Abstract: The separation between concrete face slab and rockfill due to uncoordinated deformation is a common phenomenon in the concrete-faced rockfill dam engineering. It may even cause cracking of concrete face slab and threaten the overall safety of the dam. Therefore, it is necessary to analyze whether the separation will occur and predict the separation magnitude. However, the previous calculation methods can hardly achieve a balance between intuition, accuracy, and ease of implementation. The paper attempts to treat the separation as relative displacements of discontinuous interface in an object and use the extended finite element method (XFEM) to simulate the movement. A hybrid XFEM contact constitutive model is extended to three-dimensional(3D) to describe the three dimensional opening and dislocation of discontinuous interfaces. Results are compared using the self-programming and the ABAQUS contact mechanics methods in a slider model example, and to validate the 3D interface contact algorithm. Taking the Tianshengqiao concrete face rockfill dam as an example, the separation of the face slab is calculated and compared with the measured values and simulated results by the dual mortar method, which verifies the ability of this method to calculate the large-scale practical engineering.

Key words: extended finite element method(XFEM), separation, contact constitutive model, three-dimensional