# Pullout Behavior of Nail Reinforcement in Nailed Soil Slope
## 3 Results and Discussion  
The laboratory and finite element models, constructed and discussed above, are tested to investigate the performance of the nailed soil slope under overburden pressure. Figure 12 shows the mobilization of the pullout force in nails placed at different levels within the soil slope (upper, middle, and lower nail) in the case of no footing without any overburden pressure and at an overburden pressure of 5 kN and 10 kN. It can be seen from the figures that the pullout force in the nails increases as the displacement increases. However, the increase in the pullout force is not same in the nails of different levels and the maximum pullout force is also different at low values of overburden pressures. The pullout force reaches its maximum value rapidly in lower nails but in upper and middle nails it reaches its maximum value slowly, having no or a lower overburden pressure. This may be due to the change of over burden pressures which contribute to pullout resistance. The pullout force slightly decreases after reaching the peak and then become constant in lower nails, while it becomes constant immediately in the case of middle and upper nails after reaching the peak value. It can be observed from the figure that the rate of increase of the pullout force becomes almost the same in the upper, middle, and lower nails, with further increase of overburden pressure. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter A (mm)**} & \multicolumn{2}{c}{**B**} & \multicolumn{1}{c}{**Y**} & \multicolumn{1}{c}{**Z**} & \multicolumn{1}{c}{**X**} & \multicolumn{1}{c}{**Sh = Sv**} & \multicolumn{1}{c}{**Slope**} & \multicolumn{1}{c}{**Nail**} & \multicolumn{1}{c}{**H = Ln**} & \multicolumn{1}{c}{**RD**} & \multicolumn{1}{c}{**q**} \\  & **(mm)** & **(mm)** & **(mm)** & **(mm)** & **(mm)** & **Angle (\({}^{\circ}\))** & **Inclination (\({}^{\circ}\))** & **(mm)** & **(\%)** & **(kPa)** \\ \hline
**Value** & 405 & 150 & 834 & 146 & 225 & 280 & 40 & 0 & 700 & 48 &
\begin{tabular}{c} 5, 10, \\ 20, 30 \\ \end{tabular} \\ \hline \hline \end{tabular}  
* A—Soil width beyond the footing; B—footing width; Y—soil width beyond the toe of slope; Z—soil base depth below the slope; X—distance of footing from crest; Sv—nail vertical spacing; Sh—nail horizontal spacing; H—excavation height; Ln—nail length; RD—relative density of the sand; q —footing pressure.  
\end{table} 
Table 4: Nailed soil slope parameters. Figure 11: Discretized finite element model of nailed soil slope. The relationship between the displacement of the nail and the pullout force at three different levels of nails (upper, middle, and lower) and with footing pressure of 20.0 kPa and 30.0 kPa are presented in Figure 13. From the figures, it can be seen that the maximum value of the pullout force is reached gradually in the upper nails and rapidly in the other two nails. In the lower and middle nails, the rate of increase of pullout force is very steep and becomes constant after reaching the peak value. There is a large difference in the mobilized peak value of the pullout force of lower nails, and the pullout forces of upper and middle nails. This difference is more than 100% from the pullout force of the upper and middle nails. Figure 12: Pullout force of nails with displacement; (**a**) q = 0 kN; (**b**) q = 5 kN; (**c**) q = 10 kN. Figure 14 shows the influence of the nail level at different footing pressures on the maximum pullout force of the nail. From this figure, it could be seen that the lower nail exerts more pull-out force than the middle nail and the least pull-out force occurs at the upper nail. This may be attributed to the fact that the lower nail has more overburden pressure than the middle and the upper nail. Moreover, the figure indicated that the influence of footing pressure on the pullout force is steep, increasing in the lower nail but slowly increasing or becoming constant in case of the middle and upper nail.