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Rockfalls multi-methods detection and characterization / Gaëlle Le Roy (2020)  

Public Titre : Rockfalls multi-methods detection and characterization Type de document : Thèse/HDR Auteurs : Gaëlle Le Roy, Auteur ; David Amitrano, Directeur de thèse ; Agnès Helmstetter, Directeur de thèse Editeur : Grenoble [France] : Université Grenoble Alpes Année de publication : 2020 Importance : 186 p. Format : 21 x 30 cm Note générale : bibliographie Thèse pour obtenir le grade de Docteur de l'Université de Grenoble Alpes Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] Chartreuse, massif de la (Préalpes ; France) [Termes IGN] éboulement [Termes IGN] fréquence [Termes IGN] modèle numérique de surface [Termes IGN] modèle numérique de terrain [Termes IGN] pente [Termes IGN] photogrammétrie numérique [Termes IGN] roche [Termes IGN] sismologie [Termes IGN] surveillance géologique Index. décimale : THESE Thèses et HDR Résumé : (auteur) Amongst mass wasting events, rockfalls remain the most unpredictable and the most frequent hazard in the alpine region. In a context of growing urbanization in mountainous regions, rockfalls represent an increasing risk for local communities and infrastructures. This thesis aims to develop an association of relevant methods for rockfall monitoring. One objective of this thesis is to associate topography measurement and seismological monitoring in order to improve significantly in understanding rockfalls dynamics. This work was mainly carried out in the Chartreuse massif (Isère, French Alps), and in particular two cliffs, Mount Saint-Eynard and Mount Granier. Using photogrammetry, we acquired diachronic Digital Elevation Models (DEMs) of the cliffs. Such monitoring enables us to carry out rockfall inventories and occurrence frequency analysis. It also provides us information on rockfall locations and their structural configurations. Combining DEMs and rockfall seismic monitoring allowed us to study relations between rockfall properties (location, volume, geometry, propagation, etc.) and the induced seismic signal. Characteristics of the seismic signal (duration and energy, frequency content, envelope shape) vary depending on the event propagation mode (mass-flow, free-fall, sliding, bouncing …). Selecting events with the same propagation type provides a more accurate characterization of rockfalls properties than when mixing different types of events. For free-falling rockfalls, we analyze the seismic signal of the detachment phases and first impacts. We found relations between seismic signals parameters and rockfalls potential energy, free-fall heights, and volumes. For mass-flow type events, we found a scaling law between rockfalls seismic energy and their volumes. By coupling DEMs and seismic records, we can reconstruct rockfall sequence with accurate timing and correct volume estimations. Controlled block releases were realized in laboratory and on-site to widen our observations on rockfall events. Note de contenu : 1- Slopes dynamics and weathering 2- Rockfall hazard in the Alps 3- Rockfall monitoring techniques 4- Methodological biases on rockfall inventories and empirical volume distributions 5- Morpho-structural analysis of rockfalls 6- Seismic analysis of free-falling rockfalls 7- Controlled block release experiment of free fall type events 8- Controlled block release experiment of free fall type events 9- Thermography of block impacts 10- Development outlook Numéro de notice : 25998 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Thèse française Note de thèse : Thèse de Doctorat : Terre Solide : Université Grenoble Alpes : 2020 Organisme de stage : Laboratoire Institut des Sciences de la Terre nature-HAL : Thèse DOI : sans En ligne : https://tel.archives-ouvertes.fr/tel-02921764/document Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96892