Abstract: Accurate prediction of the stress-deformation behavior of a concrete-faced rockfill dam (CFRD) under frequent reservoir stage fluctuations is critical to ensuring the safety of the pumped-storage power station. This study develops an improved constitutive model, GP_WHU, in the framework of the generalized plasticity theory, and demonstrates the application of a corresponding user module. We conduct triaxial tests on representative volume elements (RVE), and use the measurements to validate the model's performance, verifying its capability of effectively capturing the stress-strain response of rockfill materials under triaxial shear, single loading and unloading, and low-frequency multi-cycle loading and unloading conditions. We apply this new model in a case study of an upper reservoir CFRD under construction for a pumped-storage power station in Hezhou, and conduct numerical simulation of dam filling, initial impoundment, and stress-strain response under cyclic reservoir stage fluctuations. Results show the initial impoundment caused significant displacement increment and principal stress direction deviation in the upstream slope area, with the maximum displacement increment occurring at roughly one-third of the dam height from the bottom. And under cyclic hydrodynamic loading, significant cumulative displacement occurred in the dam body near the bottom of the upstream slope in the water level fluctuation zone, and the maximum settlement increment accounted for roughly 3% to 9% of the settlement at the end of construction. As the cycling number increased, both deformation and stress in the dam body and face slabs gradually incresaed but tended to stabilize after around 100 cycles. The study provides key computational support for a full consideration of the effect of frequent reservoir stage fluctuations in the design and operation of CFRD.

Key words: concrete-faced rockfill dam (CFRD), impounding process, frequent water level fluctuation, constitutive model, numerical simulation