Stress Reduction of Buried Thermoplastic Pipes Using EPS Geofoam

Abstract

Field and laboratory tests and numerical analyses of rigid culverts have shown that induced trench installation (ITI) can reduce the vertical stress acting on culverts installed under high embankments. In this research, the ITI technique was adapted by incorporating expanded polystyrene (EPS) geofoam as a compressible inclusion to reduce stresses on large-diameter thermoplastic pipes beneath high embankments, and the system was examined through numerical modelling. A numerical model representing the field configuration was calibrated using available field measurements and subsequently employed to evaluate the mechanical response of large-diameter thermoplastic pipes buried under a high embankment. The effects of EPS thickness and width on pipe stresses and deflections, together with the comparative stress responses obtained using different EPS material representations, were analysed. Creating a soft compressible zone above the thermoplastic pipe promoted positive arching and reduced the stresses acting on the pipe, while the deflection response varied with pipe type and EPS geometry. In the EPS15 thickness series, increasing the thickness beyond 1.4h (h = D/10) did not produce a consistent additional reduction in vertical crown stress. Under the fixed 1.4h-thick EPS15 condition, increasing the width beyond D did not consistently improve the stress and deflection responses. Within the adopted material representations, EPS15 produced the largest stress reductions, reaching approximately 60–85% in vertical stress and 35–52% in horizontal stress. Because different constitutive formulations were used for EPS15 and EPS20–EPS40, the observed differences reflect the combined influence of nominal EPS density, material properties, and constitutive representation.

Keywords

• Soil arching
• induced installation
• thermoplastic pipe
• EPS geofoam
• PLAXIS 2D

Supporting Institution

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Ethical Statement

This study does not involve human participants, animal experiments, or personal data. Therefore, ethical committee approval is not required.

References

1. McAffee, R.P., Valsangkar, A.J., Geotechnical properties of compressible materials used for induced trench construction, J. Test. Eval., 32(2), 143–152, 2004.
2. Kim, K., Yoo, C.H., Design loading on deeply buried box culverts, J. Geotech. Geoenviron. Eng., 131(1), 20–27, 2005.
3. McAffee, R.P., Valsangkar, A.J., Performance of an induced trench installation, Transportation Research Record, 1936(1), 230–237, 2005.
4. Sun, L., Hopkins, T., Beckham, T., Stress reduction by ultra-lightweight geofoam for high fill culvert, Proceedings of the 13th Great Lakes Geotechnical and Geoenvironmental Conference, Milwaukee, Wisconsin, USA, 146–154, 2005.
5. Kang, J., Parker, F., Yoo, C.H., Soil-structure interaction and imperfect trench installations for deeply buried concrete pipes, J. Geotech. Geoenviron. Eng., 133(3), 277–285, 2007.
6. Kang, J., Parker, F., Yoo, C.H., Soil–structure interaction for deeply buried corrugated steel pipes Part I: Embankment installation, Eng. Struct., 30(2), 384–392, 2008.
7. Kang, J., Parker, F., Yoo, C.H., Soil–structure interaction for deeply buried corrugated steel pipes Part II: Imperfect trench installation, Eng. Struct., 30(3), 588–594, 2008.
8. McAffee, R.P., Valsangkar, A.J., Field performance, centrifuge testing, and numerical modelling of an induced trench installation, Can. Geotech. J., 45(1), 85–101, 2008.

