# Analysis of Multilayered Ground Amplification Characteristics by Scaled-Down Model Tests
## 3 Multilayered Flat Model Ground Test Results and Analysis
### Comparison of Numerical Analysis Results and Shaking Table Test Results  
The response data of the accelerometer buried deep in the center of the multilayered, flat ground model and the one-dimensional ground response analysis results were compared through the peak ground acceleration and spectral acceleration curves. Figure 14 compared the peak ground acceleration for each input wave. For the peak ground acceleration, it was confirmed that the experiment and numerical analysis results of each input seismic shaking were generally consistent, but acceleration obtained by numerical analysis was less than the experimental value at the top. This is considered to be because the acceleration at the top layer of the model increases due to resonance in the process of shear wave velocity measurement, which resulted in increase of shear wave velocity. During the hammer test, the soil layer in the soil box will settle to a certain extent due to gravity and shock, resulting in a decrease in height and an increase in frequency, which just produces an enhancement effect with part of the artificial seismic waves and sine sweep wave. The objective of this paper is to compare the variation and difference of acceleration amplification characteristics at different layer and inter-layer boundary. Therefore, the difference in PGA at the top layer does not greatly affect the comparison results and conclusions. Other than this, it seems that the PGA of the numerical analysis was predicted well. Figures 15-17 present the spectral acceleration amplification for the same input wave at different depths. Figure 15 exhibits the sine wave of each layer at 10 Hz between experiment and numerical analysis comparisons. As the depth is close to the surface, the value of spectral acceleration increases. Figure 15a-c shows that, from a depth of 0.2 m from the surface, as the height increases, the difference between the experimental results and the numerical analysis results keeps increasing and the SA of the experiment is always greater than that of the numerical analysis result. Figure 15d-f shows that the difference between the experiment results and the numerical analysis results is very close with a depth of 0.3 m.  
Figure 13: Normalized soil shear modulus and material damping ratio relationship. Figure 14: Peak ground acceleration from the bottom to the surface under different input waves by experiment results and numerical analysis results. Figure 15: (**a**) SA by sine 10 Hz wave at Surface; (**b**) SA by sine 10 Hz at 0.1 m depth; (**c**) SA by sine 10 Hz at 0.2 m depth; (**d**) SA by sine 10 Hz at 0.3 m depth; (**e**) SA by sine 10 Hz at 0.4 m depth; (**f**) SA by sine 10 Hz at 0.5 m depth. Figure 16 shows the sine sweep wave of each layer between experimental and numerical analysis comparisons. Figure 16a-f shows that, from bottom to the surface, as the height increases, the difference between the experiment results and the numerical analysis results keeps increasing and the SA of the experiment is always greater than that of the numerical analysis result. This trend is similar to what has been observed in the case of sine 10 Hz wave. Figure 17 compares the experimental results and analytical values of the 1 g shaking table at different depths when the seismic wave is applied. The figure also shows that the 1D ground response analysis values of response spectral acceleration predict the experimental values well. The depth 0.3 to 0.5 m corresponding to dense ground has almost the same experimental value and analytical value. The response spectral acceleration of the depth surface to 0.3 m, which simulated the loose ground, was somewhat different from that of the dense ground, but overall it simulated the amplification well and predicted the main amplification cycle well. However, on the surface of the soft soil, the numerical analysis value is amplified less than the experimental value.