## 4 Discussion
### Interaction of Different Factors and Their Impact on Road Collapse Disasters
The lithological classification includes sedimentary rocks (SC16, SC5, SC4, SC2, SC3, SC1, SO1, SO2), varying in hardness and fracturing degree, with softer or more erodible types exhibiting increased collapse risk under rainfall conditions; metamorphic rocks (UF, MB1, MB2, MA4/MB2, MA3/MB1), characterized by pronounced fracturing, resulting in reduced stability; and igneous rocks (IB1, IB2, IA4, IA1, UM), which generally resist weathering and exhibit high cohesion, though highly fractured or weathered igneous rocks (UR, WR, RK, IP2) are prone to collapse [26]. Sotfer lithologies show a significant correlation with higher collapse risk, a conclusion further validated by the model's predictive results. (3) Precipitation: Precipitation is a key climatic factor influencing collapse risk. Excessive precipitation can lead to soil saturation, thereby increasing soil instability. As shown in Figure 9, regions with higher annual precipitation typically exhibit greater collapse risk. The effect of precipitation is not isolated but interacts with factors such as slope and soil moisture [42]. In areas with steeper slopes, increased precipitation significantly elevates soil saturation, further exacerbating the occurrence of landslides and collapses. Thus, the  
Figure 8: Lithology of the Guangxi Zhuang Autonomous Region. interaction between precipitation and other natural factors is a critical contributor to the occurrence of road collapse disasters. (4) Vegetation Cover: Vegetation coverage plays a significant role in maintaining soil stability, particularly in reducing soil erosion and retaining moisture [43]. As depicted in Figure 10, areas with dense vegetation coverage are typically classified as low-risk zones [12]. This finding suggests that vegetation can, to some extent, mitigate soil erosion and enhance soil stability. However, the effect of vegetation coverage varies across different regions and climatic conditions. Notably, in areas with high precipitation, vegetation may help alleviate soil saturation, thereby reducing collapse risk. In regions with substantial rainfall, high vegetation coverage contributes to maintaining greater soil stability, whereas in areas with sparse vegetation, even moderate precipitation can lead to soil instability and subsequent collapse. This figure illustrates the distribution of the Normalized Difference Vegetation Index (NDVI) in the Guangxi Zhuang Autonomous Region, generated based on remote sensing data [10]. The NDVI values and their implications are as follows: values below 0.2 indicate water bodies or bare surfaces with a high risk of erosion; 0.2 to 0.4 correspond to sparse vegetation with low stability; 0.4 to 0.6 represent moderate vegetation density with a reduced erosion risk; 0.6 to 0.8 denote dense vegetation with a low collapse risk; and values above 0.8 signify extremely dense vegetation, capable of significantly stabilizing soil under varying rainfall conditions. (5) Soil Moisture: Soil moisture directly affects the mechanical properties of soil and is a key factor in collapse risk assessment [44]. Higher soil moisture is typically associated with an increased risk of collapse, particularly in regions with substantial precipitation. As illustrated in Figure 11, in these areas, increased soil saturation significantly reduces stability, heightening the risk of landslides or collapses. Soil moisture also interacts with factors such as lithology and slope gradient [45]. In soft rock regions with elevated soil moisture, the soil's resistance to sliding diminishes, making collapses more likely. Figure 9: Average annual precipitation in the Guangxi Zhuang Autonomous Region. saturation zones, found in valley bottoms and gullies, with reduced stability and increased collapse risk due to significant water accumulation; and values above 16 signify surface water convergence zones, located in river channels and wetlands, with high soil moisture, markedly reduced stability, and substantially elevated collapse risk.