Behavior of Foundation Clays Supporting Compliant Offshore Structures

Piles supporting compliant offshore structures subject the foundation soils to large cyclic shear stresses superimposed on significant static (sustained) stresses. In order to investigate the behavior of foundation clays during critical undrained storm-loading conditions, an extensive experimental program involving Ko-consolidated undrained cyclic direct simple shear tests was performed on normally consolidated samples of resedimented Boston blue clay. Results are presented in a normalized format to allow generalizations and comparisons with other clays obeying normalized behavior. A simplified method is then proposed for predicting important aspects of shaft performance for a rigid rough cylindrical pile subjected to the combined static and undrained cyclic loading conditions imposed by tension leg platforms.