base reinforcement question

[gridguy]

how critical are the flexural stiffness and junction strength properties in base reinforcement? I see that woven polyester biaxial geogrids are becoming more prevalent, yet most specifications have the flex. stiffness and junction strength numbers that are obviously written around a punch and drawn polypropelene.

If the 2% strain and 5% strain values match up, can you use a woven polyester instead of the polypropelene?

 

[GeoPaveTraffic]

The choice of geotextile materials (grids, woven, and non-woven) depends greatly on the specific application. For this reason I have always specified a specific product with the "Approved Equal". That way I could evaluate the proposed substitution based on the specific application.

With respect to your specific question, if by "base reinforcement" you mean that you are installing the geotextile below the base rock of a pavement section, then I would be most concerned with the amount of strain required to mobilize the strength. But then again if the geotextile is being installed below a temporary pavement, the strain may not matter much. If you could provide more information on you specific situation, I would be happy to comment some more, hope this helped some.

By the way, specifications should always define "Approved Equal". My definition was always "Determinations of whether a product is approved will be at the sole discretion of the Engineer." That way I always get what I'm looking for.

 

[layfieldman]

If this is for base reinforcement, quite a bit about the junction strength and flexural stiffness tend to be more marketing values than real engineering values. The LTDS is the most important value. It takes into account the creep, installation damage, biological/chemical degradation and joint efficiency reduction factors into account and will give you a LTDS that you can then design with. I find that using a very stiff polypropylene or hdpe biaxial geogrid is harder to install and promotes voids due to it's stiffness. It sometimes requires staking to maintain intimate contact and prevent bridging as well. Each engineer seems to be more comfortable with one material or another depending on what they have experience with.

There is another thread on here called "Comparison of HDPE and PVC COATED PET GEOGRID" which might be of interest to you.