# Centrifugal Model Study of Seepage and Seismic Behavior in a Homogeneous Reservoir Dam with Parapet
## 3 Results and Discussion  
### Deformation Shape and Displacement  
Considering overtopping failure is related to the embankment state, deformation was observed inside the embankment zone along the parapet and dam crest. Figures 6 and 7 show the conditions without and with a parapet, respectively. In Figure 6a, only the upstream flood water level (h = 11 cm) is set as the initial condition of the model dam; Figure 6b illustrates the condition in which only seepage is applied under 50 G; Figure 6c depicts the condition in which an earthquake with an acceleration of 1.0 (m/s) is applied after penetration; Figure 6d shows the condition of seepage after the earthquake. Figure 5: Input seismic motion. In the EMB model, as with the first seepage mode, a deformation of 3 mm depth was evident in the downstream dam crest, indicating vulnerability at the top of the downstream slope. In the seismic mode, a settlement of 8-13 mm occurred from the center of the dam crest to the top of the downstream slope, indicating the widening of the vulnerable area formed in the first seepage mode. As the top of the downstream slope was located at the narrow cross-sectional area, it may have been vulnerable to hydraulic pressure or seismic stress. In the second seepage mode, it extended to 73.3% of the embankment height, i.e., the depth from the dam crest (32 mm), along the crack axis formed in the seismic mode. Additionally, a crack depth of approximately 20 mm was observed in the center of the downstream slope. These findings suggest that after an earthquake, the dam body may experience accelerated durability degradation, leading to conditions in which cracks can easily expand, which could significantly threaten the stability of earth dams if left without any maintenance. The first seepage mode in the parquet model was similar to that in the EMB model, as a slight deformation of 3-4 mm depth was evident at the top of the downstream slope. However, deformation was not observed in seismic mode, indicating a large difference from the EMB model. These results suggest that the parquet's weight acted on the dam crest and suppressed the deformation. Additionally, no other cracks or deformations were observed in the second seepage mode; therefore, it is believed that the effect of parquet weight also suppressed penetration. The deformation results suggest that the top of the downstream slope is vulnerable to pore water pressure and earthquakes. The displacement  
Figure 6: EMB model deformation: (**a**) initial mode, (**b**) 1 st seepage mode, (**c**) seismic mode, and (**d**) 2 nd seepage mode (unit: mm). Figure 7: Parquet model deformation: (**a**) initial mode, (**b**) 1 st seepage mode, (**c**) seismic mode, and (**d**) 2 nd seepage mode (unit: mm). of the model dam, presented in Figure 8, was computed using DIPP-Motion V image analysis software. Displacement calculations were performed for Section A (downstream slope), B (dam crest), and C (upstream slope), as shown in the figure, with the maximum displacement values for each section listed in Table 3.  
The upstream slope of the EMB model experienced a settlement of 11-14 mm, which remained constant until the seismic and second seepage modes. In contrast, the parapet model exhibited minimal displacement in all modes, probably due to the weight of the structure slowing down the seepage rate. During the seismic mode, the dam crest of the EMB model experienced a rapid increase in settlement resulting in a displacement more than twice that of the first seepage mode. This displacement continued to increase after the earthquake, indicating the significant effect of earthquakes on the hydraulic deformation of the dam. During the experiment, the downstream slope swelled slightly in the transverse direction; however, the displacement due to earthquakes or pore water pressure was relatively small in all modes. In contrast, the parapet model exhibited a relatively stable tendency with a gentle increase in displacement in all modes.