HAL-BRGM, les publications scientifiques en libre accès du BRGM
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Analysis of almost one thousand Thermal Response Tests in France and estimation of the energy potential of Borehole Heat Exchangers
No full textInternational audienceThe Thermal Response Test (TRT) is a well-established key procedure to estimate the average thermal properties of a Borehole Heat Exchanger (BHE) and its surrounding, namely the initial (undisturbed) temperature T0 , the average thermal conductivity of the underground λm and the borehole resistance Rb . Since 2017, the French Geological Survey BRGM has been, with the support of the French Agency for Ecological Transition ADEME, collecting, storing, analyzing and disseminating TRT reports. As of March 2025, this number stands at 1,010 reports. The key results of the TRT are made available through a dedicated web service. A regression has been built to predict T0 as a function of the coordinates, altitude and depth of the borehole. It performs quite well since the prediction error is below 1.0 °C for 80% of the records. A method was further developed to derive a reference value of λm per lithology based on the TRT dataset, and is compared to reference values
A knowledge-driven modeling formalism for automatic structural interpretation
No full textInternational audienceBuilding structural models of geological entities is generally addressed as an interpolation problem that requires human experts to interpret input data and use knowledge. Although experts can effectively interpret, their interpretations can be subjective and occasionally prone to error. This is largely due to under-sampling of data, requiring experts to make choices in the selection and preparation of these data and knowledge, and selection and configuration of modeling algorithms. Modeling algorithms also do not reflect the complex expert interpretation process, as they incorporate only a portion of the knowledge typically held by experts and have limited ability to directly interact with experts during the interpretation process itself. This makes it challenging to build geologically complex models and systematically identify and address inconsistencies in a model. Part of the solution to these issues is the formalization of the interpretation process, which incorporates more knowledge and better reflects expert decision-making. In this paper we develop and prototype such a formalization. A prototype algorithm and tool are presented and applied to simple folding structures, and the results are favorably compared to existing approaches. This comparison highlights the potential of the proposed approach to reduce the need for expert involvement and increase the range of knowledge utilize
Exploration de l’évolution future du trait de côte et de la zone proche du rivage face aux projections d’élévation du niveau de la mer : Application du modèle LX-ST à Lacanau
No full textInternational audienceThis study applies the reduced-complexity model LX-ST to simulate the future evolution of the shoreline and nearshore morphology of Lacanau, a wave-dominated, erosion-prone coastal site in southwest France. By coupling longshore transport with shoreface translation processes, the model evaluates changes under various IPCC sea-level rise scenarios through 2100. Results highlight significant spatial variability in erosion, with pronounced downdrift retreat near coastal defenses. The findings demonstrate the utility of LX-ST for informing long-term coastal adaptation strategies
Exploring the optimality of threshold-based crop irrigation feedback strategies
No full textThe development of effective crop irrigation strategies is a key element of water management in agriculture, seeking a necessary parsimonious use of resources. Years of practice and accumulation of knowledge have led to numerous irrigation policies, including Threshold-Based Irrigation Strategies (TBIS). This work involves the Controlled Crop Irrigation (CCI) model, a simple dynamical system describing the order-1 biophysical processes at play, for which optimal irrigation policies may be proven and written as TBIS. We aim at studying both the optimal TBIS and their sub-optimal declensions, to identify the most influential parameters (which dictate the structure of optimal irrigation scenarios) but also the effects of errors made on their determination. Much attention is therefore drawn to the crucial "decision time" at which the irrigator decides to increase soil water content from an initial "stress tolerance level" to a "maximal biomass production" setpoint. In this study, we couple known results from optimal control theory and numerical methods for sensitivity analysis and global model exploration. The most striking results are that the optimal decision time is mostly driven by plant growth dynamics and the correct evaluation of stress effects on biomass production, as slightly too low soil moisture levels during the productive stage induce significant losses in final biomass. The genericity of the CCI model and the modularity of the methodology offer promising perspectives for various operational contexts
