## 4 Design of Jet Columns
The values obtained were 2.71 MPa and 4.51 MPa for the X64 and X71 series specimens, respectively. These values are 3-4 times higher than the design value of 1 MPa. In order to control the obtained values, the relationships between unit weight, P-wave velocity, and uniaxial compressive strength were checked. Linear, exponential, power, and logarithmic regression functions were tried, and the function with the highest correlation coefficient was selected. The relationship between P-wave velocity and uniaxial compressive strength (UCS) is shown in Figure 9a. A linear and relatively high relationship was obtained between P-wave velocity and unit weight, as shown in Figure 9b. This is explained by the linear increase in the elastic wave velocity with increasing material density. Finally, the relationship between unit weight and uniaxial compressive strength was investigated (Figure 9c). As can be seen in Figure 9c, a linear relationship with a high-correlation coefficient was obtained between unit weight and uniaxial compressive strength. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Jet No.**} & \multirow{2}{*}{\begin{tabular}{c} **Length of** \\ **the Jet-** \\ **Column** \\ **(m)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Depth of** \\ **the Water** \\ **(m)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Injection** \\ **Pressure** \\ **(bar)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Injection** \\ **Flow Rate** \\ **(L/min)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Withdrawal** \\ **Speed** \\ **(cm/min)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Amount of** \\ **(kg)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Amount of** \\ **Cement** \\ **(kg)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Length of** \\ **Corem** \\ **Samples** \\ **(m)** \\ \end{tabular} } \\ \hline TC-19 & 10.3 & 7.20 & 430 & 54 & 35 & 5000 & 2500 & 1.5 \\ TC-26 & 10.1 & 7.40 & 440 & 54 & 40 & 4667 & 2334 & 10.1 \\ TC-35 & 10.3 & 7.40 & 420 & 53 & 40 & 4400 & 2200 & 10.3 \\ TC-37 & 10.3 & 7.30 & 440 & 54 & 40 & 4450 & 2225 & 4.5 \\ TC-38 & 10.4 & 7.30 & 420 & 53 & 35 & 4600 & 2300 & 10.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: General information on the trial jet columns. Figure 8: Drilling and core sampling on trial jet columns. When the results were examined, it was found that the X64 series specimens yielded relatively lower parameters than the X71 series specimens. When the jet grouting parameters were considered, almost the same amount of cement was used during the construction of both wells (Table 4). In addition, while the injection pressure was 420 bar in the construction of the column where X71 samples were obtained, the injection pressure was 440 bar in the construction of the column where X64 samples were obtained. However, one of the most important parameters affecting jet columns is soil properties. However, since the site is the seabed, the ground shows homogeneity in terms of geotechnical properties. Therefore, in this evaluation, it will not be an erroneous evaluation to accept the soil properties as constant. Hence, the most important parameter that draws attention here is the withdrawal speed. The 35 cm/min withdrawal speed provided a much higher performance than the 40 cm/min withdrawal speed. However, with both 35 cm/min withdrawal speed and 40 cm/min withdrawal speeds, values well above the desired values were obtained. As a result, it is understood that at least a 420 bar injection pressure, 40 cm/min withdrawal speed, and a 1:1 cement/water ratio meet the necessary conditions in terms of project design.