Behavior of Gravity Caisson on Sand

Abstract

A series of centrifuge model tests have been conducted to evaluate the vertical and horizontal displacements of a gravity caisson supported on sandkey under construction and service loads. In-flight simulation of the infilling of the caisson was achieved by releasing heavy zinc chloride solution into the model caisson while the backfilling process behind the caisson was simulated by pluviating sand into the model from a sand hopper. The results obtained from the basic tests indicate that the magnitude of horizontal sliding displacement of caisson under service loads is not acceptable even with a sandkey relative density of 70% based on the limit set for the operation of quay cranes on top of the caisson. Additional tests reveal that placing a layer of rock sill between the caisson base and sandkey will significantly reduce the horizontal displacement of the caisson. The results of parametric experiments conducted to examine the effects of caisson width, sandkey thickness, and preloading of backfill on the displacement of caisson are also presented in this paper. The relevance of the model results is assessed by comparing them with observed caisson movements from several field studies.