Enhanced remediation of diesel-contaminated soils using a novel biopolymer-based emulsion
No full textInternational audienceConventional in-situ light non-aqueous phase liquid (LNAPL) remediation techniques often face challenges of high costs and limited efficiency, leaving residual hydrocarbons trapped in soil pores. This study investigates the efficiency of an alcohol-in-biopolymer emulsion for enhancing diesel-contaminated soil remediation. The emulsion, formulated with xanthan gum biopolymer, sodium dodecyl sulfate surfactant, and the oil-soluble alcohol 1-pentanol, was evaluated through rheological tests, interfacial tension measurements, and onedimensional sand-column experiments under direct injection and post-waterflooding scenarios. The emulsion exhibited non-Newtonian shear-thinning behavior with high viscosity, ensuring stable propagation and efficient delivery of 1-pentanol to mobilize trapped diesel ganglia. It achieved 100 % diesel recovery within 1.2 PV during direct injection, outperforming shear-thinning polymer-only and polymer-surfactant solutions, which achieved recovery factors of 83.4-92.9 %. Post-waterflooding experiments also demonstrated 100 % diesel recovery within 1.3 PV, regardless of initial diesel saturation. Key mechanisms include reduced interfacial tension, diesel swelling and mobilization induced by 1-pentanol, and uniform displacement facilitated by the emulsion’s viscosity. Additionally, the emulsion required lower injection pressures compared to more viscous alternatives, enhancing its injectability into the soil and reducing energy demands. These findings highlight the emulsion’s potential to overcome conventional remediation limitations, offering a highly effective and sustainable solution for diesel-contaminated soils and groundwater
DIG-IT: A serious game for learning about subsurface exploitation for undergraduate students
No full textBackgroundSubsurface exploitation is an important subject of various environment educational major. However, the related scientific knowledge is difficult to be mentally visualized especially for beginners and during classical lectures and thereby impacts understanding. MethodTo address this issue, we developed DIG-IT, a serious card role-player game based on discussion with a game master (teachers or an invited industrial engineer) in order to immerse the student in a dynamic and progressive learning process. This game is thought to answer a first order of knowledge. Indeed, it is designed for earlier students, not specialized in geophysics or earth environment. ResultIn the game, students embody a sub-surface operator considering different more or less “clean” resources as geothermal exploitation, uranium mines for nuclear energy, carbon capture storage, but also hydrocarbon exploitation or coal mining. They must discover how they can set-up (through geological cuts and geophysical campaigns), dig boreholes, exploit them and at the end, return to the natural state. During the game, players deal with their objectives of production, planet impact, and public acceptation.ConclusionDIG-IT has been tested in instructional setting of undergraduate students at the engineering school of Polytech’Orléans. Student feedback was very positive, so this game is now part of an Ecological and Societal Transitions program. Surveys about student’s geoscience and environment knowledge has been made before and after this program highlighting the interest of such tool
Avis du conseil scientifique du comité de bassin Seine-Normandie sur l’état des lieux 2025 du bassin
No full textThis opinion from the Scientific Council concerns the 2025 status report for the Seine-Normandy basin, a mandatory exercise carried out every six years that is essential for initiating each cycle of the European Water Framework Directive and fundamental for making informed and fair decisions on the objectives and actions to be taken to restore the state of the environment.The Scientific Council appreciates the various efforts made for the 2025 inventory of the basin:the monitoring effort on which the state of the waters is based, the educational aspect, the fact of showing issues other than the strict parameters of the WFD (on medicines, plastics, etc.), the “continuity of the thermometer” when a change of method occurs, a good explanation of the links between the continent and the coast, and the monitoring of the NODU despite the change of indicator at the national level.He regrets that the long-term evolution of aquatic biodiversity in the basin is not specifically presented, and that beyond the indicators of the proportion of water bodies in good condition, other indicators, such as a proportion of surface area and arating from 0 to 100 to