Thread: TomG's Photos
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Old 04-07-2011, 09:02 PM
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TomG TomG is offline
LawnSite Senior Member
Join Date: Dec 2010
Location: Londonderry, NH
Posts: 675
DVS, wow, just wow is about all I can say, have YOU taken an NCMA class and passed? I don’t like to call people out but I will this time, nether you or your company is listed in on the NCMA website as certified installers. (I looked under Outdoor Creations in Maryland and searched all of Maryland for Andrew with no luck). I actually really respect your opinions on things because you seem very knowledgeable but I am second guessing myself now. For you to say and I quote “Tom, buddy you are WAY off. Grid IS NOT used to " reinforce soil". It is used to stabilize the block, to keep the block from rotating forward “ Is really, really surprising and quite frankly YOU are way off.

One of the first things they teach you in an NCMA class is that there are two types of SRW’s, “gravity” and “reinforced soil” and that geo-grid does not hold up the wall it stabilizes the soil behind the wall. Here is part of a recent NCMA newsletter: “Reinforced Soil Reinforced soil walls should be specified when the maximum height for conventional gravity walls is exceeded or when lower structures are surcharged by sloping backfills, live loads, and/or have poor foundations. A reinforced soil SRW is designed and constructed with multiple layers of soil reinforcement placed between the SRW courses and extending back into the soil behind the wall at designated heights and lengths as shown in Figure 1b. The geosynthetic reinforcement and the soil in the reinforced zone act as a composite material, effectively increasing the size and weight of the wall system.” How about this video from everyone’s favorite techo-employee: Or this one: Why does he keep calling it a reinforced soil wall if... as you say... the grid doesn't reinforce the soil???

Now about saying that geo-grid is basically a “tieback” for the SRW units. (that’s what I got from reading your last post) Please read this article from Allan Block. And look at this ICPI tech spec Why would a geo-grid be spec’ed into a wall on a raised patio where the maximum height is 4 feet if it is just a “tieback.” A raised patio is not considered load bearing.

Lastly you saying “Grid acts in the same capacity. Thus making the grid depicted in toms photo absolutely useless because nothing will be tugging on it. As that's what it's designed for, which is why there are different grades of grid strength.” And “The grid you folks used under the granite is doing absolutely nothing. It is not stabilizing and soil. Grid has it's strength in one direction as that is where pressure is apPlied when the block pulls on it.” I have said before that I don’t like giving out all of our secrets but I’ll share this one. Under the granite steps we put grid in and we don’t run it all in the same direction. We lay the first layer parallel with the foundation and the second perpendicular, and continue that as needed. It actually increases the strength of the soil a lot. Have a look at this video. Also take a look at the two pictures below, they are from a one day class I took on Geo-synthetics from the College of Engineering at the University of Wisconsin-Madison.
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