# Junction Properties Interpretation of Textile Geogrids Using Multi-Junction Clamp
## 4 Results and Discussion  
### Optimization of Geogrid Multi-Junction Strength Evaluation  
Table 3 shows the test results of single-junction strength classified by grip position. In the GRI test method, the upper grip position is as close as possible to the vertical center rib. However, this newly developed test method recommends the upper grip position in the middle of the vertical center rib. The values of single-junction strength tested by the newly developed method are less than those tested according to GRI GG-2 for woven and warp knitted types. The values of elongation displayed in an opposite trend. GRI \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Properties** & **Single-Junction** & **Multi-Junction** & **Single Tensile** & **Wide-Width** \\  & **Test** & **Test** & **Test** \\ \hline Scale effect & Unconsidered & Considered & Unconsidered & Considered \\ Slip & Unconsidered & Unconsidered & Considered & Considered \\ Strain rate & 70 & 70 & 70 & 70 \\ (mm/min) & (20, 50,100) & (20, 50, 100) & 70 & 70 \\ Specimen width & 1 rib & 1-8 rib & \\ Specimen length & 300 & 300 & 300 & \\ (mm) & (50, 100, 150) & (50, 100, 150) & 300 & 300 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Specifications of test conditions. GG-2 determines the specimen in an ideal condition in order to investigate the maximum junction strength. However, in soil geogrid cross rib suffers variable curvature ribbing, and the peak of the curvature is the center bearing rib. Therefore, gripping the center of the cross rib is more appropriate to represent actual utilizing condition. As with the single-junction test, the average junction strength per one rib and the geogrids junction strength per unit width are also calculated by using multi-junction test results. Firstly, geogrids which have 1-8 junctions were tested and curves of junction strength to number of junction were plotted. Secondly, normalized values of junction strength were calculated for each sample. Figure 3 shows the junction strength plotted against the number of junctions in different specimen length. Results of junction strength were carried out with different lengths showing that there was no change in junction strength at rupture point because woven and warp knitted materials contained PET filament. Therefore, in order to derive precise data, the same conditions except for specimen length were summarized and analyzed. Figure 4 shows the results of regression analysis on the number of junctions versus junction strength with strain rate of geogrids. For woven type geogrids, all the plots were divided uniformly and the curves showed the same trend. Hence, the data have good reliability. Junction strength for geogrids were linearly increased with the numbers of junction and fitting was excellent with an R-squared value greater than 0.99. The difference \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Geogrid**} & \multirow{2}{*}{**Value**} & \multicolumn{2}{c}{**20 mm/min**} & \multicolumn{2}{c}{**50 mm/min**} & \multicolumn{2}{c}{**100 mm/min**} \\ \cline{3-8}  & & **GRI** & **New** & **GRI** & **New** & **GRI** & **New** \\ \hline \multirow{2}{*}{W-GG-2} & \(\mathrm{J}_{\mathrm{single}}\) (kgf) & 19.2 & 18.5 & 19.8 & 18.8 & 20.4 & 19.7 \\  & Elongation (mm) & 3.9 & 4.1 & 4.2 & 4.3 & 4.2 & 4.2 \\ \multirow{2}{*}{WK-GG-2} & \(\mathrm{J}_{\mathrm{single}}\) (kgf) & 39.1 & 37.7 & 39 & 38 & 39.6 & 38 \\  & Elongation (mm) & 7.0 & 7.4 & 6.4 & 7.4 & 6.6 & 7.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Single-junction test results by grip position. Figure 3: Regression analysis for the number of junctions versus junction strength with specimen length for geogrids. is considered to be caused by scale effect and variation in the difference of manufactured product. For warp knitted geogrids, each normalized value is less than the value tested by single-junction test because of scale effect. The figure illustrates that junction strength strongly depends on junction number.