5 ms·

Let's say you have a load of 1000 kg on a 1 square meter steel plate on a field. What is the compression 1 meter underground directly below? Less than at the su

Let's say you have a load of 1000 kg on a 1 square meter steel plate on a field. What is the compression 1 meter underground directly below? Less than at the surface. What about compression 1 meter underground and 0.5 meters to the side from the center, ie below the edge of the plate? Even less. And 1 meter to the side, even than that. The load spreads underground. From a small point load, it dilutes fast with depth. What if you add a similar load directly adjacent to the previous one. Pressure is same but area is added. What is the compression 1 meter underground, at the border between the plates. It's more than in the previous case, since both loads now contribute to it. So there is a sort of load pyramid that has to form underground to support each point load. And the more point loads you add in a grid, the deeper you go, the pyramid overlap more together. So with constant pressure, the wider area you have, the more there is stress deeper down, and the worse the effect gets with distance.

BurningFrog 4y ago
I'm not going to try doing the math, but the deeper you go, the more the pressure will be dominated by the weight of the soil above.
boringg 4y ago
And it's exactly this part that might elude the "Farmers typically know everything" argument.
- xbar 4y ago
  I sat around with a group of farmers for years, listening to them tell me that they knew what was best to produce on their land profitably. Much of their formerly-arable land became un-arable and is today made entirely of sprawling tract homes.
  - throwaway0a5e 4y ago
    Is that because they didn't know what they were doing or because they saw the writing on the wall and planned their exit? Low margin industries tend to have a lot of things that are done "wrong" by the calculations of the clipboard warriors that dominate online discourse because said calculations tend to assume constants for things that should are variable (like the regulatory situation, state of technology in an industry or rate of progression therof) and assume amortization timelines that are unrealistic. When your margin is razor thin it often makes the most sense to do things in a manner that's non-optimal on paper but yields guaranteed returns today. Do that every day and you stay in business. You might make less money in the long run but you aren't taking on risky capital investments or boxing yourself into a risky corner with inflexible business practices. There are two metal recycling yards local to me. One is part of a chain, run by a subsidiary of a public company. All they do is scrap metal and they are highly efficient at it. Things are clean and run by the book. The facilities are orderly. The machines are new. You can't scrap a car, a street sign, or anything else that's suspect without giving them all sorts of ID. On paper, they do everything right. The other one is a 150yo family own business. They do scrap metal but have a handful of other income streams using the same facility (everything is for sale, basically). I don't think they have a single tool or piece of equipment that was made this century. The facility is always overflowing with piles of various materials that come and go in no apparent order. Their workplace safety is fine, but absolutely rife with tiny things they could get fined for. They pay their employees crap and make up for it with perks (free lunch every day, free fuel oil in the winter, can use company trucks and facilities for personal projects with permission, etc). I'm pretty sure you could scrap a stolen cop car there if you brought it in the same day that the full train cars of processed material go out. On paper all this is wrong. The clipboard warriors would have a field day making it "better" Guess who weathered the pandemic with nary a slowdown and guess who couldn't retain staff or keep their machines running and cut back hours?
    - shigawire 4y ago
      So the answer is exploiting workers better and criminal activity?
      - throwaway0a5e 4y ago
        The by the book business isn't hiring young people and teaching them how to drive heavy equipment. If their employees felt exploited they'd have problems retaining them. I think their employees care more about the perks and the fairly laid back work environment than they care about all the fire extinguishers on the property having an up to date tag. I know I did back when I worked those kinds of jobs.
        deleted 4y ago
        [deleted]
        bumby 4y ago
