# Pullout Behavior of Nail Reinforcement in Nailed Soil Slope
## 4 Conclusions  
In this study, nail pullout tests were conducted to assess the pullout behavior of soil nail reinforcement at different levels in granular materials. The laboratory models of nailed soil systems of granular with a scale of 1:10 were prepared. The construction sequence used in a full scale slope was precisely followed in the laboratory model. The construction of the nailed soil slope system models, loading stages and pullout testing procedures were clearly defined. The models consisted of a Perspex wall box filled with sand and steel bars as a reinforcement. The models of sand beds were formed using an automatic sand raining system. The devices and instruments were installed to record the nail pullout resistance and displacement. The tests were carried out at variable footing pressure to get the pullout force of the nails, with a strain controller taking horizontal speed at 0.3 mm/min. The finite element models of nailed soil slope were also analyzed to validate the laboratory model results.  
The following conclusions may be drawn from the present study.  
* The pullout force was increased as the displacement of the nail increased until it reached the maximum pullout force and then decreased or became constant;
* The lower nail exerted a greater pullout force than the middle nail and the least pullout force occurred at the upper nail. This may be attributed to the fact that the lower nail had a greater overburden pressure than the middle and the upper nails;
* There was a steep increase in the pullout force in the lower nail with an increase in the footing pressure, whereas in case of the middle nail, there was a slight increase with the increase in footing pressure;
* In the upper nail, the rate of increase of pullout forces changed from a high increase to a constant, whereas in case of the middle nail, the rate of increase of pullout forces increased slowly and became constant;
* The numerical model results point out that the laboratory models underestimate the pullout behavior of nail reinforcement in nailed soil slopes.  
Conceptualization, M.H.M. and M.A.; methodology, M.H.M. and M.A.; resources, J.M.; writing--original draft preparation, M.H.M. and M.A., writing--review and editing, J.M., project administration; funding acquisition, M.A. All authors have read and agreed to the published version of the manuscript. Funding Funding for this research was given under award numbers R.G.P2/73/41 by the Deanship of Scientific Research; King Khalid University, Ministry of Education, Saudi Arabia. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable.  
Figure 18: Shear stress during the construction and loading stage; (**a**) construction stage; (**b**) loading stage.  
**Acknowledgments:** The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through General Research Project under grant number (R.G.P.2/73/41), The authors acknowledge to the Dean, Faculty of Engineering for valuable support and help.  
**Conflicts of Interest:** The authors declare no conflict of interest.