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Millennium Tower is tilting, sinking

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Re: Millennium Tower is tilting, sinking

#151

Post by duaneb »

capkutay wrote: post #119
spikels wrote: post #94

Earlier quoted context omitted.

Almost nothing in this comment is accurate: - You CAN determine the type of rock you are drilling through as well as it's relevant characteristics. Pieces of the material are brought to the surface with the drilling mud and instruments are put down the hole. - Builders DO NOT just stop drilling when their drill won't drill no further. (This made me laugh!) There is testing, design, design review, more testing during…

Maybe I have a poor definition of 'point of refusal', but this is the term developers use. Most developers in SF don't tell you whether they drilled down to bedrock or not.

It's a real term. This is not how the pile depth is decided but a maximum depth.

Re: Millennium Tower is tilting, sinking

#152

Post by EliRivers »

WalterBright wrote: post #7

My house is on a steep hill, and Seattle has a reputation for hills sliding away under heavy rain. Before building it, I hired 3 separate geologists to evaluate the site. After digging holes, they said the site was sitting on "glacial till", which is clay that was compacted by about a mile of ice, and said there was nothing to worry about. Paying them was worth it for the peace of mind. (Turns out the till was so har…

Tangentially related, I have a chum who used to work for the UK's Environment Agency.

As some may have noticed, the UK seems to be suffering flooding more than it used to. Part of his job was to speak at town halls and village church halls and the like during and after flooding. He'd take a backup man with him whose job was to sit in the car outside with the engine running.

So he'd turn up at a newly built settlement named "Little Flodington" or some other such. He'd look at the unforgiving rocky hills surrounding it, and at the river running through the middle of it. He'd check the history to find that for the last thousand years, the only recorded usage of the land was grazing animals and growing crops that can handle a lot of water. No buildings more elaborate than temporary shepherd huts. He'd open up the department's flood-risk maps from the last fifty years and find he was standing in the middle of a big blue section.

He'd then field questions along the lines of "Why didn't you stop my house being flooded?" and "How are you going to stop it happening again?" with answers that were not well-received. "You bought a new house on a flood-plain. We're not going to stop it happening again."

He's since moved on up to work for a local council's environment dept. A council with less flooding.

Re: Millennium Tower is tilting, sinking

#153

Post by raverbashing »

SeanDav wrote: post #147

> "The Millennium’s engineers anchored the building over a thick concrete slab with piles driven roughly 80 feet into dense sand. "To cut costs, Millennium did not drill piles to bedrock,"... They built a skyscraper, on sand, in an earthquake zone!!! What the heck were they thinking? Consider me completely unsurprised that the building is sinking and tilting.

> They built a skyscraper, on sand, in an earthquake zone!!! What the heck were they thinking?

My guess is that they were thinking of something that starts with "pro" and ends with "fit"

I mean, Tokyo is earthquake zone, but it's not unsupported sandy soil

Re: Millennium Tower is tilting, sinking

#155

Post by Gibbon1 »

astrodust wrote: post #144
jondiggsit wrote: post #79

Earlier quoted context omitted.

I, for one, would rather be building on sand rather than clay. Clay is an absolutely terrible substrate for construction. Not to mention it does not drain. Hills don't become saturated with water... the water tends to flow to ze bottom of ze hill, where it will saturate things. I'd be curious to know what exactly you are draining into... drywells and clay are not friends. - High-end residential builder here

Clay can be a total pain in the ass to work with, it's more stubborn than concrete to remove, but you'd be hard pressed to find a material more solid to build on than rock. What's your beef with clay? The kind of glacial packed clay mentioned in this article is the sort of stuff even a power shovel has trouble with. It looks like light coloured slate, dry, brittle, and dense. I'm not sure what your preference for san…

Not sure but my understanding is high clay soils expand and contract seasonally due to moisture changes.

Re: Millennium Tower is tilting, sinking

#156

Post by ptaipale »

2muchcoffeeman wrote: post #108
wahern wrote: post #29

Earlier quoted context omitted.

I live in the Outer Richmond district of San Francisco, which was built on sand dunes. Most houses in my neighborhood were built in the 1920s and 1930s, +/- a decade. I was told by a contractor that it's extremely common for houses to have shifted considerably, sometimes by several feet. Mine certainly has, though not nearly that bad. Most of the houses are built on concrete foundation walls that go about 3 feet into…

How do you plan plumbing and electricity for houses moving several feet?

