The Grid That Doubles the Strength of the Ground

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.

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.

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.

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

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.

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.

what a domain

Interesting concept; horrible writing.

> 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?