avoid the threshold effects of classes, are not presented.He notes the deterioration in water quality in the basin, particularly at the headwaters, which are more fragile and better monitored. He notes a greater impact from nitrates and pesticides, but also from phosphorus.He regrets that the long-term evolution of aquatic biodiversity in the basin is not specifically presented, and that, in addition to indicators of the proportion of water bodies in good condition, other indicators, such as surface area proportion and a rating from 0 to 100 to avoid class threshold effects, are not presented.He notes the deterioration in water quality in the basin, particularly at the headwaters, which are more fragile and better monitored. It notes a greater impact from nitrates and pesticides, but also from phosphorus. It notes the footprint of past degradation, including as a result of development, which should encourage caution when considering new development projects, in order to avoid further degradation of wetlands and hydromorphology, and to support the resilience of territories in the face of climate change. It questionsthe origin of the increase in diffuse phosphorus pressure and NODU herbicides, and the stability of NODU insecticides despite the disappearance of insects.It notes that the target of a 10% reduction in withdrawals may be difficult to achieve and insists on the need to prioritize sobriety rather than efficiency and substitution.The SC points out that the inventory is the first step in each WFD cycle and forms the basis for the subsequent development of the Water Development and Management Master Plan and its Program of Measures which must guide the water agency's assistance.The Scientific Council recommends that:⚫ The results on the status of water bodies be presented as a proportion of surface area.⚫ The next inventory distinguishes between types of pesticides (insecticides, herbicides, etc.) and their level of toxicity (CMR1, CMR2, etc.), which can be done using the NODU.⚫ The development of toxic phytoplankton, an indirect consequence of eutrophication, be taken into account in coastal waters.⚫ Several hypotheses arising from this inventory should be studied, such as those relating to phosphorus and insecticides and herbicides.⚫ The term “self-purification” should not be used, but rather “resilience.”⚫ Information on the long-term evolution of aquatic biodiversity should be provided.Le présent avis du conseil scientifique porte sur l’état des lieux 2025 du bassin Seine-Normandie, exercice obligatoire réalisé tous les 6 ans et primordial initiant chaque cycle de la Directive cadre européenne sur l’eau, fondamental pour la prise de décisions éclairées et justes sur les objectifs et les actions à conduire pour restaurer l’état des milieux.Le conseil scientifique apprécie divers efforts réalisés pour l’état des lieux 2025 du bassin :l’effort de surveillance sur lequel est basé l’état des eaux, la pédagogie, le fait de montrer des enjeux autres que les stricts paramètres de la DCE (sur les médicaments, les plastiques…), la « continuité du thermomètre » lorsqu’un changement de méthode se présente, une bonne explication des liens entre continent et littoral, le suivi du NODU malgré le changement d’indicateur au niveau national.Il regrette que l’évolution de la biodiversité aquatique du bassin ne soit pas présentée spécifiquement sur le long terme, qu’au-delà des indicateurs de proportion des nombres de masses d’eau en bon état, d’autres indicateurs, comme une proportion en surface, et une notation de 0 à 100 permettant d’éviter les effets de seuil des classes, soient présentés.Il note la dégradation de la qualité des eaux du bassin, notamment des têtes de bassin, plus fragiles et mieux suivies. Il note un plus fort impact des nitrates et des pesticides, mais aussi du phosphore. Il note l’empreinte de dégradations passées, y compris du fait des aménagements, qui devrait pousser à considérer prudemment de nouveaux projets d’aménagements, pour éviter de dégrader encore les zones humides et l’hydromorphologie, et soutenir la résilience des territoires face au changement climatique. Il s’interroge surl’origine de l’accroissement de la pression en phosphore diffus, du NODU herbicides, et sur la stabilité du NODU insecticides malgré la disparition des insectes.Il note que l’objectif de baisse de 10% des prélèvements risque d’être difficile à atteindre et insiste sur la nécessité de prioriser la sobriété, plutôt que l’efficacité et la substitution.Le CS rappelle que l’état des lieux constitue la première étape de chaque cycle de la DCE et la base sur laquelle doivent ensuite être élaborés le Schéma Directeur d’Aménagement et de Gestion des Eaux, son Programme de Mesures, et qui doit guider les aides de l’agence del’eau.Le conseil scientifique recommande que :⚫ Les résultats sur l’état des masses d’eau soient présentés en proportion de surface.⚫ Le prochain état des lieux distingue les types de pesticides (insecticides, herbicides…) mais aussi leur niveau de toxicité (CMR1, CMR2…), ce que permet de faire le NODU.⚫ Le développement des phytoplanctons toxiques, conséquence indirecte de l'eutrophisation, soit pris en compte dans les eaux littorales.⚫ Plusieurs hypothèses issues de cet état des lieux soient étudiées, comme celles portant sur les phosphores et sur les insecticides et herbicides.⚫ Ne soit pas utilisé le terme “autoépuration” mais plutôt « résilience ».⚫ Soit renseignée l'évolution de l'état de la biodiversité aquatique sur le long terme
