# Analysis of Multilayered Ground Amplification Characteristics by Scaled-Down Model Tests
## 2 Materials and Methods
### Model Construction and Experimental Procedures  
In this study, the amplification characteristics of acceleration have been investigated for the flat ground model with multilayered soils. The cross-section and accelerometer location of the model ground created in this experiment are illustrated in Figure 4. The two layers consisted of loose and dense ground, respectively, and the height of each layer was 0.3 m. The upper ground was formed relatively loosely with a unit weight of 14.72 kN/m\({}^{3}\) using sampling soils, and the lower ground was densely formed with a unit weight of 19.6 kN/m\({}^{3}\) using mixing samples. In order to confirm the change in the amplification characteristics between the two layers, accelerometers were buried 5 cm apart from the ground floor to the surface at the center, which was considered to best simulate the free field behavior. However, if the accelerometer is buried on only one axis at an interval of 5 cm, the gap between the instruments is too short to disturb the ground or measure distorted signals. Therefore, it was alternately buried on two axes, 5 cm away from the center axis and center axis.  
The input seismic wave was selected from the sine wave, sine sweep wave, and artificial seismic wave. As sine wave signals, the 10 Hz signals corresponding to the Peak ground acceleration of 0.2 g were used to confirm the basic characteristics of the flat  
Figure 4: The cross-section and accelerometer location of the flat ground.  
Figure 3: Acceleration capture instrument in this study: (**a**) Data logger; (**b**) Accelerometer.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter (Accelerometer)** & **Value** & **Parameter (Data Logger)** & **Value** \\ \hline
**Model** & ARF-20A & **Model** & SDL-350R \\
**Capacity** & 20 m/s\({}^{2}\) & **Number of channel** & 24 \\
**Rateped Output(RO)** & 0.5 mV/V & **Input Sensor** & 4 Gage \\
**Frequency Response Range** & DC–80 Hz & **Low Pass filter** & 10 Hz/100 Hz/1000 Hz/Pass \\
**Natural Frequency** & 150 Hz & **Measure Hz** & 200 Hz \\
**Allowable Temperature** & \(-\)10–50 \({}^{\circ}\)C & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Main parameters of accelerometer and data logger.  
model. A simple long-period sine 10 Hz wave was chosen so that resonance would not occur due to the natural period of the shaking table or box. The artificial seismic wave is a composite seismic wave combined with the Gyeongju-Pohang earthquake, using the empirical Green's function based on raw data measured at the Kori nuclear power plant. Since artificial seismic waves have different periodic components, high amplification occurs. There is also a sine sweep wave that provides waves containing any frequency from low to high frequencies. Seismic motion includes waves of various frequency bands from low to high frequencies. They are used to determine amplification characteristics that resonate with the natural frequencies of the ground. The acceleration-time history of the input seismic wave shaking table test above is shown in Figure 5.