Utilizing PET bottles for sustainable cellular reinforcement: A study on enhancing fly ash backfill bearing strength with innovative geocell alternative

Abstract

The slow degradation rate is one of the major global concerns. Only, 60 % produced is being recycled. Among these waste materials, Polyethylene Terephthalate (PET) bottles contribute around 10 % to the total plastic waste produced. The recycling process of PET bottles considering existing capacity in environmentally responsible ways is limited. It is estimated that 60 % of PET bottles produced are being disposed of in landfills. To overcome this, past studies have suggested novel approaches for using it as substitute for conventional geocell as soil reinforcement and stability. However, past studies mostly focused on application of PET bottles as flaked, shreds and sliced form. The present study attempts on application of PET bottles under fly ash (FA) backfills without mechanical alterations. Full-scale experiments were conducted on FA backfill system, for both unreinforced and reinforced conditions. A comparative study was performed between high-density polyethylene (HDPE) geocell and PET bottle mattress to assess the bearing strength of the FA backfill. Experiments were performed in a 1 m3 tank with a loading plate width of 200 mm. Vertical loading was applied onto the backfill footing (for all the trial series), till the footing settlement of 40 mm is achieved. An aspect ratio of 2 was considered for HDPE geocell and PET bottles. Rock quarry dust (RQD) was considered as cell infill and overlay material on FA backfill. The test results showed that settlement accumulation rate was low under reinforced scenario compared to the unreinforced condition, with higher resilient (elastic) settlement. RQD over the PET-reinforced zone was also seen to have enhanced the load distribution aspect, thereby reducing deformation in PET reinforcement. This usage of waste material will contribute towards sustainable development. This work demonstrates the feasibility and effectiveness of PET reinforcement to be used as replacement for HDPE geocell, which eventually can agument the design methodology of structural backfills.