Abstract: An interactive finite element model for analyzing the unsteady seepage flow of earth dam is established by secondary development of ABAQUS user subroutines in Fortran and Python language. The non-linear dynamic loads on the surface of dam body and dam foundation can be applied in the model by programming user subroutines using the Fortran language. Meanwhile, the water level drawdown is realized by interactively processing the water level drawdown parameters by visualizing the subroutine using the Python language. The seepage field and stress field during water level drawdown of homogeneous earth dam can be calculated by the model based on the principle of fluid-structure interaction and strength reduction method. The validity of the model is verified by comparing the largest elevation of phreatic line and the transient safety factor of the dam with previous studies, and also by case study on the Shilihe reservoir project. The research finding serves as a method for calculating the seepage characteristics and stability of dams in the presence of reservoir water level drawdown, and provides a reference for risk analysis and emergency management of small and medium-sized earth and rock dams under extreme working conditions.

Key words: :earth dam, unsteady flow, interactive finite element model, fluid-structure interaction, water level fall, dam slope stability