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) off-white pebbles are perfectly aligned on a grid pattern.
Squat down to investigate, and they've got these corners of the plastic mesh geogrid topped off with little white caps that are almost indiscernible from the rounded white aggregate they're using as infill. It was almost like seeing a random dot stereogram, except completely regular (and no dinosaurs) of course.
The math is pretty interesting, and TFA didn't touch on this aspect I don't think. I'm looking to use 10-20mm irregular shaped scoria on a large-ish area, and the heuristic evidently is that your maximum aggregate size should not exceed one third of the geocell depth - so I'd want 50mm depth at most there, sitting on solid-ish sub-layer.
(I believe that heuristic goes out the window if you've got regular shaped gravel.)
The other ratio to consider is aggregate size to cell size, and that, in turn, is dependent on load and slope. Then there's the mechanical attributes of your in-fill (will it slowly crush over time, with expected loads - for softer rocks you'll definitely need a geotextile above your sub-base and below your geo-cell.) All tremendously more complicated than the 'few wheelbarrows of blue metal' I grew up with.
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…
brick pavers need a tamped gravel base, then bedding sand, and then polymeric sand to lock them together. the cost of install is not just the cost of pavers. and installation is something that requires enough skill that it's possible to do it wrong. depending on how much weight you plan to drive over it, you might also need to pour a concrete base for them.
geogrid is orders of magnitude easier and quicker to install.
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.
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 just a pile of dirt, in a place where a pile of dirt isn't enough.
The more traditional approach is to surround dirt or rubble with something that has more tensile strength. Some Egyptian pyramids were built that way. One of them fell down because the outward pressure from the load above was not sufficiently contained.
Traditional stone construction of large structures is all about containing that outward push. That's what flying buttresses and bridge abutments do.
> 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.)
I'm sort of OK with this use of plastic. Unlike all the single-use plastics we make (bottles, forks, food-wrap - the list is endless) this is going to be in use and providing value for decades. And can likely be made from recycled HDPE.
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 organizations don't bother with them. Perhaps some kind of incentive would get us moving in the right direction.
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.
That reminds me of a fun research presentation I saw a decade ago. They engineered a bioplastic which would break down on sustained contact with water. While trying to come up with applications, they proposed reducing plastic consumption by using it for ... water bottles.
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.
The problem with plastic is that it often doesn't biodegrade but loses capability with time. So you end up with it turning to rubble after few decades but still polluting the environment
There are species of wood that do very well buried. Black locust is known to last 100yr buried. I wonder if you could scale up the effect using a larger grid of black locust 2x8s [edit] or even smaller dimension mill scrap.
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
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 structure wrought to give cars purchase when the roads are wet. It’s actually because of wheels acting as friction and pushing material forward to some point after which they proceed over it and repeat. It is surprisingly periodic and I thought surely intentionally built.
As an aside, I skipped over the video and ended up reading the text (which suspiciously was like an article without web assets loaded) and I wonder if use of AI could have built a freeze frame article out of this. The video is 18 min long but the text can be read in a fraction of the time.
Regardless, top quality link. Very interesting stuff. Surprisingly old too. We’ve had the tech for 50 years and we have used it in a widespread fashion in the civil world for three decades or so.
I’ve tried to utilize this stuff on a development that is near a flood zone, and boy is it tough to get building inspectors and even engineers in the US to look at any material they haven’t already seen before.
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 usually used for parking lots as a way to control vegetation. Put some geotextile at bottom layer, put grate for structure and fill it in, you end up wih flat enough, strong enough structure that doesn't need much care weed wise coz they can't get deep roots
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...
The plastic structure could easily give problems at extreme environmental temperatures due to thermal expansion. Saw this recently at a local parking lot, laid by non-professionals.
I like concrete geogrid/cell much more, but I guess its cost a good deal more both in materials and installation. Is it really that uncommon in the US?
Disgusting. All runoff will be forever full of microplastics, especially when you can achieve something similar with raw concrete and an imprinting tool.
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) off-white pebbles are perfectly aligned on a grid pattern.
Squat down to investigate, and they've got these corners of the plastic mesh geogrid topped off with little white caps that are almost indiscernible from the rounded white aggregate they're using as infill. It was almost like seeing a random dot stereogram, except completely regular (and no dinosaurs) of course.
The math is pretty interesting, and TFA didn't touch on this aspect I don't think. I'm looking to use 10-20mm irregular shaped scoria on a large-ish area, and the heuristic evidently is that your maximum aggregate size should not exceed one third of the geocell depth - so I'd want 50mm depth at most there, sitting on solid-ish sub-layer.
(I believe that heuristic goes out the window if you've got regular shaped gravel.)
