Incompatible Deformation Mechanism and Numerical Simulation of the Concrete Face Slab and Cushion Material in Concrete-Faced Rockfill Dams under Reservoir Water-Level Fluctuation and Frost Heave

This study addresses frost-heave damage to concrete face slabs in the water-level fluctuation zone of pumped-storage power stations in cold regions. A hydro-thermal-mechanical coupling model for cold-region concrete face rockfill dams was established by adopting the Van Genuchten model for the soil-water characteristic curve of unsaturated materials and introducing contact mechanics equations based on the Lagrange multiplier method. The model accounts for incompatible deformation between the face slab and cushion layer under the combined effects of reservoir water-level fluctuation and frost heave of cushion materials. Taking a cold-region concrete face rockfill dam as an example, numerical simulations were conducted to reveal the evolution of the temperature, moisture, and displacement fields, as well as the frost-heave failure mechanism. Results show that water-level fluctuation alters moisture supply through slab defects, thereby controlling cushion-layer frost deformation and inducing slab voiding and separation. The findings provide theoretical support and scientific guidance for frost-heave prevention in cold-region pumped-storage face dams.