Determination of cyclic soil parameters for offshore foundation design from an existing data base

Determination of the soil parameters in the foundation design analyses for offshore and nearshore platforms subjected to cyclic loading from wind and waves requires extensive advanced laboratory testing. The amount of such testing can be reduced by drawing on the experience that has been gained during the design of offshore structures in the past. It is outlined how an existing data base can be used to estimate the soil parameters needed in the foundation design analyses based on conventional parameters, like undrained static shear strength, plasticity index and overconsolidation ratio for clays, and relative density and/or water content, fines content and overconsolidation ratio for sand and silt. The estimated soil parameters can be used in feasibility analyses before site-specific parameters are available and to reduce the amount of site-specific advanced laboratory testing in the final design phase. The application of the data base is demonstrated by examples for clay and for sand with different fines content.