# Geomechanical Basis for Assessing Open-Pit Slope Stability in High-Altitude Gold Mining
## 2 Materials and Methods
### Analysis of Fracture Orientations and Weakness Planes
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & & & & **Stability Coefficient n\({}_{y}\)** \\ \cline{3-6}
**Section Board** & **Name of Rocks** & **Side Height, m** & **Side Slope** & & & \\  & & & & & **Angle, Degrees** & \\ \hline
4 & Granoidorites in the weathering crust, in & & & & & \\ SE & the middle part and in bedrock at depth & 214.1 & 56 & 1.776 & 1.560 \\ \hline
4 & Limestones in the weathering crust, in & & & & \\ NW & the middle part and in bedrock at depth & 226.3 & 41 & 1.619 & 1.393 \\ \hline
5 & Granoidorites in the weathering crust, in & & & & \\ SE & the middle part and in bedrock at depth & 236.6 & 68 & 1.653 & 1.459 \\ \hline
5 & Limestones in the weathering crust, in & & & & \\ NW & the middle part and in bedrock at depth & 236.3 & 44 & 1.500 & 1.295 \\ \hline
5a & Granoidorites in the weathering crust, in & & & & \\ SE & the middle part and in bedrock at depth & 247.2 & 56 & 1.628 & 1.439 \\ \hline
5a & Limestones in the weathering crust, in & & & & \\ NW & the middle part and in bedrock at depth & 246.6 & 45 & 1.433 & 1.241 \\ \hline
7 & & & & & \\ Taking into account the & & & & & \\ curvature & & & & & \\ \hline
2-2 SE & 1. Granoidorites & & & & \\
2. Tectonic fault (K\({}^{\prime}\) = 10 t/m\({}^{2}\), \(\rho^{\prime}\) = 25\({}^{\circ}\)) & 175 & 37 & 1.880 & 1.597 \\ \hline
2-2 & 1. Granoidorites & & & & \\ SE & 2. Tectonic fault (K\({}^{\prime}\) = 1.5 t/m\({}^{2}\), \(\rho^{\prime}\) = 25.5\({}^{\circ}\)) & 175 & 37 & 1.828 & 1.552 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._The quality of sloped excavation works along the design contours at the pit is determined by the presence of traces of sloped (inclined) drill holes on the bench faces. It is worth emphasizing that any pre-shear drill hole made must be fully charged with the appropriate explosive load. Overall, when evaluating the condition of the southern wall benches set to the design contour, the following can be noted: there are several upper sections of the bench slopes with a poor sloped blasting quality (e.g., no visible traces of inclined drill holes, oversized unblasted rock blocks, diverging traces of pre-shear holes, etc.) (Figure 7). These issues account for approximately 30% of the southern pit wall surface currently set to its design position. Figure 7: Technology of slope trimming with the creation of an advance pre-shear groove: (**a**) general geological and design scheme of the southern wall section; (**b**) formation of a preliminary notch for the central height of 30 m of the final slope line; (**c**) after working the upper working horizon. The pre-shear groove method is considered the most effective technique for forming bench slopes. In this method, contour charges are detonated within the intact rock mass at a distance of at least 40-50 m from the final design slope line, where mining operations are not yet taking place. The contour charges are arranged as garlands of explosive cartridges (with diameters ranging from 30 to 90 mm) tied to a strong rope. Two lengths of detonating cord are laid along the garland. Upon detonation, a narrow groove is formed within the rock mass, which significantly reduces the impact of the main charge, prevents overbreak, and virtually eliminates rock mass deformation. As a result, a smooth and stable slope surface is formed along the line of the contour holes, with clearly visible traces of the drill holes used for blasting. However, it should be noted that even a correctly executed pre-shear groove will not ensure slope stability if the specific explosive consumption during the main blast exceeds 0.35-0.40 kg/m3. Practice shows that if this limit is exceeded, all efforts to create the pre-shear groove are rendered ineffective--the rock becomes excessively fragmented, and overbreak is evident on the safety berm. For the established pit wall slopes along the design contours of the open-pit mine, instrumental monitoring is mandatory.