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Pit Lake Slope Stability under Water Level Variations
No full textInternational audienceThis paper presents the results of a geotechnical investigation regarding the slope stability in a pit lake, emphasizing the impact of water level variations. Advanced analysis techniques were utilized for this study. The research was performed by using fully coupled flow-deformation analyses. For the fully coupled approach, Bishop’s effective-stress equation was used, and for the description of soil hydraulic behavior, the Van Genuchten’s model was applied. The analysis of slope stability associated with reservoir water level changes revealed that the slope tended to become unstable as the water level decreased; the stability factor was negatively related to the rate of water level reduction. Concerning the water level fluctuations, the analyses revealed that the soil mass seemed to become less stable as the rate of water level change increased. Under a specific range of rates of water level variation, the safety factor became higher as the number of fluctuations increased. Additionally, the simulation results concerning the water level rising indicate that the pressure due to the external water level acts on the slope surface with a positive impact on the stability factor. The results obtained reflect the effects under a specific site condition, but they can be used as a reference for evaluating slope stability in a pit lake design
Numerical investigation of the thermal hydrofracturing behavior of the Callovo-Oxfordian claystone
No full textInternational audienceThis study addresses the thermal hydrofracturing behavior in claystone within the context of the high-level and intermediate-level long-lived radioactive waste disposal. The heat generated by the waste packages will lead to a temperature increment within the host formation, inducing a pore pressure build-up essentially due to the difference between the thermal expansion coefficient of the pore water and that of the solid skeleton. If the induced pore pressure build-up is too high, the host formation will experience tensile stresses, potentially exceeding its tensile strength and resulting in fracturing. Understanding of these processes and improving numerical models to reproduce them will help the design, optimization, and safety of the repository. Additionally, it will contribute to demonstrating robustness by showing that such processes are not expected to occur at the repository scale.This study was conducted as part of the DECOVALEX-2023 project and synthesizes the efforts of six research teams modelling laboratory thermal extension tests conducted on Callovo-Oxfordian claystone (COx) samples, as well as an in-situ thermal hydrofracturing experiment conducted at the Meuse/Haute-Marne Underground Research Laboratory in France. The teams used different numerical codes with different approaches, including continuum and discrete approaches, to model these two tests. The laboratory tests were used to calibrate the teams’ models, such as the fracturing criterion. The teams considered a thermo-hydromechanical formulation under saturated conditions. One of the key features of their models was the incorporation of changes in the hydraulic properties of the COx through hydromechanical coupling.The approaches developed by the teams demonstrated their capability to analyze and reproduce fracture initiation in the COx in terms of time of occurrence and location based on their respective stress analyses. However, attempts to reproduce fracture aperture or fracture propagation were less accurate and remain areas for future research, which were beyond the scope of this study
Numerical study of the spark ignition of hydrogen-air mixtures at ambient and cryogenic temperature
No full textInternational audienceAn accurate determination of minimum ignition energy (MIE) is essential for assessing electrostatic hazards and characterising potential for occurrence of combustion in flammable mixtures. This is of utmost importance for hydrogen-air mixtures characterised by a MIE equal to 0.017 mJ, whereas conventional flammable gases are characterised by MIE typically higher than 0.1 mJ. The study aims at developing and validating a CFD three-dimensional model capable to simulate complex unsteady physical and chemical phenomena underlying capacitive discharge spark. The model accounts for the experimental apparatus details, including the effect of electrodes' gap and associated heat losses. The numerical approach accurately reproduced the experimental measurements of MIE for mixtures of hydrogen with air at initial temperature ranging from ambient (T = 288 K) to cryogenic (T = 123 K). Hydrogen concentration in air was included in the range 10–55% for tests at T = 288 K, and 20–60% for tests at T = 173 K and 123 K respectively. Simulations assess the impact of experimental characteristics and design, such as the electrodes’ dimension, and numerical features on process dynamics, growth of the flame kernel and MIE predictions
