# Pullout Behavior of a Polymeric Strap in Compacted Dry Granular Material
## 2 Materials and Methods
### Sample Preparation and Test Procedure  
The pullout tests were performed with one strap, two straps closely placed, and two straps with 200 mm of horizontal spacing. The same test procedure was used in all tests. The only differences between test setups with one and two straps was in the connection system for the arrangement of one or two straps and in the location of the points for the displacement measurements. The pullout tests with one strap setup were performed for backfill material labeled as A, B, and C under different normal stresses (50, 100, and 150 kPa), while the pullout tests with two straps were performed with well-graded backfill material C under one normal stress (50 kPa). An overview of the testing program is given in Table 3. Some tests were repeated. The number of tests shown in Table 3 represents the number of repeats of the same test setups. For the purpose of testing the geosynthetic strap, a specific fastening system was designed. In order to determine possible slippage of the geosynthetic strap on the fastening system and to determine the consistency and repeatability of the tests, individual tests were repeated several times. The repeat testing showed that no slippage occurred on the fastening system and that the displacements measured by extensometers along the length of the straps showed the same trend with increasing force. Based on these results, it was concluded that it was not necessary to repeat individual tests multiple times. For materials A and B, the tests were repeated at the same normal stresses, i.e., 50 kPa and 150 kPa for material A and normal stresses of 150 kPa material B. For material C, the tests were performed once, but an additional normal stress of 100 kPa was added for this material. The purpose of this additional test was to confirm that the point was on the failure line, which for materials A and B was defined by only two points. It also makes it easier to monitor the effects of the normal stress on the mobilization of the strap inside the box. Figure 3: Geosynthetic strap cross-section. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{3}{c}{**Sample**} & \multirow{2}{*}{\ \begin{tabular}{c} **Normal Stress** \\ **(kPa)** \\ \end{tabular}  } & \multirow{2}{*}{**Strap**} & \multirow{2}{*}{ \begin{tabular}{c} **No. of** \\ **Tests** \\ \end{tabular}  } \\ \cline{1-1}
**Label** & \begin{tabular}{c} **Grain Size** \\ **(mm)** \\ \end{tabular}  & & & & \\ \cline{1-1}
**A** & \(30\)–\(60\) & \(50\) & single & \(3\) \\ \cline{1-1}
**B** & \(4\)–\(60\) & \(50\) & single & \(1\) \\ \cline{1-1}
**C** & \(0\)–\(60\) & \(150\) & single & \(1\) \\ \cline{1-1} \cline{3-5}  & & \(100\) & single & \(1\) \\ \cline{1-1}
**C** & \(0\)–\(60\) & \(150\) & single & \The prepared backfill material samples were placed in the box in 100 mm thick layers and vibro-compacted to the height of 400 mm. The polyester strap or two straps were placed on the layers of compacted backfill material in the center of the pullout box. The strap was treated across a sleeve on the front wall and connected to the piston. At the back side of the box, the strap was threaded out of the pullout box so that the length of the straps in the box during the pullout tests was constant at 1.65 m. The displacement of the straps was measured with four extensometers and with a displacement sensor on the piston. The arrangement of extensometers was different for test setups with one and two straps. For test setup with one strap, displacement was measured with three extensometers along the emplaced strap (200 mm from the sleeve, in the middle of the emplaced strap, and 200 mm from the back end of the box). For the tests with two straps, the displacement was also measured with four extensometers, two placed 200 mm from the sleeve on each strap and two placed 200 mm from the back side of the box. In the experiments carried out with one strap, the aim of monitoring the displacement was to determine the influence of grain size distribution and normal stress on the mobilization of the strap.