Seismic cracking evolution for anti-seepage face slabs in concrete faced rockfill dams based on cohesive zone model in explicit SBFEM-FEM frame

It is critically importance to accurately locate vulnerable areas and quantitatively assess the damage of the face slab in the seismic safety evaluation of concrete faced rockfill dams (CFRDs). In this paper, the cohesive zone model (CZM) is augmented with generalized plastic models of the rockfill and state-dependent elasto-plastic model of the interface to investigate the seismic cracking evolution in the slab of CFRDs. An explicit coupled scaled boundary finite element method-finite element method (Explicit SBFEM-FEM) is developed to enable cross-scale analysis. The method considers the strain softening of rockfill and concrete after being damaged, and avoids negative stiffness and convergence problems that can be found during implicit analysis. A fine, cross-scale model of the CFRD is established based on the quadrature technique. Subsequently, simulations of the construction and impoundment processes are performed to facilitate dynamic analysis. In the first step, different damping ratios for the slab are simulated to optimize accuracy and efficiency. Then, the seismic cracking evolution of the slab is investigated in detail with consideration to the ground motion intensity and steel reinforcement. The results indicate that the computational efficiency can be significantly improved by decreasing the damping ratio of the concrete face slab in the explicit seismic analysis. Penetrating cracks are observed on the slab and the crack reaches maximum width during the earthquake. A residual width is retained after the earthquake. The simulated failure mode of face slab conforms to the characteristics of concrete. The developed method can help precisely locate weak areas of face slab, quantitatively determine the damage severity, and evaluate the ultimate seismic performance of the slab in the CFRDs. In addition, the method can be further employed for concrete cracking analysis involving soil-concrete interaction.