        >fire extinguishers on the property having an up to date tag. I know I did back when I worked those kinds of jobs. This is a problem with how you're thinking about low probability events. Yes, rules only matter when the low probability event occurs. Do you, for example, not care about up-to-date A&P logs on the aircraft you fly in as well? I'll be the first to admit that regulations can go beyond what should be considered an acceptable risk, but we have to at least acknowledge the risk they are meant to mitigate before determining if it's a reasonable regulation. That often involves understanding the consequences of low probability events, something we're usually not good at thinking about very well on a day-to-day basis.
        wolverine876 4y ago
        > If their employees felt exploited they'd have problems retaining them. That is not usually true. Lots and lots of people feel exploited by their employers, yet stay in their jobs. Generally, they have financial obligations, need money and benefits, and jobs aren't so easy to replace.
        4y ago
  - truffdog 4y ago
    There were a bunch of famous "scientific agriculture" disasters in the 20th century caused by simplifying assumptions being too simple. The pendulum of worst or best practice swings both ways and it's difficult to adjudicate without a ton of local context.
  - jessaustin 4y ago
    ...today made entirely of sprawling tract homes. Farms fail all the time for a variety of reasons, but even successful farms can be less valuable than suburban residential subdivisions. If the farms in question were further from the city, better farmers would buy/rent them and the land would be productive again.
    - CameronNemo 4y ago
      If the farms in question were further from the city, better farmers would buy/rent them and the land would be productive again. 1. You are assuming "better farms" have the capital and will available to purchase the land. 2. Just because a competent farmer purchases the land does not make the land arable. It could take decades to undo the damage from improperly cared for land.
      - jessaustin 4y ago
        I am assuming a functioning market for farmland. As I have observed over several decades, and my father and grandfather observed for much longer, the market for farmland is brutally efficient. (Insufficiently-regulated monopsonies arrange society so that their inputs are as cheap as possible.) Lots of rural land lies fallow, and much of that has ruined some poor farmer who tried to grow or graze ground that wouldn't pay him back. My point is just that while we can draw that conclusion about empty fallow ground, we can't draw it about ground that currently sees more remunerative use than farming. I don't think we can really know anything for sure about point 2 for hypothetical internet discussion agricultural ground. It is probably true that some land has been so damaged, but it is also possible for farmer B to have better results than farmer A on the same land. This is possible even if they are in some sense equally skilled and capitalized. It doesn't rain the same every year...
      - HeyLaughingBoy 4y ago
        A competent farmer isn't going to be purchasing useless land.
        CameronNemo 4y ago
  - asdff 4y ago
    I think thats only a minority of cases where land grows arid and is sold and this arid land is also valuable enough where homes can be built and immediately sold. I've lived in areas on the suburban/rural boundary and its not really like that. The farms are very productive, its just a suburban tract with homes starting at 400k makes a lot more money than a soybean harvest so when a developer comes a knocking farms are eager to sell. The children don't want to be farmers like their parents, they want capital for investment in other ventures and are happy to exit the farm business. Around these new housing tracts fields are still being plowed and harvested because the soil is still productive. Plus with modern agriculture its hard to get arid land unless you are broke and cant afford fertilizer. Plants need nitrogen, phosphorus, and potassium. they will grow in a cup with some inorganic gravel or on a pile of rusty screws or in some pocket lint if you put these three things in water.
loeg 4y ago
At the limit (infinitely wide load), the max sum somewhere in the middle is just going to be the point load at the surface (plus the weight of the dirt). The load you've described isn't an infinite motion machine. I guess you're saying constant pressure x wider = more weight? So is GP, but the other way around: more weight divided by more width keeps pressure constant.
throwaway0a5e 4y ago
>So there is a sort of load pyramid that has to form underground to support each point load. And the more point loads you add in a grid, the deeper you go, the pyramid overlap more together. So with constant pressure, the wider area you have, the more there is stress deeper down, and the worse the effect gets with distance. This only works in the land of spherical cows. In reality the pressure is never going to be higher than what it is at the contact patch and while a much wider area is bearing the load friction between particles and height of overburden dominate. If what you are proposing was true many sorts of construction projects would be much simpler

