Monday, June 11, 2012

Testing foundation for bridge of the future

Welders remove metal buildup from welded seam
of 10 foot wide shaft that will be installed in the soil.
Courtesy ODOT Photo.
The deepest shafts ever constructed for a bridge foundation in Oregon and Washington are currently being installed – and they will never support traffic.

This spring, the Columbia River Crossing project (jointly led by WSDOT and ODOT) is conducting a pre-construction test in Washington and Oregon to gain more information about soil conditions and techniques to construct foundations for a new Interstate 5 bridge over the Columbia River. Test foundations are a common pre-construction practice for engineered structures, but this test is unique.  Because of the sandy soil conditions in the Columbia River, the tests include shafts that, at up to 260 feet deep, are the deepest ever constructed by both WSDOT and ODOT.

This important step in the pre-construction phase for the CRC project could result in reducing the number or depth of foundation shafts planned because of the information gained from testing.  And fewer or smaller shafts mean reduced construction costs.

Crews are constructing three test shafts up to 10 feet wide and 260 feet deep. The shaft depths will reach a layer of partially cemented cobbles and gravel, known as “Troutdale Formation,” which lies more than 200 feet below the surface and where the new bridge foundations will be anchored.
The work site is currently visible just west of the I-5 bridge. 

The drilled shaft method involves installing steel casing into the soil, excavating the soil, installing rebar for support and filling it with concrete.

The drilled shaft test is one of two being conducted. Pile driving at this location also was tested and is complete. Both methods are expected to be used for future construction of the CRC project.
CRC is a long-term, comprehensive project to reduce congestion, enhance mobility and improve safety on Interstate 5 between SR 500 in Vancouver, Wash., and Columbia Boulevard in Portland. The project will replace the I-5 bridge, extend light rail to Vancouver, improve closely-spaced interchanges and enhance the pedestrian and bicycle path between the two cities.

Additional information about the drilled shaft and driven pile test project, including a fact sheet (pdf) and photos of the work may be found on the CRC website.

The test project is scheduled to be complete by summer 2012 and is being conducted by Max J. Kuney Construction, of Spokane, Washington, who was awarded the $4.22 million contract in December 2011.

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