Induced Seismicity Controlled by Injected Hydraulic Energy: The Case Study of the EGS Soultz‐Sous‐Forêts Site
No full textInternational audienceHow induced seismicity in deep geothermal project (enhanced geothermal systems, EGS) is controlled by fluid injection is of central importance for monitoring the related seismic risk. Here we analyze the relationship between the radiated seismic energy and the hydraulic energy related to the fluid injection during several hydraulic stimulations and circulation tests at Soultz-sous-Forêts geothermal site. Based on a harmonized database, we show that the ratio between these energies is at first order constant during stimulations and of the same magnitude independently of the stimulation protocol and injection depth. Re-stimulations are characterized by a sharp evolution of this ratio during injection which ultimately converges to the characteristic value of the reservoir. This supports that the seismicity is caused by the relaxation of the pre-existing strain energy in the stimulated volume, rather than by the deformation generated from fluid injection. The ratio appears as an intrinsic large-scale property of the reservoir that can be assessed at the very beginning of the first stimulation. Based on this property, we suggest a way to predict the largest magnitude of the induced seismic events knowing the maximum targeted hydraulic energy of the injection
Comprehensive characterization of European house dust contaminants: Concentrations and profiles, geographical variability, and implications for chemical regulation and health risk
No full textInternational audienceThis study investigated the concentration profiles and geographical variability of contaminants in house dust across Europe. A collaborative trial (CT) was organized by the NORMAN network using pooled dust and advanced chromatographic and mass spectrometric techniques combined with suspect screening and non-target screening (NTS). Over 1200 anthropogenic compounds were tentatively identified. Additionally, seventy-five individual samples were subjected to target analysis and NTS. The median concentrations of most contaminants varied <3-fold across Europe, and the contaminant profile of European dust was similar to that of North American dust, which was investigated in a previous CT. This similarity may be attributed to the use of similar consumer articles and building materials throughout the developed world. Multivariate data analysis revealed geographical trends in contaminant distribution, with north-south gradients across Europe. Geographical trends were more frequently found for compounds with rapid release (pharmaceuticals, personal care products, fragrances, pesticides, biocides) and smoke-related compounds. The concentrations of chlorinated paraffins, polycyclic aromatic hydrocarbons (PAHs), perfluorinated alkyl substances and stimulants generally increased from north to south, whereas the biocides levels decreased from north to south. Despite widespread presence of in-use contaminants in dusts, some of the highest risks come from compounds that have been restricted for decades or more. These include di(2-ethylhexyl) phthalate (DEHP), polychlorinated biphenyl (PCB) 118 and polybrominated diphenyl ethers 47, 99, and 153. DEHP remains the most abundant contaminant in European house dust, while the other compounds are classified as persistent organic pollutants (POPs). Moreover, there is a striking lack of reliable toxicity data, particularly for emerging compounds. For instance, although acceptable daily intakes (ADIs) were examined for 202 compounds, only 46 had consensus-based ADI values. The results highlight the need for proactive measures to prevent hazardous chemicals from entering the market and for careful selection of substitute chemicals, when such are needed, to avoid regrettable substitutions
Indicateurs pluriannuels et saisonniers à grande échelle pour la contamination des eaux de surface françaises par les substances de la DCE
