Pre-Compression of Concrete Breasting Dolphins Solves Construction Problem

by Robert A. Blowers, Parsons Brinckerhoff Quade &, Douglas, Boston, United States,
Alexander Matlin, Parsons Brinckerhoff Quade &, Douglas, Boston, United States,
Antoni J. Zelechowski, Parsons Brinckerhoff Quade &, Douglas, Boston, United States,

Document Type: Proceeding Paper

Part of: Ports '92


A roll-on/roll-off ferry terminal was built in Quincy, Massachusetts in 1989 as part of a marine transportation system to support construction of the sewage treatment facilities proposed for the clean-up of Boston Harbor. The terminal, designed to accommodate barges, included, among other components, two breasting dolphins. The dolphins are supported by 18 inch diameter steel pipe piles driven to bedrock, and battered in different directions to resist lateral berthing loads. The tension piles are designed to be anchored into the bedrock with high strength steel cables. During the process of anchor installation, the anchoring length of cable embedded in the bedrock did not receive proper grouting. As a result, the anchors failed the load test. To avoid re-driving of piles, which would require the re-mobilization of expensive pile driving equipment, a new design concept was developed. This concept was to pre-compress the piles against the bedrock and prevent or greatly reduce their net tension under the service loads. This was accomplished by installing two additional high capacity anchor cables through a steel casing and applying a pre-compressing force to the entire pile group through the concrete dolphin pile cap.

Subject Headings: Cables | Steel piles | Anchors | Offshore structures | Concrete piles | Load tests | Bedrock | Massachusetts | United States | Boston

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