Boston's Big Dig- One of Engineering's Biggest Mistakes?

The faulty bolt and epoxy assemblies that led to more headlines about Boston’s Big Dig/Central Artery Tunnel Project was just the kind of engineering who-done-it engineers find irresistible. Was the wrong epoxy used? Was the design faulty? Or was poor installation the reason for the failure?

The investigation, which found faulty assemblies, was sparked by the July 10 death of a 39-year-old woman after 12 tons of cement ceiling panels fell on the car her husband was driving inside the I-90 connector tunnel more than two weeks ago.

As a result, several portions of Boston’s $14.6 billion Big Dig/Central Artery Tunnel Project have been shut down. Ongoing investigations by federal and state officials are uncovering additional problems almost on a daily basis.  

On July 12, according to a Boston Globe report, inspectors found at least 60 faulty bolt fixtures in the ceiling of the tunnel. On that same day, Attorney General Tom Reilly says tests conducted in 1999 showed that the ceiling bolts had a tendency to come loose.

On Wednesday, July 26, the Herald reported they obtained documents revealing that Big Dig officials noted six years ago that epoxy ceiling supports were failing in the same tunnel section where the deadly accident occurred, but allowed the continued use of that “superglue” system to support 3-ton concrete slabs.

On Thursday, July 27,  Mass Turnpike Authority Chairman Matt Amorello stepped down from his position, overseeing the project, just before a hearing with Gov. Mitt Romney – a strong proponent of Amorello’s resignation.

While doubts about the infrastructure’s safety are only coming to light now – a December 1998 Inspector General’s Report reviewing the project’s use of anchor bolts documents numerous problems with the bolts and glue used to secure the ceiling in the Ted Williams Tunnel which opened to traffic in 1995. The  I-90 connector connects the Mass Pike with the Ted Williams Tunnel.

The Inspector General’s Report discloses several findings which would indicate a problem could occur:  poor design specifications, paying contractors to test improperly installed anchor bolts and lack of consultation with tunnel designers before allowing contractors to drill through steel reinforcements in the tunnel roof.

It also documents numerous problems with the bolts and glue used, including bolts that were too short and trouble with the epoxy used to glue the bolts into the concrete.

In the past two weeks, forums and blogs have been popping up all over the Internet where many techies are eager to speculate on what happened, why it happened and what the next steps should be under the cloak of anonymity.

Engineers, for example, have been posting their two cents across the Internet since the news broke about the deadly accident. They’re offering their thoughts on how these assemblies failed, what materials should have been used, and how the problem can be corrected.

Bloggers on the website, Dvorak Unsensored , have been discussing the failure.

“Was there a structural necessity to have big thick concrete panels on the inside of the tunnel,” posts one reader. “My guess would be that it was not necessary.

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