No full textDonnées associées : https://data.ofb.fr/catalogue (search keyword “Multi-year”)International audienceThis study offers an unprecedented valuation of the French surface waters WFD chemical monitoring dataset, covering 101 substances (metals, industrial and persistent organic pollutants (POPs), plant protection product (PPP) and biocides active substances, combustion residues) measured monthly on 4000 sites of the 6 main continental river basins, during 12 years (2009-2020). The concentration data were first made comparable through an original process removing the bias induced by the space-and-time heterogeneity of the monitoring labs performance, to gather a reference workable set of monthly contamination indicators. These were then used to display the substances' seasonal and interannual timeseries, revealing, e.g. the succession of PPP active substances contamination peaking periods in the 6 basins, or the long-term trends of the concentrations of the various chemicals, sometimes evidencing insufficiencies in the monitoring performance. These environmental observations were put in regard of the knowledge of the substances ban, restriction or reduction measures, to assess how streams' chemical quality responds to them. Additionally, the observed contamination features and their variations over the years are discussed in terms of changes in their usages, product substitution, emission sources, and linked to environmental processes like runoff, river dilution and physicochemical conditions. Some original findings and interpretation are provided on glyphosate and AMPA wide-scale data inter-relation, and some light is cast on the efficacy of the recent national policies restricting pesticides use in populated areas. For PPPs, the developed water contamination indicators were compared to tonnage data. We assessed their degree of linear relationship, which we propose to quantitatively express through a substance specific basin-to-river contamination coefficient. The interannual variations of this coefficient appear to be related to the changes in the water contamination seasonal patterns. We were also able to describe and validate the dependency of this coefficient on the molecular properties of the substances, conferring some capabilities for predicting the relative environmental risk induced by non-yet monitored compounds. We finally discuss the relevance of the developed indicators to complement the national chemical pollutants management system currently in place.Cette étude offre une évaluation sans précédent de l'ensemble des données de surveillance chimique de la DCE des eaux de surface françaises, couvrant 101 substances (métaux, composés industriels et POPs, substances actives PPP et biocides, résidus de combustion) mesurées mensuellement sur 4000 sites des 6 principaux bassins fluviaux continentaux, pendant 12 ans (2009-2020). Les données de concentration ont d'abord été rendues comparables par un processus original éliminant le biais induit par l'hétérogénéité spatio-temporelle des performances des laboratoires de surveillance, afin d’assembler un jeu d'indicateurs de contamination mensuels de référence. Ceux-ci ont ensuite été utilisés pour afficher les séries chronologiques saisonnières et interannuelles des substances, révélant, par exemple, la succession des périodes de pics de contamination des substances actives phytosanitaires dans les 6 bassins, ou les tendances à long terme des concentrations des différentes substances, mettant parfois en évidence des insuffisances dans la performance de la surveillance. Ces constats sont mis en regard de la connaissance des mesures d'interdiction, de restriction ou de réduction des substances, afin d'évaluer comment la qualité chimique des cours d'eau y répond. En outre, les caractéristiques observées et leurs variations au fil des ans sont discutées en termes de changements dans leur utilisation, de substitution de produits, de sources d'émission, et reliées à des processus environnementaux tels que le ruissellement, la dilution dans les rivières, et les conditions physicochimiques. Nous fournissons quelques observations et interprétations originales sur l'interrelation des données à grande échelle du Glyphosate et de l'AMPA, et nous apportons des éclairages sur l'efficacité des récentes politiques nationales restreignant l'utilisation des pesticides dans les territoires urbains. Pour les substances actives phytosanitaires, nos indicateurs de contamination de l'eau ont été comparés aux données de tonnage. Nous avons évalué leur degré de relation linéaire, que nous proposons d'exprimer quantitativement par un coefficient de contamination bassin/rivière spécifique à la substance. Les variations interannuelles de ce coefficient s’avèrent être bien corrélées aux changements dans les motifs saisonniers de contamination de l'eau. Nous avons pu décrire et valider la dépendance de ce coefficient par rapport aux propriétés moléculaires des substances, ce qui nous permet de prédire le risque environnemental relatif induit par des composés non encore surveillés. Enfin, nous discutons de la pertinence des indicateurs développés pour compléter le système national de gestion des polluants chimiques actuellement en place
Mise à jour des données relatives aux expositions à la silice cristalline dans l’air extérieur chez les riverains de sites d’activités émettrices de silice cristalline
