The Response of Suction Caissons to Catenary Loading

Research into the performance of suction caissons has developed in response to the demand from the offshore hydrocarbon industry for a versatile foundation solution capable of anchoring a range of alternative structures. Suction caissons are capable of providing large anchoring capacities in all directions. The simple installation procedure and high reliability has seen suction caissons employed in a range of water depths and within hydrocarbon fields from marginal to high potential. As exploration is directed toward increasing water depths, anchoring demands on the proposed structures become greater and subsequently a more detailed understanding of the limitations to caisson capabilities and performance is required.

Using the fixed beam geotechnical centrifuge facility at The University of Western Australia (UWA), the installation and response of a dimensionally scaled prototype caisson to inverse catenary chain loading was modelled with the objective of establishing a relationship between the caisson geometry, soil characteristics and the monotonic holding capacity. The installation and tensile resistances were recorded to determine the necessary installation pressures and uplift capacity of the caisson. Theory suggests that the lateral capacity is dependent upon the frictional resistance between the caisson and soil, which may be back derived through calibration of the theoretical and experimental response of the caisson to axial loading.

This paper presents the data from a series of centrifuge tests, comparing the results with the theoretical monotonic capacity of laterally loaded caissons. A smooth walled model caisson was installed and subsequently loaded with an anchor chain in normally consolidated kaolin clay. The data exhibited excellent repeatability between identical tests and a similar correlation with the adopted upper-bound plasticity solution for laterally loaded caissons.