## 3 Results and Discussion
### Performance of the Soil Nail System
#### 3.2.2 Soil Nail Pull-Out Tests Employing Strain Gauge Sensors
\[\mathrm{B}=\frac{\mathrm{Hz}^{2}}{1000} \tag{6}\]  
The stress change in the sensor is given in Equation (7):  
\[\Delta\mu\epsilon=\mathrm{B_{f}}-\mathrm{B_{i}}*\mathrm{C_{f}}*\mathrm{G_{f}} \tag{7}\]  
where \(\Delta\mu\epsilon\) is the change in the micro-tensile value, \(\mathrm{B_{f}}\) is the final B value (the data logger output), \(\mathrm{B_{i}}\) is the initial B value (the data logger output), \(\mathrm{C_{f}}\) is the calibration factor (obtained from the calibration device), and \(\mathrm{G_{f}}\) is the grout factor. The formula for the grout factor calculation is shown in Equation (8). \[\mathrm{G_{f}}=\frac{\mathrm{A_{g}}}{\mathrm{E_{ave}}} \tag{8}\]  
where \(\mathrm{A_{g}}\) is the grout cross section, and \(\mathrm{E_{ave}}\) is the average modulus of elasticity. The formula for average elasticity modulus calculation is shown in Equation (9). \[\mathrm{E_{ave}}=\frac{\mathrm{A_{r}}}{\mathrm{A_{g}}}*\mathrm{E_{r}}+\left(1- \frac{\mathrm{A_{r}}}{\mathrm{A_{g}}}*\mathrm{E_{g}}\right) \tag{9}\]  
Micro-strain values can be positive or negative. A positive value suggests tensile behavior, whereas a negative value indicates compression behavior. The soil nail tensile \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Load Stage \({}^{*}\) DL** & 0.125 & 0.25 & 0.50 & 0.75 & 1.00 & 1.25 & 1.50 & 1.75 & 2.00 \\  & DL & DL & DL & DL & DL & DL & DL & DL \\ \hline
**Time Period (min)** & 1 & 10 & 10 & 10 & 10 & 10 & 10 & 10 & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Loading stages and stage time periods. Figure 16: Placement of strain gauge sensors on nail reinforcement via welding. Figure 15: Soil nail pull-out test setup. Table 7 shows the results obtained by using Equations (8) and (9) to transform the raw data from the strain gauge sensors into micro-strain values. The changes in micro-tension were calculated using Equation (7) by comparing linear digit (B) values, strain gauge factor, and injection factor values from tensile experiments. The obtained micro-stress values were converted to kN (\(\mu\epsilon=10^{-6}\) kN). The load distribution created by tensile tests PT1 and PT2 on the strain-measuring sensors at different load levels is given in Figure 18.  
The mechanical behavior of the nails was examined using strain gauge sensors during the pull-out tests in order to determine the distribution of loads acting on them. In both experiments, the nail loads were high on the side close to the coating. The axial load \begin{table}
\begin{tabular}{c c c} \hline
**Parameter** & **Value** & **Unit** \\ \hline Strain Gauge Factor & 3.962 & Micro-strain/digit \\ Rebar Cross-Sectional Area (A\({}_{\text{r = 28 mm}}\)) & 6.16 \(\times\) 10\({}^{-4}\) & m\({}^{2}\) \\ Rebar Cross-Sectional Area (A\({}_{\text{r = 40 mm}}\)) & 50.24 \(\times\) 10\({}^{-4}\) & m\({}^{2}\) \\ Grout Cross-Sectional Area (Ag) & 1.13 \(\times\) 10\({}^{-2}\) & m\({}^{2}\) \\ Rebar Elasticity Modulus (Er) & 2.11 \(\times\) 10\({}^{8}\) & kN/m\({}^{2}\) \\ Grout Elasticity Modulus (Eg) & 10 \(\times\) 10\({}^{6}\) & kN/m\({}^{2}\) \\ Avera Elasticity Modulus (Eave) & 21 \(\times\) 10\({}^{6}\) & kN/m\({}^{2}\) \\ Grout Factor (Gf) & 5.4 \(\times\) 10\({}^{-10}\) & kN/m\({}^{2}\) \\ \hline \end{tabular}
\end{table} 
Table 7: Parameters used in calculating micro-strain values. Figure 18: Distribution of the loads on the strain gauge sensors in the tensile test stages **(a)** PT1; **(b)** PT2. acting on the nails decreases as it moves away from the coating. Experiment PT1 shows a significant decrease in the axial loads acting on the nail after the second meter, even at a maximum load level of 240 kN. Experiment PT2 showed a sudden decrease in nail loads at a maximum load level of 640 kN after two and a half meters.