Big Dig ceiling panels may have a purpose

The most convenient way for me to get to work each day is to use the Tip O'Neill tunnel. Not to use it would mean either driving over surface roads in the city (not an option) or going around the city on Route 128. That ain't happenin' either. So, I'm stuck risking my life in the Big Dig tunnels, hoping each time that some epoxy doesn't fail causing 3-ton ceiling panels to come crashing down on my head.

And so it was this morning that I found myself driving through the tunnel, and yes, I was looking up at the panels to see how if I can figure out how close this hanging system is to the one described as being used in the Ted Williams Tunnel. Turnpike Chairman Matt Amorello said the system in the Ted was used only in that section. I don't believe him, but I have no choice but to hope he's telling the truth.

A lot of the questions around the tunnel ceiling's collapse have centered on the panels, and the fact that they were made of concrete and weighed 3 tons. Most in the blogosphere have questioned the need for anything concrete, let alone 3-ton slabs, hanging from the ceiling. Well, I'm no engineer, but I have a feeling I can speculate on the need.

Planning the tunnels requires more than just positioning exit and entrance ramps and lane configurations. The tunnels need to be constructed to withstand major catastrophes. Remember when that unlicensed produce trucker went careening through the northbound side of the tunnel at 70 mph and crashed into the wall? He took out about four or five of the tile wall panels and closed the highway for several hours before and during the morning commute. At the time, Amorello said the tunnel systems worked perfectly. Indeed, they did. The actual structure of the tunnels wasn't damaged.

Now imagine a similar catastrophe that sent some kind of eruption into the ceiling. Perhaps two trucks collide and are driven upwards. Or, a truck driver hauling hazardous chemicals ignores all the signs prohibiting his vehicle from the tunnel and crashes causing a major explosion in the tunnel. The eruption would push upward to the city streets above and all the unsuspecting motorists and pedestrians on the soon-to-be-lovely Rose Kennedy Greenway.

Does anyone but me remember the Amtrak train that came into Ruggles Station at 100 mph in in early 1990s? It jumped the tracks and crashed into the ceiling of that tunnel and the force ruined the pavement on the street above it.

My guess, and it's really only a guess, is that the panels actually serve the purpose of containing a catastrophe. They need to be heavy and strong enough to withstand explosions and forceful impacts to limit the amount of destruction that can be caused. And it would take a lot of force to move something that's 3 tons upwards. Unfortunately, gravity's pull requires much less to bring it down.


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