Correction to: Bulletin of Engineering Geology and the Environment (2022) https://doi.org/10.1007/s10064-022-02594-2

Originally, Eq. 2 contains an error. This is now correctly presented here.

$$\begin{array}{lcl}{F}_{N}&=&{F}_{T}cos(\beta )\\ {F}_{R}&=&{F}_{T}sin(\beta )\\ \varphi &=&{\mathrm{cos}}^{-1}(\frac{R-P}{R}) \\ \beta &=&\varphi /2\end{array}$$

The original article has been corrected.