If it's the earth below houses also moving, then the problems in plumbing and electricity do not appear at the house; they appear at the cross section of the moving and non-moving earth masses, and are typically the responsibility of utility provider.

Re: Millennium Tower is tilting, sinking

#157

Post by neffy »

EliRivers wrote: post #152
WalterBright wrote: post #7

My house is on a steep hill, and Seattle has a reputation for hills sliding away under heavy rain. Before building it, I hired 3 separate geologists to evaluate the site. After digging holes, they said the site was sitting on "glacial till", which is clay that was compacted by about a mile of ice, and said there was nothing to worry about. Paying them was worth it for the peace of mind. (Turns out the till was so har…

Tangentially related, I have a chum who used to work for the UK's Environment Agency. As some may have noticed, the UK seems to be suffering flooding more than it used to. Part of his job was to speak at town halls and village church halls and the like during and after flooding. He'd take a backup man with him whose job was to sit in the car outside with the engine running. So he'd turn up at a newly built settlement…

Growing up in London, I remember reading at a young and impressionable age the sage advice to never buy property built on streets called Marsh Lane, and similar, so it's not a new problem. Geography would be a lot more interesting as a school subject if they taught this kind of stuff - although I rather fear for the results when the kids got home to explain it all to their parents.

Re: Millennium Tower is tilting, sinking

#158

Post by eggy »

Animats wrote: post #19

From the article: "To cut costs, Millennium did not drill piles to bedrock." I'm amazed that a building of that height would be built on a slab with friction piles in the mudflat fill zone of the SF bay. How did they get a building permit for that? 16 inches of sinkage in 8 years is huge. Building sinkage isn't all that unusual, but not for skyscrapers. There was a time when skyscrapers were only built on competent r…

Not drilling piles to bedrock is the key.

From the article too: "-the famed Petronas Twin Towers in Malaysia, for example, sank only a half inch since opening in 1998-"

I have worked and lived in SE Asia for 8 years, and I can tell you that there are always problems like this when they fail to go deep enough on the piles.

I have also been reading up on the shorter-than-expected life expectancy of iron rebar in concrete construction. They were supposed to be good for 100 - 1000 years. Now, there are studies saying remedial works will probably be needed in 20 to 75 years! I wouldn't buy into a building that sank so much so rapidly, is tilting too, and is in a seismic zone like SF. Steel would be better to fight the bending due to tilt. Concrete is good for compressive loading mainly, not bending or shear. I hope they used some sort of non-ferrous reinforcement like fibers or mesh.

On every job I have worked on, we always recommend a survey of the structure for up to 2 years each month. When settling seems to level off after initial construction for 4 months straight, it is passed to the owner to maintain a survey at their discretion.

I am used to seeing 2 inches per year on new construction, but I am amazed the Petronas Towers only have sunk a half inch.

Re: Millennium Tower is tilting, sinking

#159

Post by Mtinie »

rurounijones wrote: post #150
madaxe_again wrote: post #148

Earlier quoted context omitted.

Watching videos of the aftermath of the floods in Maryland the other day was telling - the main street had been entirely washed away, exposing the foundations of the buildings. The modern constructions essentially had none and were hanging in mid-air over voids. The older buildings were all sat upon massive and well dressed masonry. In short, people account only for risks they have experienced firsthand. When you don…

DO you have a link with visuals? sounds fascinating.

Lots of material out there to chose from, but here's a place to start:

https://www.nbcnews.com/news/us-news/amp/maryland-vows-rebui...

It happened in Ellicott City, Maryland.

Re: Millennium Tower is tilting, sinking

#160

Post by vermontdevil »

rurounijones wrote: post #150
madaxe_again wrote: post #148

Earlier quoted context omitted.

Watching videos of the aftermath of the floods in Maryland the other day was telling - the main street had been entirely washed away, exposing the foundations of the buildings. The modern constructions essentially had none and were hanging in mid-air over voids. The older buildings were all sat upon massive and well dressed masonry. In short, people account only for risks they have experienced firsthand. When you don…

DO you have a link with visuals? sounds fascinating.

Google Elliott City flooding. That's where it happened.
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