## 2 Materials and Methods
### Test Procedures  
The large-scale pullout testing program was conducted in accordance with recommendations of the ASTM D6706 standard [46] and procedures adopted by [PERSON] et al. [15]. The soils used were initially homogenized at their optimum moisture content. Then, the appropriate mass of soil for each layer was separated, considering both the target dry unit weight and the desired thickness of each layer. The compaction was carried out by utilizing a manual hammer with a 120 mm square base and 40 N weight. The hammer was dropped from a height of 450 mm to ensure proper compaction. The soil was compacted in six layers, each with a thickness of 80 mm. After the initial three layers were compacted, the geogrid specimen was attached to the clamp and placed at mid-height. As mentioned earlier, the initial three layers consisted of soil A. Once the geogrid was positioned, soil B was compacted in the upper portion of the box, following the same procedures used for the initial layers. An airbag was then fixed over the soil surface at the top plate, and a uniform distribution pressure was administered via a pneumatic system, regulated by a controlled compressor, as shown in Figure 5.  
For the small-scale equipment, the soil was mixed with the required water to attain the desired moisture content. Subsequently, it was compacted in the pullout box to the prescribed density in four layers, each with a thickness of 35 mm. The compaction was performed using a manual hammer with a 20 mm square base and 10 N weight, dropped from a height of 100 mm. The compaction procedures resulted in a consistent soil density for both types of equipment. Furthermore, the relative compaction varied from 96% to 102% of the standard proctor maximum dry unit weight. A servo-hydraulic control system, powered by an electric pump, was used to apply the pullout force to the reinforcement. Programmable software controls the system speed, displacement and applied load throughout the test. The pullout clamp has reinforcement ribs along their sides, and the tightening is performed by clamping the screws, which  
Figure 4: Measured points of GGR displacement: (**a**) large equipment; (**b**) small equipment. Figure 5: Schematic profile view: (**a**) small equipment; (**b**) large equipment. immobilizes the specimen throughout its width and minimizes the differential slips, as shown in Figure 6. The clamping system can be placed inside or outside the test box, as reported by [PERSON] and [PERSON] [14]. Initially, monotonic pullout tests were performed at a constant displacement rate of 4.0 mm/min until pullout or rupture of the geogrid was achieved. The displacement rate used in this study for geosynthetic pullout testing is different from that recommended by ASTM D6706 [40]. However, as reported by the authors of [39], the use of displacement rates of 1.0, 2.0 and 4.6 mm/min in this equipment did not lead to a high variability of results. A displacement rate of 4.0 mm/min was adopted herein to enable the comparison of the test results with those from other studies carried out using the same equipment, in which this particular rate of displacement has commonly been used. After the monotonic pullout evaluation, the cyclic load limits were estimated, and the load amplitude was defined as 20% of the monotonic maximum pullout resistance value. This load amplitude was defined based on [PERSON] et al. [47] and [PERSON] [34], which concluded that for high amplitude values (80%), the geogrid breakage tends to occur before the end of cycles, and amplitude values ranging from 20% to 40% seem to lead to similar results. In the cyclic/post-cyclic test procedure, the system was first loaded at a lower limit estimated according to ASTM D7499 [46], corresponding to 0.9 kPa for a confinement stress of 25 kPa and 3.6 kPa for a confinement stress of 100 kPa. Then, 10,000 loading cycles were applied to the reinforcement.