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Great physics discussion questions! These were written by Physicist Dr. Matt Caplan, who used to run the QuarksAndCoffee blog. That blog no longer exists, links to archived copies exist.
What are we learning?
We’re studying the engineering – applied physics – used in Boston’s Big Dig. We’ll study the effect of changing forces, loads, materials and shapes, on a structure.
Why are we learning this?
To learn how to break a complex real-world problem – building safe tunnels and related structures – into smaller parts that can be solved using scientific/engineering principles.
To learn how to use a simple computer simulation to model such systems.
compression, tension, bending, shear, torsion, loads, dead load, live load, settlement load, thermal load, wind load, earthquake load, dynamic load, arch, brace, buttress
The Central Artery/Tunnel Project (CA/T) – the Big Dig – was a megaproject in Boston that rerouted the Central Artery of Interstate 93, the chief highway through the heart of the city, into the 3.5-mile (5.6 km) Thomas P. O’Neill Jr. Tunnel. It also included the construction of the Ted Williams Tunnel (extending Interstate 90 to Logan International Airport), the Zakim Bunker Hill Memorial Bridge over the Charles River, and the Rose Kennedy Greenway in the space vacated by the previous I-93 elevated roadway. Planning began in 1982; construction work was carried out between 1991 and 2006.
- Intro adapted from Wikipedia, The Big Dig, 1/18
Here are before-and-after photos of downtown Boston, showing the removal of the Central Artery and it’s replacement with the Rose Kennedy Greenway. You can left-click on it to open in a new window, at high-res.
Use the worksheet assigned by the teacher.
Building the tunnel under Forth Point Channel
William Harris, in “How Tunnels Work: The Big Dig” (How Stuff Works) writes:
A few miles west, Interstate 90 enters another tunnel that carries the highway below South Boston. Just before the I-90/I-93 interchange, the tunnel encounters the Fort Point Channel, a 400-foot-wide body of water that provided some of the biggest challenges of the Big Dig.
Engineers couldn’t use the same steel-tube approach they employed on the Ted Williams Tunnel because there wasn’t enough room to float the long steel sections under bridges… Eventually, they decided to abandon the steel-tube concept altogether and go with concrete tunnel sections, the first use of this technique in the United States.
…workers first built an enormous dry dock on the South Boston side of the channel. Known as the casting basin, the dry dock measured 1,000 feet long, 300 feet wide and 60 feet deep — big enough to construct the six concrete sections that would make up the tunnel… The completed sections were sealed watertight at either end. Then workers flooded the basin so they could float out the sections and position them over a trench dredged on the bottom of the channel.
[They couldn’t] simply lower concrete sections into the trench [because] of the MBTA’s Red Line subway tunnel, which runs just under the trench. The weight of the massive concrete sections would damage the older subway tunnel if nothing were done to protect it. So engineers decided to prop up the tunnel sections using 110 columns sunk into the bedrock. The columns distribute the weight of the tunnel and protect the Red Line subway, which continues to carry 1,000 passengers a day.
Slider photo: Boston before- and after- Big Dig (10 years later, did the Big Dig deliver?, Boston Globe)
Extreme Engineering: Boston’s Big Dig (2003)
National Geographic MegaStructures Boston Big Dig Documentary 2016
Big Dig The Construction Story of Boston Big Dig
Underground Utility Protection
In “The Big Dig: Learning from a Mega Project”, Virginia Greiman writes
To protect against losses caused by the disruption and failure of underground utilities, a Big Dig utility program relocated 29 miles of gas, electric, telephone, sewer, water, and other utility lines maintained by thirty-one separate companies in 1996. Some of this infrastructure was more than 150 years old; a complete lack of knowledge on the age, condition, and location of most of the utilities required submission of “as-built” drawings by all project contractors—drawings of existing conditions rather than planned or proposed construction. The project had to deal with utilities that were shown on as-built drawings but never installed, and damage and flooding caused by underground sewer pipes not identified on the drawings.
2016 Massachusetts Curriculum Framework High School Technology/Engineering
HS-ETS1-1. Analyze a major global challenge to specify a design problem that can be improved. Determine necessary qualitative and quantitative criteria and constraints for solutions, including any requirements set by society.
HS-ETS1-2. Break a complex real-world problem into smaller, more manageable problems that each can be solved using scientific and engineering principles.
HS-ETS1-3. Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, aesthetics, and maintenance, as well as social, cultural, and environmental impacts.
HS-ETS1-4. Use a computer simulation to model the impact of a proposed solution to a complex real-world problem that has numerous criteria and constraints on the interactions within and between systems relevant to the problem.
HS-ETS1-5(MA). Plan a prototype or design solution using orthographic projections and isometric drawings, using proper scales and proportions.
HS-ETS1-6(MA). Document and present solutions that include specifications, performance results, successes and remaining issues, and limitations.
It’s amazing how motivated students can be to do real, quantitative physics, with the right set-up 🙂
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