## 3 Results and Discussion
### Distribution Characteristics of the Subgrade Vibration Acceleration  
Vibration acceleration is an indicator reflecting the intensity of vibration at a specific point. Due to the high frequency and amplitude changes in the vibration acceleration curve, to reduce experimental error, the vibration acceleration amplitude was taken as the average of the five peak absolute values. The spatial distribution relationship of vibration acceleration amplitude at the measurement points on survey lines 1 and 3 under different conditions is illustrated in Figure 12. The vertical vibration acceleration amplitude under the condition without a soil hole was consistently higher than that under the condition with a soil hole. At the position 10 m from the toe of the slope, the subgrade vibration acceleration amplitude showed significant attenuation compared to the toe position. Specifically, at the toe position with a soil hole, the vertical vibration acceleration curve featured smaller values in the middle and larger values on both sides, indicating that the closer the location is to the soil hole, the greater the attenuation of vibration acceleration. At the position 10 m from the toe of the slope, the subgrade vibration acceleration amplitude curve showed a wavy pattern, with the presence of the soil hole having little impact. Under the condition without a soil hole, the peak vertical vibration accelerations were 200.56 mm/s\({}^{2}\), 208.34 mm/s\({}^{2}\), and 242.41 mm/s\({}^{2}\) at various positions, while with a soil hole, the peak values decreased to 164.31 mm/s\({}^{2}\), 136.98 mm/s\({}^{2}\), and 176.72 mm/s\({}^{2}\), representing reductions of 18.07%, 36.26%, and 27.09%, respectively. This demonstrates that the vertical vibration accelerations were significantly higher without a soil hole at all positions. At the \(-\)16 m position, the vibration acceleration increased by 3.73% compared to the 0 m position without a soil hole, while it decreased by 19.95% in the presence of a soil hole. Similarly, at the 16 m position, the vibration acceleration decreased by 14.05% without a soil hole and by 29.01% with a soil hole. These results indicate that when a soil hole is present, the closer the distance to the hole, the greater the impact on elastic wave propagation, leading to more significant vibration attenuation. This occurs because the presence of the soil hole affects the propagation of elastic waves; as  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Survey Lines 1**} & \multicolumn{3}{c}{**Survey Lines 3**} \\ \cline{2-7}
**Distance from** & \multicolumn{2}{c}{**Dynamic Displacement**} & \multicolumn{2}{c}{**Dynamic Displacement**} & \multirow{2}{*}{**Attenuation**} & \multirow{2}{*}{**Amplitudes (mm)**} & \multirow{2}{*}{**Attenuation**} \\
**Soil Cavity (m)** & & & & & & \\ \cline{2-7}  & \multicolumn{1}{c}{**Normal**} & & & & \\
**Subgrade** & \multicolumn{1}{c}{**Kars Subgrade**} & & & & \\ \hline \(-\)16 & 0.1620 & 0.1422 & 12.35 & 0.0677 & 0.0472 & 30.22 \\ \(-\)12 & 0.1635 & 0.1280 & 21.73 & 0.0629 & 0.0483 & 23.11 \\ \(-\)8 & 0.1541 & 0.1073 & 30.33 & 0.0601 & 0.0543  
elastic waves pass through an air medium, the energy attenuation is greater than when they propagate through dense soil, resulting in a corresponding reduction in vertical vibration acceleration amplitude. Calculations show that the attenuation range at the toe of the slope was approximately 30-40%, while the attenuation range at the position 10 m from the toe was about 10-30%, with more significant attenuation closer to the soil hole. Further calculations reveal that the vertical vibration acceleration at the monitoring point 15 m from the toe of the slope drops below 80 mm/s\({}^{2}\), which could be affected by environmental factors, leading to potential monitoring errors. Therefore, monitoring points 15 m from the toe of the slope are not considered suitable for dynamic monitoring of the internal health of the subgrade.