No full textCitation suggérée : Anses. (2024). Mise à jour des données relatives aux expositions à la silice cristalline dans l’air extérieur chez les riverains de sites d’activités émettrices de silice cristalline (saisine 2023-SA-0052). Maisons-Alfort : Anses, 78 p.L’Anses a publié en 2019 un rapport d’expertise sur les « dangers, les expositions et les risques sanitaires relatifs à la silice cristalline ». Concernant les risques pour la population générale, l’expertise conclut que les données recueillies sur les niveaux d’exposition à la silice cristalline de la population générale ne permettaient pas de réaliser une évaluation des risques sanitaires. De plus, l’expertise souligne qu’il n’existe pas de réglementation environnementale spécifique pour la silice cristalline en France. Dans le cadre de la réglementation relative aux Installations Classées pour la Protection de l’Environnement (ICPE), les installations d’extraction et de premier traitement de minéraux naturels, dans le cadre du régime d’autorisation, sont soumises à des dispositions particulières visant à contrôler l’émission de poussières susceptibles d'incommoder le voisinage et de nuire à la santé et à la sécurité publiques, mais il n’est pas fait mention de silice cristalline. Des mesures de concentrations en silice cristalline dans l’air ambiant peuvent être réalisées lors d’études d’impact, mais les données ne sont pas centralisées.Ainsi, dans son avis, l’Anses a recommandé pour la prévention des risques, y compris pour la population générale, de documenter les concentrations environnementales en silice cristalline dans l’air extérieur, au travers d’études réalisées aussi bien en station de fond qu’à proximité de sites susceptibles de générer des aérosols contenant de la silice cristalline, tels que les axes routiers et chantiers BTP. Puis, selon les résultats, d’évaluer l’intérêt d’inclure la silice cristalline dans le cadre de la surveillance de la qualité de l’air extérieur.Plus spécifiquement sur les carrières, l’Anses a recommandé, pour la protection de la population générale, de surveiller dans le cadre de la réglementation relative aux ICPE les émissions de silice cristalline, notamment à l’attention des riverains de ce type d’installation.L’Agence a également recommandé que les données issues de cette surveillance soient centralisées et accessibles.Suite à cette recommandation, la Direction générale de la prévention des risques (DGPR) a sollicité les fédérations professionnelles des industries de carrières (Union nationale des industries de carrières et des matériaux de construction (UNICEM) et fédération Minéraux Industriels-France (MIF)) afin d’évaluer les suites possibles à donner aux recommandations de l’Agence. Ces dernières ont conduit une étude visant à mesurer l’exposition à la silicecristalline autour d’une sélection de carrières réalisée par un bureau d’expertise. Cette étude fait l’objet d’un rapport en trois parties qui a été transmis à l’Anses (EVADIES, MIF et UNPG 2022a, 2022b, 2022c). [Saisine liée 2015-SA-0236
Caractérisation expérimentale et modélisation numérique de l'influence de la saturation sur le comportement mécanique de la craie de Château-Landon
No full textWith climate change and the increased risk of exceptional flooding, the stability of underground mines, formerly exploited and now abandoned, is a pressing concern. This is particularly the case for the Royer chalk mine in Château-Landon (Seine-et-Marne), which has geological and geotechnical similarities with the Beaulieu chalk mine that collapsed in January 1910 following extreme rainfall. The aim of this work is to study the effects of changes in the water saturation of the chalk massif on the mechanical behaviour of the Château-Landon chalk. The mechanical response of partially and fully saturated Château-Landon chalk has been studied experimentally. Hydrostatic compression, triaxial, and creep tests were conducted to investigate the hydromechanical response in the short and long term. The tests were performed under different stress levels and saturation conditions in drained conditions. The results confirm the sensitivity of this chalk to water and highlight the transition from a brittle elastoplastic behaviour to ductile behaviour depending on saturation and confining pressure. A pore collapse mechanism is revealed in hydrostatic tests, with the limit of pore collapse decreasing with saturation. A micromechanics-based model, taking into account plastic mechanisms related to the microstructure of porous chalk, was proposed. To validate this model, several simulations were carried out and compared to experimental data. The results showed that the proposed model accurately describes the influence of water content on the mechanical behaviour of Château-Landon chalk.Avec le