## 3 Stability Analyses for the Initially Designed Geometry  
### Modeling the Analysis Section  
In order to be able to model the stability analysis section of the working fronts of the Jilt North open pit, several stages were completed.  
The first consisted of drawing the calculation section on the situation plan provided by the mining operator (Figure 8). Thus, through the central area of the mining perimeter, the cross section 1-1' was drawn, which intersects both the working fronts of the open pit and the deposition fronts of waste rocks in the internal dump.  
Because the object of this study is to analyze the stability of the working fronts (not the internal dump), from the initial cross section 1-1', only the part that intersects the open pit steps was selected, and later renamed I-I, for the existing situation (at the level of May 2023), F-F, for the designed situation at the end of 2023, respectively (Figure 9a).  
Then, based on the coordinates for the section in Figure 9a, taking into account the stratigraphy of the deposit (Figure 9b), and the information from the written documentation [43], the section from May 2023 (Figure 10a) and the calculation model (Figure 10b) were created using the Slide software, having the same order of scale horizontally and vertically.  
Figure 7: Continuous exploitation method with the transshipment of a part and the transport of another part of the waste rocks to internal dumps.  
Figure 8: Situation plan of Jilt North open pit (1–1\({}^{\prime}\) cross section trough the entire open pit, including the internal waste dump; I–I cross section trough the existing working fronts, in May 2023; F–F cross section trough the designed working fronts, end of December 2023) [43].  
Figure 9: (**a**) The working fronts (I–I, existing geometry—May 2023; F–F, designed geometry—end of 2023; T1–T6 step no.; E–BWE’s no.) and (**b**) general geological section through Jilt North open pit [43].  
With the help of the measuring tools within the Slide software, the geometric elements of the working fronts were determined on the created models, for the existing situation in May 2023 and the designed one at the end of 2023, presented in Table 3.  
\begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{1}{c}{**Geometric Elements**} & \multicolumn{3}{c}{**Slopes of the Open Pit**} \\ \cline{2-3}  & **Existing (May 2023)** & **Designed (End of 2023)** \\ \hline Development of the steps system (m) & 1024.93 & 874.91 \\ \hline Working fronts development (m) & 841.62 & 633.27 \\ \hline Total height, (m) & 195.00 & 151.00 \\ \hline Number of steps & 6 & 6 \\ \hline General slope angle, (\({}^{\circ}\)) & 13 (21) \({}^{\ast}\) & 13 \\ \hline Height of steps, (m) & 25.40–40.00 & 20.00–30.00 \\ \hline Length of steps, (m) & 200.00–1550.00 & 160.00–1600.00 \\ \hline Berm widths, (m) & 44.44–347.19 & 61.10–116.66 ** \\ \hline Slope angle of individual steps, (\({}^{\circ}\)) & 32–59 & 42–53 \\ \hline \end{tabular} \({}^{\ast}\) The value in parentheses represents the overall slope angle determined between T2 and T6 steps. ** Except the upper berm of T1 step.  
\end{table}
Table 3: Existing and designed geometric elements (cross sections I–I and F–F).  
Figure 10: (a) Cross section I–I (May 2023) and (b) cross section F–F (designed geometry at the end of 2023).