Geotechnical properties in relation to grain-size and mineral composition: The Grohovo landslide case study (Croatia)

• Published in: Geologia Croatica 2014, Vol.67 (2), p.127-127
• Main Authors: Benac, Cedomir, Ostric, Maja, Jovancevic, Sanja Dugonjic
• Format: Article
• Language: English
• Subjects: Freshwater
• ISSN: 1330-030X; 1333-4875
• DOI: 10.4154/gc.2014.09

The Grohovo landslide is the largest active slope movement along the Croatian coast, situated on the north-eastern slope in the central part of the Rjecina River Valley (north-eastern coastal part of Adriatic Sea, Croatia). Slopes in this valley are formed of siliciclastic rocks (i.e., flysch), while the limestone rock mass is visible on the cliffs around the top of the river valley. The slopes are at the limit of a stable equilibrium state, and slope movement phenomena have been recorded since the 19th century. Samples for laboratory testing were taken from the flysch bedrock, weathered zone and slope deposits to provide specimens for determination of their mineralogical, physical and geotechnical properties. Correlation between mineralogical and geotechnical properties and their influence on sliding processes are presented here. The clay fraction in samples ranges from 17 % to 38 %. Clay activity of the tested samples is from 0.45 to 0.89, and the residual friction angle varies from 13.0° to 17.7°. These results correspond to the presence of kaolinite and illite groups of clay mineral. Both the mineral composition and decrease in strength of fine-grained soil materials, due to the increase of pore water pressures, contributes to slope movements.