## 3 Overview of the Cases Studied  
Three locations were selected for this investigation. Site 1 is found at the Freeway 1 Wudu exit (Figure 1), while Site 2 is located at Freeway 5 at a mileage of 7K + 082 (Figure 2), and Site 3 is located at Freeway 5 at a mileage of 7K + 410. The geological data and the overview of the slope protection project for each site are described below, and they act as a guide for the input values utilized in the subsequent numerical analysis. The geological map of Site 1 is shown in Figure 3 [34]. The stratum on the slope belongs to the Nankang Formation, which is composed of thick layers of blue-gray, fine-grained gray sandstone and dark shale. Figure 4 displays Site 1's drilling locations (BH6-1 to BH6-3) and core pictures [35]. Drilling-derived core pictures revealed that the rock disk in this region contains some joints, with laminae or thin shale layers serving as the primary weak surfaces. Tables 1 and 2 display the drilled cores' uniaxial compression and triaxial test results [35]. The slope is protected by four stages of RC curtain walls, free-styled grill beams, and grouted anchor bars, as shown in Figure 5 [35]. The grouted anchor bars are composed of three-meter-long #8 steel bars spaced three meters apart horizontally. Figure 1: Schematic diagram of Site 1. Figure 2: Schematic diagram of Site 2 and Site 3. Figure 4: Drilling location and core photos of Site 1. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Drilling Code** & **Depth (m)** & \begin{tabular}{c} **Moisture** \\ **Content (\%)** \\ \end{tabular} & \
\begin{tabular}{c} **Unit Weight** \\ **(t/m3)** \\ \end{tabular} &
\begin{tabular}{c} **Compression** \\ **Strength (MPa)** \\ \end{tabular} & **Strain (\%)** & **Lithology** \\ \hline BH6-1 & 11.1 & 2.6 & 2.63 & 30.9 & 1.44 & Sandstone \\ BH6-2 & 23.1 & 2.5 & 2.60 & 28.4 & 1.38 & Sandstone \\ BH6-3 & 3.1 & 3.1 & 2.61 & 17.2 & 1.59 & Sandstone \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Uniaxial compression test results of Site 1 core. Figure 3: Geological map of Site 1. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Drilling** & **Depth (m)** & \begin{tabular}{c} **Moisture** \\ **Content (\%)** \\ \end{tabular} & \
\begin{tabular}{c} **Peak Strength** \\ **\end{tabular} &
\begin{tabular}{c} **Residual Strength** \\ **\(\mathbf{\varphi_{p}}\) (\({}^{\circ}\))** \\ \end{tabular} & **Lithology** \\ \hline BH6-1 & 3–4 & 3.3–5.5 & 0.70 & 29.6 & 0.34 & 28.8 & Sandstone \\ BH6-2 & 12–13 & 2.5–6.5 & 9.09 & 53.8 & 1.26 & 44.2 & Sandstone \\ BH6-3 & 4–5 & 5–9.3 & 2.50 & 44.6 & 1.21 & 37.5 & Sandstone \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Triaxial test results of Site 1 core. The geological map of Site 2 is shown in Figure 6[34]. This stratum, which is a component of the Nankang Formation, is primarily composed of thick sandstone. The slope direction is northwest diagonal. Drilling data indicate that interbedded sandstone and shale are found beneath colluvial strata, which are located 4.9 m below the surface [34]. A total of 26 layers of 30 tons of prestressed ground anchors are used to protect the slope. The current ground anchors consist of a fourth-stage, 15-layer ground anchor; a free section of five meters; an anchor section of five meters; and a horizontal spacing of three meters, as shown in Figure 7[36]. After that, eleven levels of ground anchors were placed, spaced three meters apart horizontally, with ten meters for the free section and five meters for the anchor section. Figure 5: Slope cross-section and slope protection engineering facilities at Site 1. Figure 6: Geological map of Site 2. The geological map of Site 3 is shown in Figure 8 [33]. The formation here belongs to the Nankang Formation, which is composed of sandstone. The slope of Site 3 is approximately westward and is a diagonal slope. Drilling data show that the area from the surface to 4 m underground at Site 3 is colluvium, with siltstone underneath [33]. Ten layers of sixty tons of prestressed ground anchors are used to protect the slope.