FEATURE ARTICLE SPECIAL ISSUE : P R O J E C T S Foundation Design of the Abraham Lincoln Bridge Challenging subsurface conditions at The new Abraham Lincoln Bridge, previously known as the Ohio River Bridges Downtown Crossing, is a three-tower, cable-stayed bridge over the Ohio River connecting downtown Louisville, Ky., to Jeffersonville, Ind. The construction and design contract was awarded through the design-build selection process. The design- build (D-B) team led by Walsh Construction (contractor), Jacobs Engineering (designer) and the cable-stayed bridge designer COWI North America (formerly Buckland & Taylor), encountered several unique challenges. Close collaboration between the geotechnical and structural designers and the contractor resulted in an innovative, cost-effective design that provided the owner, Kentucky Transportation Cabinet, the most desirable technical solution delivered on time and on budget. The project was completed on an aggressive design and construction schedule; the design was started in January 2013 and the bridge opened on December 5, 2015. the site, which included highly-variable depth to bedrock at each end of the bridge, resulted in a stiffness contrast for the structure that required careful consideration of foundation axial capacity and lateral stiffness in order for the bridge to remain technically acceptable and economically feasible. For both the bid and detailed design phases, 12 ft (3.7 m) diameter drilled shafts were selected to support the three main tower foundations. During construction, the project sche- dule and foundation design were jeo- pardized when defective concrete was identified in one of the shafts. Remediation of the defective shaft in the midst of bridge construction was accomplished without delays to the project or significant cost increases through close coordination between the design team and contractor. The shaft remediation deployed state-of- the-art concrete testing technologies, which eventually made this project a success for the owner and the D-B team. Geotechnical Conditions The Abraham Lincoln Bridge is six-lane, 2,106 ft (642 m) long with two main spans of 750 ft (229 m) each and end spans of 303 ft (92 m) each. The towers and the anchor piers are supported by 12 ft (3.7 m) diameter drilled shafts founded on rock that varies significantly in depth from one side of the bridge to the other. Within the Ohio River, overburden soils are primarily glacial outwash, typically consisting of thin zones of silt and/or clay at the river bottom, which quickly transition into sand with some gravel over the depth. The thickness of these deposits decreases sharply from south to north toward Indiana as the bedrock surface rises. On the south side near Kentucky, the top of bedrock is about 95 ft (29 m) below the normal pool whereas the river bottom on the north side typically contains only a thin amount of sediment directly over the bedrock surface. AUTHORS Dan Yang, P.E., P.Eng., Yu Zhang, P.E., and Sam Christie, P.E., G.E., COWI North America 94 • DEEP FOUNDATIONS • NOV/DEC 2016
