In the second quarter of 2010, after catastrophic precipitation throughout the country (mainly in the south part), a large number of landslides were activated, what caused damages to infrastructure and buildings. This entailed the need of documenting the geotechnical conditions of landslide areas for the purposes of protection designs of the areas endangered or destroyed by landslides. Geotechnical designing process requires determination of the real values of the strength parameters of soils occurring within the main slope and colluvium of landslide. This paper describes how to determine the strength parameters based on direct testing (triaxial apparatus) verified by back analysis with using numerical stability calculation methods. The geodesic measurements (slope geometry before and during the development of the landslide) and geotechnical tests carried out within the framework of the geological-engineering documentation of the landslide within the Flysch Carpathian Mountains were the base for conducting the back analysis.

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