Mineralogical and geotechnical characterization of structurally complex formations invlved in the slow moving landlides affecting the Southern Apennine

Slow-moving landslides affect several areas in the Apennine chain (Italy). They involve sedimentary rocks that are weathered in the more surficial parts. The occurrence of weathering-related clay minerals (e.g. smectites) able to trap high amounts of water is generally considered a predisponding factor for these landslides. The main goal of this research is to verify this statement, carrying out a mineralogical-geotechnical characterization of clayey rocks occurring in the Termini Nerano slow-moving landslide (Massalubrense, Italy).The mineralogical composition of soils involved in the landslide was evaluated on several drill-core samples from the studied area, by using quantitative X-ray powder diffraction analyses, calibrated through chemical bulk rock analyses. Clay separates allowed to determine the composition of the clay fraction. The results confirm that the total amount of clays, and specifically the smectite amount in mixed layers I/S, could have played a role in the landslide development. However, relationships between mineralogical composition and weathering zones in the soil have not been observed.Geotechnical analyses attested that the mechanical behavior of the material involved in the landslide depends on the amount of granulometric clay fraction in the samples, but, differently from what expected, no correlations were observed between this behavior and the measured amounts of smectite or mixed layers I/S.