# Study on the Early Warning Methods of Dynamic Landslides of Large Abandoned Rockfill Slopes
## 5 Method Validation
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Landslide Number** & **Types of Slopes** & **Duration of** & & \\
**Number** & **and Landslides** & **Displacement to Failure** & & \\ \hline Landslide 44 & Type “B1” & 40 min & 5 October 2013 4:55 & 450 m\({}^{2}\) \\ Landslide 53 & Type “B1” & 40 min & 10 October 2013 2:45 & 1000 m\({}^{2}\) \\ Landslide 67 & Type “B2” & 40 min & 15 October 2013 3:00 & 1100 m\({}^{2}\) \\ Landslide 71 & Type “B2” & 50 min & 15 October 2013 21:00 & 1600 m\({}^{2}\) \\ Landslide 72 & Type “B2” & 60 min & 16 October 2013 9:38 & 1100 m\({}^{2}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Characteristics of the five test landslides. From the analysis results of the above examples, the landslide early warning method and the early warning classification established in this paper could provide a warning to avoid risks before the occurrence of all five tested landslides. Compared with the traditional landslide warning method based on slope deformation, it mainly depends on the displacement of some points on the slope. For a loose rockfill slope, it is feasible to express the deformation of the slope by the displacement of a certain point, but it is difficult to find a suitable point. However, as described in Section 3.3, the variation curve of a \(-0.5\) mm equal displacement cross-sectional area over time conforms to the form of a \"three-section\" curve. Combined with previous research experience, this will make it easier for the equal displacement cross-sectional area to be used as an early warning indicator. It should be noted that this verification was based on the last instance of landslide of each type on the site, and the actual working conditions were similar to the previous landslides. The establishment of the landslide warning standard also depends on the statistical results of these previous similar landslide cases. Therefore, these four successful landslide warnings are limited by certain working conditions, such as rock lithology, rubble particle gradation, rolling of vehicles during the accumulation of rock mass, rainfall, and so on. These conditions will directly affect the repose angle of the rockfill, and the repose angle is an important factor affecting rockfill landslides. Generally, when the angle of the slope is less than the repose angle, the slope is unstable. Rainfall has a direct impact on the water content of rockfill, which is directly proportional to the angle of internal friction. For loose rockfill, due to the structural characteristics of the large pores, leakage and evaporation are rapid, so water content is usually small. Particle gradation will also directly affect the repose angle of the rockfill body. Small-particle-size rubble plays a particular \"lubrication\" role in the rockfill body. When the content of small-particle-size rubble is relatively low, large-particle-size rubble relies on friction and the \"aggregate interlock capacity of rubble\" to keep the slope in a stable state. When the content of small-particle-size rubble is high, due to the \"lubricating\" effect of small-particle-size rubble particles, the relative movement between large-particle-size rubble particles is more likely to occur, resulting in slope instability. Therefore, for the slopes of other rockfill bodies under similar working conditions, the actual situation should be considered to make appropriate adjustments to the early warning standard. Figure 13: The normalized \(-0.5\) mm equal displacement body cross-sectional area change rate. In general, most landslide warning models are based on the displacement-time curve of a single point on the slope. According to the curve change that conforms to the three stages of \"initial deformation-uniform deformation-accelerated deformation\", the landslide warning levels are divided into \"caution-vigilance-danger\".