# Study on the Early Warning Methods of Dynamic Landslides of Large Abandoned Rockfill Slopes
## 2 Project Overview  
The waste rockfill is located about 500 m southwest of the underground project entrance, and the floor area is approximately \(9.6\times 10^{4}\) m\({}^{2}\). The ground where the waste rockfill body is located is high in the north and low in the south, and the difference of elevation between the south and north is about 20 m. The east and west directions are relatively gentle, and there is a slightly protruding depression in the middle part. The difference of elevation is about 4 m. The waste rockfill is dumped by a dump truck [26], and it is leveled by a bulldozer. The rockfill body slopes can be divided into two stages based on the formation process. The boundary between the two stages are shown in Figure 1 (the yellow dotted line).  
The waste is mainly rubble produced by the blasting and crushing of granite gneiss. Table 1 shows the petrophysical and mechanical properties of granite gneiss in intact rock mass. The rockfill is highly porous and unconsolidated with high permeability of the rubble. The bottom of the rockfill body is composed of large rubbles with an average particle size of 1 m, and the rubble particles are independent of each other. The slope within the monitoring area (the red polygon area in Figure 1) is the residual slope after the occurrence of the previous landslides, and many large boulders are already broken, having an average size of 10-50 cm (Figure 2). Besides, due to the occurrence of landslide, the rock rolling and impact will be broken, resulting in much coarse-grained soil left on the slope.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Classification**} & \multirow{2}{*}{\begin{tabular}{c} **Specific** \\ **Gravity** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Uniaxial Saturation** \\ **Compressive** \\ **Strength (MPa)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Elasticity** \\ **Modulus (GPa)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Shearing Strength** \\ **Cohesion (MPa)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Tensile** \\ **Friction** \\ **Angle (°)** \\ \end{tabular} } \\ \hline \hline \multicolumn{2}{c}{Granite gneiss below +20 m} & \multirow{2}{*}{2.6} & \multirow{2}{*}{90.7} & \multirow{2}{*}{52.7} & \multirow{2}{*}{10.2} & \multirow{2}{*}{71.1} & \multirow{2}{*}{11.7} \\ \multicolumn{2}{c}{(the elevation of the underground cavern roof is \(-30\) m)} & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Physical and mechanical properties of intact rocks (from geological survey report).  
Figure 2: Rock fragments left on the slope after the previous landslide.  
Due to the stacking height limits and the economic value of rubble, rubble waste is transferred to a dumping site about 1 km south of the site of rubble transfer, as shown in Figure 3.  
To prevent uncontrollable large-scale slippage caused by an excavation-related disturbance, rubble excavation is carried out in two phases. In the first phase, a \"C\"-shaped platform is constructed above the platform of the original rockfill body. Excavation is carried out using construction equipment located on the platform (Figure 4) to control the location and slope height of the area affected by the excavation, thereby controlling the scale of the landslide and the direction of the sliding body. After the removal of most of the rubble via the above the platform, the second phase of the operation is to transport the rubble under the platform.  
Slope Monitoring of Large-Scale Abandoned Rockfill Based on Ground-Based Interferometric Synthetic Aperture Radar