# Pullout Behavior of Nail Reinforcement in Nailed Soil Slope
## 2 Materials and Methods for Soil Nail Reinforcement Pullout Test
### Soil Nailing System  
The soil nailing system consists mainly of backfill material, reinforcement, facing unit and strip footings. The air-dried clean siliceous yellow sand was used in the preparation of the models. The physical and mechanical properties of the tested sand were determined. The sand samples were tested for grain size distribution as per ASTM D421, specific gravity as per ASTM D854, minimum and maximum densities, moisture content and shear strength parameters as per ASTM D3080. Figure 1 shows the grain size distribution of several samples (two samples each for dry and wet sand) used. The physical properties of the soil materials are given in Table 1. Table 1 indicates that the tested sand was classified as poorly graded sand (SP) according to the unified soil classification system. It is known that the angle of internal friction (\(\varphi\)) of sand depends on the relative density of the sample. Six samples were tested at different densities and varied from the relative density of 0.0% to the relative density of 100%. Figure 2 shows the relationship between the angle of shearing resistance and the relative density. For pullout test, sand with a relative density of 48% and medium sand (\(\gamma=16.41\) kN/m\({}^{3}\)), which has an angle internal friction \(\varphi_{\text{medium}}\) as 34\({}^{\circ}\). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Property** & **Value** & **Property** & **Value** \\ \hline \% of Clay & 0.00 & Specific gravity (G\({}_{\text{s}}\)) & 2.62 \\ \% of Silt & 1.33 & Minimum density (\(\gamma_{\text{min}}\)) (kN/m\({}^{3}\)) & 15.30 \\ \% of fine Sand & 39.17 & Maximum density (\(\gamma_{\text{max}}\)) (kN/m\({}^{3}\)) & 17.80 \\ \% of medium Sand & 58.63 & Minimum void ratio (\(\epsilon_{\text{min}}\)) & 0.472 \\ \% of coarse Sand & 0.87 & Maximum void ratio (\(\epsilon_{\text{max}}\)) & 0.712 \\ \% of fine Gravel & 0.00 & Angel of internal friction (\(\Phi^{\circ}\)) & 34 \\ Effective diameter (D\({}_{10}\)) mm & 0.126 & Bulk Density (\(\gamma_{\text{p}}\)) (kN/m\({}^{3}\)) & 16.41 \\ Coefficient of uniformity (C\({}_{\text{u}}\)) & 1.99 & Void ratio (e) & 0.597 \\ Coefficient of gradation (C\({}_{\text{u}}\)) & 1.00 & Relative density (\%) & 48 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physical and Mechanical Properties of Soil. Figure 1: Grain size distribution of the tested sand. The nails used were steel bars of circular cross section with a constant diameter of 5 mm and lengths of 700 mm. The nails were chosen to accommodate the electrical strain gauge. A direct tension test was performed to determine the strength characteristics of the nail. Figure 3 shows the stress-strain relationship for nail materials. The mechanical properties of nails are given in Table 2. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Element**} & **Length** & **Maximum** & **Strains at** & **Maximum** & **Young’s** & **Flexural** & **Normal** \\  & **(mm)** & **Tensile Force** & **Ultimate** & **Tensile Strength** & **Modulus** & **Rigidity, EI** & **Stiffness, EA** \\  & **(kN)** & **Stress (\(\pm\epsilon\))** & **(kPa)** & **(kPa)** & **(kPa)** & **(kN\(\cdot\)mm\({}^{2}\))** & **(kN\(\cdot\)m)** \\ \hline
5 mm Steel & \multirow{2}{*}{700} & \multirow{2}{*}{17.4} & \multirow{2}{*}{7625} & \multirow{2}{*}{\(8.8\times 10^{5}\)} & \multirow{2}{*}{\(21.2\times 10^{7}\)} & \multirow{2}{*}{6.51\(\times 10^{-3}\)} & \multirow{2}{*}{4165.9} \\ Nails & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Properties of Reinforcement (Nails). Figure 3: Stress–strain curve of the tested nail. Figure 2: Relationship between relative density and angle of internal friction. The facing unit selected was a Perspex plate with a thickness of 5.0 mm to simulate the shotcrete in the prototype soil nailing system of a thickness of 140.0 mm. The dimensions of the facing panel were 848.0 mm wide and 140.0 mm vertical (projected) in height. Holes of 8.0 mm in diameter were provided in panels to fix the nails' head.