9. Parker, B.A., McAffee, R.P., Valsangkar, A.J., Field performance and analysis of 3-m-diameter induced trench culvert under a 19.4-m soil cover, Transp. Res. Rec., 2045(1), 68–76, 2008.
10. Kim, H., Choi, B., Kim, J., Reduction of earth pressure on buried pipes by EPS geofoam inclusions, Geotech. Test. J., 33(4), 304–313, 2010.
11. McGuigan, B. L., Valsangkar, A. J., Centrifuge testing and numerical analysis of box culverts installed in induced trenches, Canadian Geotechnical Journal, 47, 2, 147–163, 2010.
12. Vaslestad, J., Sayd, M.S., Johansen, T.H., Wiman, N.L., Load reduction and arching on buried rigid culverts using EPS geofoam: design method and instrumented field tests, Proceedings of EPS 2011, Lillestrøm, Norway, 10–36, 2011.
13. Meguid, M.A., Hussein, M.G., Ahmed, M.R., Omeman, Z., Whalen, J., Investigation of soil–geosynthetic–structure interaction associated with induced trench installation, Geotext. Geomembr., 45(4), 320–330, 2017.
14. Ma, Q., Ku, Z., Xiao, H., Model tests of earth pressure on buried rigid pipes and flexible pipes underneath expanded polystyrene (EPS), Adv. Civ. Eng., 2019, Article ID 9156129.
15. Bryden, C., Arjomandi, K., Valsangkar, A., Evaluation of induced trench twin culverts constructed in deep fill, Can. Geotech. J., 57(9), 1388–1403, 2020.
16. Bryden, C., Arjomandi, K., Valsangkar, A., The mechanics of arching in induced trench construction – a new theoretical formulation, Can. Geotech. J., 59(2), 203–224, 2022.
17. Marston, A., The theory of external loads on closed conduits in the light of the latest experiments, Bulletin 96, Iowa Engineering Experiment Station, Iowa State College, Ames, Iowa, USA, 1930.
18. Spangler, M.G., Field measurements of the settlement ratios of various highway culverts, Bulletin 170, Iowa Engineering Experiment Station, Ames, Iowa, USA, 1950.
19. Spangler, M.G., A practical application of the imperfect ditch method of construction, Proceedings of Highway Research Board, 271–277, 1958.
20. Larsen, N.G., Hendrickson, J.G., A practical method for constructing rigid conduits under high fills, Proceedings of the 41st Annual Meeting of the Highway Research Board, Washington, D.C., USA, 273–280, 1962.
21. Deen, R.C., Performance of a reinforced concrete pipe culvert under rock embankment, Research Report, Division of Research, Department of Highways, Commonwealth of Kentucky, Kentucky, USA, 1968.
22. Taylor, R.K., Induced-trench method of culvert installation, Highway Research Record No. 510, Highway Research Board, Washington, D.C., USA, 41–55, 1973.
23. Bacher, A.E., Banke, A.N., Kirkland, D.E., Reinforced-concrete pipe culverts: design summary and implementation (discussion), Proceedings of the 61st Annual Meeting of the Transportation Research Board, Washington, D.C., USA, 83–92, 1982.
24. Sladen, J.A., Oswell, J.M., The induced trench method: a critical review and case history, Can. Geotech. J., 25(3), 541–549, 1988.
25. Oshati, O.S., Valsangkar, A.J., Schriver, A.B., Performance of two cast-in-place box culverts under high embankments, Can. Geotech. J., 49(12), 1331–1346, 2012.
26. Vaslestad, J., Johansen, T.H., Holm, W., Load reduction on rigid culverts beneath high fills: long-term behavior, Transp. Res. Rec., 1415, 58–68, 1993.
27. Vaslestad, J., Yesuf, G.Y., Johansen, T.H., Wendt, M., Damtew, T., Instrumented field test and soil–structure interaction of concrete pipe with high fill, Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering, 2009.
28. Vaslestad, J., Sayd, M.S., Load reduction on buried rigid culverts: instrumented case histories and numerical modeling, Proceedings of the 5th International Conference on Geofoam Blocks in Construction Applications (EPS 2018), 115–128, 2019.
29. Tyler, M., Earth pressures on induced trench conduits, MSc Thesis, University of New Brunswick, New Brunswick, Canada, 2003.
30. Katona, M.G., CANDE: A modern approach for the structural design and analysis of buried culverts, Report No. FHWA-RD-77-5, U.S. Department of Transportation, Federal Highway Administration (FHWA), Washington, DC, USA, 1976.
31. Yoo, C.H., Parker, F., Kang, J., Bedding and fill heights for concrete roadway pipe and box culverts, Report, Highway Research Center, Auburn University, Auburn, Alabama, USA, 2005.
32. Sun, L., Hopkins, T.C., Beckham, T.L., Reduction of stresses on buried rigid highway structures using the imperfect ditch method and expanded polystyrene (geofoam), Report No. KTC-07-14-SPR-228-01-1F, University of Kentucky, Kentucky, USA, 2009.
33. Yang, X., Zhang, Y., Load reduction method and experimental study for culverts with thick backfills on roadways in mountainous regions, China Civ. Eng. J., 38(7), 116–121, 2005.
34. Zhang, W., Liu, B., Xie, Y., Field test and numerical simulation study on the load reducing effect of EPS on the highly filled culvert, J. Highway Transp. Res. Dev., 23(12), 54–57, 2006.
35. Terzaghi, K., Theoretical Soil Mechanics, New York, Wiley, 1943.
36. Kılıç, H., Akınay, E., Effects of using EPS geofoam as compressible inclusion on HDPE pipe behavior, J. Pipeline Syst. Eng. Pract., 10(2), 04019006, 2019.
