## 4 Measurement and Results/Discussion
### Highway 84 Slope  
Figure 10 displays the layout of the overall deformation measurement line utilizing the DSS method. Meanwhile, Figure 10 depicts the DSS based strain measurement results, with negligibly low strain. Here, the DSS cables were tightly wound around the posts three times, resulting in additional bending strain in the DSS cables. Notably, the ambient temperature at the site was frequently below the freezing point. Based on previous experience--the 1000 W lithium-ion battery did not work very well for the I-180 site on cold days--a 2000 W pure sine wave generator was used for this site.  
The overall strain was at the \(\pm\)50 micro strain level. Assuming that the thermal strain might take about 20 microstrains, as previously discussed for the case of the I-180 slope, the mechanical strain was \(\pm\)30 micro strain range, which is practically an elastic strain level in clay-reach soils. This analysis is based on the notion that the behavior of clayey soils is essentially elastic when the strain level is close to or lower than 50 microstrains ([PERSON] and [PERSON] II, [34]). The measurement readings of this site were halted due to snow. In Spring 2021, measurement readings were resumed, but the DSS cables were observed to be loose in many sections. Careful investigation showed abundant animal droppings in the measurement site. According to a local resident, the issue with the DSS cables could be attributed to the activity of wild deer in the area. As a result, the cables were re-tightened and measurement readings resumed in the summer of 2021. However, it was discovered that the cable posts had become loose again due to the widespread shrinkage cracks found around them. Unfortunately, the DSS cables installed at the Highway 84 slope failed to provide the expected data. Moreover, it is noted that the DSS monitoring system has a potential limitation in that the obtained signals may not be as distinct as those obtained through the FBG (Fiber Bragg Grating) method, which utilizes factory-generated clear cracks or mirrors ([PERSON] et al., [35]), despite being a more cost-effective alternative. Additionally, it is important to handle the DSS cables properly as slight mishandling can result in damage and prevent the glass fiber from transmitting accurate signals. Therefore, proper knowledge and handling of the fiber optic cable are critical for the successful deployment of the DSS monitoring system. However, the economy of the DSS method is not matched by the FBG method because the technique essentially utilizes the same fiber optic cable used for the telecommunication business.  
On the other hand, the UAS-based method showed a clear deformation profile of the slope and surrounding area, as shown in Figure 11. The target area is shown in the black inset box. Due to the upgraded hardware, the resolution of the deformation is higher than in the previous case for the I-180 slope. The red color shown at the bottom indicates approximately 15 cm of false settlement caused due to the disturbance and surface movement by the mobilization of the drilling equipment.  
Overall, the slope showed zero (blue to green color) to 8 cm (red color) deformation, but it did not indicate any major movement of the slope.  
Figure 10: Instrumentation on Highway 84 slope. (**a**) Alignment of DSS line (Large solid circle: PVC Pole, Black Line: DSS line). (**b**) Measured Strain by DSS.