Questions about geogrid and cinderblock wall

[Sebculb]

So actual geogrid is kind of an overpriced ripoff. Unfortunately I dont think the type of plastic fence you're talking about would be very effective in clay since it'd basically flow through it over time. I think you could use a solid woven landscape fabric with better success. Its a bit unfortunate that you wont have a good way to anchor it to the wall but putting a layer down, backfilling a foot and doubling it back over top would be better than nothing.

Is there any way to keep the backfill permanently dry after its done? since you arent dealing with any frost heaving that wall would never move if the clay behind it could be kept dry. Its a little hard from the picture to tell how the project is going to look completed so i dont know if thats even remotely possible

Here we go, you think similarly to me. I've considered geotextile also but based on my Google and YouTube level research there's something about the different layers contacting each other that added a level of cohesion. But the truth is I don't know. Does it matter at this point? This is the direction I'm thinking in, though, and real geotextile is available here as opposed to the green snow fence.

The soil is a kind of Sandy clay for what it's worth, not slick orange snot.

I have *definitely* been thinking about putting a layer of plastic under the top layer of backfill soil to keep the whole thing dry. Maybe under the top row of weep holes...

I've been thinking about all this stuff, but dunno exactly what we're going to do yet. But yes, this is exactly what I'm thinking about.

Thanks!

Any other input along these lines?

 

[Sebculb]

Has anyone ever substituted geotextile for geogrid under a given set of circumstances?

 

[Alan W.]

Never saw geogrid used with masonry block. Have used it quite a bit with actual retaining wall block.
Depending on the height of the wall the engineer will specify at what levels to install it.
If the engineer wants it at every 5 runs then after the fifth run you backfill with rock level with the block. Place the geogrid on top of the block and over the backfill. The block locating pins will secure it to the block. Then you proceed to lay more block and backfill with rock. It holds the wall exceptionally well.
A bit over simplified but hopefully you get the idea.

 

[amhicks21]

Ah, yeah. We have the slick orange snot around my area so you're better off than I would be. I think a layer of maybe 10 mil plastic at the top would definitely be helpful as long as there isnt too much debris that would put holes in it. I honestly think you're headed in the right direction considering the circumstances. geotextile layers with a moisture barrier at the top sounds like a good plan. Tbh, my experience is mostly with retaining wall block with geogrid between the layers but Ive had to repair some walls built by other people. Here's a video that does a really great job of detailing what ive learned about fixing walls.

 

[Streetcar]

The orange construction fence looks similar to Geogrid but is not close to same properties.waste of money to use plastic fence
geo fabric does not have the strength of Geogrid. Do not use fabric
most retaining walls fail due to pressure from water behind the wall, drain the water and the wall will last longer
geogrid is installed in layers with depth between layers and length of Geogrid controlled by type of soil
Geogrid does not have to be attached to wall for it to work.

 

[Sebculb]

There's good stiff flat fencing here that I'm certain would work well as geogrid. But it costs at least $3.50 per meter and since I need about 100 meters to do what I need to do, that kind of gets too expensive. Remember there is a significant instalation cost in addition to the cost of the materials. The idea of geotextile as a substitute gets my attention as well. However since I think part of the deal is it's supposed to be stiff, and considering that it's also expensive, I won't be gambling on that for the customers project.

I am going to bury a plastic barrier close to the top to help keep water from filtering down and saturating the fill soil.

Thanks everyone for the advice and helping me brainstorm!

 

[Streetcar]

There's good stiff flat fencing here that I'm certain would work well as geogrid. But it costs at least $3.50 per meter and since I need about 100 meters to do what I need to do, that kind of gets too expensive. Remember there is a significant instalation cost in addition to the cost of the materials. The idea of geotextile as a substitute gets my attention as well. However since I think part of the deal is it's supposed to be stiff, and considering that it's also expensive, I won't be gambling on that for the customers project.

I am going to bury a plastic barrier close to the top to help keep water from filtering down and saturating the fill soil.

Thanks everyone for the advice and helping me brainstorm!

Geofabric has no tensile strength . It will not help retaining wall
if you want to use fence look at chain link not the plastic fence

 

[amhicks21]

Geofabric has no tensile strength . It will not help retaining wall
if you want to use fence look at chain link not the plastic fence

What is the required tensile strength?

 

[Streetcar]

Tensile strength required depends on height of wall and properties of the soil

 

[erikjohn67]

Has anyone ever substituted geotextile for geogrid under a given set of circumstances?

No, do not do this. I will preface my comment to you by stating that I am an engineer and have have been a contractor in heavy civil construction for 25+ years building roads, bridges and complex civil works. I have years of experience with mechanically stabilized earth walls which includes geo grid walls. We use geo grid walls as temporary walls with a wire face for phased construction.

The geo grid tie back is absolutely necessary even though it may seem like to the layman that it is not. You would be surprised how much force that geo grid will resist as it may not seem strong but when wedges between dirt layers it resists a lot of force.

1) Using filter fabric can reduce the drainage behind the wall which will creat unnecessary head pressure against the wall and can cause it to blow out, unless it was specifically designed that way. The geo grid is free draining and does not have this issue.

2) The fact that you have a solid wall is only that, the wall is solid. It could be a foot think steel plate standing up but unless there is something keeping it from tipping over(tiebacks like the geogrid or chance anchors) the stiffness of the wall means nothing when it is being used to retain earth because their is nothing to resist the moment(overturning force) the wall is feeling.

Install the geogrid per the manufactures specifications for a wall that height. Use the proper backfill. Clay and silty material does not work as it has slip planes in the material(hence why clay is so slippery when wet). It need to be free draining sandy material without organics.

Do not compact to hard next to the wall as you it is not the hard to move the wall out of place. Consider some minimal hydro compaction within 3 foot of the wall after a very lightly compacting mechanically. Out side of three feet you should be good but start at the middle of the geogrid and compact away from the wall and then come back and compact towards the wall.

Im sure there is lots of videos and literature online to watch but you you absolutely have to properly tie back that wall or it will fail.