Deepening of the Terminal 5 Wharf, Port of Seattle

In the era of post-panamax container vessels, ports are increasing their berthing depths to accommodate larger ships. This paper presents the results of geotechnical engineering analyses related to deepening three berths along the Terminal 5 Wharf, in the Port of Seattle, Washington. The Port of Seattle hired KPFF Consulting Engineers and Hart Crowser to investigate deepening of the berths along the pier by as much as 3 meters. The intent of the analyses was to determine what, if any, structural support was necessary to maintain the static and seismic stability of the under pier slope and to prevent increased deflections of the wharf structure in a seismic event. Stability and deformations were analyzed using slope stability and finitie difference analyses. Soldier piles, sheet piles, and "pinch piles" under the wharf to densify the potentially liquefiable soils were modeled in these analyses. Based on the results of these analyses, sheet piles were used for berths being deepened by 3 meters, and a wall of closely spaced soldier piles was installed for areas deepened by 1.5 meters.