Abstract: Since many earth dams were built and are to be built on overburden, it is essential to describe the dynamic interaction behaviour between earth dams and the overburden reasonably for the seismic safety evaluation of dams. The seismic wave input method is based on the equivalent load and artificial boundary. This method can well reflect the dynamic soil-structure interaction, and thus it has been widely used in dam engineering and underground engineering. Moreover, this method is easy to be realised in the homogeneous linear elastic foundation but difficult in the overburden foundation with the soil nonlinearity. In this study, a simplified finite element model for the free field is established according to the deformation mode of the free field at the lateral boundary. This simplified model can conveniently and precisely obtain the nonlinear dynamic response of homogeneous or layered overburden under the action of normal incidence of the multi-direction earthquake. Then, a seismic wave input method is developed for nonlinear dynamic analysis of earth dams built on overburden. Besides, the established method is combined with the dynamic real-time nonlinear artificial boundary of ground material parameters. The numerical examples show that this method can reduce the amount of calculation grid remarkably, meanwhile can reflect the effect of overburden on the spectrum of earthquake response with high accuracy.

Key words: earth dam, overburden, seismic wave input, free field, nonlinear artificial boundary