This will revolutionise Yorkshire.
Autonomous excavator constructs a six-metre-high dry-stone wall
151–160 of 190 posts
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#152Earlier quoted context omitted.
It's very common in Croatia, too.
And Malta: https://www.google.com/search?q=malta+rubble+wall There they are called rubble walls ("hajt tas-sejjieh" in Maltese). Seems pretty common in Mediterranean countries.
Thank you, there is a great explainer in those search results: https://environmentalmalta.com/wp-content/uploads/2019/12/IR...
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#153Just wanted to share that in my country (Spain) and more concretely in my area (rural part of Catalonia) we have a building technique called “Pedra Seca” literal translation is “Dry Stone”. It basically involves building stuff with just rocks, nothing more. It’s still in use mostly in agricultural fields. Here are a few examples: https://dd9de8c7b7.cbaul-cdnwnd.com/b5fbcf0e77b7b72ef95acd62... https://static1.ara.cat/…
Interesting! I am living in Catalonia now, but in Barcelona. I haven't seen (or paid attention) to a wall like that. Will pay more attention and try to find some nearby. Thanks!
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#154Earlier quoted context omitted.
So are you saying we couldn’t estimate the structural properties of autonomous built dry walls from local stone? Or that the error bars would be unacceptably large? Or just that this approach would only work with certain stone in certain locations?
I think the problem is more that you cannot at all guarantee a specific performance of the structure ahead of time, because you can't know what the properties of the local rocks will be before you are on site and have measured them all.
Geotechnical engineering is all about taking samples and using wide enough safety margins. And in the vast majority of cases, the end result is a building that doesn't fall down.
Sure, you might have been really unlucky that all your test samples of soil and rock were really strong granite, but the exact spot you put the main structural pile, unknown to you, was all mud and silt... But the chances are so vanishingly unlikely we accept it.
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#155Earlier quoted context omitted.
Not only is this a technical marvel, but it has potential construction physics implications. In simple terms, currently we expend energy to fragment rock, and then we expend additional energy (as concrete) to glue it back together. We do all this to re-arrange rocks into a shape (and strength) we want, and most importantly to do it cheap . Suddenly, an alternative just got a lot cheaper. Clearly this isn't fully bake…
Tensile strength will be a problem. Compression will be solved eventually, the tetris part also. But if there are to be tensile or twisting loads - there will be trouble.
Add steel/fiberglass tension rods and you can trade off compressive for tensile strength.
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#156Having made a few dry stone walls I can attest to the merit of this achievement. Judging where rocks are to be placed, and in what orientation is a zen art. Anecdotally... I once tried to get wild flowers to grow on a stone wall. Every year we would seed the wall, only for the seeds to fall out or be eaten by birds. On inspiration, my boss filled a few shotgun cartridges up with seeds and fired them at the wall. Perf…
This isn't really a proper wall though, it's a single thickness stack. I don't think it could handle any lateral force at all without toppling. If this machine could build a double skin wall with batter, wall heads, and hearting throughout the center, I'd be really impressed!
I suspect all those things are just fairly minor software changes...
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#157Nice. Heavy equipment with many degrees of freedom is hard for humans to control. Some operators are really good, but not all of them. A backhoe hooked up to a virtual reality input arm with force feedback was built several decades ago. The operator could feel obstructions, and dig out the dirt around a pipe by feel. Never became a product, though. Probably too early.
The force feedback would be yet another layer of tetchy stuff to keep running in a really harsh environment. I've know backhoe operators who strongly preferred older equipment, when its too new the pins are too tight and they have no "slop" to work with. That slop is what they're using for sensory input, if you watch them. With attention and experience that's real time feedback. The whole machine is the force feedbac…
> The force feedback would be yet another layer of tetchy stuff to keep running in a really harsh environment.
Luckily, hydraulics offer a very easy way to do force feedback: Just measure the post-valve cylinder pressure.
That means you can have all your wiring and sensors in the cab far away from the dirt and rain. Makes force feedback pretty easy and cheap.
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#158Earlier quoted context omitted.
> You could stop water draining through the retaining wall and turn it into a dam, which will not end well. Which is why gravel backfill with a perforated pipe at the base (that drains to day light) is specified by many/most building codes.
So what you're saying is we made a problem for ourselves, and then we hacked on additional cost (and plastic) to fix it? I'm starting to see the advantages of this dry stone wall technique.
Eh, the perforated pipe technique can efficiently collect the water and move it somewhere else entirely. It's nice that dry stone can just let water fall through, but then it just runs out at the base. Which might be fine, but you might still want a french drain anyway.
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#159One might call it a... Deus Ex Cavator.
Re: Autonomous excavator constructs a six-metre-high dry-stone wall
#160Earlier quoted context omitted.
It could perhaps if it had all rocks available up front to scan and plan the entire wall with. But it retrieves one rock at a time and can only place on the top row somewhere. Given the geometries are random I wouldn’t expect it to reliably have tight fits given how it’s sampling and placing.
Even then, if you make one long row, you have hundreds of available spots to place it, with at least 6 sides to decide on which orientation to place the stone. If there are no good spots currently, it could place the stone down next to the pile and go collect another stone until a better spot materialized.
No, I was wrong. It has a collection of 30 or so rocks per section and optimizes their placement in the entire section. I’ll still posit the randomness of the geometry requires more rocks than that to find a smooth fitting, and I imagine human wall makers select rocks up front with similar geometries before even beginning out of thousands of rocks then optimizes their placement during construction in a similar but less preside way than the machine.
If you watch the video closer than I did you will see it plans each stone for optimal stability and placement.