TOP 10 ROADS: No. 5—Footprint binding

Tunnel must fit into tight quarters

Article October 04, 2012
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The Doyle Drive Battery Tunnel has to squeeze into an extremely restricted footprint between the San Fancisco National Cemetery and the existing Doyle Drive.

The project is located in the Presidio of San Francisco, a former U.S. Army base. One retaining wall was only 5.5 in. from the cemetery. The project team worked closely with the Department of Veterans Affairs to ensure protection of the cemetery land and historic resources.

The Doyle Drive Battery Tunnel and Temporary Bypass project dug its way into position 4 on the ROADS & BRIDGES Top 10 Roads list for 2012.

The southbound Battery Tunnel and temporary roadway are portions of Phase 1 of the Presidio Parkway. Traffic was transferred to the new structures in April 2011, and they will carry traffic until construction of the entire project is complete in 2015. The existing Doyle Drive is an elevated roadway constructed in 1936 and now structurally and seismically deficient. The new Presidio Parkway will incorporate modern design improvements, wide landscaped medians, continuous shoulders, twin bridges, two sets of short cut-and-cover tunnels and a new interchange providing direct access from San Francisco.

Excavation of the tunnels was complicated by unrecorded underground utilities. Most of the utilities on the project site were placed by the military in the early 1930s. Since then, records of the network have been poorly maintained, and changes have gone unrecorded. Relocating unexpected utilities delayed tunnel excavation into one of the rainiest winters in recent San Francisco history. A shoring system using struts and tie-backs was designed to support a 30- to 40-ft cut, minimize deflection and still allow for removal of nearly 100,000 cu yd of material. To expedite tunnel construction, a custom traveling form system and high-early-strength concrete mix designs were used.

Another challenge was to design the tunnel-systems substation, which needed to be hidden within the structure, because of the lack of available space and the project’s architectural criteria. The substation houses extensive lighting, electrical, telecommunications, traffic-monitoring and fire-suppression systems. The design team used 3-D modeling to help visualize and analyze options and determine the most space-efficient and constructable solution. With the 3-D modeling, project designers developed a system to reduce bends in rigid counduit and a more efficient and accessible substation.

A five-lane temporary bypass road was built at the eastern end of the project to enable traffic to continue flowing after the original roadway was demolished and before the final Presidio Parkway is completed. R&B

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