Efficiency of stabilization techniques in Acqualoreto landslide area (Umbria, Italy)

This work, based on the results of a series of geotechnical and monitoring studies, analyses two landslides composed of heterogeneous altered marly clayey arenaceous rock and eluvial-colluvial deposits, located near the village of Acqualoreto (Central Italy). The landslides (called here A and B) are characterized by retrogressive movements approaching buildings and roads near the village and by different sliding surfaces between 10 and 25 m b.g.l. Maximum displacement rates were measured after the most significant rainfall events in autumn months. Four years after the installation of drainage systems in both landslides, some considerations on the efficiency of stabilization techniques (horizontal drains and drainage wells) are presented, with analysis of inclinometric and piezometric data, both pre- and post-installation. Results indicate that single alignment of drainage wells in the upper part of landslide A cannot be considered resolutive in reducing the landslide hazard: therefore, new drainage works in the central part of landslide mass and in the accumulation zone should be considered. The horizontal drains in the central/upper part of landslide B did greatly reduce movement, although new drains should be installed along the toe of the landslide for definitive control the groundwater rise.