| Portland Light-Rail Transit Tunnel Project |
| Introduction to the Good, the Bad, and the
Lessons Learned |
| By David S. McAllister, Portland, OR 503-417-9354,
mcallister@pbworld.com |
|
The Westide Light
Rail Tunnel Project articles were presented as part of a special
printing of PB Network that was distributed at the North American
Tunneling ’98 Conference and the World Tunnel Congress
‘98, and is available for other tunneling and geotechnical
conferences.
The articles are sponsored by PAN 19 Geotechnical Engineering
and PAN 37, Tunneling and Underground Engineering. Some other
activities being sponsored by the PANs include:
• Preparation of an FHWA report on the use of slurry walls
as part of the final underground structure
• Compilation of tunnel lessons learned
• Guidelines for geotechnical baseline report
• Guidelines for tunnel layout geometric design
• Preparation of PB tunneling engineering seminars
• Guidelines for soil/structure interaction analysis
• Tunneling update for PB resident engineers manual.
Please contact PAN Coordinators Amanda Elioff (LA EMC, 213-312-3214,
amanda.elioff@pbdmjm.com)
or Brian Brenner (Boston Central Artery, 617-951-6276, brbrenne@bigdig.com)
if you would like to participate in these PAN projects. |
Figure 1. The 29-km (18-mile) long extension to Portland,
Oregon’s light rail transit system. |
The Pacific Northwest is a major growth center in the U.S., with Portland,
Oregon being one of its rapidly growing metropolitan centers. Near
Portland, most of the expansion is in Washington County, particularly
in the areas surrounding Beaverton and Hillsboro. The West Hills separate
Portland from Beaverton, and are connected by the Sunset Highway.
The Portland Light Rail Project, undertaken by the Tri-County Metropolitan
Transportation District (Tri-Met) of Portland, Oregon, is a 29-km
(18-mile) extension to the existing Tri-Met Metropolitan Area Express
(MAX) light rail transit system. It adds service from downtown Portland
to the suburban communities of Beaverton and Hillsboro, located west
of Portland’s downtown central business district (Figure 1).
The overall goal of the project is to operate an optimal transit system
while maintaining each community’s values and sensitivities
for the environment. A 4.6 km (2.75-mile) twin bore tunnel through
the West Hills with a deep, underground station at Washington Park
was selected as the best route for achieving this goal. The tunnel
minimizes the impacts to and preserves the aesthetics of the Sunset
Highway canyon while providing flatter grades than other alignments
and winter weather protection.
PB’s design and construction management contributed to the success
of the entire project. The articles in this section focus on some
specific design and construction elements of the tunnel contract,
the primary features of which are:
- 4.6 km (2.75 miles) of twin bore tunnels, 5.7 m (18 feet 8
inches) in diameter
- 79-m (260-foot) deep transit station at
Washington Park , the deepest in North America
- Twin shafts, 9.4 m (31 feet) in diameter
for access to the station platforms and for ventilation
- A ventilation shaft 5 m (17 feet) in diameter.
The other articles focus on certain design and construction elements
of the tunnel contract and provide in-depth information on tunnel
liner problems and managing noise and vibration. A previous PB
Network article, “Careful Design Results in Cost Savings
on the Westside Corridor Project” by Rick Mayes (Winter ‘93/94,
pp 13-15, 41-42) discussed the use of ground-structure interaction
concepts in the design, especially at Washington Park Station. Another
interesting article that appeared earlier is “Hydraulic
Modeling of Fire Protection Pipelines for the Westside Rail Tunnels”
by Ken Harris, Spring ‘96, pp 24, 25. |
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