## 3 Results and Discussion  
### Microscopic Morphology Analysis  
We used scanning electron microscopy (SEM) to observe the fiber internal structure of three types of geotextiles: new unused (referred to as X), top of slope protection (referred to as D), and covered in mud (referred to as N). This is shown in Figure 6. The fiber structure of the X geotextile is relatively complete, with no cracks or fractures on the surface. There are no signs of aging, discoloration, or chemical reactions. The surface of geotextile fibers  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Factor Level**} & **Geotextile** & **Mix Proportion** & **Spray Thickness** \\  & **A (g/m\({}^{2}\))** & **B (Content of Cementitious Materials/\%)** & **C (mm)** \\ \hline
1 & 300 g/m\({}^{2}\) & 14.29/16.28/18.18 & 1 layer (approximately 2 mm) \\
2 & 400 g/m\({}^{2}\) & 14.29/16.28/18.18 & 2 layers (approximately 4 mm) \\
3 & 500 g/m\({}^{2}\) & 14.29/16.28/18.18 & 3 layers (approximately 6 mm) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Test factors and level design.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Test Group**} & \multicolumn{3}{c}{**Influence Factor**} \\ \cline{2-4}  & **Geotextile** & **Content of Cementitious Materials** & **Spray Thickness** & **Empty** \\  & **A/(KN/m)** & **B/(\%)** & **C/(mm)** & **Column** \\ \hline
1 & 300 g/m\({}^{2}\) & 14.29 & 1 layer (approximately 2 mm) & 1 \\
2 & 300 g/m\({}^{2}\) & 16.28 & 2 layers (approximately 4 mm) & 2 \\
3 & 300 g/m\({}^{2}\) & 18.18 & 3 layers (approximately 6 mm) & 3 \\
4 & 400 g/m\({}^{2}\) & 14.29 & 2 layers (approximately 4 mm) & 3 \\
5 & 400 g/m\({}^{2}\) & 16.28 & 3 layers (approximately 6 mm) & 1 \\
6 & 400 g/m\({}^{2}\) & 18.18 & 1 layer (approximately 2 mm) & 2 \\
7 & 500 g/m\({}^{2}\) & 14.29 & 3 layers (approximately 6 mm) & 2 \\
8 & 500 g/m\({}^{2}\) & 16.28 & 1 layer (approximately 2 mm) & 3 \\
9 & 500 g/m\({}^{2}\) & 18.18 & 2 layers (approximately 4 mm) & 1 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Orthogonal experimental design scheme.  
is relatively rough, and there is a phenomenon of darkening in color. This color change is the result of the material undergoing ultraviolet oxidation reaction under long-term exposure to light. As the usage time increases, the fiber filaments break and crack, causing longer fibers to gradually decompose into shorter fibers. The surface of N geotextile fibers is covered with large areas of irregular soil particles, with a small amount of breakage and damage, indicating a slow rate of ultraviolet oxidation reaction and a relatively mild degree of aging.  
Through sampling and scanning electron microscope (SEM) observations of the three types of geotextiles, it is evident that the fibers of the D geotextile (slope top) exhibit significant signs of aging, including surface roughness, wear, and noticeable darkening, indicating severe degradation. In contrast, the fibers of the N geotextile (mud-covered) show only minor roughness and wear, with the mud particles covering the surface significantly slowing down the aging process. These findings highlight the protective effect of mud coverage against environmental degradation.