Proceedings of the 26th Annual Members' Conference, 2001, St. Louis, MO "Designing Deep ~ Building Deep", (DFI)
New Outfall Bridge Structures At Bonneville Dam: Design, Construction, and Lateral Testing
Lance Helwig, Amir Asaidali, Katzenberger
Two new outfall bridge structures near Bonneville Dam in Oregon have been constructed in the Columbia River in 1999. This drilled shaft project case study contains several design, construction, and lateral load testing features of interest to the deep foundation industry, including: Design: Numerous design challenges were created by the demanding design criteria for the project. The 10-foot-diameter drilled shaft piers experience repeated very large lateral forces and deflections when the outfall bridge superstructures, projecting 400 feet out into the river and 80 feet above the river bottom, are submerged for long periods of time in 15-feet-per-second river water flow. Construction: The construction conditions and time constraints were very challenging for this project. The six 10-foot-diameter, 1-inch-thick steel permanent casings for the piers were vibrated into the river bottom approximately 100 feet and were eventually socketed into bedrock. These casings varied from 136 feet to 207 feet in length and were installed with the larges vibratory hammer ever manufactured in the United States. Numerous construction photographs recorded the progress and the challenges met by the construction team. Testing: Each of four permanently-cased 10-foot-diameter drilled shaft piers were laterally tested for a two week period in an extensive test program. Lateral loads up to 600 kips were applied cyclically at approximately 80 feet above the mudline. The purposes of the testing included 1) to evaluate the need for soil improvement collar bid options to reduce lateral deflection, 2) to verify the soil-structure model accuracy, and 3) to evaluate the cumulative deflection permanent-set characteristics of the soil. Considering that Lateral Load Test results for 10-foot-diameter drilled shafts are quire rare in the literature and in the industry, the usefulness of these test results extend well beyond this specific project.
|article #940; publication #56 (AM-2001)|