# Deformation Analysis of Large-Scale Rock Slopes Considering the Effect of Microseismic Events
## 3 Engineering Background  
### Project Overview  
The Baihetan hydropower station, located on the convergence of Ningnan County in Sichuan Province and Qiaojia County in the Yunan Province of China, is a large project recently constructed on the Jinshajiang River. Figure 1 shows the location of the hydropower station. The project has a double-curvature arch dam with a height of 289 m and a total installed capacity of 16,000 MW. The underground powerhouse's cavern systems are located in both the left and right bank mountains, 350 m downstream from the dam, with horizontal and vertical depths of 110-380 m and 160-420 m, respectively [25; 26]. The left bank is the southeast slope of the Dalianing Mountain region, with a peak height of 2600 m, and it has a sloped terrain inclined towards the Jinshajiang River. The right bank is the west slope of the Yao Mountain, with a peak height of 3000 m, and its landform is characterized by steep and gentle slopes. Figure 2 shows the high slopes of the spandrel groove after excavation. Hydro China Huadong Engineering Corporation is responsible for slope excavation design work. Through the experimental data of Hydro China Huadong Engineering Corporation, we produced Tables 1-4. We have considered the main geological conditions that are conducive to the numerical simulation analysis. Figure 3 shows a typical section of the left bank slope along the dam-arch axis. The left bank abutment has an approximate north to south direction, inclining to the east with a slope of 60\({}^{\circ}\). The stratum lithology of the left dam foundation is mainly composed of P\({}_{2}\)\(\beta_{3}\)-P\({}_{2}\)\(\beta_{4}\) laminar basalt. The first type of basalt with columnar joints is mainly distributed at an elevation of 700-600 m--generally with a length of 3 m and a diameter of 13-25 cm. The left bank slope is a bedding slope with a shape of N30\({}^{\circ}\)-50\({}^{\circ}\) E and SE\(\angle\)15-25\({}^{\circ}\). There are many interlayer staggered zones (i.e., the appearance of C3 is N40\({}^{\circ}\)-55\({}^{\circ}\) E, the appearance of C3-1 is SE, 15\({}^{\circ}\)-20\({}^{\circ}\)) and the faults with high deep angles are in the NE-direction (i.e., F17, F16 and F14). The characteristics of the main interlayer rock mass and faults are listed in Tables 1 and 2, respectively. According to in situ stress measurements, the maximum principal stress is \(\sigma_{1}\) = 8-11 MPa, the medium principal stress is \(\sigma_{2}\) = 7-9 MPa, and the minimum principal stress is \(\sigma_{3}\) = 6-8 MPa [25; 26; 27]. Figure 1: Project location map [26] (Copyright © 2017, Springer Nature). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Occurrence** & **Thickness(cm)** & **Extension Length (m)** \\ \hline C3 & N40\({}^{\circ}\)–55\({}^{\circ}\)E, SE\(\angle\)15\({}^{\circ}\)–20\({}^{\circ}\) & 10–40 & 850 \\ C3-1 & N40\({}^{\circ}\)–50\({}^{\circ}\)E,SE\(\angle\)15\({}^{\circ}\)–20\({}^{\circ}\) & 5–30 & 800 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of the interlayer zones. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Occurrence** & **Width (cm)** & **Condition** \\ \hline LS337 & N20\({}^{\circ}\)–45\({}^{\circ}\)E, SE\(\angle\)18\({}^{\circ}\)–30\({}^{\circ}\) & 20–50 & The thickness is 10–40 cm, and the occurrence varies greatly \\ \hline LS331 & N47\({}^{\circ}\)E, SE\(\angle\)16\({}^{\circ}\) & 2–30 & Breccia and cuttings are the main ones, and the thickness varies greatly \\ \hline LS3318 & N34\({}^{\circ}\)E, SE\(\angle\)30\({}^{\circ}\) & 20–30 & The breccia and the cuttings are mainly distributed, and the top and bottom are distributed with a small amount of mud \\ \hline LS3319 & N20\({}^{\circ}\)–30\({}^{\circ}\)E, SE\(\angle\)22\({}^{\circ}\)–28\({}^{\circ}\) & 20–40 & The breccia and the cuttings are mainly distributed, and the top and bottom are distributed with a small amount of mud \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Intraformational disturbed belts.