Hydromechanical modeling of a large moving rock slope inferred from slope levelling coupled to spring long-term hydrochemical monitoring: example of the La Clapière landslide (Southern Alps, France)

Taking the example of the La Clapière landslide, the influence of water infiltration on large moving rock mass stability is investigated. Based on the analysis of geological, hydrogeological, hydrogeochemistry and landslide velocity measurements, a hydromechanical conceptual model is proposed. Then,...

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Bibliographic Details
Published in:	Journal of hydrology (Amsterdam) Vol. 291; no. 1; pp. 67 - 90
Main Authors:	Cappa, F, Guglielmi, Y, Soukatchoff, V.M, Mudry, J, Bertrand, C, Charmoille, A
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier B.V 31-05-2004 Elsevier Science Elsevier
Subjects:	Coupled hydromechanical modeling Earth sciences Earth, ocean, space Engineering and environment geology. Geothermics Exact sciences and technology Geochemistry Groundwater chemistry Hydrogeology Hydrology. Hydrogeology Large moving rock mass Mineralogy Natural hazards: prediction, damages, etc Silicates Universal Distinct Element Code Water geochemistry Alpes-Maritimes France Alps France French Alps Western Europe Universal Distinct Element Code Large moving rock mass Groundwater chemistry Coupled hydromechanical modeling strain springs Europe ground water digital simulation sulfates slopes nitrates spatial distribution infiltration aquifers hydrochemistry numerical models landslides instability two-dimensional models saturated zone fractures landform evolution slope stability
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Summary:	Taking the example of the La Clapière landslide, the influence of water infiltration on large moving rock mass stability is investigated. Based on the analysis of geological, hydrogeological, hydrogeochemistry and landslide velocity measurements, a hydromechanical conceptual model is proposed. Then, a two-dimensional numerical modeling with the Universal Distinct Element Code (UDEC) was carried out to determine the influence of the location and the amount of water infiltration on the hydromechanical behaviour of La Clapière slope. Geological and hydrogeological analyses indicate a perched water-saturated zone connected by large conducting-flow fractures to a basal aquifer. The comparisons of spring water chemistry data and meteorological data from the slope area show a large variability of groundwater transits in the slope through time (transit durations of 1–21 days) and space. Water infiltration transient signals correspond to accelerations of the slope downward motion. Infiltration rates are comprised between 0.4 and 0.8 l s −1. The most pronounced hydromechanical response of the slope instability is due to snowmelting in the stable area located between elevations 1800 and 2500 m above the unstable slope. The hydromechanical modeling performed with the UDEC code concerns firstly a model of a slope without any unstable zone, and, secondly, a model including a failure surface in order to simulate the current instability. Numerical computations are done in order to localize the area through which water infiltration is the most destabilizing. The most destabilizing area is the one that has the largest influence on the spatial distribution of strain fields. It corresponds to water infiltration located in the middle part of the slope and characterized by weak flow rates of 0.75 l s −1. This approach can easily be applied to the monitoring of other unstable rocky slopes. As it gives relevant information about the spatial and temporal effects of meteoric infiltration, it can be applied to improve remedial protocols.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0022-1694 1879-2707
DOI:	10.1016/j.jhydrol.2003.12.013