REGIONAL CONNECTOR PROJECT
Angeles Times headquarters building. Numerous unknown site conditions encountered during excavation only compounded the challenge. “It was truly a team effort between
ourselves, Metro, and the City of Los Angeles to encounter these unknowns and then come up with solutions very quickly, a lot of which had to be engineered,” Schiraldi said. “To be able to work through these in real time and keep the Project moving forward, on a megaproject of this size was a real achievement.” All totaled, the Project has
excavated nearly 1 million cubic yards of earth. Tat includes cut and cover work, excavation of the twin tunnels via a Herrenknecht AG tunnel boring machine (TBM), and employing the sequential excavation method to carve
out a 300-ft.-long “cavern” under 2nd Street, providing room for trains to switch between tracks.
Tunneling Challenges Christophe Bragard, Tunnel
Manager at the Skanska/Traylor JV on the Regional Connector Project, described some of the challenges that the team encountered during tunneling work. During the “eventful” mining process for the first tunnel, he noted, the TBM bore through an unknown metallic structure that was later determined to be a 21-inch steel pile. Resulting damage to the TBM required quick action to procure replacement parts from Germany in order to get the machine up and running again for excavation of the second tunnel.
“We were in a little
bit of a race against time, because encountering the obstructions had delayed our schedule about a month,” he said. “But we had a great relationship with the owner, and we were making decisions together for the benefit of the Project. Good teamwork allowed us to move fast; we quickly replaced those parts and then were able to start mining again.” To make up for lost
The dismantled tunnel boring machine front shield was lifted out of the receiving shaft at Flower Street in downtown LA, marking the retirement of the TBM known as “Angeli.” Photo by Ken Karagozian
www.AGC-CA.org
time, the contractor added a third tunneling crew. Mining took place around the clock, 24 hours a day, 5 days a week on the second bore. Crews of 15-20 workers per shift set a record for the fastest /most productive day in tunnel boring in the LA region – clocking in a record 190 feet mined in a single 24-hour day in late 2017. “Tat really was a
bit of a success story on this job,” said Bragard, pointing out that the
Regional Connector Project Fast Facts
Owner: Los Angeles County Metro- politan Transportation Agency
Design-Build Contractor: Regional Connector Constructors JV (a joint venture of Skanska USA Civil and Traylor Bros Inc.)
Designer: Mott MacDonald
Total Cost: $1.81 Billion (estimated)
A Few Stats and Specs: Over 220,000 cubic yards of concrete
35,000,000 lbs of rebar 20 miles of vertical pile 1,000,000 cubic yards of earth excavated
1.9 miles of double track light rail transit
Design includes over 5,000 drawings and 300 specs
Over 200 subcontractors Construction Start: 2014 Slated Completion: 2022
experienced and committed craft workers came together as a team and leveraged the lessons learned on prior work to deliver the second tunnel in record time. “Te work ethic and pride crews had on this Project was amazing,” he added. “I’ve worked on four different continents, and this is the best experience that I’ve witnessed in terms of crews really pulling together for the Project and just for their own pride and satisfaction.”
Cavern Excavation Via SEM Following the twin tunnel
excavation, Regional Connector Constructors JV undertook excavation of the egg-shaped, 57-ft.-wide by 38-ft.-tall cavern section underneath Second Street, using the sequential excavation method (SEM).
Continued on page 8 Associated General Contractors of California 7
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