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The Grid That Doubles the Strength of the Ground

practical.engineering

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Re: The Grid That Doubles the Strength of the Ground

#31

Post by margalabargala »

Animats wrote: post #5

Of course, you need "forever plastics" to make this work long term. It's like everything else where you have a material with decent compressive strength but weak tensile strength. You need something with some tensile strength to hold it together. That's what rebar does. It's why rebar rusting out destroys concrete structures. The same problem applies to geotextile containment of dirt. If the textile degrades, it's ju…

> It's why rebar rusting out destroys concrete structures

That isn't really why. The loss of tensile strength from rebar decomposition isn't what kills it.

Steel expands as it rusts. It breaks apart the concrete via expansion just like freezing water would. If you had a mix of steel and stainless steel rebar, the rusting of the normal steel would destroy the concrete all the same.

Re: The Grid That Doubles the Strength of the Ground

#32

Post by jacobolus »

arjie wrote: post #9

Woah dude this is fantastic. I’ve definitely seen this stuff in some places like in unpaved parking lots. Another mystery this has solved for me that I forgot to look into is washboarding on roads. If you’ve ever been to Chilean Patagonia you’ll know that the national park roads there have extraordinary traffic and consequently have quite an intense amount of washboarding. I thought perhaps this was some intentional…

He made a previous video about washboarding: https://practical.engineering/blog/2026/6/2/why-roads-get-wa...

Re: The Grid That Doubles the Strength of the Ground

#33

Post by milesvp »

I was suprised to see the use of wiremesh in sand castle building some years ago. Same concept though. You add something that helps with shear strength and you can build much taller sand buildings. It’s really counter intuitive to see too, since the sand could clearly sieve through the mesh.

Ha! just looked up the video, seems it’s another practical engineering video I was thinking of

https://youtu.be/0olpSN6_TCc?si=8woq9mRHNpWrwCKi

Re: The Grid That Doubles the Strength of the Ground

#34

Post by masklinn »

40four wrote: post #6

A few of my local parks have used this technique in their parking lots. I didn’t know they were called “geo-cells” so that’s interesting. They filled them with gravel. I imagine it was a good way to save some budget versus a traditional paved parking lot

It's not just a budget saver (and possibly an aesthetic decision), it also keeps the ground permeable which has all sorts of impacts in terms of acquifers, ground subsidence, sewer service, etc...

Re: The Grid That Doubles the Strength of the Ground

#36

Post by inigyou »

strken wrote: post #21
inigyou wrote: post #13

Earlier quoted context omitted.

You can have material that biodegrades, or material that doesn't biodegrade. But you can't have material that doesn't biodegrade that biodegrades. Plastic is a wonder material because it's a forever material.

There's a bit of nuance here. A material which doesn't biodegrade but is inert, a material which biodegrades but only when exposed to light or moisture or heat, a material which biodegrades into something else which is in turn inert, etc. Not really relevant to geocells but quite relevant for e.g. timber, which might last a hundred years in a roof but start to rot in six months of composting.

Plastic is inert, but microplastics harm us anyway, and don't go away, because it's inert.

Re: The Grid That Doubles the Strength of the Ground

#37

Post by Animats »

margalabargala wrote: post #31
Animats wrote: post #5

Of course, you need "forever plastics" to make this work long term. It's like everything else where you have a material with decent compressive strength but weak tensile strength. You need something with some tensile strength to hold it together. That's what rebar does. It's why rebar rusting out destroys concrete structures. The same problem applies to geotextile containment of dirt. If the textile degrades, it's ju…

> It's why rebar rusting out destroys concrete structures That isn't really why. The loss of tensile strength from rebar decomposition isn't what kills it. Steel expands as it rusts. It breaks apart the concrete via expansion just like freezing water would. If you had a mix of steel and stainless steel rebar, the rusting of the normal steel would destroy the concrete all the same.

Good point. The steel rusts, expands, more water gets in, more rust, concrete cracking, exposed rebar, rebar rusts away, no tensile strength, collapse.

(I was going to link to a picture, but at least half the images of corroded rebar found by search are AI-generated. Bogus technical pictures are getting out of control. Just saw some of the construction of the Panama Canal. No, steam shovels there did not have cowcatchers.)

Re: The Grid That Doubles the Strength of the Ground

#38

Post by strken »

inigyou wrote: post #36
strken wrote: post #21

Earlier quoted context omitted.

There's a bit of nuance here. A material which doesn't biodegrade but is inert, a material which biodegrades but only when exposed to light or moisture or heat, a material which biodegrades into something else which is in turn inert, etc. Not really relevant to geocells but quite relevant for e.g. timber, which might last a hundred years in a roof but start to rot in six months of composting.

Plastic is inert, but microplastics harm us anyway, and don't go away, because it's inert.

Plastics tend to be more chemically active than a lot of rocks, for example.

Although that's not going to protect you from crystalline dust from silica and asbestos.

Re: The Grid That Doubles the Strength of the Ground

#39

Post by Jedd »

lathiat wrote: post #14
Jedd wrote: post #10

I saw some examples of this while travelling in Japan last year, and am keen to replicate. I suspect, like a lot of things, the local product there is superior to what I could find back home here in AU. At some castle courtyard, we were walking around on a smooth-white-gravel surface, and I didn't immediately register how different it felt. Stare at the ground for a few moments, and notice some of the small (15-20mm)…

The sad part is how expensive it is (I’m in Australia too). Seems up front like a cheaper alternative to pavers but both the moulded plastic and the soft plastic that fans out versions are a solid $40-$45/sqm AUD. Can buy brick pavers for that and you still have to purchase the pebbles to go in it…

Pavers for $40-45 - are going to be pretty unattractive grey concrete (well, cement) ones, right?

Even Bunnings (albeit marketplace) has 100mm geogrid for $20 / square metre.

Most local vendors have 'call us for pricing', but I've found a few others in the $10-20 range. Obviously, yes, in-fill on top of that - say $250 a cube depending on your tastes, so add $12-25 per square metre.

As per sibling comment - with some fabric underneath, and a modest amount of ground prep, installation of this stuff sounds fast and easy.

Re: The Grid That Doubles the Strength of the Ground

#40

Post by Dylan16807 »

inigyou wrote: post #13
avesi wrote: post #7

Earlier quoted context omitted.

There appears to be a bamboo-derived plastic out there with high tensile strength, but I don't think it'd work for this application, because it degrades within 50 days of being buried in soil. I wonder if being in gravel would delay that, due to the different microbes present? It seems like there are usually biobased solutions out there, but they aren't as cost-effective or easy to procure as the forever plastics, so…

You can have material that biodegrades, or material that doesn't biodegrade. But you can't have material that doesn't biodegrade that biodegrades. Plastic is a wonder material because it's a forever material.

Plastic that disappeared after 50 or 100 years would still be very useful for making things. Plastic for packaging only needs to last months or years.

You need to avoid certain kinds of biodegradation but you don't need "forever".

And in particular if you could make very small pieces biodegrade quickly, and only those, you'd instantly solve microplastics.

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