# Geotechnical Study of Raspadalica Cliff Rockfall, Croatia
## 4 Results
### Stability Analysis  
According to the results of the kinematic analyses conducted for each zone of the cliff (Zones Z1 to Z5) presented in Figure 10 and Table 5, the probability of planar sliding and direct toppling in all five zones is relatively low, while the probability of flexural toppling has a relatively high failure (>40%). Analyzing the possibility of flexural toppling at the Raspadalica Cliff, it was determined that the rock mass conditions those have significant impact on occurrence of flexural toppling are not present at the Raspadalica Cliff. The process of flexural toppling is usually formed in slopes built of continuous columns of rock separated by well-developed, steeply dipping discontinuities breaking in flexure as they bend forward. Block-flexure toppling is characterized by pseudo-continuous flexure along long columns that are divided by numerous cross joints, which are not present at Raspadalica Cliff, and there is no evidence of any block-flexural toppling failure at the Raspadalica Cliff in the past. It is very clear that in a case of flexural toppling, rockfall occurrences should be evident at the top of the cliff and not in the middle part of the rock face, as it is at the Raspadalica Cliff. Analyzing toppling stability of single blocks at the top of the cliff as well as the stability of fictive single columns to the bottom of the cliff, taking into account unfavorable dimensions and maximal determined dip of the base, neglecting the impact of friction at the side walls of a block, centers of gravity of all blocks, and fictive lie inside their bases, confirming the stability regarding toppling. Additionally, based on determined bedding and joint set dips and dip direction, no change was found in the sense of increasing the dips of the layers in the upper part of the cliff that would point to development of flexural toppling mechanisms in the cliff rock mass. Finally, it was concluded that flexural toppling, despite the relatively high percent of possible flexural failure (>40%), is just a result of kinematic conditions for flexural toppling built into _Roccience Dips software_[91] but has no real basis in in situ phenomena and can be neglected in further stability analyses. The remaining two mechanisms of failure in rock mass predestined by orientations of joint sets and bedding, planar sliding, and direct toppling, have relatively very low probability of failure occurrences (planar sliding < 3.93%; direct toppling < 11.22%, Table 5) that is supported by general joint set orientations and dip directions and discontinuity features that affect stability of the cliff. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Cliff Zone** & **Type of Failure** & **Probability (\%)** & **Number of Planes** \\ \hline \multirow{3}{*}{Z1} & Planar sliding & 3.06 & \multirow{3}{*}{914} \\  & Direct toppling & 11.11 & & \\  & Flexural toppling & 22.76 & \\ \hline \multirow{3}{*}{Z2} & Planar sliding & 3.10 & \multirow{3}{*}{3099} \\  & Direct toppling & 8.25 & & \\  & Flexural toppling & 43.21 & & \\ \hline \multirow{3}{*}{Z3} & Planar sliding & 3.93 & \multirow{3}{*}{2750} \\  & Direct toppling & 11.22 & & \\  & Flexural toppling & 40.73 & & \\ \hline \multirow{3}{*}{Z4} & Planar sliding & 3.73 & \multirow{3}{*}{3301} \\  & Direct toppling & 8.33 & & \\ \cline{1-1}  & Flexural toppling & 43.93 & & \\ \hline \multirow{3}{*}{Z5} & Planar sliding & 2.43 & \multirow{3}{*}{2260} \\  & Direct toppling & 9.94 & & \\ \cline{1-1}  & Flexural toppling & 32.88 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Summary of conducted kinematic analyses according to cliff zones. Probability is expressed as the ratio of number of planes (or combination of planes) meeting the conditions for a failure related to the number of all planes (or combination of planes). All planes determined in a zone are used in verification of all kinematic mechanisms.