29 ms·

>using a pile foundation of course you need piles deep enough, and boreholes soil test results probably factor into the decision of how deep it should be. The

by trhway 5y ago

>using a pile foundation of course you need piles deep enough, and boreholes soil test results probably factor into the decision of how deep it should be. The $100M fix for the tilting and sinking 58-story SF tower built in 2009 with "floating" piles not reaching the bedrock : https://www.sfgate.com/news/editorspicks/article/SF-s-sinking-Millenium-Tower-to-finally-get-fixed-15439863.php# https://www.sfgate.com/news/editorspicks/article/SF-s-sinkin... "The solution, likened to putting a bumper jack next to a flat tire, will involve the installation of 52 piles along the north and west sides of the tower. The piles will be beneath the sidewalk, 250 feet into the bedrock of downtown San Francisco, and be tied with the original 60-90-feet-deep foundation piles."

lokar 5y ago
A floating foundation can be safe. But not if you dig a giant hole next to it and pump out all the water. SF quietly settled and paid for most of the repairs. Soil stability and it's ability to support a building depends a lot on water situation.
- trhway 5y ago
  >A floating foundation reminded - back at University i worked summers on construction mostly doing foundations in Siberia in permafrost zone. The most memorable part of the quick introduction to the profession there was when they showed us several buildings which didn't have piles deep enough - most of those you could easily spot from a distance by the building shape defects like tilting, bended roofline, etc... because if piles aren't deep enough the foundation pretty much becomes really "floating" during warm season after several cycles of freezing/thawing. Related, at a bigger scale, global warming affecting foundations in the permafrost zone https://www.theguardian.com/cities/2016/oct/14/thawing-permafrost-destroying-arctic-cities-norilsk-russia https://www.theguardian.com/cities/2016/oct/14/thawing-perma...

by trhway 5y ago

lokar 5y ago

A floating foundation can be safe. But not if you dig a giant hole next to it and pump out all the water. SF quietly settled and paid for most of the repairs. Soil stability and it's ability to support a building depends a lot on water situation.

trhway 5y ago
>A floating foundation reminded - back at University i worked summers on construction mostly doing foundations in Siberia in permafrost zone. The most memorable part of the quick introduction to the profession there was when they showed us several buildings which didn't have piles deep enough - most of those you could easily spot from a distance by the building shape defects like tilting, bended roofline, etc... because if piles aren't deep enough the foundation pretty much becomes really "floating" during warm season after several cycles of freezing/thawing. Related, at a bigger scale, global warming affecting foundations in the permafrost zone https://www.theguardian.com/cities/2016/oct/14/thawing-permafrost-destroying-arctic-cities-norilsk-russia https://www.theguardian.com/cities/2016/oct/14/thawing-perma...