Abstract:Dynamic interaction between arch dam and unbounded foundation has great significance on the seismic response of dam structure. Although various computational models for arch dam-foundation interaction have been developed by researchers,most of these models were based on the assumption of uniform homogeneous foundation medium. Taking advantages of the scaled boundary finite element method(SBFEM),the influence of the foundation inhomogeneity on the seismic response of high arch dams is studied. The arch dam,the unbounded foundation and the reservoir are all modeled by the SBFEM. Discretization is carried out only on dam-foundation interface and the surfaces of dam structure,thus the computational effort is reduced to a great extent. Assuming that the elastic modulus of the unbounded foundation varies according to an exponential law along the depth,complex frequency-response functions of a 210 m high double curvature arch dam are calculated. Three cases have been studied and compared,namely,massless foundation,homogeneous unbounded foundation and inhomogeneous unbounded foundation. It is found that,in contrast with the case of gravity dams,the foundation inhomogeneity brings little influence on the seismic response of arch dams. This phenomenon can be physically explained as follows. Unlike the gravity dam,where the connection between the dam and the foundation is very massive,the connection between the arch dam and the foundation is more flexible;far-field foundation impedance has little influence on the seismic response of the dam,only the near-field impedance affects the arch dam response to some extent. In order to get a better understanding of the effects of the near-field impedance,some cases of the variation of the near-field foundation models have been examined. The general tend of the conclusions is applicable for the design of high arch dams located in high seismic area.