Big Dig Tunnel--

TheRifleman

Banned
Joined
Sep 25, 2008
Messages
4,431
Reaction score
0
Anybody a Structural Engineer on this site?

I have a question: Driving into the big dig tunnel the other day I saw the developments above the tunnel near North Station. Looking above going through the tunnel those structures seem a bit heavy to be sitting on the tunnel.

Any thoughts?
 

fattony

Senior Member
Joined
Jan 28, 2013
Messages
1,882
Reaction score
3
I am certain the whole thing is going to collapse any day now.
 

CSTH

Senior Member
Joined
Oct 5, 2009
Messages
1,794
Reaction score
1
1. The tunnel walls got to bedrock, and held up the old artery during construction.
2. There is a lot of steel bracing and truss work in the new buildings to distribute the loads onto the walls.
3. Think of the tunnels like a parking garage with big entrances and exits.
4. Beyond that - magic.
 

Arlington

Moderator
Staff member
Joined
Dec 10, 2011
Messages
3,796
Reaction score
67
I have a very clear recollection that all surface building sites were planned from the beginning, and that the necessary foundations for future buildings were incorporated during tunnel construction.

Where we see buildings, it is because they were provisioned

Where we see foundations capped off, buildings are yet possible.

Where no foundations were built (where none were planned) no buildings are possible.
 

TheRifleman

Banned
Joined
Sep 25, 2008
Messages
4,431
Reaction score
0

CSTH

Senior Member
Joined
Oct 5, 2009
Messages
1,794
Reaction score
1
Ok I see what you’re asking - how big is the bezel? It’s a difficult question; not even the bezzler knows for sure in a case like this...
 

TheRifleman

Banned
Joined
Sep 25, 2008
Messages
4,431
Reaction score
0
My point is with the additional developed buildings near North Station could the Big Dig tunnel become top heavy overtime? I believe most the highway is right under the Greenway so there is really not much built over it besides the beginning of the tunnel.
 

JeffDowntown

Senior Member
Joined
May 28, 2007
Messages
2,851
Reaction score
29
My point is with the additional developed buildings near North Station could the Big Dig tunnel become top heavy overtime? I believe most the highway is right under the Greenway so there is really not much built over it besides the beginning of the tunnel.
All that development at North Station (as well as a few other parcels over the tunnel) was planned for during the construction of the Big Dig foundation. Acceptable building envelopes (massing/height) were established so that the foundation could carry the planned load.

Same thing is true out in the Seaport district.
 

falcon42

Active Member
Joined
Dec 1, 2015
Messages
366
Reaction score
8
Yes I believe they are building a few building over the SL tunnel in the Seaport.
 

datadyne007

Moderator
Staff member
Joined
Sep 15, 2010
Messages
8,769
Reaction score
64
Is this thread for real? No, the structural loads aren't inflicted on the tunnel itself. They are transferred to columns attached to footings that are either between the highway lanes and/or outside the ROW. The friggin Prudential Center was built on air-rights in the 1960s and its doing just fine along with Copley Place from the 1980s. I can assure you: we've definitely figured out how to do air rights construction in 2017.
 

autonomy

New member
Joined
Jun 3, 2014
Messages
42
Reaction score
0
A slightly different question - I remember a couple years ago there was a flurry of articles about how the supposedly frozen soil under the MassPike Tunnel (Ted Williams) was thawing too fast. Any concerns over that still?
 

bakgwailo

Active Member
Joined
Apr 15, 2016
Messages
889
Reaction score
13
A slightly different question - I remember a couple years ago there was a flurry of articles about how the supposedly frozen soil under the MassPike Tunnel (Ted Williams) was thawing too fast. Any concerns over that still?
Why would soil be frozen under there? It would be well deep enough to not freeze in cold weather. All I can think of is that they did some trickery building it with freezing the soil to give it more rigidity while tunneling under the old elevated/south station/etc, but that wasn't permanent.
 

HenryAlan

Senior Member
Joined
Dec 15, 2009
Messages
2,107
Reaction score
57
Yes, they did freeze the soil during part of the construction, but certainly that would not still be frozen today, nor would the engineers have planned on it being forever frozen.
 

Arlington

Moderator
Staff member
Joined
Dec 10, 2011
Messages
3,796
Reaction score
67
Recall that Soil Freezing was used both for tunneling the SL under (then) Russia Wharf (now a more marketable "Atlantic Wharf"), and for freezing under the South Station approach tracks.

The soil under the South Station approach tracks was frozen so that the connector section could be dig between the old I-90@Artery and the large stretch of I-90 that was made in the Fort Point casting basin* So that under-the-tracks section is the part that we'd worry about in this thread.

Foam Tech, which insulated the exposed frozen faces as they were dug-through, has great pictures on their site, including this aerial view of the tunnel going under the tracks with frozen soil above:


I found this story from 2011 that said that afther the freeze plant was shut off in 2002, the thawing soil had taken longer and shrunk more than expected, leaving voids in that area (and that they expected that thawing would have ended by then, but would probably continue until 2013:
When constructing the I-90 connector tunnel, an area of about 200-feet-by-160-feet was frozen to allow for excavation without disrupting train service above to depths of about 130 feet below the ground surface. The freeze plant was shut down in 2002, as engineers expected the clay soil to settle approximately the same amount it had swelled during the freezing process.
...
The highway department hired an independent engineering firm, STV Parsons, to analyze the tunnel structure in light of the settling, and DePaola said it was determined the tunnel, acting as bridge, is able to withstand the additional pressure being put on the structure from above even when assuming the void spans the entire length and width of the tunnel section.

*casting basin video shows the cast-float-sink sections of tunnel that the dug-through-frozen-soil connector tunnel was connecting to.
Casting Basin.
 

HalcyonEra

Active Member
Joined
Mar 6, 2012
Messages
405
Reaction score
0
I honestly would support criminalizing doing something like that.
At a minimum an automatic and permanent loss of their CDL is appropriate. Who knows what else they ignore.

There is really no excuse for it.

Some of the Storrow stuff you can understand...college kids and out of towners... but given all of the signage even those should be severely punished.
 

mass88

Senior Member
Joined
Jan 10, 2008
Messages
1,985
Reaction score
1
The cleanup costs for the carrier will most likely exceed 6 figures for this accident. So even if he/she doesn't lose his CDL (his CSA score will take a beating), I am going to guess he/she will be terminated due to the cost of cleanup, the hit their motor cargo insurance will take and the overall bad publicity they'll have due to this accident.
 

CSTH

Senior Member
Joined
Oct 5, 2009
Messages
1,794
Reaction score
1
Wait, that's a load issue, not a sign-following issue, right?

Clearance is 13'6" there, which is standard everywhere. If you're above that you need mucho permits and escorts etc.

So...probably they put the wrong kind of container on the wrong kind of trailer? Maybe that's the driver's call, maybe its the company - maybe both.

I'm willing to accept the argument that 'the driver is always ultimately responsible for knowing his load' ... but the point is that this not like missing a clearance sign when entering Storrow (or the Callahan, for that matter).
 

Top