Debris flows are non-Newtonian fluids. Their rheological parameters depend on the volume concentration, grain size composition, fines content and fines plasticity. To get realistic data for modelling of debris flows, the rheological parameters had to be measured at different volume concentrations, taking into account the whole grain size distribution. Rheometers for fluids are limited with the gap size and usually only fine grained suspensions could be investigated. The results measured in such device on coarse grained soils may not be representative. The paper presents the study in which two shear rate controlled coaxial cylinder rheometers were used to investigate the influence of maximum grain size on rheological parameters of the Stože debris flow: the larger ConTec Viscometer 5, in which the maximum grain size is 22.4 mm and the smaller Brookfield DV3T HB rheometer. Rheological parameters obtained by using both devices were compared based on water content, volume concentration and maximum grain size.
COBISS.SI-ID: 8111201
Landslides are an important source of debris flows and this paper presents a multi-model approach of identification. The village of Koroška Bela in NW Slovenia has a history of debris flows and active landslides in the watershed of the Bela torrent, which presents a sediment source for potential debris flows in the future. Two models were applied for landslide identification in the watershed. A detailed field survey was carried out for model results validation. A GIS-based landslide susceptibility model was applied to identify areas susceptible to landslides and the LS Rapid triggering model was applied also to identify landslides and simulate the triggering phase. The study results show good agreement of the field survey and the models, particularly considering the completely different origin of both models and their development. These results show the possibility of applying numerical models to identify landslide sources and encourage their implementation in debris flow hazard assessment. But as with all models, a high level of expert knowledge and users’ experience is required to get useful, and what is more important, reliable results.
COBISS.SI-ID: 2631765
This paper summarizes the observation of the Potoška planina landslide, which is located in the Karavanke mountain range in NW Slovenia. Due to prevailing geological, tectonic and hydrological conditions, the Potoška planina area is highly prone to different slope mass movements. This paper presents the monitoring of surface movement patterns at the toe of the Potoška planina landslide. The sliding mass is composed of tectonically deformed and weathered Upper Carboniferous and Permian clastic rocks covered with a large amount of talus material, which is unstable and prone to landslides. Additionally, the Bela torrent causes significant erosion and increases the possibility of mobilization of the sliding mass downstream. Based on said conditions and field survey work, the toe of the landslide is considered to be the most active part of the landslide. In order to estimate surface movement patterns over a monitoring period of 22.5 months and five reconnaissance campaigns, periodic monitoring was conducted using unmanned aerial vehicle (UAV)-based photogrammetry, which provides high-resolution images and tachymetric geodetic measurements that enable accurate control of photogrammetric analysis of surface displacements. Using the results of said periodic monitoring, analyses of UAV-based displacement patterns, surface elevations and volume changes were all modelled for four observation periods. According to our results, the movement pattern at the toe of the Potoška planina landslide indicates a steadily downslope movement of the entire area with localized surges superficial slips.
COBISS.SI-ID: 2566485