Environment, Coasts, Oceans, & Infrastructure

Dear All,

I need to know which is better PVC geomembrane or HDPE geomembrane. we are using it in the Raw water reservoir (earthen with concrete lined) and the geomembrane is sandwiched between the concrete 75mm on each side. 7m depth of water over the geomembrane. The region temperature is 35 to 40 degrees C.

Please Guide

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Syed Alvi R.Eng
Karachi
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Geomembrane interface frictional failure has been identified as the root cause of numerous geosynthetic lined slope failures. As a result, the interface frictional strength of any geomembrane interface has to be determined with the utmost care.

PVC geomembranes are flexible and relatively easy to handle, while HDPE Geomembranes is tough and non-flexible. HDPE geomembranes tend to exhibit a sharp peak in their stress-strain curve and therefore tend to undergo a relatively abrupt failure whereas PVC undergoes a very large amount of elongation before failure.

Due to its flexibility, it is possible to do a majority of PVC seams under controlled conditions because they can be folded easily. HDPE geomembranes, however, still need to be seamed in the field. A PVC liner may require as low as 20 percent the field seams required by a HDPE liner. 

To conclude-

Even after reaching yield stress of the interface, PVC interfaces will not fail but maintain stability by stretching of the membrane material without loss of strength or material damage.

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Ankur Agarwal Aff.M.ASCE
Lead Civil Engineer
Greater Noida
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The better choice often comes down to the amount of material being installed.  PVC can be very effective in smaller installations (especially <2000sm) that can be done with a single prefabricated panel that can be shipped from a fabrication shop on a pallet.  The economics of HDPE generally become more favorable in installations where mobilization of installation and quality crew is amortized to become the more cost-effective and equally high quality option. 

Where slopes are involved, textured HDPE (blown-film texturing has very good adhesion properties) works very well.  Pneumatically-applied concrete can be applied to textured HDPE at slopes up to 2H:1V with the right mix.  When doing so, it is important to use frequent temperature-crack control joints (much like the joints in a sidewalk, but should be 25mm deep for 75mm thick concrete placed every 2-3m in each direction). 

Both PVC and HDPE have extended stress/strain properties (700% ultimate strain for PE).  HDPE transitions from elastic to plastic deformation at lower strains, but has very high plastic elongation capacity (plastic strains can slowly relieve stresses in the material).  All told, it is far better to create a smooth, firm, and unyielding foundation for any geomembrane rather than relying on the membrane acting as a tensile unit.  Best practice is to use the geomembrane as a barrier layer, load in in uniform compression and shear if needed so that loads are mobilized to the materials below the membrane rather than putting the membrane under long-term tension.

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Adam Maskal P.E., M.ASCE
Senior Technical Manager
Solmax Geosynthetics
Visalia CA
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Dear,

I have completed a waterproofing project for a Fuel Element Factory in Brazil with approximately 15 thousand m², I carried out several studies and the safest and most viable was the PVC blanket. It's not a reservoir, it's a roof, but the study could be similar, in our roof we have a temperature close to 45°C.

If you need more details, you can send me an email and I will be happy to help.

Prezados, 

Estou terminado um projeto de impermeabilização de uma Fábrica de Elemento Combustível no Brasil com aproximadamente 15 mil m², realizei vários estudos e o mais seguro e viável foi o de Manta em PVC. Não é reservatório é cobertura mas o estudo pode ser similar, em nossa cobertura temos temperatura próxima aos 45°C. 

Caso precise de mais detalhes pode me enviar um e-mail que eu terei um prazer em ajudar.

 

 

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Andre Landim Fernandes C.Eng, M.ASCE
Engenheiro Civil
Resende
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