# Investigation of Geotechnical Seismic Isolation Systems Based on Recycled Tire Rubber-Sand Mixtures
## 3 Results and Discussions
### Ground Motions Selection
The Fourier amplitude ratio for the isolation layer containing 5% granular rubber and subjected to a confining pressure of 50 kPa, applied at thicknesses of 1, 2, and 3 m is shown in Figure 19, with a summary of these results provided in Table 13.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline Shear Wave Velocity of Clay & & & 200 \\ Soil Layer (m/s) & & & & \\ \hline Profile Depth (m) & 20 & 19 & 18 & 17 \\ \hline Isolation (m) & 0 & 1 & 2 & 3 \\ \hline Shear Wave Velocity of & - & 196.09 & 196.09 & 196.09 \\ Isolation Layer (m/s) & - & 6.59 & 6.59 & 6.59 \\ \hline Initial Damping Ratio (\%) & - & 2.498 & 2.495 & 2.493 \\ \hline Natural Frequency (Hz) & 2.5 & 0.4004 & 0.4008 & 0.4012 \\ \hline Natural Period (s) & 0.4 & \multicolumn{2}{c}{0.4004} & \multicolumn{2}{c}{0.4012} \\ \hline \multirow{3}{*}{Earthquake} & \multirow{3}{*}{EL (Hz)} & \%5-100 kPa 1 Amp. Ratio (\%) & Damping Ratio (\%) & \%5-100 kPa 3 Amp. Ratio (\%) & Damping Ratio (\%) \\ \cline{1-1} \cline{3-  
The Fourier amplitude ratio for the isolation layer containing 0% granular rubber and subjected to a confining pressure of 100 kPa, applied at thicknesses of 1, 2, and 3 m is shown in Figure 20, with a summary of these results provided in Table 14. \begin{table}
\begin{tabular}{c c c c c} \hline \hline Shear Wave Velocity of Clay & & & 200 \\ Soil Layer (m/s) & & & \\ \hline Profile Depth (m) & 20 & 19 & 18 & 17 \\ \hline Isolation (m) & 0 & 1 & 2 & 3 \\ \hline Shear Wave Velocity of & - & 155.45 & 155.45 & 155.45 \\ Isolation Layer (m/s) & - & 5.80 & 5.80 & 5.80 \\ \hline Natural Frequency (Hz) & 2.5 & 2.465 & 2.43 & 2.397 \\ \hline Natural Period (s) & 0.4 & 0.4057 & 0.4115 & 0.4175 \\ \hline \multirow{2}{*}{Earthquake} & \multirow{2}{*}{EL (Hz)} & \%5-50 kPa & Damping & \%5-50 kPa 2 m Amp. & Damping \%8-50 kPa 3 m Amp. & Damping \%8-50 kPa Ratio (Hz) \\  & & & & \\ \hline ChiChi & 3.702 & 3.210 & \(-\)13.29\% & 3.187 & \(-\)13.91\% & 3.158 & \(-\)14.69\% \\ \hline Coyote & 4.056 & 3.566 & \(-\)12.08\% & 3.547 & \(-\)12.55\% & 3.533 & \(-\)12.89\% \\ \hline Imp. Valley & 3.873 & 3.379 & \(-\)12.75\% & 3.355 & \(-\)13.37\% & 3.336 & \(-\)13.87\% \\ \hline Kocaeli & 4.200 & 3.748 & \(-\)10.76\% & 3.774 & \(-\)10.14\% & 3.802 & \(-\)9.48\% \\ \hline \multicolumn{3}{c}{Mean Value} & \multicolumn{3}{c}{\(\mathbf{-12.22\%}\)} & \multicolumn{3}{c}{\(\mathbf{-12.49\%}\)} & \multicolumn{3}{c}{\(\mathbf{-12.73\%}\)} \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Table of dominant frequencies based on the measured Fourier amplitude ratio for the isolation layer composed of sand containing 5% rubber content (\(\sigma_{0}\) = 50 kPa). Figure 19: Fourier amplitude ratio for the ChiChi, Coyote, Imperial Valley, and Kocaeli earthquakes with the isolation layer composed of sand containing 5% rubber content and subjected to a confining pressure of 50 kPa. The Fourier amplitude ratio for the isolation layer containing 0% granular rubber and subjected to a confining pressure of 50 kPa, applied at thicknesses of 1, 2, and 3 m is shown in Figure 21, with a summary of these results provided in Table 15.