# Investigation of Geotechnical Seismic Isolation Systems Based on Recycled Tire Rubber-Sand Mixtures
## 3 Results and Discussions
### Ground Motions Selection
Ground response spectra 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 are shown in Figure 13, with a summary of these results provided in Table 7. \begin{table}
\begin{tabular}{c 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 & & & & & \\ Isolation Layer (m/s) & - & 196.09 & 196.09 & 196.09 \\ \hline Initial Damping Ratio (\%) & - & 6.59 & 6.59 & 6.59 \\ \hline Natural Frequency (Hz) & 2.5 & 2.498 & & 2.495 & 2.493 \\ \hline Natural Period (s) & 0.4 & 0.4004 & & 0.4008 & 0.4012 \\ \hline \multirow{2}{*}{Earthquake} & \multirow{2}{*}{EL PSA (g)} & \%5–100 kPa & Damping & \%5–100 kPa & Damping & \%5–100 kPa & Damping \\  & & 1 m PSA (g) & Ratio (\%) & 2 m PSA (g) & Ratio (\%) & 3 m PSA (g) & Ratio (\%) \\ \hline ChiChi & 1.574 & 1.384 & \(-12.07\%\) & 1.374 & \(-12.71\%\) & 1.370 & \(-12.96\%\) \\ \hline Coyote & 0.915 & 0.857 & \(-6.34\%\) & 0.819 & \(-10.49\%\) & 0.789 & \(-13.77\%\) \\ \hline Imp. Valley & 1.162 & 1.100 & \(-5.34\%\) & 1.045 & \(-10.07\%\) & 1.005 & \(-13.51\%\) \\ \hline Kocaeli & 1.176 & 1.049 & \(-10.80\%\) & 1.009 & \(-14.20\%\) & 0.975 & \(-17.09\%\) \\ \hline \multicolumn{5}{c}{Mean Value} & \multicolumn{2}{c}{\(\mathbf{-8.64\%}\)} & \multicolumn{2}{c}{\(\mathbf{-11.87\%}\)} & \multicolumn{2}{c}{\(\mathbf{-14.33\%}\)} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Measured maximum response spectrum acceleration in the condition where the isolation layer is composed of sand containing 5% rubber content (\(\sigma_{0}=100\) kPa). Figure 12: Ground response spectrum 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 100 kPa. Ground response spectra 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 are shown in Figure 14, with a summary of these results provided in Table 8. \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 & & & & \\ Isolation Layer (m/s) & - & 155.45 & 155.45 & 155.45 \\ \hline Initial Damping Ratio (\%) & - & 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 PSA (g)} & \%5-50 kPa & Damping & \%5-50 kPa & Damping \\  & & 1 m PSA (g) & Ratio (\%) & 2 m PSA (g) & Ratio (\%) \\ \hline ChiChi & 1.574 & 1.385 & \(-12.01\%\) & 1.381 & \(-12.26\%\) & 1.378 & \(-12.45\%\) \\ \hline Coyote & 0.915 & 0.859 & \(-6.12\%\) & 0.825 & \(-9.84\%\) & 0.797 & \(-12.90\%\) \\ \hline Imp. Valley & 1.162 & 1.101 & \(-5.25\%\) & 1.054 & \(-9.29\%\) & 1.013 & \(-12.82\%\) \\ \hline Kocaeli & 1.176 & 1.060 & \(-9.86\%\) & 1.048 & \(-10.88\%\) & 1.039 & \(-11.65\%\) \\ \hline Mean Value & & \(\mathbf{-8.31\%}\) & & \(\mathbf{-10.57\%}\) & & \(\mathbf{-12.46\%}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Measured maximum response spectrum acceleration in the condition where the isolation layer is composed of sand containing 5% rubber content (\(\sigma_{0}=50\) kPa). Figure 13: Ground response spectrum 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. Ground response spectra 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 are shown in Figure 15, with a summary of these results provided in Table 9.