Papel del agua subterránea en la concentración de arcillas de elevada plasticidad en la superficie de rotura de deslizamientos (Caso de Diezma, Granada, España)

Abstract

Slope instabilities with a low basal slope (<15º) are lately researched. In these landslides, mechanical properties of the rupture surface are exceptionally low. The increase of the pore pressure has been commonly postulated to explain the drastic reduction of strength properties. In some landslides around the world, a clay-bearing layer of extraordinary purity, have been detected in the rupture surface. Mechanical properties of this layer are lower than the rest of the slided mass conditioning the slope stability. In this case, Diezma’s landslide is conditioned by a centimetre layer of smectite clay (montmorillonite-beidellite). This layer controls the strength properties of the whole slided mass. The triggering factor of this landslide is linked to the infiltration of water from a karstic aquifer located in the head area. Water circulation through contacts levels between materials of different permeability, promotes an active hydrolysis of marls fragment and the follow-up of their argillation, typical of chemical and mineralogical interactions between the slip-zone materials and the slip-zone groundwater. In this study, we analyze the water-soils interactions and the possible impact on the formation/destruction of carbonates, sulfates phases and clay minerals that explain the elevated concentration of high-plasticity in landslide-slip zones.