Site and laboratory investigation of the Slano blato landslide

The Slano blato landslide is situated above the village of Lokavec, in the western part of Slovenia. This area is one of the seismically most active parts of the country. Considering just the last decade, movement of the landslide was observed in November 2000, when the displaced material reached a velocity of 60–100 m/day. Silty and clayey gravel above flysch layers of marl and sandstone formed the landslide mass.Geotechnical investigations of the landslide were performed in 2003 and 2004, when the depth of the landslide was determined, as well as the geotechnical parameters and the sliding mechanism. Rheological tests were also carried out for further analysis. Based on the investigation results and the observed landslide velocity, the landslide was classified as an earth flow. Inclinometer measurements showed that the landslide has two shear surfaces, with different behaviour shown as each.A stability analysis was carried out numerically by applying the Mohr–Coulomb and Burger elasto–plastic models. The Mohr–Coulomb model indicated that the high water level influences the landslide instability. In the case of the Burger elasto-plastic model, a higher velocity was calculated, at a water content of between 35 and 40%.