Bearing capacity under cyclic loading — offshore, along the coast, and on land. The 21st Bjerrum Lecture presented in Oslo, 23 November 2007This paper represents the written version of the 21st Bjerrum Lecture. While it has been edited for the present publication, it retains the general structure of the original lecture, which was intended for a general geotechnical audience. The Bjerrum Lecture is presented in Oslo in alternate years by the Norwegian Geotechnical Society with the support of the Bjerrum Memorial Fund (Laurits Bjerrums Minnefond).

Cyclic loading can be important for the foundation design of structures, both offshore, along the coast, and on land, and for the stability of slopes. This is illustrated by several examples. The paper discusses how soil behaves under cyclic loading, both for structures and for slopes, and shows that the cyclic shear strength and the failure mode under cyclic loading depend strongly on the stress path and the combination of average and cyclic shear stresses. Diagrams with the cyclic shear strength of clay, sand, and silt that can be used in practical design are presented. Comparisons between calculations and model tests indicate that foundation capacity under cyclic loading can be determined on the basis of cyclic shear strength determined in laboratory tests.