To describe the soil structure-interaction of cyclic loaded structures, centrifuge model tests are carried out on laterally loaded piles and vertically loaded shallow foundations. The principle of deformation behaviour of sand will be with briefly. In addition to the presentation of the test results, possibilities of research on cyclic problems in the Bochum geotechnical centrifuge are presented. The obtained data from centrifuge model tests under dry conditions is related to foundations of coastal and offshore structures. It is shown, that the observed mechanisms have to be regarded even in saturated conditions too. The evaluated data is compared with the results and equations obtained from cyclic and dynamic triaxiai tests. Thus, the differences between element tests and the real soil-structure interaction behaviour are established.
Foundations of coastal and offshore structures are quite often experienced with cyclic loadings. These loadings cause displacements and affects the structures resting on such foundations. In saturated conditions of sand, the developements of the displacements are treated as a problem of the combination of the influencing load and the development of pore pressures, which possibly leads to extreme liquifaction contitions. With the results of centrifuge model tests, presended in this paper, it will be shown that large deformations and changing of the boundary conditions also occur in dry soil. In addition to the influence of the pore pressure developement, the soil structure interaction under dry conditions can not be described sufficiently. Higher loads require different model laws, so that the description of the soil-structure interaction becomes much more complicated. Empirical models for the description of the displacement of structures have been formulated regarding the results of cyclic and dynamic tests, but they often suffers under the boundary conditions of the test equipments or under the estimation of the influencing prameter.
