Abstract: It is shown that sand has significant viscous properties related to loading rate. The stress-strain curve will jump abruptly upon a sudden change in strain rate. This strain rate effect will gradually fade as loading progresses. The TESRA (Temporary Effects of Strain Rate and its Acceleration) model which highlights the strain rate as the core variable rather than the conventional time variable is used to consider the viscous properties of sand. The dynamic relaxation-finite element method (DR-FEM), which has a high reputation in solving highly nonlinear geotechnical boundary value problems, is chosen as the numerical method. Return mapping method is used for stress update during the calculation. The laboratory tests on sandy foundation under variable loading rates were then simulated numerically by the nonlinear finite element method. The simulated results reproduced reasonably the load-settlement relations under loading conditions such as the changes of loading rate，creep and stress relaxation; and it also performed the decaying of viscosity as the loading progressed. Comparisons are made between test and simulated results to present the viscous properties of sandy foundation. The results also validated the rationality of the proposed nonlinear three-component visco-elastoplastic model for sand.

Key words: sandy foundation, finite element simulation, loading rate, temporary viscosity, creep, stress relaxation