Bridges...

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crfriend
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Re: Bridges...

Post by crfriend »

FranTastic444 wrote:
Mon Nov 25, 2019 11:45 pm
Over the last few months I've enjoyed watching the clearing of a site next to our office (an old concrete multistory car park) and the insertion of very deep slurry walls to act as the foundations for what will be the second tallest building in downtown Boston. This video gives an idea of what was going in (it is the same company - East Coast Slurry).
That tactic was heavily used in the construction of "The Big Dig" which relocated a congested section of elevated roadway into what would become an equally-congested tunnel below the original elevated structure. I hope they poured the foundations well enough to support the next expansion project which will be the rebuilding the elevated structure to, once again, relieve congestion.

The place in that project that I referred to was the I-90/I-93 interchange just south of South Station Terminal. This congested area joins two of the major motorways of Boston fairly seamlessly in a very congested space in full 3-D glory underground, and with the added complication of a very heavily-travelled railway line at the surface. East/west from surface downwards is the railway that connects Boston to New York, Route I-90, in a depressed tunnel entrance to the tunnel under the Fort Point Channel, and North/South I-93 beneath that for grade-separation of N/S and E/W traffic. Ramps and connectors were required for full access in all directions. And all of this had to be done without disrupting (too badly) what was happening at the surface.

From the train I commuted on from Worcester to Boston, I passed over this twice per day -- and revelled in it. That was the last job I had where I actually felt I was making a difference in the world, and it was magical. Each day I'd see the drawings being created by the engineers and architects on the computers I kept running -- and each day, I'd witness the drawings produced months before become real beneath me. This is, indeed, the stuff of dreams.
Apparently this method of construction is well suited to the geology of the Boston area.
It's at least as effective as piles, and, if done really well, likely even better.
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dillon
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Re: Bridges...

Post by dillon »

FranTastic444 wrote:
Mon Nov 25, 2019 11:45 pm
When I worked in civil engineering and construction, my claim to fame was that I helped with the setting out for a section of the "retaining wall" around Winson Green prison.

Here is a link to the Google view of the site. I moved on to another project before the old wall was pulled down, but when they came to that part of the project they were expecting to come across lots of human bones. When inmates were hanged at the prison, they were buried at the foot of the old wall in an unmarked grave.

Over the last few months I've enjoyed watching the clearing of a site next to our office (an old concrete multistory car park) and the insertion of very deep slurry walls to act as the foundations for what will be the second tallest building in downtown Boston. This video gives an idea of what was going in (it is the same company - East Coast Slurry). To give you some idea of how deep the foundations run, you will be able to see the red crane in the video lifting a re-bar cage into position. For the build site next to us, they were inserting two of these cages on top of each other (near the full height of the red crane) into each trench. I guessed at this being 150 feet down, but my boss (who smokes with some of the construction workers when she is in town) was told that some of them are nearer 200 feet deep. Apparently this method of construction is well suited to the geology of the Boston area.
I can imagine that considerable depth is required to support heavy structures in MA. As a teen I spent two summers in the Boston suburbs ostensibly “working “ on remodeling an old New England house, although I mostly remember playing a lot of vacant-lot baseball (in the era of Carl “Yaz” Yastrzemski) and my adolescent lusting for the brown-haired girl next door. But I remember hand-digging footings for stone masonry in sandy, stony glacial till. Engineering has to find a stable base for enduring projects.

But it amused me to hear the term “slurry” used as a colloquial synonym for concrete. Around my world, slurry refers to liquified manure!
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crfriend
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Re: Bridges...

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dillon wrote:
Thu Dec 05, 2019 12:42 pm
But it amused me to hear the term “slurry” used as a colloquial synonym for concrete. Around my world, slurry refers to liquified manure!
Actually, in this usage the slurry is a semi-liquid substance with the right characteristics to hold thin trenches open through which excavation at depth can be undertaken -- sometimes straight down to bedrock -- then the reinforcing-steel cages lowered into the trench, and the trench then filled with concrete which the displaces the slurry upwards where it's collected for use in the next trench section.

It's a rather ingenious construction method.

And, yes, large-scale construction in Boston can "get interesting". When the new John Hancock Tower (aka The Plywood Palace) was constructed, it turns out that the piles it was built on weren't quite sufficient for the job and the adjacent historic Trinity Church in Copley Square was almost sucked into the area that was settling (well, it shifted substantially and required quite a lot of work to make right).
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Re: Bridges...

Post by Kirbstone »

That is frequently the problem for adjacent old buildings when a new construction right next door is undertaken. Deep foundations require serious shoring up all round to protect adjacent structures.
At last someone's posted a decent pic. of the full length of Ireland's 'Millau' bridge. A lovely addition to the landscape and a credit to the designers & builders.
We're not going to see anything like that built again in my lifetime, that's for sure.

Tom
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