3 ms·

It's kind of mind blowing that a building of this magnitude would go in a location that is bay fill in a region renowned for earthquakes, yet not have pilings g

by pstuart 10y ago

It's kind of mind blowing that a building of this magnitude would go in a location that is bay fill in a region renowned for earthquakes, yet not have pilings going down to bedrock. The real aftershocks are going to be the lawsuits over this.

nashashmi 10y ago
Unless I am losing my memory, I remember learning in geology class that seismic waves travel the least in clay and most in rock.
- knorby 10y ago
  Soil liquefaction is the real risk during earthquakes. Clay absorbs the energy and shakes a great deal more, and the soil can potentially destabilize further and allow structures to sink in.
  - wlesieutre 10y ago
    For anyone not familiar, this is an effect where if you load wet soil just right it will break the structure of the soil grains and turn into a fluid. Demo here, you can skip the first minute if you're short on time: https://www.youtube.com/watch?v=-X9-4tWpMCo https://www.youtube.com/watch?v=-X9-4tWpMCo Wikipedia has more information and some good photos: https://en.wikipedia.org/wiki/Soil_liquefaction https://en.wikipedia.org/wiki/Soil_liquefaction It's a really cool and equally terrifying phenomenon if you're used to thinking of the ground as a solid object. Plenty of videos on YouTube as well. EDIT- Here's a car that sunk into the ground, which then resolidified around it: https://youtu.be/2WoKu5VxKgs?t=50 https://youtu.be/2WoKu5VxKgs?t=50 http://izismile.com/2012/08/31/christchurch_liquefaction_26_pics.html http://izismile.com/2012/08/31/christchurch_liquefaction_26_...
myegorov 10y ago
Pile foundations are impractical for much of San Francisco founded on bay mud (bedrock hundreds of feet below surface). There're other practical solutions - including soil improvement, micropiles and/or raft foundation - that have been proved capable of supporting highrises. On a different note, a settlement (even differential) in excess of one foot is expected for a significant fraction of building stock in SF in the event of a "design-level" earthquake. The tower is reportedly 6" out of plumb. Over its 600ft height, that's 0.08%. For perspective, it is generally accepted that construction tolerances will result in a building 1/500, or 0.2%, out of plumb at the time of erection.

by pstuart 10y ago

nashashmi 10y ago

Unless I am losing my memory, I remember learning in geology class that seismic waves travel the least in clay and most in rock.

knorby 10y ago
Soil liquefaction is the real risk during earthquakes. Clay absorbs the energy and shakes a great deal more, and the soil can potentially destabilize further and allow structures to sink in.
- wlesieutre 10y ago
  For anyone not familiar, this is an effect where if you load wet soil just right it will break the structure of the soil grains and turn into a fluid. Demo here, you can skip the first minute if you're short on time: https://www.youtube.com/watch?v=-X9-4tWpMCo https://www.youtube.com/watch?v=-X9-4tWpMCo Wikipedia has more information and some good photos: https://en.wikipedia.org/wiki/Soil_liquefaction https://en.wikipedia.org/wiki/Soil_liquefaction It's a really cool and equally terrifying phenomenon if you're used to thinking of the ground as a solid object. Plenty of videos on YouTube as well. EDIT- Here's a car that sunk into the ground, which then resolidified around it: https://youtu.be/2WoKu5VxKgs?t=50 https://youtu.be/2WoKu5VxKgs?t=50 http://izismile.com/2012/08/31/christchurch_liquefaction_26_pics.html http://izismile.com/2012/08/31/christchurch_liquefaction_26_...

myegorov 10y ago

Pile foundations are impractical for much of San Francisco founded on bay mud (bedrock hundreds of feet below surface). There're other practical solutions - including soil improvement, micropiles and/or raft foundation - that have been proved capable of supporting highrises. On a different note, a settlement (even differential) in excess of one foot is expected for a significant fraction of building stock in SF in the event of a "design-level" earthquake. The tower is reportedly 6" out of plumb. Over its 600ft height, that's 0.08%. For perspective, it is generally accepted that construction tolerances will result in a building 1/500, or 0.2%, out of plumb at the time of erection.