Why does Benders want you to use geotextile like this?

[andreascarlsson]

I am building a wall, Benders Megawall. According to their instructions, they want an extra geotextile fabric at the bottom.
Can anyone explain to me what function this geotextile fabric serves?
(taken from https://www.benders.se/globalassets/c4-assets/document/MA-SE-2016-MARK-Murar-MEGAWALL-GARDEN-HU.pdf)

 

[huvudtystnad]

A pure guess - don't really know anything about this, but could it be an extra protection from below against roots that can creep under the wall from the lower ground level on the other side of the wall? Or am I thinking wrong?

 

[andreascarlsson]

A pure guess - know nothing about this really, but could it be extra protection from below against roots that can creep under the wall from the lower ground level on the other side of the wall? Or am I thinking wrong?

That could be the case, but why not put it under the wall then…? 🤔

I have also sent the question to Benders customer service, with a bit of luck I'll get a reply from them.

 

[Taxture]

The image clearly shows that it is protection for the drainage……?

 

[andreascarlsson]

The picture clearly shows that it is protection for the drainage...?

I don't understand? Do you mean extra ground fabric is needed for the drainage?

 

[Hybro]

My guess is to prevent the drainage pipe's slots/small openings from being clogged by finer materials.

 

[andreascarlsson]

My guess is to prevent the drainage pipe's cracks/small openings from getting clogged by finer material.

Sounds perfectly reasonable. Thanks for the insight!

 

[cpalm]

My guess is that it is to prevent the drainage pipe's slots/small openings from being clogged by finer material.

Sounds like a good guess. But for the same reason, it's a bit strange that they show the drainage pipe being laid in compacted 0-63. Or is it 24-63? A bit unclear from the picture. Usually, the construction is that the pipe should be laid in a "loaf" of drainage gravel, with at least 1 dm of gravel around the pipe.

 

[snickar]

I think it looks like they just want different sizes of gravel, which feels strange because they show that there should be a geotextile around everything. Then there's no point in adding an extra geotextile. I would have laid a layer from top to bottom with gravel for drainage and separated everything with a geotextile. The geotextile should also be under the wall.

 

[topmount]

Sounds like a good guess. But for the same reason, it's a bit strange that they show the drainage pipe laid in compact 0-63. Or is it 24-63? A bit unclear from the picture. Usually, the construction is that you should lay the pipe in a "bed" of drainage gravel, with at least 1 dm of gravel around the pipe.

Not entirely clear, but they do have draining material over the pipe and then compact material underneath, surely they could have lifted the pipe in the drawing by a few mm.

 

[cpalm]

It's not entirely clear, but they do have draining material over the pipe and then compact material underneath, sure they could have raised the pipe in the drawing by a few mm

It's not that the pipe is too low, but that the gravel mound normally encompasses the drainage pipe rather than sits on top of it. Compare (borrowed image from https://silbodalssten.se/dranering-stockholm/):

 

[topmount]

It's not that the pipe is too low, but that the gravel loaf normally encloses the drainage pipe rather than lying on top of it. Compare (borrowed image from [link]):
[image]

Yes, but do you really want to let all the water fall under a freestanding wall? A bit different from a house foundation as your image shows.

 

[cpalm]

Yes, but do you really want to let all the water down under a freestanding wall? A bit different from a house foundation as your picture shows

Good question. I realize I chose a less suitable picture, but I didn't mean that the wall necessarily should stand on draining material. The point was that if you want to ensure that fine-grained material doesn't clog the drainage pipe, there is no logic in embedding the pipe in such material.

 

[fribygg]

My guess is to prevent the slits/small openings of the drainage pipe from being clogged by finer material.

In that case, shouldn't the drainpipe be placed in macadam surrounded by geotextile?

 

[andreascarlsson]

As Hybro and several others have correctly figured out, it is protection for the drainage pipe. Benders responds as follows:

"Hello,

It doesn't really serve a major function, but we show it to clarify the separation of materials so that fine material doesn't enter the drainage pipe.
The most important is the geotextile, which holds the soil, i.e., the solid yellow line in the rest of the image.

Take care!"

I don't have a drainage pipe myself, so it won't matter...