# 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 \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) & - & 152.14 & 152.14 & 152.14 & \\ \hline Initial Damping Ratio (\%) & - & 9.91 & 9.91 & 9.91 & \\ \hline Natural Frequency (Hz) & 2.5 & 2.461 & & 2.424 & 2.387 \\ \hline Natural Period (s) & 0.4 & 0.4063 & & 0.4126 & 0.4189 \\ \hline Earthquake & EL PSA (g) & \begin{tabular}{c} \%10–100 kPa \\ 1 m PSA (g) \\ \end{tabular} & \begin{tabular}{c} Damping \\ Ratio (\%) \\ \end{tabular} & \begin{tabular}{c} \%10–100 kPa \\ 2 m PSA (g) \\ \end{tabular} & \begin{tabular}{c} Damping \\ Ratio (\%) \\ \end{tabular} & \
\begin{tabular}{c} \%10–100 kPa \\ 3 m PSA (g) \\ \end{tabular} &
\begin{tabular}{c} Damping \\ Ratio (\%) \\ \end{tabular} \\ \hline ChiChi & 1.574 & 1.395 & \(-11.37\%\) & 1.380 & \(-12.33\%\) & 1.377 & \(-12.52\%\) \\ \hline Coyote & 0.915 & 0.869 & \(-5.03\%\) & 0.846 & \(-7.54\%\) & 0.825 & \(-9.84\%\) \\ \hline Imp. Valley & 1.162 & 1.116 & \(-3.96\%\) & 1.083 & \(-6.80\%\) & 1.052 & \(-9.47\%\) \\ \hline Kocali & 1.176 & 1.067 & \(-9.27\%\) & 1.067 & \(-9.27\%\) & 1.055 & \(-10.29\%\) \\ \hline Mean Value & & \(-\mathbf{7.41\%}\) & & \(-\mathbf{8.98\%}\) & & \(-\mathbf{10.53\%}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Measured maximum response spectrum acceleration in the condition where the isolation layer is composed of sand containing 10% rubber content (\(\sigma_{0}\) = 100 kPa). Figure 10: Ground response spectrum for the ChiChi, Coyote, Imperial Valley, and Kocali earthquakes with the isolation layer composed of sand containing 10% rubber content and subjected to a confining pressure of 100 kPa. Ground response spectra for the isolation layer containing 5% granular rubber and subjected to a confining pressure of 100 kPa, applied at thicknesses of 1, 2, and 3 m are shown in Figure 12, with a summary of these results provided in Table 6.  
Figure 11: Ground response spectrum for the ChiChi, Coyote, Imperial Valley, and Kocaeli earthquakes with the isolation layer composed of sand containing 10% rubber content and subjected to a confining pressure of 50 kPa. \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) & - & 120.61 & 120.61 & 120.61 & \\ \hline Initial Damping Ratio (\%) & - & 4.07 & 4.07 & 4.07 & \\ \hline Natural Frequency (Hz) & 2.5 & 2.42 & 2.346 & 2.275 & \\ \hline Natural Period (s) & 0.4 & 0.4132 & & 0.4263 & 0.4395 \\ \hline Earthquake & EL PSA (g) & \begin{tabular}{c} \%10-50 kPa \\ 1 m PSA (g) \\ \end{tabular} & \begin{tabular}{c} Damping \\ Ratio (\%) \\ \end{tabular} & \begin{tabular}{c} \%10-50 kPa \\ 2 m PSA (g) \\ \end{tabular} & \begin{tabular}{c} Damping \\ Ratio (\%) \\ \end{tabular} & \
\begin{tabular}{c} \%10-50 kPa \\ 3 m PSA (g) \\ \end{tabular} &
\begin{tabular}{c} Damping \\ Ratio (\%) \\ \end{tabular} \\ \hline ChiChi & 1.574 & 1.397 & \(-\)11.25\% & 1.388 & \(-\)11.82\% & 1.399 & \(-\)11.12\% \\ \hline Coyote & 0.915 & 0.872 & \(-\)4.70\% & 0.854 & \(-\)6.67\% & 0.842 & \(-\)7.98\% \\ \hline Imp. Valley & 1.162 & 1.119 & \(-\)3.70\% & 1.092 & \(-\)6.02\% & 1.072 & \(-\)7.73\% \\ \hline Kocaeli & 1.176 & 1.087 & \(-\)7.57\% & 1.141 & \(-\)2.98\% & 1.205 & 2.47\% \\ \hline Mean Value & & \(-\)**6.80\%** & & \(-\)**6.87\%** & & \(-\)**6.09\%** \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Measured maximum response spectrum acceleration in the condition where the isolation layer is composed of sand containing 10% rubber content (\(\sigma_{0}\) = 50 kPa).