# Dynamic Response and Geogrid Strain Analysis of GRS Retaining Wall
## 3 Test Results and Analysis  
### Lateral Deformation of Wall Facing  
Figure 7 shows the variation in lateral displacement of the GRS retaining wall panel under dynamic load versus wall height \(H\), where the equal amplitude loading retains only the lateral displacement at 8 Hz except for the dynamic load of 190 \(\pm\) 10 kN. From the figure, it can be seen that the lateral displacement of the retaining wall increases with the increase in the peak load and finally reaches the limit state. Numerous test results have been obtained worldwide showing that the retaining wall deforms more under dynamic load compared to static load. This is due to the fact that the impact of the loading plate on the soil below is more violent under dynamic load, the repeated tension and relaxation of the uppermost geogrid make the embedded locking effect between the geogrid and the soil particles not strong under static load, which will affect the restraint effect of the geogrid on the horizontal direction of the upper soil. During the loading process, the two groups of test geogrids were arranged in the same way, but the damage patterns were obviously different. In the case of constant amplitude, the lateral displacement of the facing panels in Figure 7a was \"wall facing outward curved\", and the deformation range was between 0.4\(H\) and 0.95\(H\) of the retaining wall. The authors concluded that the lower amplitude dynamic load makes the reinforced soil structure denser through vibration and strengthens the soil integrity, so that the GRS retaining wall can withstand higher peak dynamic loads, and with the increase in the peak dynamic load, the lateral additional stress in the middle of the retaining wall gradually increases [37], and finally leads to bulging damage of the retaining wall. As shown in Figure 7b, the lateral displacement of the facing panel is \"wall facing outward tilt\" at constant frequency,  
Figure 6: Dynamic load loading method. (**a**) Equal amplitude loading. (**b**) Equal frequency loading. Figure 7: Lateral deformation of wall facing. (**a**) Equal amplitude loading. (**b**) Equal frequency loading. and the lateral displacement is maximum at 0.83\(H\). The reason is that during the loading process, the increase in dynamic load amplitude makes the impact of the loading plate on the reinforced soil structure intense, and the uppermost layer of the geogrid is repeatedly tensioned and relaxed, thus the embedded locking effect between the geogrid and soil particles is weakened. With the increase in peak dynamic load, the loading plate gradually sinks, so that the soil below the loading plate spreads to both sides, and the extruded soil imposes additional lateral additional stress on the upper panels. This is the main reason for the increasing lateral displacement of the upper panels of the retaining wall, which is expressed as \"wall facing outward tilt\". In addition, from the results of this test, among the two wall damage modes, the ultimate bearing capacity of \"wall facing outward curved\" is 1.5 \(\times\) 10\({}^{3}\) kPa (\(F\) = 170 \(\pm\) 10 kN) higher than that of \"wall facing outward tilt\" of 1.08 \(\times\) 10\({}^{3}\) kPa (\(F\) = 70 \(\pm\) 60 kN). The authors believe that the role of the panel is mainly to ensure the local stability of the fill near the panel, the deformation mode of \"wall facing outward curved\" is multiple panels to bear the deformation, which can improve the bearing capacity, while the stress of \"wall facing outward tilt\" is concentrated in the upper part of the retaining wall, leading to the reduction in bearing capacity. Figure 8 shows the relationship between the lateral displacement of the facing panels and the magnitude and frequency of the dynamic load. From the figure, it can be seen that the lateral displacement is influenced more by the peak dynamic load and less by the frequency and the number of load cycles, and continuing to increase the average dynamic load will increase the effect of frequency on the lateral displacement.