## 3 Installation of Sensors and Measuring Devices  
To analyze the behaviors of the RSR which was applied to the abutment transition zone, 19 geogrid strain gauges, 3 horizontal earth pressure gauges, and settlement rods for the ground and the backfill surface were installed and measured during the construction process. The long-term measurements were conducted over a period of 16 months, including the 2.6 month-long construction period, and the RSR behaviors were identified. A schematic view of the measuring sensors is illustrated in Figure 5.  
To distinguish the settlement of the ground and embankment, the settlement rods were placed on the ground and backfill surface, respectively. The settlement rod for the ground comprised a 1 m \(\times\) 1 m square plate and a rod with a 15 mm diameter that could be extended as the backfill height was increased by 1 m. The surface settlement rod, featuring a circular steel plate with a 300 mm diameter and an attached 400 mm high rod, was installed at a distance of 0.5 m from the edge of the backfill. Considering the field conditions, the settlement measurements were performed after the completion of the  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Zones** & **Materials** & **Properties and Compaction Conditions** \\ \hline \multirow{3}{*}{a} & Reinforced roadbed & \multirow{3}{*}{D\({}_{\text{max}}\)1 = 31.5 mm, over 100\% OPM 2  \\  & (Crushed gravel) & \multirow{3}{*}{D\({}_{\text{max}}\) = 63 mm (Cement 3\%), \(E_{\text{v2}}\)3 \(\geq\) 120 Mpa, \(E_{\text{v2}}\)/\(E_{\text{v1}}\)3 \(<\) 2.2} \\  & & D\({}_{\text{max}}\) = 63 mm, \(E_{\text{v2}}\)\(\geq\) 80 Mpa, \(E_{\text{v2}}\)/\(E_{\text{v1}}\)\(<\) 2.2 \\  & & (Upper roadbed) \\ \multirow{3}{*}{a} & Soil & \multirow{3}{*}{E\({}_{\text{v2}}\)\(\geq\) 80 Mpa, \(E_{\text{v2}}\)/\(E_{\text{v1}}\)\(<\) 2.3, over 95\% \(\rho_{\text{d,max}}\)4  \\  & & (Lower roadbed) \\ \multirow{3}{*}{a} & \multirow{3}{*}{E\({}_{\text{v2}}\)\(\geq\) 60 Mpa, \(E_{\text{v2}}\)/\(E_{\text{v1}}\)\(<\) 2.7, over 90\% \(\rho_{\text{d,max}}\)} \\ \cline{1-1}  & & \\ \end{tabular}
\end{table}
Table 4: Properties and compaction conditions for backfill materials.  
Figure 4: Backfill materials of transition zone.  
embankment construction (from day 23 to day 274). The horizontal earth pressure gauges were installed at the net of the welded rebars at the 2 nd, 10 th, and 16 th layers to observe the variation in the horizontal earth pressure with respect to the height. The strain gauges were installed on the 2 nd and 5 th layers and the 10 th, 13 th, and 16 th layers for the short and long geogrids, respectively. The strain gauges on the short geogrids were installed at a distance of 0.5, 1.5, and 2.5 m from the exterior of the reinforced backfill. The strain gauges on the long geogrids were installed at a distance of 0.5, 1.5, and 2.5 m for the 10 th layer, 0.5, 1.5, 3.5, and 5.5 m for the 13 th layer, and 0.5, 1.5, 3.5, 5.5, 7.5, and 9.5 m for the 16 th layer. The installed sensors used for the measurements are shown in Figure 6.  
Figure 5: Location of installed sensors.  
Figure 6: Installed sensors: (**a**) surface settlement rod; (**b**) ground settlement rod; (**c**) horizontal earth pressure meter; (**d**) strain gauge.