Mineralogical and Geotechnical Characterization of the Clay Layers within the Basal Shear Zone of the 1963 Vajont Landslide

Geosciences

Daniela Pinto¹  Davide Lenaz²  Alberto Bolla³  Paolo Paronuzzi³  Marco Del Fabbro³ 

[1] Department of Earth and Geoenvironmental Sciences, Aldo Moro University of Bari, 70125 Bari, Italy;Department of Mathematics and Geosciences, University of Trieste, 34128 Trieste, Italy;Polytechnic Department of Engineering and Architecture, University of Udine, 33100 Udine, Italy;

关键词: Vajont landslide;    large rockslide;    shear zone;    Fonzaso Formation;    clay;    illite/smectite mixed layer;   

DOI  :  10.3390/geosciences10090360

来源: DOAJ

【 摘 要 】

The 1963 Vajont landslide is a reference example of large rockslides involving clay interbeds emplaced in sedimentary rock masses in correspondence with the basal rupture zone (thinly stratified cherty limestone of the Fonzaso Formation dated to Middle–Upper Jurassic). The basal shear zone of the 1963 Vajont landslide was made up of a chaotic assemblage of displaced rock masses, limestone angular gravel, and spread clay lenses. The mineralogical investigations showed that the clays are characterized by complex assemblages of illite/smectite mixed layers (36–96%) admixed with variable amounts of calcite (4–64%) and quartz (0–6%). The clay layers show highly variable plasticity properties and shear strength characteristics. The samples with a large prevalence of clay mineral content (CM) (CM > 79%) are characterized by low values of the residual friction angle (6.7–14.9°), whereas clay materials characterized by a higher content of granular minerals (calcite and quartz) clearly show greater friction angle values (19.5–26.7°). The high permeability of the limestone angular gravel, which caused a rapid reservoir-induced inflow (1960–1963), together with the low friction angle of the clay layers were responsible for the overall shear strength reduction in correspondence with the basal rupture zone, thus favoring the huge sliding on 9 October 1963.

【 授权许可】

Unknown