# Effect of Soil Box Boundary Conditions on Dynamic Behavior of Model Soil in 1 g Shaking Table Test
## 3 Analysis of 1 g Shaking Table Test Result
### Analysis of SA  
Ground response to the dynamic load varies with the natural frequency of the ground and the frequency of seismic vibration. The response spectrum is the maximum response to seismic vibration with different natural frequencies. When acceleration is defined as a response variable, it is called SA (Spectral Acceleration). SA shows the maximum response acceleration given by dynamic load to the vibration meter of different periods. Using this feature, it is possible to examine the amplification occurring in other frequency ranges for the dynamic load used in the actual test. Figure 10 shows the 5% damped response acceleration spectra measured by the accelerometer (acc6 shown in Figure 5) in the center of the soil box for 2 Hz sine wave of 0.07 g, 0.1 g and 0.154 g, as well as the artificial seismic wave. This aimed to examine the difference of amplification characteristics occurring in the center of each soil box. For 2 Hz of 0.07 g and 0.01 g, Figure 10a,b do not show a great difference between the soil boxes. Since the period of 2 Hz does not match the natural period of the soil box and the ground model, much amplification does not occur. For 2 Hz of 0.154 g, Figure 10c shows that the ground model of the flexible soil box and the soil box with the attached sponge did not react, but much amplification took place on the surface acceleration of the RB. This is due to the quite large magnitude of the earthquake load that caused unnecessary amplification. For 2 H of 0.154 g, Figure 10d shows the surface acceleration spectrum in vibration with artificial seismic waves, in which greater amplification occurs with height, to suggest clearer amplification differences between the soil boxes because the artificial seismic wave has different period components. The flexible soil box and the soil box with the attached sponge show similar amplification, but the soil box with the attached sponge showed slightly greater amplification, and major amplification periods were also similar. In contrast, the RB showed different major amplification periods from the flexible soil box and the soil box with the attached sponge, and showed greater amplification. Figure 11 shows acceleration spectra in the center and the wall of the soil box at the same depth for the artificial seismic wave shown in Figure 7d. Figure 11a-c show acceleration spectra for the RB with depths. The results show that the center has slightly higher amplification than the wall at the depths of 0.4 m and 0.2 m, and the center of the RB clearly has more amplification on the surface, exhibiting a very different spectrum from the wall. This indicates that that different amplification occurred in  
Figure 10: Surface acceleration spectrum by input motion: (**a**) Sine wave 2 Hz, 0.07 g; (**b**) Sine wave 2 Hz, 0.1 g; (**c**) Sine wave 2 Hz, 0.154 g; (**d**) Artificial seismic wave. the ground model. It appears that the shear wave reflected on the constrained rigid lateral boundary surface had an effect, as great PGA was measured in the center of the RB. Figure 11d-f show the 5% damped acceleration spectra for each depth of the LSB, showing almost the same spectrum in the center and the wall at the depths of 0.4 m and 0.2 m. In other words, the flexible soil box experienced the same acceleration amplification in the center and the wall, like free field behaviors of a semi-infinite half-space. However, the wall showed greater amplification than the center on the surface. When a dynamic load was used in the flexible soil box for vibration, most layers in the wall showed integrated behaviors with the ground model and simulated the behaviors of the semi-infinite half-space. However, because of no surcharge load, the wall in the top layer was affected significantly by inertia to make a difference from the behaviors of the model.