## 2 Full-Scale Experimental Model
### Model Design
#### 2.1.3 Reinforcement  
In this study, a self-fabricated galvanized steel grid (GSG) of CB300V steel with a diameter of 10 mm was used, provided by the Viet Nhat Steel Joint Stock Company. The CB300V steel type has been widely used in Vietnam, and the \(\Phi\) 10 mm steel reinforcement met the requirements for the mechanical, physical, and chemical properties as well as the design strength when used as the reinforcement in the MSE walls. The steel grid had ribs that were 3 cm high at the interaction between the longitudinal and transverse directions to increase the backfill-soil-reinforcement interactions.  
The tensile strength of the steel reinforcement (yield strength), F\({}_{0}\), was 49,000 N. However, we also considered the effect of the backfill soil, the service life of the wall, corrosion due to sulfate ions, and metal loss during the 100-year design life of the MSE wall. Regarding the service life of the wall, [PERSON] et al. [29] recommended that an MSE structure needs to be monitored and repaired when the values of the remaining tensile strength within the reinforcement are equal to 65% F\({}_{0}\), with F\({}_{0}\) being the initial tensile strength of the reinforcement. Thus, in this study, the tensile strength of the reinforcement was 31,850 N at the initial stage, as illustrated in Table 2.  
To consider the reduction in the tensile strength of the reinforcement, [PERSON] et al. [29] drilled the reinforcement bars to reduce their cross-sectional area. This method is also recommended in the design rules and calculation process for MSE walls in AFNOR NF P94-270:2020 [12]. Therefore, this study also carried out drilling to reduce the cross-sectional area of the reinforcement (as shown in Figure 3) with a proportional loss of tensile strength (AF) equal to 35% F\({}_{0}\), as indicated in Table 2.  
Furthermore, to the enhance corrosion resistance of the reinforcement, the steel bars were galvanized with a zinc layer of 70 \(\upmu\)m thickness. The length of the reinforcement bars was L = 2.1 m. The vertical spacing between the reinforcement layers was S\({}_{\text{v}}\) = 0.75 m (4 reinforcement layers along the height of the wall, H = 3 m). In each layer, 4 longitudinal steel reinforcement bars were installed with a space of 0.375 m. In addition, the horizontal spacing between the reinforcement bars (the transverse direction) was 0.45 m. Ribs that were 3 cm high were bonded to the reinforcement mesh to enhance the soil-reinforcement interaction, as shown in Figure 4. The steel reinforcement grids were rigidly connected to the facing panels.  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Parameter** & **Unit** & **Value** \\ \hline Initial tensile strength of the steel reinforcement & N & 49,000 \\ Loss of tensile strength & N & 17,150 \\ Remaining tensile strength within the reinforcement & N & 31,850 \\ Drilling the reinforcement bars to reduce their cross-sectional area & \% & 26.6 \\ Drilling depth (\(\Phi\) 5) & mm & 8.1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Reducing the cross-sectional area of the reinforcement bars.  
Longitudinal steel reinforcement bars were installed at symmetrical locations. The initial test indicated that the deformation of all longitudinal steel reinforcement bars in the same layer was similar. In the following section, the behavior of one longitudinal steel reinforcement bar is presented.