## 3 Results
### Analysis of the Surface Deformation Mechanism of the Channel Slope  
Based on Figure 7 and previous analysis, it is evident that the surface deformation of the slope of the channel section in the study area was mainly uplifted. Among the areas studied, the most severe uplift deformation was observed in area C, while a certain degree of uplift deformation was also produced in area D. These deformations can be attributed to the long-term impact of expansive soil on the channel slope in the study area. Expansive soil has the characteristics of high water absorption, high plasticity, fissure, and intense expansion and contraction because its composition contains strong hydrophilic minerals. During the early stages of deposition, when the consolidation characteristics are prominent, the surface plasticity of expansive soil was not significant. However, during the construction of the channel project, the excavation of the slope disrupted the soil consolidation, leading to the release of internal expansion forces and subsequent expansion deformation. Moreover, due to rainfall, the expansive soil underwent repeated expansion and contraction deformation, leading to expansive-soil channel landslide deformation with gradual and long-term characteristics. In area B, slight settlement deformation was  
Figure 9: Temporal deformation laws of the three monitoring sites. observed. Considering the geographical environment of area B, which is characterized by numerous residential buildings and a major traffic road traversed by large trucks, it can be inferred that this type of deformation is likely caused by the combined effect of static loads from buildings and dynamic loads generated by the substantial number of trucks exceeding the capacity of the expansive soils in the area to accommodate expansion. In order to further analyze the influence of the soil moisture content on the deformation of expansive-soil channel slopes, we examined the relationship between surface deformation and soil moisture content by combining the real-time monitoring data of GNSS and soil moisture content in the area of uplift deformation (Figure 10). The monitoring data revealed that both uplift and subsidence deformations occurred vertically at the monitoring site due to changes in the soil water content, although the overall trend was the occurrence of an uplift. From 31 December 2020 to 26 February 2021, the soil moisture content remained relatively stable, at approximately 26.5%, and no significant lifting or settling deformation was observed on the surface during this period. From 27 February to 30 April, the soil water content increased to about 28.5%, and the surface was slightly lifted, with a maximum lift of 5 mm. From 1 May 2021 to 16 May 2021, the soil water content first decreased from 28% to 25.5% and then increased to 28%, and the surface was first deformed by subsidence and then by lift; from May 17 to July 3, the soil water content decreased from 28% to 22.5%, with fluctuations near the lowest point, and surface deformation also occurred as well as obvious fluctuations; from July 4 to July 8, the soil moisture content rose from 22.5% to 33%, and the surface also showed an obvious lifting deformation; from July 8 to September 17, the soil moisture content fluctuated in the range of 30 to 36%, and the surface lifting deformation basically moved up and down around a 5 mm axis, with a maximum lifting value of 14 mm and a minimum of 0 mm. In the horizontal plane, notable displacements occurred in north and west directions. Both the northward and westward displacements exhibited an increasing trend in absolute values. It is worth noting that the northward displacement was toward the interior of the channel, reaching a maximum horizontal displacement of 17 mm. Consequently, the channel management department has implemented necessary restoration measures. On the other hand, the westward displacement was relatively small, measuring at only 7 mm, and it aligned with the channel direction.