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Experimental Evaluation of Geocell and EPS Geofoam as Means of Protecting Pipes at the Bottom of Repeatedly Loaded Trenches

Moghaddas Tafreshi, S. N.; Joz Darabi, N.; Dawson, A. R.; Azizian, M.

Authors

S. N. Moghaddas Tafreshi

N. Joz Darabi ndarabi@mail.kntu.ac.ir

A. R. Dawson

M. Azizian m.azizian@mail.kntu.ac.ir



Abstract

© 2020 American Society of Civil Engineers. With growing populations and continuing urban development, embedding pipes in the ground that are then overrun by traffic is inevitable. This paper describes full-scale prototype tests on high-density polyethylene (HDPE) flexible pipes (of 250 mm diameter), buried at shallow depth, under simulated traffic loading. The paper studies the effect of surface load diameter (0.6×, 0.8×, and 1× pipe diameter) and the amplitude of repeated load (400 or 800 kPa) on pipe behavior. The effects of expanded polystyrene (EPS) geofoam blocks of various densities and also of geocells as a three-dimensional (3D) reinforcement in reducing the pressure transferred to the pipe, the deformation of the pipe, and the surface settlement of the backfill were investigated. The results show that, with an increase in loading surface diameter, the pipe's vertical diametral strain, the pressure transferred to the pipe, and the surface settlement grow significantly, irrespective of applied pressure. Using an EPS block over the pipe increases the soil settlement but reduces transferred pressure onto the pipe and, consequentially, results in lower pipe deformations. The increase in density of an EPS block helps improve response but was still found to be insufficient to prevent increase in surface deflections. The use of geocell reinforcement beneath the loading surface not only reduces the pressure transferred to the pipe and decreases its deformation but also significantly negates the tendency of the EPS block to increase the soil surface settlement. Thus, a geocell reinforcement layer placed over two EPS geofoam blocks (with total thickness 0.3× and width 1.5× the pipe diameter) all above a pipe buried at a depth of twice the pipe diameter, was found to deliver an acceptable, stable response. By these means, the vertical pipe strain, transferred pressure over the pipe, and soil surface settlement were reduced, respectively, by 0.45, 0.37, and 0.53× those obtained for the comparable unmodified buried pipe installation and are within allowable limits.

Citation

Moghaddas Tafreshi, S. N., Joz Darabi, N., Dawson, A. R., & Azizian, M. (2020). Experimental Evaluation of Geocell and EPS Geofoam as Means of Protecting Pipes at the Bottom of Repeatedly Loaded Trenches. International Journal of Geomechanics, 20(4), 04020023. https://doi.org/10.1061...%29GM.1943-5622.0001624

Journal Article Type Article
Acceptance Date Sep 11, 2019
Online Publication Date Jan 31, 2020
Publication Date Jan 31, 2020
Deposit Date Sep 17, 2019
Publicly Available Date Sep 17, 2019
Journal International Journal of Geomechanics
Print ISSN 1532-3641
Electronic ISSN 1943-5622
Publisher American Society of Civil Engineers
Peer Reviewed Peer Reviewed
Volume 20
Issue 4
Pages 04020023
DOI https://doi.org/10.1061/%28ASCE%29GM.1943-5622.0001624
Keywords Soil Science
Public URL https://nottingham-repository.worktribe.com/output/2624735
Publisher URL https://ascelibrary.org/doi/full/10.1061/%28ASCE%29GM.1943-5622.0001624
Related Public URLs http://cedb.asce.org
Additional Information Received: 2019-03-18; Accepted: 2019-09-10; Published: 2020-01-31

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