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Etude des mécanismes de déformation d'un glissement-coulée par une approche multi-méthodes

Abstract : Ground movements affecting clay materials constitute a major risk to infrastructure and populations, with sudden episodes of reactivation that can lead to rapid movements (flow type). This thesis work is interested in understanding the different mechanisms of reactivation and deformation in a landslide of this type, by studying mass transfers in a material with a solid behavior at the top of the landslide and a fluid behavior at the toe. The study site is the Harmalière landslide (Trièves, French Alps), consisting of glaciolacustrine clays. Since the major event of March 1981 which took away 45 ha, this landslide has undergone numerous retrogression episodes with an average rate of 4 m/year at the headscarp and mass transfers of several million m3. The study was based on a multi-method approach, combining remote sensing (satellite images, LiDAR, GNSS, UAV), geophysical and mechanical techniques. In a first part, an analysis of the various recent events (from 2016) made it possible to describe and quantify the various mass transfers during reactivations. In a second part, a more detailed study of the reactivations at the head of the landslide was carried out. First, a study of the seismic background noise recorded continuously during the 4 months preceding the rupture of a clay blockat the headscarp was carried out. Five seismic parameters were monitored (cumulative number of events, seismic energy, resonance frequency, Rayleigh wave velocity variations and associated correlation coefficient). All these parameters showed a precursor signal prior to the rupture. Then, a preliminary study focuses on the evolution of the mechanical properties of a low mechanical strength layer close to the headscarp. In a third part, the degradation mechanisms of the material leading to flow type behavior were explored using a mechanical approach and UAV imaging. The mechanical approach allowed to study the evolution of the geotechnical properties of the clayey material in the landslide. UAV imaging was used to follow the evolution of the clay blocks at the head of the landslide and to quantify the degradation rate of the material.
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Submitted on : Tuesday, February 23, 2021 - 9:46:46 PM
Last modification on : Sunday, May 1, 2022 - 3:41:50 AM
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  • HAL Id : tel-03150587, version 1

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Sylvain Fiolleau. Etude des mécanismes de déformation d'un glissement-coulée par une approche multi-méthodes. Mécanique des solides [physics.class-ph]. Université Grenoble Alpes [2020-..], 2020. Français. ⟨NNT : 2020GRALU025⟩. ⟨tel-03150587⟩

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