## 3 Results and Discussion  
### Physical Property Characterization  
The test results provided a specific gravity (Gs) of 2.71 for the undisturbed loess and a Gs value of 2.72 for the landslide deposit. As depicted in Figure 4, both the undisturbed loess and the deposit exhibit a gradual increase in the \(\gamma\) and \(\gamma_{d}\) with depth. However, at the same depth, the deposit's \(\gamma\) and \(\gamma_{d}\) surpass those of the undisturbed loess. Analyzing the moisture content-depth curve, the undisturbed loess maintains a relatively stable and low moisture content at depths shallower than 10 m. Between 10 and 20 m, it experiences a gradual rise in the moisture content, followed by a rapid surge in moisture below 20 m. The saturation level reaches approximately 80% at a depth of 30 m. In contrast, the deposit at the same depth showcases higher saturation than the undisturbed loess, with \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Index Properties** & **Standard** & **Parameters** & **Samples** \\ \hline Density, dry density & ASTM D7263 & \(\gamma_{r}\), \(\gamma_{d}\) & all \\ Initial void ratio & \(e\) & all \\ Specific gravity & ASTM D854 & \(G_{s}\) & all \\ Grain size & ASTM D422, D1140 & \(D_{60},D_{50},D_{30},D_{10},C_{u}\), & all \\ Water content & ASTM D2216 & \(w\) & all \\ Index test & ASTM D4318 & PL, LL, PI & all \\ One-dimensional & \(\text{ ASTM D2435}\) & \(C_{c}\), \(\text{\it OCR}\) & all \\ consolidation & & & D04, D10, D20, D30 \\ Resonant column test & ASTM 4015 & \(G_{max}\), \(G_{d}\) & S04, S10, S20, S30 \\ \hline \hline \end{tabular} Note: \(D_{60}\), \(D_{50}\), \(D_{30}\), \(D_{10}\) mean: the diameter of the soil particles for which 60%, 50%, 30%, 10% of the particles are finer; \(C_{u}\): uniformity coefficient = \(\frac{D_{60}}{D_{60}}\); \(C_{c}\): coefficient of curvature = \(\frac{(D_{50})^{2}}{D_{10}D_{60}}\); PL means: plastic limit; LL: liquid limit; PI: plastic index; \(C_{c}\): compression index; \(\text{\it OCR}\): overconsolidation ratio; \(G_{max}\): the maximum dynamic shear modulus; \(G_{d}\): dynamic shear modulus.  
\end{table} 
Table 1: The summary of laboratory tests and standards for soil properties. Figure 4: Density, water content, dry density, initial void ratio, and saturation degree of undisturbed loess and landslide deposit at different depths. its moisture content uniformly increasing as the depth grows. At 30 m deep, the saturation level approaches 90%. The alterations in the physical properties of these two materials stems from the notable changes in their porosity. The undisturbed loess, known for being a wind-blown soil with large pores, loose structure, and weak cohesion, exhibits a surface porosity ratio of 1.3. With greater depth, this ratio decreases, reaching 0.86 at 30 m deep, while still maintaining its character as a porous and loosely packed soil. Conversely, at the same depth, the deposit's porosity ratio is significantly lower than that of the undisturbed loess. It reaches a maximum of 0.89 at the surface and declines with depth, reaching only 0.58 at a depth of 30 m.  
This suggests that the loose and porous structure of the undisturbed loess becomes disrupted after undergoing the seismic landslide process. After deposition, the landslide deposit experiences reduced porosity, a compacted structure, increased density, and dry density. The grain size distribution is presented in Figure 5. The results showed that the samples of undisturbed loess in the slope contain 8.1-14.8% of clay (<0.002 mm), 80.0-84.2% of silt (0.002-0.075 mm), and 3.8-7.7% of sand (0.075-0.25 mm). At a depth of 30 m, the soil sample exhibits the highest concentration of sand and the lowest concentration of clay. The samples of deposits contain 12.3-17.3% of clay (<0.002 mm), 77.1-84.5% of silt (0.002-0.075 mm), and 1.6-6.3% of sand (0.075-0.25 mm). Compared to the undisturbed loess, the landslide deposits exhibit an increase in the clay particle content and a decrease in the sand particle content.