Assessment of Failure Mechanism and Rehabilitation of a Landslide Within Marly Formations in NW Greece: From the Site Investigation to the Geotechnical Design

Abstract

The article describes the investigation of a landslide incident in Epirus (NW Greece), on an embankment of the National Road connecting the towns Igoumenitsa and Preveza. The main geomaterials involved are cyan marl to very stiff clay and soft clay materials. The landslide destroyed part of the road embankment covering the natural slope above the “Despo” stream. The failure evolved in two phases, the first occurring in the winter of 2004, 30 years after the embankment construction, most possibly due to significant fill loading at the embankment toe and heavy rainfalls. After its reconstruction, accompanied by mild rehabilitation works, a landslide reactivation took place in winter of 2005–2006. The resulting scarp, ~30 m in width and ~10 m in height, developed within the embankment. Moreover, indications of minor destabilisation were observed on the so far stable part of the embankment, suggesting a potential extension of the landslide eastwards. The information collected during numerous site visits, from the evaluation of a full-scale geotechnical survey (boreholes, laboratory testing and instrumentation including piezometers, inclinometers, crackmeters and optical targets) and the stability analyses performed, led to the assessment of the failure mechanism. Possible rehabilitation solutions were then investigated, concerning both the main landslide area and the area of its possible extension.