## 2 Materials and Methods
### Investigation
#### 2.3.3 Laboratory Testing  
Laboratory testing was conducted to define the basic identification and classification characteristics of the displaced material. Samples were collected from multiple locations of the landslide, excluding the deposition zone where the largest material was deposited. Given the significance of fine-grained material in defining landslide movements, care was taken in selecting samples to ensure the representation of fine particles, which are integral to the fluid.  
The laboratory tests included sieving of the material, separation of the fine fraction for hydrometer analysis, selection of a portion of the fine fraction for determining specific gravity, and tests for plasticity and the falling cone test. To classify the landslide based on its grain size composition, laboratory tests for determining particle size distribution and hydrometer analysis were performed. The falling cone test, conducted to determine the flow limit, followed the standard SRPS EN ISO 17892-12 [26].  
A sample prepared by adding water is placed in a vessel with a diameter of 55 mm. Each subsequent measurement is performed on the same sample with additional water  
Figure 5: Position of the ERT profiles on the Digital Terrain Model.  
Figure 6: Results of ERT profile 5.  
added. The values of cone penetration are read on the scale, and based on the recorded values, the flow limit value is obtained. Three measurements are taken on each sample.  
For the classification of the mobilized material, the obtained samples are presented on the USCS diagram (Figure 7). The results show that the matrix has low to medium plasticity. Two samples, S1 taken from the initial zone and S4 from the deposition zone, are in the low-plasticity zone CL and on the border with the medium-plasticity state CL, while the other samples are characterized as clayey material of medium-plasticity CL. The results are within approximate limits and, considering the heterogeneous nature of the material and the large dimensions of the flow, they show a very good correlation when comparing the mobilized material in different elements of the flow.  
The plasticity test was conducted on selected samples by the Casagrande test, while the cone penetration test was conducted to determine the liquidity index, both according to the standard SRPS EN ISO 17892-12.  
The consistency index (Ic) indicates the consistency (hardness) of the soil. As seen in Table 1, the Ic values range from \(-0.7\) to \(0\). A negative value of the index indicates that the soil is in a liquid state. The natural moisture content of all samples was assumed to be 40%, as it was not possible to measure it in the field (samples were taken 3 years later), and the material behaved like a fluid. The obtained results for soil consistency and the determination of Atterberg consistency limits are presented in Table 1.  
According to the established experiment, the specific weight of a sample with a mass of 49.73 g was determined. Based on this value, the density of solid particles was used as one of the input parameters in the SPH Geoflow modeling program. The results are presented in Table 2.  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Samples** & **S1** & **S2** & **S3** & **S4** & **S5** & **S6** \\ \hline w (\%) & 40.0 & 40.0 & 40.0 & 40.0 & 40.0 & 40.0 \\ \hline LL (\%) & 33 & 37 & 40 & 34 & 38 & 37 \\ \hline PL (\%) & 23 & 21 & 23 & 23 & 22 & 22 \\ \hline I\({}_{\text{P}}\) (\%) & 10 & 16 & 17 & 11 & 16 & 15 \\ \hline I\({}_{\text{c}}\) (-) & \(-0.700\) & \(-0.188\) & \(0.000\) & \(-0.545\) & \(-0.125\) & \(-0.200\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Soil consistency parameters.  
Figure 7: USCS diagram based on soil consistency parameters.