## 3 Results and Discussion
### Physical Property Characterization
The particle size distributions of the two sample types, undisturbed loess and landslide deposits, were subjected to statistical analysis by measuring their \(D60,D50,D30,\) and \(D10\) values at different depths. The results depicted in Figure 6 indicate that, for the undisturbed loess, the \(D60\) values display a fluctuating pattern with depth, ranging between 19.5 \(\upmu\)m and 33.2 \(\upmu\)m. The \(D50,D30,\) and \(D10\) values exhibit relatively minor variations with depth, except for a more significant shift at a depth of 30 m.  
Figure 5: Grain size distribution curve of undisturbed loess and landslide deposit in different depths. In contrast, the landslide deposits exhibit consistent \(D60\), \(D50\), \(D30\), and \(D10\) values at various depths. When compared to the undisturbed loess, the landslide deposits display relatively uniform \(D60\), \(D50\), \(D30\), and \(D10\) values above a depth of 15 m. However, beyond the 15 m mark, the \(D60\), \(D50\), \(D30\), and \(D10\) values of the landslide deposits decrease, with the reductions being particularly pronounced for \(D60\), \(D50\), and \(D30\). Simultaneously, both the undisturbed loess and the landslide deposits have relatively high uniformity coefficients (\(C_{u}>4\)), and their coefficients of curvature (\(C_{c}>1\)) are also large. This indicates a wider distribution of particle sizes, implying a well-graded nature. In such cases, the soil particles exhibit significant variations in size, encompassing both larger and smaller particles. In Table 2, the average \(D60\), \(D50\), \(D30\), and \(D10\) values of the landslide deposits are smaller than those of the undisturbed loess by 6.1 \(\upmu\)m, 1.3 \(\upmu\)m, 1.8 \(\upmu\)m, and 0.4 \(\upmu\)m, respectively. After experiencing seismic sliding, the larger particles in the soil have reduced. The coefficient of variation indicates that the particle size differences at various depths of the landslide deposits are minimal, suggesting that the particles have become more uniform across different depths due to the soil sliding process. Soils with a higher proportion of smaller particles typically exhibit higher liquid limits. As shown in Figure 7, according to [PERSON] classification method based on the liquid limit and the plasticity index, both the undisturbed loess and landslide deposit fall between the A-line and U-line. The undisturbed loess has a lower liquid limit, closer to silty loess, while \begin{table}
\begin{tabular}{l l l l l l l l} \hline  & & \(D_{00}\) (\(\upmu\)m) & \(D_{00}\) (\(\upmu\)m) & \(D_{00}\) (\(\upmu\)m) & \(D_{00}\) (\(\upmu\)m) & \(C_{c}\) & \(C_{c}\) \\ \hline Samples in Slope & Mean value & 25.6 & 18.3 & 8.8 & 1.4 & 19.3242 & 2.2822 \\  & Coefficient of variation & 0.1549 & 0.1680 & 0.1821 & 0.4366 & 0.2490 & 0.2833 \\ Samples in deposit & Mean value & 19.5 & 15.5 & 7.0 & 1.0 & 20.1573 & 2.5852 \\  & Coefficient of variation & 0.0811 & 0.1309 & 0.2721 & 0.2729 & 0.1766 & 0.3723 \\ \hline \end{tabular}
\end{table} 
Table 2: Mean value and coefficient of variation in grain size distribution of undisturbed loess and landslide deposit. Figure 6: The different diameter of undisturbed loess and landslide deposit in different depths. the landslide deposit has a higher liquid limit, closer to clayey loess. The liquid limit test results are consistent with the particle analysis results. Based on the variations in the pore structure and particle size of the undisturbed loess and landslide deposits, it can be inferred that during the occurrence and movement of a landslide, the loose and porous structure of the undisturbed loess undergoes fragmentation. Larger soil particles experience compression, friction, fragmentation, and abrasion during their movement, resulting in the formation of smaller particles (Figure 8). Additionally, as the landslide progresses, continuous collisions among larger particles cause them to move downward, leading to further fragmentation and abrasion.