Marine Foundations of Bridges in the Northeastern USA-PDF

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The paper reviews the design and construction of caisson foundations for major bridges across waterways in the northeastern United States, from the Brooklyn Bridge (1870–1883) through the Newport Bridge (1965–1969). It expands on geotechnical studies of bridge sites by describing how foundations were built under differing subsurface and water-depth conditions.<br /><br />The Brooklyn Bridge established the model: large timber caissons were floated into place, weighted, and sunk as workers excavated beneath them in pressurized chambers. Later bridges adapted the method to new materials and equipment. The Ben Franklin Bridge also used pneumatic caissons, while the Delaware Memorial, Walt Whitman, Throgs Neck, and Verrazano Narrows bridges used open caissons with dredging wells and mechanical excavation, often sealed with tremie concrete. Where bedrock lay too deep for practical caisson sinking, foundations incorporated piles. At the Newport Bridge, pile-supported caissons were installed on the bay floor.<br /><br />The Tappan Zee Bridge used an unusual hybrid system: concrete caissons were partly supported by long piles and partly by controlled buoyancy maintained by pumps. Its western causeway also relied on untreated timber piles, which became vulnerable as improved water quality allowed marine borers to return.<br /><br />Across the projects, foundation methods responded to local geology, water depth, and construction technology. The paper notes that pneumatic caissons are now largely obsolete, with open dredged caissons favored. Future cable-stayed bridges may avoid costly anchorages but will still require substantial tower foundations, including caissons and cofferdams in deep water.

Keywords

caisson foundations

bridge construction

geotechnical studies

pneumatic caissons

open caissons

Brooklyn Bridge

pile-supported caissons

tremie concrete

dredging wells

bridge foundations