Articles - Papers by Cecile Verdet
NEMESIS 1, 2023
https://una-editions.fr/the-rapsodie-project/
Hiriart, E., J. Hantrais, A. Beyrie, C. Chevillot,... more https://una-editions.fr/the-rapsodie-project/
Hiriart, E., J. Hantrais, A. Beyrie, C. Chevillot, S. Colin, J.-M. Fabre, A. Glais, M. Larcanché, C. Leroyer, Chantal, S. Lopez, P. Paillou, C. Sirieix, R. Steinmann, C. Verdet, V. Mathé (2023) : “The RAPSODIE project. First results from the sites of La Peyrouse and Blis (Dordogne)”, in : Hiriart, E., Krausz, S., Alcantara, A., Filet, C., Goláňová, P., Hantrais, J., Mathé, V. dir. (2023) : Les agglomérations dans le monde celtique et ses marges. Nouvelles approches et perspectives de recherche, Pessac, Ausonius Éditions, collection NEMESIS 1, 297-330.
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Papers by Cecile Verdet
HAL (Le Centre pour la Communication Scientifique Directe), Mar 10, 2021
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Geophysics, Nov 1, 2018
Electrical resistivity tomography (ERT) profiles including finite steel-rod electrodes have been ... more Electrical resistivity tomography (ERT) profiles including finite steel-rod electrodes have been widely used in assuming a surface-node current injection for inversion. This hypothesis was shown by others to be safe for ratios of electrode embedment to electrode spacing smaller than 20%. Relying on the conductive cell model (CCM), we took into account the complete electrodes in the DC forward problem. We found that an electrode effect is included in resistivity sections inverted with a surface point electrode model. Several synthetic examples indicated that this unwanted effect is particularly developed when the electrode spacing does not meet a double constraint from the characteristic size of a shallow heterogeneity and from the electrode embedment. This effect deserved correction. A point approximation for a finite electrode referred to as the equivalent electrode point (EEP) was sought by placing a point-source current in the ground along the electrode length. The appropriate EEP depth was the one for which the CCM and a buried point source minimized a systematic geometric error; i.e., the relative change of the geometric factors obtained with the CCM and with an EEP. An EEP placed at 73% of the electrode length was declared as a suitable point approximation for an electrode. Use of this point assumption for inversion remedied efficiently the electrode effect subject to conditions. More precisely, the electrode spacing should stay within a lower bound equal to twice the electrode embedment and an upper bound equal to the shallow heterogeneity characteristic size divided by 0.75. The interest of such a metrological appraisal of the suitable acquisition layout to be used on the field was illustrated by a small-scale ERT field survey. This case study permitted us to understand more reliably the impact from fires upon a centimetric shallow layer in a calcareous wall.
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Geophysical Journal International, Jun 22, 2021
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Proceedings, Sep 3, 2017
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HAL (Le Centre pour la Communication Scientifique Directe), Jan 28, 2019
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Geophysical Journal International
SUMMARY The goal of data classification is to organize them into relevant groups using algorithms... more SUMMARY The goal of data classification is to organize them into relevant groups using algorithms. In this study, two clustering algorithms are applied to classify a set of geophysical measurements performed around the Lascaux Cave (Dordogne, France). Based on a non-destructive geophysical method, electrical resistivity tomography (ERT), the data (resistivity values) are supposed to characterize the rock mass around the cave. The rock mass must be divided into an optimal number of homogeneous domains with specific thermal properties to integrate them in the future thermo-aeraulic simulations of the cave. Since the data are georeferenced, a given resistivity cluster corresponds to a specific spatial domain of the rock mass. This study aims to compare two different clustering methods, the Hierarchical Agglomerative Clustering (HAC) and the K-means methods, on the resistivity data set. Thus, the objective of this study is to determine which of the two methods leads to a partition of th...
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NSG2022 28th European Meeting of Environmental and Engineering Geophysics
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Le milieu karstique, et tout particulièrement sa partie superficielle, est caractérisé par une al... more Le milieu karstique, et tout particulièrement sa partie superficielle, est caractérisé par une altération importante responsable sur le site de Lascaux de formations calcaires en plaquettes mais aussi de dissolutions importantes pouvant laisser place à des sables, argiles, etc. La présence de grottes ornées dans ce milieu nécessite la caractérisation du milieu environnant afin de protéger les grottes et contribuer à la conservation des œuvres pariétales. Cette thèse porte sur la caractérisation du milieu karstique à plusieurs échelles au moyen de deux méthodes : la géophysique avec la Tomographie de Résistivité Electrique (TRE), et la caractérisation pétrophysique, à l’échelle du laboratoire, avec la microscopie, la porosimétrie au mercure et des mesures électriques sur échantillons. A l’échelle du massif, nous avons caractérisé l’amont hydraulique de la grotte de Lascaux par un suivi temporel par TRE durant 6 ans et par trois modélisations géostatistique 3D, à trois dates. Le suivi...
