A Study of the Effects of Differential Loadings on Cofferdams

Recent studies have suggested that most existing design methods are excessively conservative. This investigation is directed toward providing a data base through the documentation and comparing five case histories where instrumentation was used to monitor the behavior. Primary consideration was given to the response of the cofferdams under differential loading. In the course of the investigation, the response of each cofferdam was documented and dissected in terms of the behavior at each stage of the differential loading. A strong correlation is found to exist between the lateral cell deflection and the level of differential loading, with the exact nature of the correlation depending on certain key parameters including cell foundation, cell fill material, cell width to height ratio, presence of a stabilizing berm, and nature of loading. It is found for conservatively designed cells that the response falls into a predictable pattern which can be characterized in terms of nondimensionalized parameters for both normal and more severe levels of loading. In addition to deformations, information is provided on interlock tensions where available. The results are believed to provide a baseline for cofferdam behavior that can be useful in gaging the expected behavior of other cofferdams and for verifying the accuracy of new forms of predictive tools such as the finite element method. (jhd) Original contains color plates: All DTIC and NTIS reproductions will be in black and white.