## 5 Field Test Results and Discussion
\[\text{ARR}=\frac{\text{Maximum spectral amplitude before isolation}}{\text{Maximum spectral amplitude after isolation}} \tag{4}\]  
\[\text{VMP}=(1-\text{ARR})\times 100 \tag{5}\]  
In this study, the maximum spectral amplitudes used to calculate the vibration attenuation performance through ARR values are derived from the recorded acceleration data's  
Figure 24: Comparative acceleration–time responses of a single impact test for each accelerometer. absolute maximum values (PGA), the absolute maximum value of velocity obtained by integrating the acceleration data once (PGV), and the absolute maximum value of displacement obtained by integrating the acceleration data twice (PGD). However, to accurately assess vibration performance, it is essential to reduce the standard deviation between the maximum amplitudes of vibrations produced by the hammer impact, meaning that the maximum acceleration amplitude of the load source must be equalized for all conditions, and the vibration attenuation performance must be generalized by averaging multiple data points. In this context, the PGA, PGV, and PGD amplitudes obtained from the accelerometer located immediately in front of the load source (M129) were adjusted to be of the same magnitude in all directions. For example, the PGA values of all impacts in the EW direction for the M129 accelerometer are averaged. This average PGA magnitude is then divided by the PGA magnitude of each individual impact in the same direction and on the same accelerometer. The resulting coefficients, calculated specifically for each impact, are multiplied by the PGA values obtained from both M129 and the other accelerometers for that impact. This process ensures that the acceleration data for each impact in the direction of interest is adjusted according to the amplitude generated by the same load source. The described procedures were also performed for all other directions and maximum spectral magnitudes. Both due to the large amount of data and to provide a clearer understanding of the adjustments made, the data in Figure 24 were adjusted and presented in Figure 25.  
An example of the procedure applied to organize the vibration data as if they originated from the same load source is given in Figure 25 as an acceleration-time response. When examining all three directions, it is observed that the vibrations reach their peak amplitudes of equal magnitude within a short period (0.01-0.02 s) and then decay within a short time with similar attenuation trends. These characteristics are similarly close for all spectral magnitudes in other impacts as well. Although the isolation performance of the vibration data will be detailed in terms of spectral magnitudes in the section below, some general conclusions can be drawn from the acceleration-time relationships in Figure 25. The first of these is that, especially in the NS direction, the vibration amplitudes measured immediately behind the barrier are lower compared to the no-barrier condition. This indicates that the barriers significantly reduce vibrations. Additionally, it was found that barriers with different characteristics cause differences in the behavior of time-dependent acceleration vibrations. Another observation is that the vibration amplitudes obtained from the accelerometers decrease as the distance from the load source increases, due to both the barrier and the damping effect of the soil relative to the distance. Secondly, the averages of the adjusted spectral magnitudes from the impact tests were calculated for each direction of each test condition, resulting in the average spectral magnitudes. After obtaining the spectral magnitudes, the ARR values were computed using Equation (4) and are presented in Figure 26.  
Figure 24.0 Cont. Figure 24.1 Comparative of normalized acceleration\(-\)time responses for each accelerometer. Figure 26 shows that the BCCB Trench and the Styrofoam-filled BCCB Trench provide a minimum of approximately 50% improvement in overall vibration reduction performance across all cases.