4 ms·

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

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 baked yet (and it's hardly a drop-in replacement for reinforced/pretensioned/cantilevered/etc) but for things like heavy infrastructure and civil engineering this might offer a way to achieve fundamental thermodynamic improvements. Excited to see where this technology goes.

samtho 3y ago
The problem with dry stone construction is that you cannot determine the performance characteristics required for, say, a building foundation. Not all boulders are created equal, but a professional concrete pour, mixed and installed to the manufacturer’s specification is going to have a guaranteed maximum strength- something random boulders will not have. What we can do is create our own concrete mix using Portland cement (the “glue”) and locally sourced materials to bulk it up such as gravel, aggregates, sand, etc.
- schiffern 3y ago
  So the question becomes, how do existing concrete manufacturers determine whether locally sourced materials ("random rocks") are suitable? In traditional dry stone construction, strength of each rock is determined by sound and by sight. It seems crazy, but nowadays this should be feasible with a neural net. If you want to get fancy (or achieve high reliability) add ultrasound in the grippers or other sensor modalities. Or... you target a market other than building foundations? :) I suspect different groups could pursue both paths.
  - beambot 3y ago
    > how do existing concrete manufacturers determine whether locally sourced materials ("random rocks") are suitable? They test individual samples from each pour on a calibrated press. For large buildings and critical pours, they'll keep & test multiple samples that undergo accelerated aging to make sure they're up to spec for the anticipated lifetime of the building (or until the concrete fully stabilizes over a few months / years).
    - diroussel 3y ago
      So could catagorization of local stone based on acoustic and visual indicators, combined with random sampling and strength testing provide the assurance needed that a wall will have the required structural properties?
      - crotchfire 3y ago
        The point is that the concrete manufacturers pulverize and homogenize the aggregate. This makes random sampling acceptable. If you haven't pulverized and mixed the inputs, a random sample is merely a random sample. It isn't meaningful unless it comes from a high-entropy source.
        diroussel 3y ago
        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?
        SiempreViernes 3y ago
        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.
        londons_explore 3y ago
        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.
  - nabla9 3y ago
    A Deep Learning Based Method for the Non-Destructive Measuring of Rock Strength through Hammering Sound Appl. Sci. 2019, 9(17), 3484; https://doi.org/10.3390/app9173484 https://doi.org/10.3390/app9173484 Acoustic inverse problems are solved routinely in seismology and exploration geophysics. Seeing trough a rock the cracks and internal structure using acoustics seems solvable.
- galaxyLogic 3y ago
  Why not do a stones-wall like in the article, but add cement as glue between the rocks?
  - actionfromafar 3y ago
    The wall will then dam up water or crack instead of shifting slightly, I read in another comment.
  - jelliclesfarm 3y ago
    I did this for a landscaping project because I was not confident enough that it will stay ..lasted ten plus years and then it started cracking. I am now left with unsightly gray blotches and worried the rest might tumble.. It was/is gorgeous..I did three sections ..mostly for three very large kidney shaped raised beds..moss has grown over the stone and I also tried sticking thyme and mint in some of the suitable gaps.. I guess it’s diff if it’s enclosed and filled with soil. I wish i had the confidence and skill to attempt an actual wall. I used to drive past a house here where the guy took like three years to complete a 80 ft long dry wall and he planted all kinds of beautiful flowering plants ..it was stunning and when it was done, the flowers and fruit trees popped up with their colours too ..it took forever but he didn’t care..you could tell that it was a labour of love and he was really enjoying it.
