# Effect of Using Plastic Waste Bottles on Soil Response above Buried Pipes under Static Loads
## 4 Summary and Conclusions  
With the increased use of drinking water and soda drink bottles, there is a need for a green yet environmentally friendly approach to adopting PET plastic bottles. In this paper, the benefits of using mattresses made from used PET bottles filled with soil to improve  
Figure 12: Variation of applied pressure with footing surface settlement for different relative densities of soil, H/B = 1.4, and u/B; b/B = (**a**) 0.5; 1.04, (**b**) 1.0; 1.04, (**c**) 1.5; 1.04, (**d**) 0.5; 1.56, and (**e**) 0.5; 2.08, respectively.  
foundation response under static loading were examined. The influence of bottle placement depth ratio (u/B) and reinforced mattress width ratio (b/B) was investigated. The following conclusions can be drawn from the reported results of the experimental work:  
* Tied soil-filled PET bottles perform best when located close to the loading steel plate. The soil bed's ultimate bearing capacity increases as the bottle's placement depth decreases.
* As the width of the bottle's reinforcement block increases, the ultimate bearing capacity of the soil slightly increases too. However, the improvement of the ultimate bearing capacity of bottle-reinforced soil's bed due to increasing the width of bottle reinforcement mattresses is not significant.
* The bearing capacity ratio (BCR) of the soil bed was improved by a factor of \(\sim\)1.71 (resulting in an average 71% improvement in ultimate bearing capacity at RD = 30%), which, in turn, will reduce the surface settlement of backfilled soil and result in a firm soil bed above the buried pipe.
* As the relative density of the bottle-reinforced soil bed increases, the bearing pressure increases (and the footing surface settlement decreases) due to the inclusion of a bottle reinforcement mattress. In addition, at a given applied pressure, the footing surface settlement decreases as the relative density of the sand bed increases.
* The optimum placement depth and width of the bottle-reinforced mattress were 0.50 and 2.08 B, respectively.  
Although the concept in this paper might be used in pursuit of some compaction to fill the bottles, practical field implementation might require more research. For such a technology to become more widely used, an automatic system for filling and arranging plastic bottles may be necessary. The adopted reinforcement system is reasonably best suited when the project site has relatively fine-grained soil and is not proper for subgrades in their original shape without treatment.  
It is important to note that only a small number of experiments were conducted, utilizing only one backfill and infill soil, one plastic bottle dimension (in both total length and outer diameter), uPVC pipe's mechanical properties and dimensions (i.e., wall thickness and diameter), and one size of loading steel plate. As long as the earth has acceptable high frictional properties, it is probably not too significant what kind of soil is put in the bottles. Even if cohesive plastic soil could be placed successfully into the bottles, it would probably not be preferred. While the frictional soil utilized in the research detailed in this study would have worked to prevent bottle deformation under the confining stress supplied by the confinement of the plastic bottle, such soil would allow gradual plastic deflections.  
Conceptualization, F.H.A.-A. and M.Y.F.; methodology, S.A.A.-H., F.H.A.-A. and M.Y.F.; software, S.A.A.-H.; validation, F.H.A.-A. and M.Y.F.; formal analysis, M.Y.F.; investigation, S.A.A.-H.; resources, S.A.A.-H., F.H.A.-A. and M.Y.F.; data curation, S.A.A.-H.; writing--original draft preparation, S.A.A.-H.; writing--review and editing, F.H.A.-A. and M.Y.F.; visualization, S.A.A.-H.; supervision, F.H.A.-A. and M.Y.F.; project administration, M.Y.F.; funding acquisition, Not applicable. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data that have been used are confidential.  
The authors declare no conflict of interest.