggesting an increased need for energy to maintain homeostasis and other physiological functions or a divergence in energy allocation strategy. Moreover, females exhibited lower sexual maturation and egg quality under the RCP8.5 scenario, which could have contributed to the lower fertilisation rate observed. Males were more resilient to the RCP8.5 scenario, exhibiting only a trend for lower kidney somatic index scores. Altogether, these results suggest a delay and/or an inhibition of gametogenesis and maturation in fish in warmed and acidified waters. The analysis of blood sex steroid concentrations, brain gene expression profiles, and physiological indexes did not allow us to discriminate between a delay and an inhibition of maturation in the RCP8.5 scenario. Overall, these findings clearly indicate that there is a long-term global impact of combined acidification and warming on the mortality and reproductive performance of three-spined stickleback
Characterizing site-specific ground motion at great depth in a low seismicity region: challenges and perspectives for a nuclear waste repository project
No full textInternational audienceThe quantification of earthquake-generated site-specific ground motions is necessary for accurate and reliable seismic hazard assessment for critical structures. To this aim, empirical and numerical approaches are typically used in order to characterize the site response at the target site. This is not straightforward in low-seismicity regions and even more challenging when the target structure is located at great depth. This article, focusing on a practical application for an underground radioactive waste repository project to be located in the eastern part of the Paris Basin (France), presents and discusses the results and the faced challenges in the characterization of the site transfer function (TF) from surface to several depths as well as when assessing the applicability of the ergodic site terms from empirical ground motion models to the target site. We first present the data collected in the last years at the project site and the empirical TFs between the surface and two locations at depth (–490 m and –445 m). The empirical transfer function is robust in the frequency range 0.5–10 Hz and less reliable above 10 Hz due to the reduced number of usable recordings. A good consistency is found with the numerical transfer function based on a 1D soil model derived from local boreholes data. A transfer function based on noise recordings is also computed and compared to the earthquake-based one showing a good agreement of the horizontal components. These results clearly open several perspectives on the potential use of ambient noise data and numerical modelling in order to quantify the site response at any point of the underground project layout. Then, we investigate the site-specific high-frequency decay parameter using the available earthquake recordings at the surface. The estimates of obtained combining both acceleration- and displacement-based approaches are affected by large uncertainties owing mainly to the lack of data at short distances (< than 100 km). Nonetheless, a range of values having a central =0.042 s and lower and upper bounds of 0.02 s and 0.058 s is proposed and adjustment factors are calculated using the IRVT approach (Al Atik 2014 BSSA 104:336–346 ) for few example cases. Such adjustment factors together with the empirical TFs and related uncertainties can be used to remove the ergodic assumption on the site term of GMMs in order to improve classical ergodic seismic hazard assessment for structures at surface and at depth
Influence of radiofrequency electromagnetic fields exposure on sleep patterns in preterm neonates
No full textInternational audienceThe study objective was to assess the influence of radiofrequency electromagnetic fields (RF-EMF) exposure on sleep patterns in preterm newborns. We hypothesized that an increase in RF-EMF exposure levels would alter infants' sleep structure parameters.Materials and methodsIndividual, continuous measurements of RF-EMF levels were performed in 29 hospitalized preterm newborns throughout the first 21 days after birth. The last day, overnight sleep structure was recorded by polysomnography. Relationships between both chronic (three-week period) and acute (polysomnographic period) RF-EMF levels with sleep parameters were computed.ResultsAt median levels, the main chronic effect was an increase in indeterminate sleep with RF-EMF exposure. At the highest exposure levels found in our study, an increase in RF-EMF levels increased sleep fragmentation. No significant relationship was found between acute RF-EMF levels and sleep parameters.ConclusionsDespite no consolidated disruption in sleep structure, this study is the first to show that some sleep parameters seem to have a certain sensitivity to chronic - but not acute - RF-EMF exposure in preterm newborns. Further studies are needed to confirm our results and examine possible mid- to long-term, sleep-related cardiorespiratory and neurodevelopmental outcomes
Sub-lethal toxicity of five disinfection by-products on microalgae determined by flow cytometry – Lines of evidence for adverse outcome pathways
No full textInternational audienceStandardised tests are often used to determine the ecotoxicity of chemicals and focus mainly on one or a few generic endpoints (e.g. mortality, growth), but information on the sub-cellular processes leading to these effects remain usually partial or missing. Flow cytometry (FCM) can be a practical tool to study the physiological responses of individual cells (such as microalgae) exposed to a stress via the use of fluorochromes and their morphology and natural autofluorescence. This work aimed to assess the effects of five chlorine-based disinfection by-products (DBPs) taken individually on growth and sub-cellular endpoints of the green microalgae Raphidocelis subcapitata. These five DBPs, characteristic of a chlorinated effluent, are the following monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), bromochloroacetic acid (BCAA) and 1,1-dichloropropan-2-one (1,1-DCP). Results showed that 1,1-DCP had the strongest effect on growth inhibition (EC 50 = 1.8 mg.L-1), followed by MCAA, TCAA, BCAA and DCAA (EC 50 of 10.1, 15.7, 27.3 and 64.5 mg.L-1 respectively). Neutral lipid content, reactive oxygen species (ROS) formation, red autofluorescence, green autofluorescence, size and intracellular complexity were significantly affected by the exposure to the five DBPs. Only mitochondrial membrane potential did not show any variation. Important cellular damages (>10%) were observed for only two of the chemicals (BCAA and 1,1-DCP) and were probably due to ROS formation. The most sensitive and informative sub-lethal parameter studied was metabolic activity (esterase activity), for which three types of response were observed. Combining all this information, an adverse outcome pathways framework was proposed to explain the effect of the targeted chemicals on R. subcapitata. Based on these results, both FCM sub-cellular analysis and conventional endpoint of algal toxicity were found to be complementary approaches
