Experimental field study on the fatigue and failure mechanisms of coastal chalk cliffs: Implementation of a multi-parameter monitoring system (Sainte-Marguerite-sur-Mer, France)

Pauline Letortu; Nicolas Le Dantec; Emmanuel Augereau; Stéphane Costa; Olivier Maquaire; Robert Davidson; Cyrille Fauchard; Raphaël Antoine; Reynald Flahaut; Yan Guirriec; Laurent Longuevergne; Jérôme de la Bernardie; Laurence David

doi:10.1016/j.geomorph.2022.108211

Journal articles

Experimental field study on the fatigue and failure mechanisms of coastal chalk cliffs: Implementation of a multi-parameter monitoring system (Sainte-Marguerite-sur-Mer, France)

Pauline Letortu ^{1, *} Nicolas Le Dantec ² Emmanuel Augereau ^{1, 2, 3} Stéphane Costa ³ Olivier Maquaire ³ Robert Davidson ³ Cyrille Fauchard Raphaël Antoine Reynald Flahaut ⁴ Yan Guirriec ⁴ Laurent Longuevergne ⁵ Jérôme de la Bernardie ⁵ Laurence David ¹

* Corresponding author

1 LETG - Littoral, Environnement, Télédétection, Géomatique UMR 6554

2 IUEM - Institut Universitaire Européen de la Mer

3 UNICAEN - Université de Caen Normandie

4 Cerema Direction Normandie-Centre - Centre d'Etudes et d'Expertise sur les Risques, l'Environnement, la Mobilité et l'Aménagement - Direction Normandie-Centre

5 GR - Géosciences Rennes

Abstract : Between November 2018 and January 2020, a continuous multi-parameter survey, using nine types of sensors, was carried out on a coastal chalk cliff in Sainte-Marguerite-sur-Mer (Normandy, France) with the objective of gaining a deeper understanding of the forcing agents and processes that lead to cliff fatigue and failure. This paper will present the survey instrumentation, the results on the internal characteristics of the chalk massif, initial results (from November 2018 to March 2019) of the thermal subsurface behaviour along the cliff face, and the analyses of the observed cliff-top ground motion and the movement of existing fractures on the cliff face in relation to forcing agents. Our main results show that 1) the magnitude of cliff-top displacement on this coastal chalk cliff is consistent with prior studies conducted in different settings showing rather high displacement amplitudes (up to 50 μm in relatively calm conditions) likely to be related to chalk elasticity; 2) the displacement on existing fractures is partly controlled by the tidal amplitude, with a threshold response, but not only. Statistical analyses help the identification of other controls. The processing of the entire dataset from November 2018 to January 2020 with a combined analysis of multiple sensors output is expected to provide further insight on cliff fatigue and failure.

Document type :

Journal articles

Domain :

Sciences of the Universe [physics] / Earth Sciences / Geomorphology

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Experimental field study on the fatigue and failure mechanisms of coastal chalk cliffs: Implementation of a multi-parameter monitoring system (Sainte-Marguerite-sur-Mer, France)

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Experimental field study on the fatigue and failure mechanisms of coastal chalk cliffs: Implementation of a multi-parameter monitoring system (Sainte-Marguerite-sur-Mer, France)

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