# Effect of Using Plastic Waste Bottles on Soil Response above Buried Pipes under Static Loads
## 3 Results and Discussion
### Bottles-Reinforcement Placement Depth (u/B) Effect  
Figure 8a-c illustrates the vertical applied pressure-surface settlement of footing graphs with different relative densities for the unreinforced and plastic bottles reinforced beds at various placement depths (u/B). The values of reinforcement width and height ratios are b/B = 1.04 and H/B = 1.4 for all tests. The improvement of ultimate bearing capacity decreases as the placement depth ratio (u/B) increases without a distinct optimum value. Compared to more flexible reinforcements such as geogrid, geocell, and geotextile, the mechanism behind the improvement in the ultimate bearing capacity of soil bed brought about by relatively tough soil-filled plastic bottles appears to be different. By decreasing the shear stresses transported to the weaker soil beneath the subbase when the vertical loads are applied, the tension created in the flexible reinforcements increases bearing capacity [32]. The optimum covering soil thickness is necessary to enable soil-geosynthetic interaction and full deployment of ultimate reinforcement capacity. For the tough soil-filled plastic bottles utilized in this work, a thinner soil surface cover prevents more settlement at any given applied load because of compression in the soil above the reinforcement bottles [22]. However, lower (u/D) ratios are desirable with the configuration and plastic bottle reinforcement investigated. To maintain a leveled surface of the soil to which the applied loading can be applied, the ideal covering soil thickness is most likely that amount. Nevertheless, the bottle-reinforced sand bed performs are better at lower u/B ratios because there is less soil between the model footing and the bottle reinforcement, decreasing the probability of lateral soil shear. Additionally, since the soil is so thin, there is little opportunity for compression. However, when soil covering increases, the bottle reinforcement's contribution decreases because of less stress and, thus, less strain reaches the reinforcement. This means that the reinforcement has less of an effect on the overlying soil's shear movement [22]. However, these results are in agreement with [33], \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Test No.** & \
\begin{tabular}{c} **Reinforcement** \\ **Condition** \\ \end{tabular} & **u/B** & **b/B** & **H/B** & **DR (\%)** &
\begin{tabular}{c} **Ultimate Bearing** \\ **Capacity (kPa)** \\ \end{tabular} & **BCR** \\ \hline
1 & Unreinforced & — & — & — & & 26.5 & — \\ \hline
2 & & 0.5 & 1.04 & & & 42.8 & 1.62 \\ \hline
3 & Bottle & 1 & 1.04 & & 30 & 39.3 & 1.48 \\ \hline
4 & reinforced & 1.5 & 1.04 & 1.4 & & 34.5 & 1.30 \\ \hline
5 & & 0.5 & 1.56 & & & 43.3 & 1.63 \\ \hline
6 & & 0.5 & 2.08 & & & 45.3 & 1.71 \\ \hline
7 & Unreinforced & — & — & — & & 93.8 & — \\ \hline
8 & & 0.5 & 1.04 & & & 128.1 & 1.37 \\ \hline
9 & Bottle & 1 & 1.04 & & & 115.9 & 1.24 \\ \hline
10 & reinforced & 1.5 & 1.04 & 1.4 & & 105.2 & 1.12 \\ \hline
11 & & 0.5 & 1.56 & & & 132.1 & 1.41 \\ \hline
12 & & 0.5 & 2.08 & & & 139.0 & 1.48 \\ \hline
13 & Unreinforced & — & — & — & & 255.5 & — \\ \hline
14 & & 0.5 & 1.04 & & & 305.5 & 1.20 \\ \hline
15 & Bottle & 1 & 1.04 & & & 295.6 & 1.16 \\ \hline
16 & reinforced & 1.5 & 1.04 & 1.4 & & 280.0 & 1.10 \\ \hline
17 & & 0.5 & 1.56 & & & 321.3 & 1.26 \\ \hline
18 & & 0.5 & 2.08 & & & 337.3 & 1.32 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Ultimate bearing capacity and BCR ratios for various reinforcement parameters (reported at S/B = 10%). who conducted that the decrease in cover depth leads to better performance of buried concrete pipes. Referring to Figure 9a-c derived from Figure 8a-c, the variation in BCR and PRS with different reinforcement placement depth ratios at various relative densities is shown. The BCR values decrease as the placement depth ratio increases. However, the behavior is similar for PRS, with a more marked decrease as the placement depth ratio increases.