Cyclic properties of dense to very dense silica sand

This paper presents results of a series of cyclic laboratory test performed on dense to very dense silica sand. Triaxial and direct simple shear tests were performed on reconstituted sand. The test program aimed to determine the cyclic shear strength and soil deformation properties for foundation design of offshore wind turbine structures on the Dogger Bank site, offshore United Kingdom, but is also applicable for foundation design of other offshore structures and other locations. Two sand batches were used, one with clean silica sand and one with 20% silt content. Normally consolidated specimens from both batches were reconstituted to a target relative density approximately equal to 100% and 80%. On the clean sand with a target relative density of 80%, tests were also performed on specimens with an overconsolidation ratio of OCR = 4. Various contour diagrams, presenting cyclic shear strength and average and cyclic shear strains for different number of cycles, are presented. These diagrams can be used in the front-end engineering design (FEED) stage of commercial design projects on similar soil conditions, to define soil behavior when limited cyclic data is available, or in the planning stage of a cyclic laboratory test program. Effects of precycling and fines content on the cyclic behavior of triaxial and DSS specimens are discussed.