# Dynamic Response and Geogrid Strain Analysis of GRS Retaining Wall
## 3 Test Results and Analysis
### Geogrid Strain  
The above sections mainly shows that the good engineering properties of GRS retaining walls depend mainly on the interaction between tendons and soils. However, under long-term loading, geogrids can deform and affect the working performance of GRS retaining walls [42; 43; 44; 45]. In order to study the mechanical response law of geogrids under the action of traffic load, three flexible displacement meters at different horizontal distances from the retaining wall panel were selected to record the geogrid strain, and the results are shown in Figures 9 and 10. It can be seen from the figure that along the height direction of the retaining wall from bottom to top, the distribution of geogrid strain shows a growing trend, and the peak dynamic load has a large effect on the geogrid strain, which is consistent with the trend of lateral displacement of the retaining wall. As the reinforcement depth increases,  
Figure 8: Variation in lateral displacement and frequency. the strain of the last layer of the geogrid is relatively small and does not give full play to the performance of the geogrid. This is consistent with the test law of [PERSON] et al. [46]. From Figures 9 and 10, at the connection position to the facing panels (C1-1 to C5-1), where the strain of the geogrid is mainly controlled by the horizontal displacement of the facing panels, the strain of the geogrid at the maximum lateral displacement is also maximum, but the strain is small. In addition, the soil near the facing is not easily compacted under the action of dynamic load, so the embedded ability of the geogrid to the surrounding soil is weak. Once there is a gap between the facing and the surrounding soil, the geogrid will bear the shear stress and stress concentration, which is caused by the uneven settlement of the soil, resulting in a large strain. This is extremely evident when the stress peaks reach 1 \(\times\) 10\({}^{3}\) kPa (\(P\) = 110 \(\pm\) 10 kN) (Figure 9) and 750 kPa (\(P\) = 50 \(\pm\) 40 kN) (Figure 10). This mechanical behavior at the location of the connection between the panel and the geosynthetic material is in general agreement with the \"stress concentration-separation-deformation\" phenomenon of [PERSON] et al. [47]. Below the loading plate (C1-2 to C5-2), the strain of the geogrid increases with the increase in the peak load. As can be seen from Figure 10, when keeping the peak load constant and changing the average value and amplitude of the load, almost no strain occurs in the geogrid in the soil, indicating that the strain in the geogrid is mainly affected by the peak load. In addition, the mechanical response of the geogrid under both loading methods was maximum at C1-2, and the maximum value of geogrid strain reached 4.5% and 3.6%,  
Figure 9: Geogrid strain (equal amplitude loading). (**a**) Connection position to the facing panels. (**b**) Below the loading plate. (**c**) Anchorage position. indicating that the actual tensile stress on the geogrid did not reach its tensile strength. [PERSON] et al. (2018), through a field test of a geogrid GRS retaining wall for a passenger line, measured that the tensile force of the geogrid during service is much less than its tensile strength value, and the maximum strain accounts for less than 30% of the peak strain. However, despite this, the strain of the uppermost geogrid still accounts for more than 30% of the total strain, which means that the geogrid nearest to the loading plate takes on the main job of controlling settlement and plays an important role in the foundation bearing capacity and overall stability of the retaining wall. At the anchorage position in the geogrid (C1-3 to C5-3), the strains in all layers are not obvious except for the upper geogrid, where the strain tends to increase. The closer to the end of the geogrid, the smaller the reinforcement effect, so that the reinforced area and non-reinforced area forms an excess, not producing a large uneven settlement. In addition, the strain of the geogrid at C3-3 and C2-3 showed negative growth.