Finite element analysis of cellular steel sheet pile cofferdams

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Virginia Tech


A cellular cofferdam represents a challenging soil-structure interaction problem. The cellular system consists of a combination of a flexible structure formed from interlocking sheet piles that is filled with soil. In the past, the cellular cofferdam has been viewed as a temporary structure, and the design procedures have been based on empirical concepts. Basic to these approaches are assumptions of soil and structural behavior that have, at best, only a rough accounting for soil-structure interaction.

In the last decade, work on cofferdams has improved our understanding of the behavior of these systems. Documentation of performance has increased, and in a few cases major instrumentation efforts have been undertaken. Concurrently, finite element methods have been introduced for the analysis of cofferdams. Where the finite element models have been properly calibrated by field performance, they have reasonably predicted the principal aspects of cofferdam behavior. Results of the finite element models have also served to help explain some aspects of the soil-structure interaction process in the cofferdam system.

Two finite element programs are used in this research, AXISHL and GPS. The first of these is an axisymmetric analysis tool which is applicable to the case of filling of a main cell. The second program provides a simplified means of analyzing the main/arc cell and common wall system. Both programs are used in a series of parameter studies with the objective to provide information that will allow improvement of the state-of-the-art of design for cofferdams. An analytical solution is proposed which allows an insight to be developed as to how the clamping effect at the dredge line affects the behavior of the system. A simplified calculation procedure which has some of the characteristics of the finite element analysis is developed to supplement the need for a finite element analysis.