# Stability and Distribution of Rock Slope under Asymmetric Excavation
## 2 Mining Analysis of Fushun West Open Pit
### Rock Mechanics Parameters and Slope Stability Analysis Method  
Based on the mining data of the West Open-Pit Mine in Fushun, the actual excavation conditions of part of a section of the West Open Pit were simulated. The constitutive model of the rock and soil layer was a Mohr-Coulomb model, and the physical and mechanical parameters referred to the doctoral thesis of [PERSON] [23], as shown in Table 1.  
In order to analyze the influence of mining activities on the stability of the open-pit slope, the strength reduction analysis method inherent in Midas GTS NX was used, and the strength parameters of the rock and soil mass, namely cohesion and the internal friction angle, were continuously reduced until the rock and soil mass was destroyed. The final reduction ratio was the slope stability coefficient. The calculation formula was as follows:  
\[\overline{c}=\frac{c}{F_{\mathrm{s}}} \tag{1}\]  
\[\overline{\varphi}=\arctan\biggl{(}\frac{\tan\varphi}{F_{\mathrm{s}}}\biggr{)} \tag{2}\]  
where \(c\) and \(\overline{c}\) represent the cohesion of the rock and soil mass before and after the strength reduction, respectively, and \(\varphi\) and \(\overline{\varphi}\) represent the internal friction angles of the rock and soil before and after the strength reduction, respectively. \(F_{\mathrm{s}}\) indicates the safety factor.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Formation**} & **Elastic** & **Density** & **Cohesion** & **Friction** & **Poisson’s** & **Strength** \\  & **Modulus** & **(GPa)** & **(GPa)** & **(Mpa)** & **Angle (\({}^{\circ}\))** & **Ratio** & **(Mpa)** \\ \hline Plain fill & 0.2 & 1.8 & 0.1 & 20 & 0.29 & 0 \\ Marlstone & 12 & 1.6 & 1.1 & 30 & 0.27 & 3 \\ Granitic gneiss & 30 & 2.74 & 0.24 & 54 & 0.23 & 5 \\ Basalt & 25 & 2.7 & 0.25 & 48 & 0.23 & 2.5 \\ Tuff & 0.32 & 2.35 & 0.18 & 32 & 0.36 & 0.26 \\ Coal seam & 0.22 & 1.3 & 0.28 & 15 & 0.36 & 0.24 \\ Kerogen shale & 2.8 & 1.8 & 0.6 & 30 & 0.29 & 1.8 \\ Green mudstone & 1.6 & 2.25 & 0.5 & 25 & 0.32 & 0.22 \\ Cretaceous & 2.8 & 2.3 & 0.58 & 29 & 0.25 & 1.8 \\ sandstone & 0.1 & 1.8 & 0.13 & 7 & 0.4 & 0.22 \\ Faultage & 0.1 & 1.8 & 0.13 & 7 & 0.4 & 0.22 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Physical and mechanical parameters of rock mass and faults.  
When calculating the slope stability coefficient of the model, the Mohr-Coulomb strength criterion was used to judge the failure of the rock and soil mass; that is, the cohesive force and internal friction angle of the rock and soil mass were the factors that determined its shear failure. The calculation results are shown in Equation (3). When the shear stress exceeded the shear stress controlled by the cohesive force and the internal friction angle of the rock and soil mass, the rock and soil mass of the slope would have shear failure.  
\[f_{s}=\sigma_{1}-\sigma_{3}\frac{1+\sin\varphi}{1-\sin\varphi}-2c\sqrt{\frac{1 +\sin\varphi}{1-\sin\varphi}} \tag{3}\]  
where \(f_{s}\) is the shear stress and \(\sigma_{1}\) and \(\sigma_{3}\) are the maximum and small principal stress values.