Strategies to stabilise a complex instability phenomenon in Central Italy

Abstract

Abstract The instability phenomena that regards very large and complex landslides are a challenge to minimize social and economic losses. In this paper we present the studies to programme and design the stabilizing works of the complex slope instability phenomena in the town of Lettomanoppello (Central Italy). It is located in the central-eastern margin of the Apennines, along the north-western foothills of the relief of the Maiella Mountain (2793 m a.s.l.). The slope, on which the village of Lettomanoppello (350 m a.s.l.)is located, is historically known for its susceptibility to landslides. These phenomena involve geo-morphological aspects and geotechnical conditions and complex geo-materials characteristics. The area incudes Quaternary continental deposits (detritus deposits, limestone debris hetero-metrics, landslide body) and Mio-Pleistocene marine deposits (clay, clay, marl and chalk alteration; limestone). The hydrogeological conditions of the area are characterized by a complex drainage system that affects the stability of the slope. Among the stabilization works that are provided in design, the drainage works take a prominent role. The paper presents the geotechnical characterization for the design (location and dimensions) of the tunnel for deep water drainage. The location of drainage tunnel was design according to the hydraulic condition. The tunnel crosses a horseshoe shaped underneath the historical centre of Lettomanoppelllo and the elevation of its mouths are at 290 m a.s.l. The total length is about 1000 m, and the coverings vary from 60 m to 100 m. The operation of drainage tunnel improves the overall stability of the slope and the drainage waters will be conveyed to pipe towards a hydraulic turbine located at 190 m a.s.l. in the lower part of the slope to produce electric energy.