Performance of Urban Cofferdams Braced with Segmental Steel and Reinforced Concrete Ring Beams

Abstract

The performance of two urban cofferdams is presented in this paper. The first case history is a cofferdam built for the One Museum Park West structure (OMPW), braced with segmental steel ring beams. The second is a cofferdam braced with cast-in-place reinforced concrete ring beams. The main goal of this paper is to study the excavation-induced ground deformations arising from these two cofferdams built in similar geologic settings but different bracing systems, installation sequences, and material responses to time-dependent effects. The deformations at the OMPW cofferdam are attributed to the compliance in the overall retaining system caused by a large initial unsupported cantilever depth and gaps left open between segmental steel ring beams and sheet piles. For the cofferdam at Site 2, observed ground movements are attributed to a rapid construction sequence, low temperatures during concrete curing, and concrete material time-dependent behavior of the concrete ring beams.