## 4 Test Results and Discussion
### Prediction of Bearing Resistance  
Figure 7 shows a comparison between the predicted values and observed results of bearing-resistance stress according to the number of transverse members. The predicted bearing resistance used in soil strength parameters is calculated from the general shear failure [19] and punching shear failure [8]. Pullout force based on the design guidelines  
Figure 5: Relationship between normal stress and pullout strength. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Test Classification**} & \multicolumn{2}{c}{**Pullout Parameter**} \\  & **Adhesion of Soil Reinforcement** & **Interface Friction Angle of Soil** \\  & **(\(c_{p}\), kPa)** & **Reinforcement (\(\delta\), \(\circ\))** \\ \hline SN & 22.8 & 20.3 \\ PS1-1 & 39.7 & 25.5 \\ PS2-1 & 56.9 & 33.2 \\ PS3 & 88.2 & 39.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Soil characteristics. Figure 6: Relationship between normal stress and bearing strength. specified by the Federal Highway Administration (FHWA) [30] was applied in order to calculate bearing-resistance stress using test results, of which the value at the front displacement was 50 mm. Pullout force was also applied to the maximal pullout force regardless of pullout force and pullout displacement, which calculate bearing-resistance stress at that point due to the transverse member. Bearing-resistance stress in all cases, which had applied pullout force at 50 mm front displacement, was close to the general shear failure in the lower normal stress condition. Figure 7: Comparison of predicted and observed bearing-resistance stress according to number of transverse members: (**a**) PS1-1, (**b**) PS2-1, and (**c**) PS3. However, it was close to the punching shear failure if normal stress increased because there were considerable gaps between the pullout force at 50 mm front displacement and maximal pullout force, as seen in Section 4.1. Bearing-resistance stress closed from punching shear failure to general shear failure according to the increment of the transverse member due to the small interference effect between transverse members. The interference effect showed the same results according to the set installation location of transverse members as those for the pullout force of PS2-1, which was lower than that in the other cases (see Figure 4b). On the other hand, bearing-resistance stress applied with maximal pullout force was close to general shear failure regardless of the normal stress condition or number of transverse members, as the maximal pullout force appeared when soil mass was close to shear failure. The observed bearing-resistance stress of all cases was plotted between the lower and upper boundaries, with similar results to those of existing studies [9; 24; 27; 31; 32; 33]. Existing studies are applied to reinforcements such as welded steel grids and geogrids, and the bearing resistance of these types has about 70-80% total pullout resistance [25]. However, the bearing resistance of the reinforcement used in this study had about 33%-66% in total pullout resistance according to the number of transverse members, meaning that friction and bearing resistance were evenly distributed. Therefore, the reinforcement used in this study can solve problems of existing reinforcement, such as those in the welding of welded steel grids and geogrid junctions after construction. In the case of more than two transverse members, pullout resistance was affected by the distance between transverse members, as mentioned in Section 2.3. Figure 8 shows the relationship between bearing bond coefficient and normal stress for PS1-1, PS2-1, and PS3 considering the interference effect, which is calculated using Equation (12), and pullout force at 50 mm front displacement. The bearing bond coefficient was greatly reduced with a decrease in the number of transverse members in lower normal stress conditions.