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Because of soil issues, the Transbay Terminal (Salesforce) builders had to anchor the foundations in the bedrock, which is unfortunately deep under layers of la
by 60654 9y ago
Because of soil issues, the Transbay Terminal (Salesforce) builders had to anchor the foundations in the bedrock, which is unfortunately deep under layers of landfill and soft sand. But this fill and sand is exactly what will get liquified during a big one, so they didn't have much choice.
But what's weird, IMO, is that some of the shorter highrises like the Millennium Tower were approved to be built not anchored, but on pylons floating in the soil layer:
https://sf.curbed.com/2016/9/16/12945600/why-millennium-tower-sinking https://sf.curbed.com/2016/9/16/12945600/why-millennium-towe...
https://sf.curbed.com/2016/9/15/12930402/millennium-towner-sinking-foundation-buildings https://sf.curbed.com/2016/9/15/12930402/millennium-towner-s...
I mean, sure, as long as things are stable, the weight of the building will keep it in place. But I don't think anyone knows how the soft layer underneath most of SOMA will behave, when a big earthquake comes. People know it will undergo liquification, but by how much, and what will it do to buildings on "floating" foundations, that's not certain...
- wahern 9y agoYou assume, based on the journalists' innuendo, that friction piles are per se not seismically safe. That's wrong. Friction piles are well studied and used for tall towers in seismic zones all around the world, including Japan. That the Millennium Tower is sinking asymmetrically doesn't necessarily mean the design was flawed, even in a high-risk earthquake zone. It could be flawed, but the very fact that it's sinking doesn't tell us that. It could merely be that out of the hundreds of towers constructed globally each year, Millennium Tower was the unlucky outlier which defied the otherwise carefully weighed odds.