# Slope Stability Analysis of Open-Pit Mine Considering Weathering Effects
## 3 Numerical Simulation of Slope Stability Analysis  
### Numerical Simulation Methodologies  
To incorporate the influences of weathering into slope stability analysis, Fast Lagrangian Analysis of Continua (FLAC3D, Version 5.00) was utilized, which was developed by the Itasca Company, USA. FLAC3D is a simulation and calculation software that specializes in simulating and analyzing the plastic flow behavior of three-dimensional structures composed of soil, rock, and other materials. The software can accurately simulate the plastic failure and flow characteristics of materials, making it particularly suitable for simulating large deformation problems and nonlinear stress-strain relationships. The physical and mechanical parameters of the rock mass and various rock types within the mining area were obtained through site investigation. The method for obtaining the overburden thickness and mechanical properties of the open-pit mine was through drilling measurement technology. The cores extracted from the boreholes were analyzed for their physical and mechanical properties. A total of 12 boreholes were drilled, with the obtained results displayed in Table 7. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Parameters** & **Type of Function** & **Fitting Formula** & **Correlation Coefficient (R2)** \\ \hline Uniaxial tensile strength & Exponential & y = 9.4964 \(\times\) 10\({}^{-0.042}\)x & 0.9957 \\ Uniaxial compression strength & Exponential & y = 64.337 \(\times\) 10\({}^{-0.067}\)x & 0.9982 \\ Elastic modulus & Quadratic & y = 0.0157 \(\times\) 2 \(-\) 0.7738x + 13.079 & 0.9939 \\ Poisson’s ratio & Quadratic & y = \(-\)0.0003 \(\times\) 2 \(+\) 0.0171x + 0.1693 & 0.9797 \\ Cohesion & Exponential & y = 3.0276 \(\times\) 10\({}^{-0.074}\)x & 0.9916 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The correlation function between mechanical parameters and weathering time. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Rock Properties** & \begin{tabular}{l} **Uniaxial** \\ **Compressive** \\ **Strength/MPa** \\ \end{tabular} & \begin{tabular}{l} **Elastic** \\ **Modulus/GPa** \\ \end{tabular} & \begin{tabular}{l} **Tensile** \\ **Strength/MPa** \\ \end{tabular} & \begin{tabular}{l} **Poisson’s** \\ **Ratio** \\ \end{tabular} & \
\begin{tabular}{l} **Cohesive** \\ **Strength/MPa** \\ \end{tabular} &
\begin{tabular}{l} **Internal** \\ **Friction** \\ **Angle/\({}^{\circ}\)** \\ \end{tabular} \\ \hline Phosphate one layer & 50.27 & 15.80 & 5.57 & 0.29 & 12.78 & 41.30 \\ Light gray & 48.13 & 12.05 & 3.68 & 0.34 & 7.48 & 31.30 \\ dolomite & 59.10 & 16.26 & 6.18 & 0.28 & 13.05 & 47.23 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: The physical and mechanical parameters of other rock types in mining areas. During the modeling process, a reasonable degree of simplification was applied to the geological prototype of the slope to ensure computational efficiency and accuracy. For the boundary conditions, the exposed surface of the slope was designated as the free boundary, while the bottom and both sides were constrained with normal displacement boundaries. The initial stress field was primarily determined by considering the self-weight stress of the rock mass. Initially, the stress field of the model was set to achieve equilibrium, reflecting the undisturbed geological conditions. The constitutive model and material division within the mining areas are clearly depicted in Figure 5. The model was configured with the X-direction aligned with the slope inclination and extending 1000 m in length, while the Y-direction represented the vertical direction with a height of 500 m. Taking into account the geological environment conditions, topography, and lithology of the open-pit slope in the mining areas, two models were specifically designed with final slope angles of 45\({}^{\circ}\) and 47\({}^{\circ}\). These models were employed to simulate the gradual development of the open-pit slope.