  - Daub 3y ago
    That is what I assumed when I first started drywalling. However, in the wild, I can't see such a solution working. Unlike the walls of a house, walls bedded on soil move all the time. In the ever-moving domain of the Welsh hillsides, cement glue would crack within a year. Ideally, drystone walls are composed of two skins. The way the stones are arranged tends these skins to each incline inwards slightly. In this way, the wall as a whole acquires cohesion through physics.
  - alistairSH 3y ago
    Several reasons… Primarily, because the ground underneath shifts overtime, particularly in area, subject to a freeze and fall cycle. But you also have to solve for water flow - if you build a solid stone wall with concrete, you also need to add drainage on the backside of the wall. With dry, stacked stone, you can often get away without a complex drainage solution
- koolba 3y ago
  > Not all boulders are created equal, but a professional concrete pour, mixed and installed to the manufacturer’s specification is going to have a guaranteed maximum strength- something random boulders will not have. Random boulders surely have some guaranteed maximum strength. Now minimum strength is the real problem.
- hedora 3y ago
  Modern concrete only lasts a hundred years or so. Stone walls last much longer when correctly constructed. Presumably the placement algorithm understands compression strength of the local rocks, soil heaving, etc. So, software addresses the initial problems you describe at construction, and geology/materials solve the problem of needing to inspect it every decade or so, and replace it in 50-100 years.
- worik 3y ago
  With concrete you have outsourced, not solved, that problem There's a lot of drystone walls here, in Aotearoa, but not of buildings. There is a related technique for buildings, building from rubble, using lime morter. I live in a building partly built that way
- legulere 3y ago
  It’s more difficult but still possible. Mountain passes in Switzerland are often built on dry walls
ReptileMan 3y ago
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.
- londons_explore 3y ago
  Add steel/fiberglass tension rods and you can trade off compressive for tensile strength.
  - klyrs 3y ago
    So... reinforced concrete.
rewmie 3y ago
> Not only is this a technical marvel, but it has potential construction physics implications. I don't think this is true. Gabion walls are already widely used, particularly in geotechnical structures, and masonry structures have been around for literally thousands of years. The reason modern building technologies such as concrete/steel/composite structures replaced these techniques is that they are far safer, easier to maintain, far more space-efficient and and impose far fewer architectural constraints. Automating this process helps drive down the cost, but cost is one of many factors and not a critical one. > Suddenly, an alternative just got a lot cheaper. Not really. This article just showcases a way to automate the construction of a particular wall type. This by no means implies these walls are now competitive. Other than aesthetics, I don't see how it's possible to even conceive standard techniques such as gabion walls being replaced by dry-stone walls. The cost of building a gabion wall is literally the cost of a metal mesh and filling it with rocks. Gabion walls are even used by armed forces as rapid-deployment defensive walls in the form of Hesco bastions. https://en.wikipedia.org/wiki/Hesco_bastion https://en.wikipedia.org/wiki/Hesco_bastion

