# 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 Peak Ground Acceleration  
PGA means the maximum acceleration at which the ground moves by means of dynamic load. In this study, the PGA was measured at the same depth in the center and the wall of the soil boxes to analyze acceleration distributions depending on the distance from the center of the model ground to the wall. As the ground acceleration at the same depth in the free field should be the same regardless of the distance, the effect of boundary conditions is evaluated by investigating whether the acceleration in the wall is different from that in the center of the soil box closer to the free field. Since the center acceleration in the soil box is not or little affected by the wave reflection, this acceleration was assumed to be the response acceleration occurring in the free field. The acceleration at the wall was measured from the location 5 cm apart from the wall. The level of bad effect of rigid boundary related to the resonance of the wall was evaluated with the PGA/ response spectrum at the center and end of the RB and the LSB.  
Figure 9 shows graphs depicting the peak ground acceleration for each depth of the ground model for various input motions shown in Figure 7. The graphs compare the PGA at the center and the wall in the soil box for each depth of the center, and the wall for each soil box. Almost no amplification was observed from the bottom to the top of the ground model in the wall of the RB, but a significant amplification was observed in the center, implying a great difference between them. Meanwhile, in the flexible soil box, the amplification in the center and the wall was shown to be very similar from the bottom to the top of the ground model. Where a sponge was attached to the rigid wall, greater amplification was observed at the wall than the center, regardless of the thickness of the sponge, and at the center a similar amplification was measured to that of the flexible soil box. In the RB, the lateral boundary was constrained to cause the model ground to have a motion different from the free field, and the reflected wave occurring in the wall caused different stresses, resulting in the excessive amplification in the center. The flexible soil box is considered to simulate the free field behavior of semi-infinite-half-space well to show the amplification factor similar at the same depth in  
Figure 8: Shear wave velocity measurement and result: (**a**) Shear wave velocity measurement; (**b**) Travel time of elastic wave obtained by using the Piezoelectric stack.  
the center and the wall of the soil box. While the sponge attached to the RB contributes to reducing the effect of boundary conditions of the RB so that the center can show similar amplification to the flexible soil box, the wall is affected by the boundary conditions to show different amplification from the center.  
Figure 9: Peak ground acceleration by input motions: **(a)** PGA of RB by Sine wave 2 Hz, 0.1 g; **(b)** PGA of LSB by Sine wave 2 Hz, 0.1 g; **(c)** PGA of sponge by Sine wave 2 Hz, 0.1 g; **(d)** PGA of RB by Sine wave 2 Hz, 0.154 g; **(e)** PGA of LSB by Sine wave 2 Hz, 0.154 g; **(f)** PGA of sponge by Sine wave 2 Hz, 0.154 g; **(g)** PGA of RB by Artificial seismic wave; **(h)** PGA of LSB by Artificial seismic wave; **(i)** PGA of sponge by Artificial seismic wave.