Undrained cyclic loading on a saturated dense sand stratum

Abstract

An analytical approach using finite elements is employed to study the validity of a hypothesis for explaining the presence of spiky acceleration records observed in centrifuge model earthquake tests on embankments and islands. This hypothesis attributes the presence of spiky acceleration records to the recoupling of motions caused by the transient recovery of stiffness of the dense sand in a state of cyclic mobility. The analyses show that spiky acceleration records similar to those observed experimentally can be generated analytically in the problem of a saturated dense sand layer if the material behaviour is of a hardening type. These acceleration spikes coincide with the onset of the hardening phase, thus supporting the above hypothesis. The analyses also show that this type of acceleration response cannot be obtained if the material behaviour is of a softening type. As the behaviour of saturated dense sand under undrained cyclic loading belongs to the hardening type, the mechanism discussed may be present in such sand layers when the latter is subjected to earthquake loadings. -Authors