changement climatique et devant le risque accru de crues exceptionnelles, se pose aujourd'hui la question de la stabilité des carrières souterraines anciennement exploitées et aujourd'hui laissées à l'abandon. C'est notamment le cas de la carrière de craie Royer à Château-Landon (Seine-et-Marne), présentant des similitudes géologiques et géotechniques avec la carrière de craie Beaulieu effondrée en janvier 1910 à la suite à de précipitations extrêmes. L'objectif de cette thèse est d'étudier les effets des changements du degré de saturation en eau du massif sur le comportement mécanique de la craie de Château-Landon. La réponse mécanique de la craie de Château-Landon partiellement et totalement saturée a été étudiée expérimentalement. Des essais de compression hydrostatique, triaxiale et de fluage ont permis d'étudier la réponse hydromécanique de la craie à court et à long terme. Les essais ont été menés sous différents niveaux de contrainte et de saturation en condition drainée. Les résultats confirment la sensibilité de cette craie à l'eau et mettent évidence le passage d'un comportement élastoplastique fragile à ductile en fonction de la saturation et de la pression de confinement. Un mécanisme de pore collapse est mis en évidence avec les essais hydrostatiques. La limite de pore collapse diminuant avec le degré de saturation. Un modèle basé sur la micromécanique tenant en compte les mécanismes plastiques liés à la microstructure de la craie poreuse a été proposé. Pour valider ce modèle de comportement, plusieurs simulations ont été effectuées et comparées aux données expérimentales. Les résultats ont montré que le modèle proposé permet de décrire correctement l'influence de la teneur en eau sur le comportement mécanique de la craie de Château-Landon
La diminution de la fécondité chez le poisson zèbre: Inhibition de l’aromatase gonadique et autres chemins de toxicité conduisant à une diminution de la fécondité chez le poisson zèbre : de l’événement initiateur aux impacts sur les populations
No full textNational audienc
Seismic hazard related to deep geothermal operations (Part I): identification of key criteria for hazard assessment
No full textInternational audienceDeep geothermal projects can trigger seismic events depending on geological context and operations. This seismicity is generally of low magnitude but, in some cases, larger events may occur, which could lead to geothermal project abandonment and could present risk to neighboring populations. Thus, development of deep geothermal projects requires the management of induced seismicity to control it and to avoid any surface disturbance. It is from this perspective that, in 2023, Ineris and BRGM published a guide of good practices and recommendations for operators and French administration involved in deep geothermal energy.The guide provides recommendations for assessing geothermal-induced seismic hazard, depending on the type of geothermal system and its intrinsic and operational characteristics, at each key step of a project (i.e. from the exploration phase until the end of the project). A worldwide review of deep geothermal projects, carried out with the aim of identifying key factors triggering induced seismicity, has enabled the definition of the most relevant criteria to take into account in the hazard assessment. In this review, geothermal projects were chosen to be representative of different types of geothermal systems (e.g. deep sedimentary aquifers, volcanic and plutonic regions, deep dry crystalline basements, etc.) and operating conditions (e.g. well configuration, type of operation, etc.). Moreover, the review includes projects associated with several episodes of induced seismicity, ranging in magnitude from microseismicity (M < 2) to large seismic events (M > 5), as well as projects marked by the absence of induced seismic activity.From the 53 projects and 77 seismic episodes analyzed in this review, we can state that not all geothermal projects are equally prone to seismic events. The occurrence and the intensity of induced seismicity are the results of interactions between several natural (intrinsic) and anthropogenic (operational) factors, often concomitant and dependent on each other. Seismic response of analyzed projects appears to be largely different depending on the type of geothermal system. Indeed, the type of geothermal system characterizes reservoir porosity, as well as heat transfer and fluid circulation modes in the reservoir. Other key factors include the presence of faults that can be critically loaded and/or connected with the basement, the use of EGS technologies, and situations where injected and produced volumes are highly unbalanced. These results allowed defining key criteria for seismic hazard assessment methodology proposed within the good practice guide