# Study on the Early Warning Methods of Dynamic Landslides of Large Abandoned Rockfill Slopes
## 2 Project Overview
### Early Warning Indicators and Grading Standard  
Considering the needs of on-site early warning in terms of the number of data calculations and the data extraction speed, under the condition of ensuring the accuracy of radar displacement monitoring, the deformation of \(-0.5\) mm on the slope is easier to identify in time. Therefore, the cross-sectional area of the \(-0.5\) mm equal displacement body was used as an index to validate the early warning method of the rockfill slope during excavation and transportation [2]. The on-site conditions of waste rockfill slope landslides are complicated, and both different and similar types of landslides often occur in the same area. Therefore, the cross-sectional area of the \(-0.5\) mm equal displacement body was normalized, and then the rate of change was used as a warning indicator of landslides. The cross-sectional area of the \(-0.5\) mm constant displacement body at each moment after normalization is  
\[S_{-0.5}^{*}(t)=\frac{S_{-0.5}(t)}{S_{\mathrm{max}}} \tag{2}\]  
where \(S_{-0.5}(t)\) is the measured or predicted value of the cross-sectional area of the \(-0.5\) mm constant displacement body at time \(t\) and \(S_{\mathrm{max}}\) is the cumulative value of the cross-sectional area of the \(-0.5\) mm equal displacement body obtained from the last measurement before the slope starts sliding.  
The normalized \(-0.5\) mm equal displacement body cross-sectional area change rate is  
\[V_{-0.5}^{*}(t)=\frac{S_{-0.5}(t)^{\prime}}{S_{\mathrm{max}}} \tag{3}\]  
Based on the field measurement results and the analogy between landslide cases, the characteristics of the cross-sectional area of the \(-0.5\) mm equal displacement body of the two types of \(29\) landslides that were previously monitored in the rockfill were statistically analyzed. Then, early warning standards were developed according to two different types of landslides. Since the data selected were actually measured landslide data, the lower limit of the \(95\%\) confidence band of the mean value of the cross-sectional area of the two types of landslides of the \(-0.5\) mm equal displacement body was selected as the standard to formulate the landslide warning level. According to the characteristic values of \(50\%\), \(30\%\), and \(10\%\) of the lower limit of the \(95\%\) confidence band of the average displacement rate of the cross-sectional area of the \(-0.5\) mm equal displacement body before sliding, the landslide warning was divided into five levels, as shown in Figure 6. Note that the rate of change of the cross-sectional area of the \"B1\"-type landslide of the \(-0.5\) mm equal displacement body shows a decreasing trend within a certain period of the initial stage of the development of the displacement field. Therefore,  
Figure 10: Early warning method of landslides.  
the maximum value of \(V^{*}_{-0.5}(t)\) before the start of deformation acceleration is defined as the upper limit of the yellow warning for class B landslides. To make the early warning method more convenient and to ensure the compatibility of the two types of landslides, the early warning standard was uniformly divided into four levels based on the statistical results of the early warning thresholds of the two types of landslides, as shown in Figure 11. The grading results and construction regulations were then established, as shown in Table 4.