# Centrifugal Model Study of Seepage and Seismic Behavior in a Homogeneous Reservoir Dam with Parapet
## 3 Results and Discussion
### Pore-Water-Pressure Variation  
The results of the deformation, displacement, and crack depth of the body and the dam crests show that the pore water pressure after an earthquake is critical for stability. Consequently, a comparison was conducted for pore-water-pressure changes in the embankment before and after the earthquake. In particular, the pore water pressure from reaching 50 G in each mode to the point at which 50 G ended (15 min) was compared for the EMB and parapet models. Figure 12 illustrates the comparison results for the pore water pressure between the EMB and parapet models.  
In this comparison, the pore water pressure of the upstream side (P4) of the first seepage mode was the same. However, in the EMB model, the pore water pressure at the center of the embankment (P3) and the downstream side (P2) was relatively lower, whereas the slope end (P1) was relatively higher. This result is attributed to the relatively lower pore water pressure at P3 and P2 as the EMB model infiltrated to the end of the slope in the first seepage mode.  
The increase in P1 indicates that seepage water in the embankment rapidly reached the slope end. In the parapet model, P1 showed a remarkably low pore water pressure, indicating that the seepage rate at the end of the slope was relatively slow during the same time, with the infiltration progress inhibited by the parapet's weight.  
In the second seepage mode, both the EMB and parapet models exhibited pore-water-pressure change patterns similar to the first seepage mode for P4, P3, P2, and P1. However, the pore-water-pressure levels increased for all, compared to the first seepage mode. Thus, it can be considered that the pore water pressure measured in the first seepage mode increased after the earthquake, in which the dam body changed to a more porous condition. The only difference between the first and second seepage modes was the change in pore water pressure for P4. In the second seepage mode, P4 of the EMB model showed a relatively lower pore water pressure than that of the parapet model. This result suggests that infiltration in the embankment progressed rapidly in the EMB model, despite the increase in pore water pressure in both the EMB model and the parapet model.  
In contrast, in the parapet model, P4 and P3 showed an increase in pore water pressure of 6-8 kPa compared to the first seepage mode, whereas P2 and P1 showed an increase of 2-3 kPa, with the change in pore water pressure considered insignificant. As a result, the parapet model was found to have a suppressing effect on seepage flow in the dam body after an earthquake. The slope end is an area where the self-weight of the embankment is  
Figure 12: Comparison of pore water pressure between the EMB and parapet models: (**a**) 1 st seepage mode and (**b**) 2 nd seepage mode.  
relatively small due to the trapezoidal shape of the embankment, making it a structurally vulnerable area for erosion. As the parquet induces low pore water pressure at the end of the slope, it provides a reinforcing effect in terms of disaster prevention.