The other ratio to consider is aggregate size to cell size, and that, in turn, is dependent on load and slope. Then there's the mechanical attributes of your in-fill (will it slowly crush over time, with expected loads - for softer rocks you'll definitely need a geotextile above your sub-base and below your geo-cell.) All tremendously more complicated than the 'few wheelbarrows of blue metal' I grew up with.
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…
brick pavers need a tamped gravel base, then bedding sand, and then polymeric sand to lock them together. the cost of install is not just the cost of pavers. and installation is something that requires enough skill that it's possible to do it wrong. depending on how much weight you plan to drive over it, you might also need to pour a concrete base for them.
geogrid is orders of magnitude easier and quicker to install.
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.
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 just a pile of dirt, in a place where a pile of dirt isn't enough.
The more traditional approach is to surround dirt or rubble with something that has more tensile strength. Some Egyptian pyramids were built that way. One of them fell down because the outward pressure from the load above was not sufficiently contained. Traditional stone construction of large structures is all about containing that outward push. That's what flying buttresses and bridge abutments do.
> 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.)
I'm sort of OK with this use of plastic. Unlike all the single-use plastics we make (bottles, forks, food-wrap - the list is endless) this is going to be in use and providing value for decades. And can likely be made from recycled HDPE.
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 organizations don't bother with them. Perhaps some kind of incentive would get us moving in the right direction.
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.
That reminds me of a fun research presentation I saw a decade ago. They engineered a bioplastic which would break down on sustained contact with water. While trying to come up with applications, they proposed reducing plastic consumption by using it for ... water bottles.
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.
The problem with plastic is that it often doesn't biodegrade but loses capability with time. So you end up with it turning to rubble after few decades but still polluting the environment
There are species of wood that do very well buried. Black locust is known to last 100yr buried. I wonder if you could scale up the effect using a larger grid of black locust 2x8s [edit] or even smaller dimension mill scrap.
>If the textile degrades, it's just a pile of dirt, in a place where a pile of dirt isn't enough.
It's now a pile of dirt with loads of bits of plastic and slowly leeching plasticisers.
Yep, my first thought when I saw this was "and everywhere this is used, microplastics out to wazoo."
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
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 structure wrought to give cars purchase when the roads are wet. It’s actually because of wheels acting as friction and pushing material forward to some point after which they proceed over it and repeat. It is surprisingly periodic and I thought surely intentionally built.
As an aside, I skipped over the video and ended up reading the text (which suspiciously was like an article without web assets loaded) and I wonder if use of AI could have built a freeze frame article out of this. The video is 18 min long but the text can be read in a fraction of the time.
Regardless, top quality link. Very interesting stuff. Surprisingly old too. We’ve had the tech for 50 years and we have used it in a widespread fashion in the civil world for three decades or so.
He made a previous video about washboarding: https://practical.engineering/blog/2026/6/2/why-roads-get-wa...
Watching the video clearly shows example of how this drastically lessens the washboarding you specifically mentioned.
I’ve tried to utilize this stuff on a development that is near a flood zone, and boy is it tough to get building inspectors and even engineers in the US to look at any material they haven’t already seen before.
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 usually used for parking lots as a way to control vegetation. Put some geotextile at bottom layer, put grate for structure and fill it in, you end up wih flat enough, strong enough structure that doesn't need much care weed wise coz they can't get deep roots
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...
The plastic structure could easily give problems at extreme environmental temperatures due to thermal expansion. Saw this recently at a local parking lot, laid by non-professionals.
There are metal versions available
Neat to read about that technique being used in port of Los Angeles while sitting here eating breakfast in my boat. Unexpected.
I like concrete geogrid/cell much more, but I guess its cost a good deal more both in materials and installation. Is it really that uncommon in the US?
I have no interest in this topic at all, but I couldn't stop watching the video. It turned out to be really interesting!
Disgusting. All runoff will be forever full of microplastics, especially when you can achieve something similar with raw concrete and an imprinting tool.
[dead]
what a domain
Interesting concept; horrible writing.
It's a transcript of the video, which I enjoyed.
I found it okay! With how much AI slop is out there, human writing will usually make me appreciative.
> And these strips don’t just engage with the backfill like geogrid; they encapsulate it.
I wonder when grady is going to issue a mea culpa for using too much AI in his video production?
AI has been trained on real data, and some real human speech uses the same catchy hooks as an AI.
In this case, the style seems consistent with his earlier work.
https://youtu.be/SW-NoiM726U?si=D_ehA4N8HzHYiZkf&t=142 (from 2017)
> Expansive clay isn't just an issue for buildings. All kinds of infrastructure are at risk of damage from a shifting foundation.
His production style is consistent over the past decade.