## 2 Experimental Study
### Centrifuge Test Results  
To determine the uplift capacity, tests were completed after a vertical displacement of d = 12 mm (prototype value \(d_{p}\) = 0.36 m), which corresponds to a higher capacity than the ultimate uplift capacity. The relationship between uplift capacity and displacement in unreinforced sand is shown in Figure 5. The peak value was reached in most of the experiments, and the uplift capacity/displacement curve obtained in dense sand for an embedment ratio  
Figure 4: Configuration of geogrid reinforcement used in centrifuge tests. of H/B = 5, is typically presented in Figure 5. As generally known for the uplift behavior of anchors, the outer failure plane developed at smaller deformations than the second inner plane obtained at much greater strains. At this depth, a failure plane was not obtained for the loose sand conditions. As seen the anchor quickly reaches its maximum uplift capacity in dense sand. The corresponding failure displacements increased significantly as the embedment ratio of the anchors increased from H/B = 2 to H/B = 5. In both cases, further displacement appears to cause a steady decrease in uplift capacity. This post-peak behavior has been observed in a study reported by [PERSON] [7] for different shapes of non-reinforced anchors. In loose sand conditions, the peak uplift capacities of buried anchors at shallow depths were more pronounced, while softening occurred after reaching the peak uplift capacity in deeper anchors. Ultimate bearing capacities occurred after slightly higher deformations than under dense sand conditions. Depending on the increase in the density of the sand material, the uplift capacity of the anchor increased by 19% when the embedding ratio was H/B = 2, and 55% when the embedding ratio was H/B = 5. The results obtained in soil reinforced with a single geogrid of 150 mm length are presented in Figure 6. When the curves in Figure 6 are examined, it is seen that the rate of increase in the uplift capacity of the anchor plates is less than 20% in both loose and dense sand conditions. A much greater increase in the uplift capacity of the anchor was obtained when the geogrid was placed with a 45-degree inclination as shown in Figure 4b. This increased rate was 96 and 27% in dense sand and 73 and 29% in loose sand at embedment ratios 2 and 5, respectively. Post-peak reductions in uplift capacity were observed only in the case of a plate buried more deeply in dense sand. Figure 5: Variation of Q\({}_{u}\)–d (no geogrid). A dimensionless factor, the breakout factor, was used to compare the uplift capacities. The breakout factor, N\({}_{\text{UR}}\), is expressed as:  
\[N_{\text{{{U}}}LR}=\frac{Q_{u}}{\gamma A_{b}H} \tag{1}\]  
where \(Q_{u}\) is the uplift capacity, \(\gamma\) is the unit weight of the sand, \(A_{b}\) is the area of the anchor plate, and H is the embedment depth of the anchor. In the case of using geogrids oriented vertically downwards, the increase in the uplift capacity of the anchors shows an intermediate level increase compared to the unreinforced condition. When the geogrid configurations are compared, as seen in Figure 7, the best performance is obtained when the geogrid is used with a 45\({}^{\circ}\) inclination for the increases in uplift capacity both for soil densities and anchor embedment ratios. In all cases, the increase in improvement percentage decreases for deeper burial rates. Figures 8 and 9 show the variation of \(N_{\text{{{U}}}LR}\) with H/B for loose and dense sand conditions, respectively. From the Figures it is seen that the \(N_{\text{{{U}}}LR}\) values increase remarkably with burial depth and unit volume weight of the soil. The results obtained from centrifuge experiments were compared with the tests performed on unreinforced soils by [PERSON] [7], and as seen in Figures 8 and 9. These results confirm the data of the strip anchor plates embedded in unreinforced sand obtained in this study. They also provide a sensitive lower bound on their uplift capacity for reinforced strip anchors in any direction.