Future Circular Collider Feasibility Study Report: Volume 3, Civil Engineering, Implementation and Sustainability: Volume 3 Civil Engineering, Implementation and Sustainability
No full textInternational audienceVolume 3 of the FCC Feasibility Report presents studies related to civil engineering, the development of a project implementation scenario, and environmental and sustainability aspects. The report details the iterative improvements made to the civil engineering concepts since 2018, taking into account subsurface conditions, accelerator and experiment requirements, and territorial considerations. It outlines a technically feasible and economically viable civil engineering configuration that serves as the baseline for detailed subsurface investigations, construction design, cost estimation, and project implementation planning. Additionally, the report highlights ongoing subsurface investigations in key areas to support the development of an improved 3D subsurface model of the region. The report describes development of the project scenario based on the 'avoid-reduce-compensate' iterative optimisation approach. The reference scenario balances optimal physics performance with territorial compatibility, implementation risks, and costs. Environmental field investigations covering almost 600 hectares of terrain - including numerous urban, economic, social, and technical aspects - confirmed the project's technical feasibility and contributed to the preparation of essential input documents for the formal project authorisation phase. The summary also highlights the initiation of public dialogue as part of the authorisation process. The results of a comprehensive socio-economic impact assessment, which included significant environmental effects, are presented. Even under the most conservative and stringent conditions, a positive benefit-cost ratio for the FCC-ee is obtained. Finally, the report provides a concise summary of the studies conducted to document the current state of the environment
From oceanic subduction to continental collision: Revisiting the Permian–Triassic magmatism of the Indosinian orogenic belt, Vietnam
No full textInternational audienceIndosinian orogenic belt resulted from the Early Mesozoic collision between the South China block and the Indochina block, driven by the closure of Eastern Paleo-Tethys Ocean. In this study, we revisit Early Permian to Middle Triassic magmatic rocks in the Western Ailaoshan-Truong Son-Sam Nua magmatic unit (North Vietnam segment), Indosinian orogenic belt. New petrological, geochronological, geochemical, and zirco
Deeper, faster, stronger? Extreme magma ascent rates and explosive eruption metrics at Stromboli volcano (Italy)
No full textInternational audienceDetermining the ascent rate of magma during its rise to the surface is challenging yet crucial as it may relate to the style of volcanic eruptions, and modelling dissolved volatiles in crystal-hosted melt embayments is one effective method to estimate these rates. Previous studies suggest that magma ascent rates in basaltic volcanoes may positively correlate with eruption magnitude. Stromboli volcano (Italy) is an ideal case study because its unique plumbing system produces eruptions with variable eruption styles and magnitudes. Magma ascent rates of eight historical eruptions were calculated using (1) diffusion of H2O in embayments, and (2) vesicle population and textural analysis. Embayments record rapid ascent initiation from 1.6 to 7.2 km deep. We obtained average decompression rates of 0.32─6.2 MPa·s−1 (ascent rate of 11─226 m·s−1) for the last step of magma ascent within the conduit system, which agrees with Li diffusion in plagioclase and the timescales of ground deformation at Stromboli recorded immediately before explosive events. Vesicle number density of tephra clasts provides decompression rates within the same order of magnitude (0.55─6.09 MPa·s−1), confirming shallow very fast ascent within the conduit. We identify a strong positive correlation between decompression rates with (1) eruption magnitude, (2) mass eruption rate and (3) embayment H2O-CO2 solubility pressure for eruptions spanning several orders of magnitude in intensity, with faster decompression rates from greater pressures producing the highest intensity eruptions. We suggest such behaviour should be expected at other basaltic volcanoes as well