The Eaux-Bonnes landslide (Western Pyrenees,France): overview of possible triggering factors with emphasis on the role of groundwater |
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Authors: | Bruno Martins-Campina Frédéric Huneau Richard Fabre |
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Institution: | (1) Centre de Développement des Géosciences Appliquées, Université Bordeaux-1, B18 avenue des Facultés, 33405 Talence Cedex, France |
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Abstract: | The purpose of this study is to achieve an understanding of the failure mechanisms which caused the Eaux-Bonnes landslide.
The geological investigations carried out on the slope of the landslide showed that the sliding mass was cut by numerous faults.
The factors controlling the landslide failure were complex, and it is known that neither earthquakes nor heavy precipitation
could have triggered the disruption. The groundwater within the solid rock mass has been surveyed, because significant precipitation
events during the 2 years preceding the beginning of the paroxysmal phase of the landslide could have led to an increase in
pore water pressure along these fractures, thereby triggering the landslide. In order to achieve a full understanding of the
failure mechanism, and to identify the origin of the groundwater, a hydrogeochemical survey was carried out over a period
of 1 year. The results reveal the existence of high sulphate concentrations in the groundwater originating in springs located
at the bottom of the landslide. The sulphate concentrations are correlated with high calcium concentrations, and clearly indicate
the presence of gypsum in the vicinity of the lower reaches of the landslide. The presence of gypsum in this area of the Pyrenees
suggests that deep groundwater played a role in triggering the landslide. |
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Keywords: | Landslide Triggering factors Groundwater Hydrogeochemistry Pyrenees |
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