# Investigation of Geotechnical Seismic Isolation Systems Based on Recycled Tire Rubber-Sand Mixtures
## 3 Results and Discussions
### Ground Motions Selection
\begin{table}
\begin{tabular}{c c c c c c} \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 & & - & 243.15 & 243.15 & 243.15 & 243.15 \\ Isolation Layer (m/s) & & & & & \\ \hline Initial Damping Ratio (\%) & - & 9.38 & 9.38 & 9.38 & 9.38 \\ \hline Natural Frequency (Hz) & 2.5 & 2.522 & 2.545 & 2.568 & \\ \hline Natural Period (s) & 0.4 & 0.3965 & & 0.3929 & 0.3894 \\ \hline Earthquake & EL PSA (g) & \%0–100 kPa 1 m PSA (g) & Damping Ratio (\%) & \%0–100 kPa 2 m PSA (g) & \%0–100 kPa 3 m PSA (g) & Damping Ratio (\%) \\ \hline ChiChi & 1.574 & 1.382 & \(-12.20\%\) 1.378 & \(-12.45\%\) 1.366 & \(-13.21\%\) \\ \hline Coyote & 0.915 & 0.848 & \(-7.32\%\) 0.804 & \(-12.13\%\) 0.767 & \(-16.17\%\) \\ \hline Imp. Valley & 1.162 & 1.087 & \(-6.45\%\) 1.026 & \(-11.70\%\) 0.996 & \(-14.29\%\) \\ \hline Kocaeli & 1.176 & 1.038 & \(-11.73\%\) 0.983 & \(-16.41\%\) 0.929 & \(-21.00\%\) \\ \hline Mean Value & & \(\mathbf{-9.43\%}\) & & \(\mathbf{-13.17\%}\) & & \(\mathbf{-16.17\%}\) \\ \hline \end{tabular}
\end{table} 
Table 8: Measured maximum response spectrum acceleration in the condition where the isolation layer is composed of sand containing 0% rubber content (\(\sigma_{0}=100\) kPa). Figure 14: Ground response spectrum for the ChiChi, Coyote, Imperial Valley, and Kocaeli earthquakes with the isolation layer composed of sand containing 0% rubber content and subjected to a confining pressure of 100 kPa. The Fourier amplitude ratio for the isolation layer containing 10% granular rubber and subjected to a confining pressure of 100 kPa, applied at thicknesses of 1, 2, and 3 m is shown in Figure 16, with a summary of these results provided in Table 10. \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) & - & 192.77 & 192.77 & 192.77 \\ \hline Initial Damping Ratio (\%) & - & 6.23 & 6.23 & 6.23 \\ \hline Natural Frequency (Hz) & 2.5 & 2.495 & & 2.491 & 2.486 \\ \hline Natural Period (s) & 0.4 & 0.4008 & & 0.4015 & 0.4023 \\ \hline Earthquake & EL PSA (g) & \(\frac{\%\text{0}-50\,\text{kPa}}{1\,\text{mPSA (g)}}\) & Damping & \(\frac{\%\text{0}-50\,\text{kPa}}{2\,\text{mPSA (g)}}\) & Damping & \(\frac{\%\text{0}-50\,\text{kPa}}{3\,\text{mPSA (g)}}\) & Damping \\  & 1 m PSA (g) & Ratio (\%) & 2 m PSA (g) & Ratio (\%) & 3 m PSA (g) & Ratio (\%) \\ \hline ChiChi & 1.574 & 1.382 & \(-12.20\%\) & 1.373 & \(-12.77\%\) & 1.373 & \(-12.77\%\) \\ \hline Coyote & 0.915 & 0.849 & \(-7.21\%\) & 0.793 & \(-13.33\%\) & 0.773 & \(-15.52\%\) \\ \hline Imp. Valley & 1.162 & 1.088 & \(-6.37\%\) & 1.007 & \(-13.34\%\) & 1.001 & \(-13.86\%\) \\ \hline Kocaeli & 1.176 & 1.043 & \(-11.31\%\) & 0.985 & \(-16.24\%\) & 0.968 & \(-17.69\%\) \\ \hline Mean Value & & \(\mathbf{-9.27\%}\) & & \(\mathbf{-13.92\%}\) & & \(\mathbf{-14.96\%}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Measured maximum response spectrum acceleration in the condition where the isolation layer is composed of sand containing 0% rubber content (\(\sigma_{0}=50\) kPa). Figure 15: Ground response spectrum for the ChiChi, Coyote, Imperial Valley, and Kocaeli earthquakes with the isolation layer composed of sand containing 0% rubber content and subjected to a confining pressure of 50 kPa. The Fourier amplitude ratio for the isolation layer containing 10% granular rubber and subjected to a confining pressure of 50 kPa, applied at thicknesses of 1, 2, and 3 m is shown in Figure 17, with a summary of these results provided in Table 11.