2 ms·
> That's not how that works... Any granular material, even sand, will spread the forces laterally. It's impossible for the full weight of the soil above to be a
by lmilcin 5y ago
> That's not how that works... Any granular material, even sand, will spread the forces laterally. It's impossible for the full weight of the soil above to be applied to the steel structure.
Absolutely false.
The ground may be plastic on a long time scales (depends on the material) and over time full weight of it can be transferred to the structure.
Do following thought experiment: build a bridge out of clay over a scale. The bridge might not suddenly collapse, but it will slowly deform and over time all weight of it will rest on the scale.
If you have noticed, the top layers of the tunnel are made of clay. Clay is plastic and will creep over time.
It is the same basic principle as buildings falling due to ground giving under foundations.
- Diggsey 5y agoEven with a totally plastic material (which is a stretch, since there are certainly granular elements even in clay soil) the material will deform until it fills the gaps around the arch shape. At that point the material itself is forming an arch, and even clay has compressive strength since it has nowhere else to go. While it may increase the load on the steel, it's still a long way from having to support the full weight of the material above.