BurningFrog 4y ago

I'm not going to try doing the math, but the deeper you go, the more the pressure will be dominated by the weight of the soil above.

boringg 4y ago

And it's exactly this part that might elude the "Farmers typically know everything" argument.

xbar 4y ago
I sat around with a group of farmers for years, listening to them tell me that they knew what was best to produce on their land profitably. Much of their formerly-arable land became un-arable and is today made entirely of sprawling tract homes.
- throwaway0a5e 4y ago
  Is that because they didn't know what they were doing or because they saw the writing on the wall and planned their exit? Low margin industries tend to have a lot of things that are done "wrong" by the calculations of the clipboard warriors that dominate online discourse because said calculations tend to assume constants for things that should are variable (like the regulatory situation, state of technology in an industry or rate of progression therof) and assume amortization timelines that are unrealistic. When your margin is razor thin it often makes the most sense to do things in a manner that's non-optimal on paper but yields guaranteed returns today. Do that every day and you stay in business. You might make less money in the long run but you aren't taking on risky capital investments or boxing yourself into a risky corner with inflexible business practices. There are two metal recycling yards local to me. One is part of a chain, run by a subsidiary of a public company. All they do is scrap metal and they are highly efficient at it. Things are clean and run by the book. The facilities are orderly. The machines are new. You can't scrap a car, a street sign, or anything else that's suspect without giving them all sorts of ID. On paper, they do everything right. The other one is a 150yo family own business. They do scrap metal but have a handful of other income streams using the same facility (everything is for sale, basically). I don't think they have a single tool or piece of equipment that was made this century. The facility is always overflowing with piles of various materials that come and go in no apparent order. Their workplace safety is fine, but absolutely rife with tiny things they could get fined for. They pay their employees crap and make up for it with perks (free lunch every day, free fuel oil in the winter, can use company trucks and facilities for personal projects with permission, etc). I'm pretty sure you could scrap a stolen cop car there if you brought it in the same day that the full train cars of processed material go out. On paper all this is wrong. The clipboard warriors would have a field day making it "better" Guess who weathered the pandemic with nary a slowdown and guess who couldn't retain staff or keep their machines running and cut back hours?
  - shigawire 4y ago
    So the answer is exploiting workers better and criminal activity?
    - throwaway0a5e 4y ago
      The by the book business isn't hiring young people and teaching them how to drive heavy equipment. If their employees felt exploited they'd have problems retaining them. I think their employees care more about the perks and the fairly laid back work environment than they care about all the fire extinguishers on the property having an up to date tag. I know I did back when I worked those kinds of jobs.
      - deleted 4y ago
        [deleted]
      - bumby 4y ago
        >fire extinguishers on the property having an up to date tag. I know I did back when I worked those kinds of jobs. This is a problem with how you're thinking about low probability events. Yes, rules only matter when the low probability event occurs. Do you, for example, not care about up-to-date A&P logs on the aircraft you fly in as well? I'll be the first to admit that regulations can go beyond what should be considered an acceptable risk, but we have to at least acknowledge the risk they are meant to mitigate before determining if it's a reasonable regulation. That often involves understanding the consequences of low probability events, something we're usually not good at thinking about very well on a day-to-day basis.
      - wolverine876 4y ago
        > If their employees felt exploited they'd have problems retaining them. That is not usually true. Lots and lots of people feel exploited by their employers, yet stay in their jobs. Generally, they have financial obligations, need money and benefits, and jobs aren't so easy to replace.
        4y ago
- truffdog 4y ago
  There were a bunch of famous "scientific agriculture" disasters in the 20th century caused by simplifying assumptions being too simple. The pendulum of worst or best practice swings both ways and it's difficult to adjudicate without a ton of local context.
- jessaustin 4y ago
  ...today made entirely of sprawling tract homes. Farms fail all the time for a variety of reasons, but even successful farms can be less valuable than suburban residential subdivisions. If the farms in question were further from the city, better farmers would buy/rent them and the land would be productive again.
  - CameronNemo 4y ago
    If the farms in question were further from the city, better farmers would buy/rent them and the land would be productive again. 1. You are assuming "better farms" have the capital and will available to purchase the land. 2. Just because a competent farmer purchases the land does not make the land arable. It could take decades to undo the damage from improperly cared for land.
    - jessaustin 4y ago
      I am assuming a functioning market for farmland. As I have observed over several decades, and my father and grandfather observed for much longer, the market for farmland is brutally efficient. (Insufficiently-regulated monopsonies arrange society so that their inputs are as cheap as possible.) Lots of rural land lies fallow, and much of that has ruined some poor farmer who tried to grow or graze ground that wouldn't pay him back. My point is just that while we can draw that conclusion about empty fallow ground, we can't draw it about ground that currently sees more remunerative use than farming. I don't think we can really know anything for sure about point 2 for hypothetical internet discussion agricultural ground. It is probably true that some land has been so damaged, but it is also possible for farmer B to have better results than farmer A on the same land. This is possible even if they are in some sense equally skilled and capitalized. It doesn't rain the same every year...
    - HeyLaughingBoy 4y ago
      A competent farmer isn't going to be purchasing useless land.
      - CameronNemo 4y ago
- asdff 4y ago
  I think thats only a minority of cases where land grows arid and is sold and this arid land is also valuable enough where homes can be built and immediately sold. I've lived in areas on the suburban/rural boundary and its not really like that. The farms are very productive, its just a suburban tract with homes starting at 400k makes a lot more money than a soybean harvest so when a developer comes a knocking farms are eager to sell. The children don't want to be farmers like their parents, they want capital for investment in other ventures and are happy to exit the farm business. Around these new housing tracts fields are still being plowed and harvested because the soil is still productive. Plus with modern agriculture its hard to get arid land unless you are broke and cant afford fertilizer. Plants need nitrogen, phosphorus, and potassium. they will grow in a cup with some inorganic gravel or on a pile of rusty screws or in some pocket lint if you put these three things in water.

loeg 4y ago

At the limit (infinitely wide load), the max sum somewhere in the middle is just going to be the point load at the surface (plus the weight of the dirt). The load you've described isn't an infinite motion machine. I guess you're saying constant pressure x wider = more weight? So is GP, but the other way around: more weight divided by more width keeps pressure constant.

throwaway0a5e 4y ago

>So there is a sort of load pyramid that has to form underground to support each point load. And the more point loads you add in a grid, the deeper you go, the pyramid overlap more together. So with constant pressure, the wider area you have, the more there is stress deeper down, and the worse the effect gets with distance. This only works in the land of spherical cows. In reality the pressure is never going to be higher than what it is at the contact patch and while a much wider area is bearing the load friction between particles and height of overburden dominate. If what you are proposing was true many sorts of construction projects would be much simpler