samtho 3y ago

The problem with dry stone construction is that you cannot determine the performance characteristics required for, say, a building foundation. Not all boulders are created equal, but a professional concrete pour, mixed and installed to the manufacturer’s specification is going to have a guaranteed maximum strength- something random boulders will not have. What we can do is create our own concrete mix using Portland cement (the “glue”) and locally sourced materials to bulk it up such as gravel, aggregates, sand, etc.

schiffern 3y ago
So the question becomes, how do existing concrete manufacturers determine whether locally sourced materials ("random rocks") are suitable? In traditional dry stone construction, strength of each rock is determined by sound and by sight. It seems crazy, but nowadays this should be feasible with a neural net. If you want to get fancy (or achieve high reliability) add ultrasound in the grippers or other sensor modalities. Or... you target a market other than building foundations? :) I suspect different groups could pursue both paths.
- beambot 3y ago
  > how do existing concrete manufacturers determine whether locally sourced materials ("random rocks") are suitable? They test individual samples from each pour on a calibrated press. For large buildings and critical pours, they'll keep & test multiple samples that undergo accelerated aging to make sure they're up to spec for the anticipated lifetime of the building (or until the concrete fully stabilizes over a few months / years).
  - diroussel 3y ago
    So could catagorization of local stone based on acoustic and visual indicators, combined with random sampling and strength testing provide the assurance needed that a wall will have the required structural properties?
    - crotchfire 3y ago
      The point is that the concrete manufacturers pulverize and homogenize the aggregate. This makes random sampling acceptable. If you haven't pulverized and mixed the inputs, a random sample is merely a random sample. It isn't meaningful unless it comes from a high-entropy source.
      - diroussel 3y ago
        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?
        SiempreViernes 3y ago
        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.
        londons_explore 3y ago
        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.
- nabla9 3y ago
  A Deep Learning Based Method for the Non-Destructive Measuring of Rock Strength through Hammering Sound Appl. Sci. 2019, 9(17), 3484; https://doi.org/10.3390/app9173484 https://doi.org/10.3390/app9173484 Acoustic inverse problems are solved routinely in seismology and exploration geophysics. Seeing trough a rock the cracks and internal structure using acoustics seems solvable.
galaxyLogic 3y ago
Why not do a stones-wall like in the article, but add cement as glue between the rocks?
- actionfromafar 3y ago
  The wall will then dam up water or crack instead of shifting slightly, I read in another comment.
- jelliclesfarm 3y ago
  I did this for a landscaping project because I was not confident enough that it will stay ..lasted ten plus years and then it started cracking. I am now left with unsightly gray blotches and worried the rest might tumble.. It was/is gorgeous..I did three sections ..mostly for three very large kidney shaped raised beds..moss has grown over the stone and I also tried sticking thyme and mint in some of the suitable gaps.. I guess it’s diff if it’s enclosed and filled with soil. I wish i had the confidence and skill to attempt an actual wall. I used to drive past a house here where the guy took like three years to complete a 80 ft long dry wall and he planted all kinds of beautiful flowering plants ..it was stunning and when it was done, the flowers and fruit trees popped up with their colours too ..it took forever but he didn’t care..you could tell that it was a labour of love and he was really enjoying it.
- Daub 3y ago
  That is what I assumed when I first started drywalling. However, in the wild, I can't see such a solution working. Unlike the walls of a house, walls bedded on soil move all the time. In the ever-moving domain of the Welsh hillsides, cement glue would crack within a year. Ideally, drystone walls are composed of two skins. The way the stones are arranged tends these skins to each incline inwards slightly. In this way, the wall as a whole acquires cohesion through physics.
- alistairSH 3y ago
  Several reasons… Primarily, because the ground underneath shifts overtime, particularly in area, subject to a freeze and fall cycle. But you also have to solve for water flow - if you build a solid stone wall with concrete, you also need to add drainage on the backside of the wall. With dry, stacked stone, you can often get away without a complex drainage solution
koolba 3y ago
> Not all boulders are created equal, but a professional concrete pour, mixed and installed to the manufacturer’s specification is going to have a guaranteed maximum strength- something random boulders will not have. Random boulders surely have some guaranteed maximum strength. Now minimum strength is the real problem.
hedora 3y ago
Modern concrete only lasts a hundred years or so. Stone walls last much longer when correctly constructed. Presumably the placement algorithm understands compression strength of the local rocks, soil heaving, etc. So, software addresses the initial problems you describe at construction, and geology/materials solve the problem of needing to inspect it every decade or so, and replace it in 50-100 years.
worik 3y ago
With concrete you have outsourced, not solved, that problem There's a lot of drystone walls here, in Aotearoa, but not of buildings. There is a related technique for buildings, building from rubble, using lime morter. I live in a building partly built that way
legulere 3y ago
It’s more difficult but still possible. Mountain passes in Switzerland are often built on dry walls

ReptileMan 3y ago

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.

londons_explore 3y ago
Add steel/fiberglass tension rods and you can trade off compressive for tensile strength.
- klyrs 3y ago
  So... reinforced concrete.

rewmie 3y ago

> Not only is this a technical marvel, but it has potential construction physics implications. I don't think this is true. Gabion walls are already widely used, particularly in geotechnical structures, and masonry structures have been around for literally thousands of years. The reason modern building technologies such as concrete/steel/composite structures replaced these techniques is that they are far safer, easier to maintain, far more space-efficient and and impose far fewer architectural constraints. Automating this process helps drive down the cost, but cost is one of many factors and not a critical one. > Suddenly, an alternative just got a lot cheaper. Not really. This article just showcases a way to automate the construction of a particular wall type. This by no means implies these walls are now competitive. Other than aesthetics, I don't see how it's possible to even conceive standard techniques such as gabion walls being replaced by dry-stone walls. The cost of building a gabion wall is literally the cost of a metal mesh and filling it with rocks. Gabion walls are even used by armed forces as rapid-deployment defensive walls in the form of Hesco bastions. https://en.wikipedia.org/wiki/Hesco_bastion https://en.wikipedia.org/wiki/Hesco_bastion