Permanent Displacements Due to Cyclic Wave Loading

The permanent deformation of soils as the result of cyclic loads is an important consideration in the design of offshore structures. Experimental studies show that the permanent strains are influenced by the porosity, the intitial shear and effective normal stresses, and the amplitude of the cyclic shear stress, as well as by the number of cycles of loading. These effects are combined into a logarithmic relation. The resulting equations have been incorporated into a finite element program that calculates permanent displacement without changes in net boundary loads or stresses. The analyses are applied to a proposed offshore barrier to show the importance of the ways in which cyclic loads combine with monotonic loads due to tides to give permanent displacements.