Abstract: The traditional finite element method has certain limitations in modeling the dam-irregular foundation-reservoir system. Based on the ABAQUS secondary development interface, the scaled boundary finite element method (SBFEM) and the octree mesh are combined in this paper, and an automatic model generation method considering real terrain is established. The constructed octree SBFEM is used to numerically verify the seismic response of a gravity dam. Subsequently, the elastic and nonlinear dynamic response of the NG5 arch dam system was analyzed based on the flat foundation and the irregular foundation, respectively. The results show that, under seismic action, compared with the simplified flat foundation arch dam system, the transverse river relative displacement of the top and bottom and the peak of first principal stress of the undulating foundation arch dam system change greatly, increasing by 73.5% and 103.6% respectively. Considering the transverse joint and material nonlinearity of the arch dam, the relative displacement and velocity of the top and bottom of the arch dam increase by 43.9%, 32.0% and 56.6%, respectively. At the same time, the normal opening of the edge joint increases significantly, increasing by 388.9% and 381.8%, and the peak opening increases by 105%. In terms of stress and damage, the peak of first principal stress increases by 81.6%, and the area with damage also expands along the bottom of the dam.

Key words: scaled boundary finite element method (SBFEM), high arch dams, octree mesh, nonlinear response, irregular terrain