Abstract
Geophysical and geotechnical surveys were conducted in the Western Cameroon (Kekem area) following a landslide on argillaceous material in order to understand the triggering processes and mechanisms of this landslide and to assess the stability of the slope. The geophysical soundings consisting of vertical electrical soundings with the Schlumberger electrode array configuration were carried out to monitor the behaviour of electrical resistivity in the landslide. Geoelectrical data showed a zone of low resistivity values identified as a clayey sand-filled aquifer. This aquifer played an important role in the triggering process of the landslide. Geotechnical soundings showed that the aquifer had a thickness of 7.0 m. The depth from the landslide crest level to the failure surface reached 3.0 m and 20.6 m. Laboratory tests were then carried out in order to evaluate the cohesion of the soil and the angle of internal friction, and to calculate the safety factor in view of making a stability analysis. The laboratory results exhibited a soil with low consistency, almost doughy. The mean value of the safety factor (1.4) been lower than the slope stability coefficient (1.5), revealed that the slope is unstable, likely to know at any moment a reactivation of the slide. This study showed that electrical soundings coupled with geotechnical surveys are useful tools for the characterization of landslides.
Highlights
Geophysical methods are more and more used for landslide investigations
Geophysical and geotechnical surveys were conducted in the Western Cameroon (Kekem area) following a landslide on argillaceous material in order to understand the triggering processes and mechanisms of this landslide and to assess the stability of the slope
Penetrometer surveys confirmed the presence of these fractures and the aquifer. These results made it possible to determine the depth to the failure surface; from the landslide crest level, it varies between 3.0 m and 20.6 m
Summary
Soil modifications due to ground movement generally lead to the change of physical parameters of the sub soil. Two main situations can potentially occur: 1) the geophysical contrast is related to a lithological change [1,2]; 2) the movement takes place within a homogeneous geological layer, but alters its physical characteristics. In this case, the geophysical contrast exists between the moving mass and the unaffected consolidated mass [3,4,5,6]. Geophysical surveys applied to ground movements can be used to estimate the lateral extent of the landslide, the depth to the failure surface [7,8]; and to detect water in the active mass [9]
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