37. Kang, J., Soil–structure interaction and imperfect trench installations as applied to deeply buried conduits, PhD Thesis, Auburn University, Auburn, Alabama, USA, 2007.
38. Kang, J., Parker, F., Yoo, C.H., Soil–structure interaction and imperfect trench installations for deeply buried corrugated polyvinyl chloride pipes, Transp. Res. Rec., 2028(1), 192–202, 2007.
39. Witthoeft, A. F., Kim, H., Numerical investigation of earth pressure reduction on buried pipes using EPS geofoam compressible inclusions, Geosynthetics International, 23(4), 287-300, 2016.
40. Akınay, E., Investigating the effect of using compressible bedding material on the behavior of buried flexible pipes, PhD Thesis, Institute of Science and Technology, Yildiz Technical University, Istanbul, Turkey, 2017.
41. Söylemez, B., Laboratory experiments on improvement of buried flexible pipes by using geofoam, MSc Thesis, Middle East Technical University, Ankara, Turkey, 2017.
42. Akyelken, F.A., Kılıç, H., Investigation of effects of EPS material use on buried flexible pipe behavior by numerical analysis, Proceedings of the 8th Geotechnical Symposium, Istanbul Technical University, Istanbul, Turkey, 2019, 1–10.
43. Akyelken, F.A., Investigation of effects of expanded polystyrene material use on buried flexible pipe behavior by numerical analysis, MSc Thesis, Yildiz Technical University, Istanbul, Turkey, 2020.
44. Kefci, Y., Determination of the most geofoam geometry for shallowly buried flexible pipe by finite element analyses, MSc Thesis, Middle East Technical University, Ankara, Turkey, 2020.
45. Akyelken, F.A., Kılıç, H., Experimental and numerical analyses of buried HDPE pipe with using EPS geofoam, KSCE J. Civ. Eng., 26(9), 3968–3977, 2022.
46. Akınay, E., Kılıç, H., Induced trench installation of the high-density polyethylene pipe using geofoam inclusion, Geosynthetics International, 31(3), 327–344, 2024.
47. Kılıç, H., Biçer, P., Bozkurt, S., A numerical investigation of induced and embedded trench installations for large-diameter thermoplastic pipes under high fill stresses, Appl. Sci., 13(5), 3040, 2023.
48. Gulen, M., Kilic, H., Effect of EPS Geofoam on Deformation and Stress Distribution in Shallow Buried Flexible Pipes, Indian Geotechnical Journal, 1–19, 2025.
49. Sargand, S.M., Masada, T., White, K.E., Altarawneh, B., Profile-wall high-density polyethylene pipes 1050 mm in diameter under deep soil cover: Comparisons of field performance data and analytical predictions, Transp. Res. Rec., 1814(1), 186–196, 2002.
50. PLAXIS 2D, Manual Connect Edition V21, Bentley Systems, Delft, The Netherlands, 2020.
51. Sargand, S.M., Masada, T., Long-Term Monitoring of Pipe under Deep Cover. Report No. FHWA-OH-2007/15, Ohio Research Institute for Transportation and the Environment, Ohio, USA, 2007.
52. O’Rourke, T.D., Druschel, S.J., Netravali, A.N., Shear strength characteristics of sand–polymer interfaces, J. Geotech. Eng., 116(3), 451–469, 1990.
53. Sheeley, M., Negussey, D., An investigation of geofoam interface strength behavior, Soft Ground Technology, 2001, 292–303.
54. Xenaki, V.C., Athanasopoulos, G.A., Experimental investigation of the interaction mechanism at the EPS geofoam–sand interface by direct shear testing, Geosynth. Int., 8(6), 471–499, 2001.
55. Tefera, T.H., Aboøe, R., Bruun, H., Aunaas, K., FEM simulation of full-scale and laboratory model tests of EPS, Norwegian Public Roads Administration, Norway, 2011.
56. Bozkurt, S., Reduction of Stresses Acting on Buried Flexible Pipe by Using Compressible Material. MSc Thesis, Institute of Science and Technology, Tekirdag Namik Kemal University, Tekirdag, Turkey, 2021.
57. Brachman, R.W.I., Moore, I.D., Munro, S.M., Compaction effects on strains within profiled thermoplastic pipes, Geosynth. Int., 15(2), 72–85, 2008.
58. Kang, J., Finite element analysis for deeply buried concrete pipes in proposed imperfect trench installations with expanded polystyrene (EPS) foams, Eng. Struct., 189, 286–295, 2019.
59. Norwegian Public Roads Administration (NPRA), 016: Geoteknikk i vegbygging, Report, Norwegian Public Roads Administration, Norway, 2010.
60. Khalaj, O., Azizian, M., Darabi, N.J., Moghaddas Tafreshi, S.N., Jirková, H., The role of expanded polystyrene and geocell in enhancing the behavior of buried HDPE pipes under trench loading using numerical analyses, Geosciences, 10(7), 251, 2020.
61. Kılıç, H., Akınay, E., Gömülü HDPE borularda esneme davranışının incelenmesi, Teknik Dergi, 30(5), 9373–9398, 2019.
62. Al-Naddaf, M., Han, J., Xu, C., Rahmaninezhad, S.M., Effect of geofoam on vertical stress distribution on buried structures subjected to static and cyclic footing loads, J. Pipeline Syst. Eng. Pract., 10(1), 04018027, 2019.
63. Witthoeft, A. F., Kim, H., Kim, D., Impacts of EPS inclusion density and backfill soil type on earth pressure reduction around a buried pipe, 11th International Conference on Geosynthetics, Seoul, Korea, 1680-1689, 2018.