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HAL (Le Centre pour la Communication Scientifique Directe), 2020
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E3S Web of Conferences, 2022
Les algorithmes de classification permettent de gérer de grandes quantités de données. L'obje... more Les algorithmes de classification permettent de gérer de grandes quantités de données. L'objectif de cette étude est de comparer deux méthodes de classification, la Classification hiérarchique Ascendante (CHA) et la méthode des Centres Mobiles (CM) sur des données de Tomographie de Résistivité Electrique (TRE) caractérisant le massif entourant la grotte de Lascaux. Le rendu de ces méthodes est analysé en tenant compte de la connaissance a priori de la géologie du site. Dans ce projet, la structuration des données en 2 à 5 classes vise à subdiviser le massif en domaines les plus homogènes possible afin de leur affecter des propriétés thermiques différentes dans un modèle 3D. Ces dernières serviront de paramètres d’entrée nécessaires aux simulations thermo-aérauliques de la grotte soumise à différentes conditions météorologiques.
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NSG2020 26th European Meeting of Environmental and Engineering Geophysics, 2020
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Geophysical Journal International, 2021
Water migration within the rock mass during a fire has not yet been studied. Here, an innovative ... more Water migration within the rock mass during a fire has not yet been studied. Here, an innovative high-resolution micro-ERT method is developed at a centimetric scale to measure this phenomenon. The method is two-step based: first, a correction of the electrode effect, and second, the correction of resistivity for rapid variations in temperature with high values. Water migration is successfully described within the wall of an underground limestone quarry with three phases: from fire ignition to 36 min, the surface dries to a 3-cm depth and a higher saturated layer forms deeper than 0.10 m; from 36 min to 46 min (fire supply stops), the rock dries out and water migrates from deeper parts of the rock wall, deeper than 20 cm, towards the surface; finally, after fire extinction, the water migrates through a readjustment phase until it returns to its initial state.
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NSG2021 27th European Meeting of Environmental and Engineering Geophysics, 2021
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Geomorphology, 2020
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GEOPHYSICS, 2018
Electrical resistivity tomography (ERT) profiles including finite steel-rod electrodes have been ... more Electrical resistivity tomography (ERT) profiles including finite steel-rod electrodes have been widely used in assuming a surface-node current injection for inversion. This hypothesis was shown by others to be safe for ratios of electrode embedment to electrode spacing smaller than 20%. Relying on the conductive cell model (CCM), we took into account the complete electrodes in the DC forward problem. We found that an electrode effect is included in resistivity sections inverted with a surface point electrode model. Several synthetic examples indicated that this unwanted effect is particularly developed when the electrode spacing does not meet a double constraint from the characteristic size of a shallow heterogeneity and from the electrode embedment. This effect deserved correction. A point approximation for a finite electrode referred to as the equivalent electrode point (EEP) was sought by placing a point-source current in the ground along the electrode length. The appropriate EE...
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Articles - Papers by Cecile Verdet
Hiriart, E., J. Hantrais, A. Beyrie, C. Chevillot, S. Colin, J.-M. Fabre, A. Glais, M. Larcanché, C. Leroyer, Chantal, S. Lopez, P. Paillou, C. Sirieix, R. Steinmann, C. Verdet, V. Mathé (2023) : “The RAPSODIE project. First results from the sites of La Peyrouse and Blis (Dordogne)”, in : Hiriart, E., Krausz, S., Alcantara, A., Filet, C., Goláňová, P., Hantrais, J., Mathé, V. dir. (2023) : Les agglomérations dans le monde celtique et ses marges. Nouvelles approches et perspectives de recherche, Pessac, Ausonius Éditions, collection NEMESIS 1, 297-330.
Papers by Cecile Verdet
Hiriart, E., J. Hantrais, A. Beyrie, C. Chevillot, S. Colin, J.-M. Fabre, A. Glais, M. Larcanché, C. Leroyer, Chantal, S. Lopez, P. Paillou, C. Sirieix, R. Steinmann, C. Verdet, V. Mathé (2023) : “The RAPSODIE project. First results from the sites of La Peyrouse and Blis (Dordogne)”, in : Hiriart, E., Krausz, S., Alcantara, A., Filet, C., Goláňová, P., Hantrais, J., Mathé, V. dir. (2023) : Les agglomérations dans le monde celtique et ses marges. Nouvelles approches et perspectives de recherche, Pessac, Ausonius Éditions, collection NEMESIS 1, 297-330.