Laboratory tests of small-diameter HDPE pipes buried in reinforced sand under repeated-load

Experimental and numerical studies on protection of buried pipelines and underground utilities using geocells

“…However, the use of geosynthetic reinforcement to protect buried pipes and underground utilities is relatively a new concept. Moghaddas Tafreshi and Khalaj (2008) conducted the laboratory studies on small diameter HDPE pipes buried in the geogrid reinforced sand subjected to repeated load. Researchers observed the significant reduction in the deformation of the pipe in the presence of geogrids.…”

Combined use of geocell reinforcement and rubber–soil mixtures to improve performance of buried pipes

“…Moghaddas Tafreshi and Khalaj (2008) assessed the behaviour of small-diameter high-density polyethylene (HDPE) pipes (110 mm diameter and 4.03 mm wall thickness) buried in reinforced sand that was then subjected to repeated loading (of amplitude 550 kPa). They examined the influence of between 1 and 5 layers of reinforcement in soil having relative densities of 42%, 57%, and 72%.…”

“…These authors reported, for example, that the proportion of vertical pipe diameter change and soil surface settlement can be reduced by up to 40% and 51%, respectively, when using the most reinforcement in backfill of the highest density when the pipe is at its deepest embedment. Tavakoli also developed a genetic algorithm linked together with a neural network (based on the test results of Moghaddas Tafreshi and Khalaj (2008)) and found out that to achieve 10 mm soil surface settlement and 2% pipe vertical diametral strain, one layer of geogrid, 75% soil relative density and a ratio of 2.5 for embedment depth of the pipe to pipe diameter would be required.…”

Reply to the discussions by Huang, C.C. on “Comparison of bearing capacity of a strip footing on sand with geocell and with planar forms of geotextile reinforcement” [Geotextiles and Geomembranes 28(1), 2010, pp. 72–84]

“…It is on the basis of these results that the subsequent comparison of efficient use of geosynthetic mass was made. For the planar installation, the optimal depth for the top is centrally within the range suggested by several researchers (Akinmusuru and Akinbolade, 1981;Yoon et al, 2004;Ghosh et al, 2005;Moghaddas Tafreshi and Khalaj, 2008), i.e. a depth of u ¼ 0.25Be0.5B.…”

“…12b and 13b in the paper) strongly suggest that reinforcement lengths with b p > 2.8B (or b g > 3.2B) provide no additional benefit in terms of IF and PRS and the authors intentionally used inefficient length of b p ¼ 4.1 and 5.5, merely to obtain a reinforcement mass equivalent to that for a geocell-reinforced ground! The authors accept that, in practice, wide reinforcements are inefficient (indeed, the authors observed this as one of their conclusions and also other researchers found the same result (Yoon et al, 2004;Ghosh et al, 2005;Sitharam and Sireesh, 2005;Sitharam et al, 2007;Moghaddas Tafreshi and Khalaj, 2008)), but the authors cannot agree with the discusser's overall conclusion that these results don't demonstrate that a geocell reinforcement has a better performance, weight-for-weight, than the comparable planar reinforced installation and also the authors cannot accept using, intentionally inefficient lengths of b p > 2.8B, merely to obtain a reinforcement mass equivalent to that for a geocell-reinforced ground.Figs. 3 and 4 in the discussion, or Figs.…”