Wednesday, December 8, 2021

Up, up, and away

As I noted just three weeks ago, the first test of the new Millenium Tower stabilization procedures was completed and "a second test will follow".

Not a promising early result from the new test, though: SF Millennium Tower Tilts Quarter Inch in Four Days

Newly released monitoring data shows that San Francisco’s Millennium Tower tilted a quarter inch during the four days it took to install the first test pile to bedrock last month.


The latest data – including the four days that the test pile was installed from Nov. 15 to Nov. 19 – shows a quarter inch of new tilt, as well as a tenth of an inch of settlement at the time the test installation occurred. At the same time, there was marked fluctuation of water pressure below the foundation on the Mission Street side of the structure.


While the data shows plunging pressure level quickly came back up, Pyke said the brief loss would likely generate settlement.


“You can accidentally remove soil that you want to stay in place,” said Rune Storesund, a geotechnical engineer who runs UC Berkeley’s Center for Catastrophic Risk Management. He says the water pressure data suggests engineers could clearly do more to refine their methods. “You’re always going to get settlement, obviously you want that to be as low as possible.”

It's not like they didn't expect there would be some impact; they're just discussing how substantial the measured impact was.

I guess that if the building settles evenly, that's the most important thing; the tilt is far more of a challenge than the settling.

Not that this is easy, but it sure would be nice if the overall result were successful.

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