Abstract: he seismic design of a high concrete face rockfill dam (CFRD) sitting on thick layered alluvial deposit poses a significant challenge. This study focuses on seismic responses of both its deep alluvial deposit and its structure, using a plasticity constitutive model for large post-liquefaction deformation of sand (CycLiq) and a high-performance GEOSX platform for solid-fluid coupled analysis. The findings reveal the seismic responses are notably stronger in areas adjacent to the banks, where the alluvial deposit is thinner. This underscores the limited reinforcement effect of gravel columns if located on the floor of the valley where alluvial deposit is deep. This study suggests an optimized treatment scheme, emphasizing the reinforcement of alluvial deposit near both banks. Our analysis shows that for these areas, the scheme of adopting a large area replacement ratio of gravel columns can yield a significant improvement on the reinforcement, an 80% decrease in gravel column treating work, and up to 26% reduction of joint deformation.

Key words: high CFRD, thick layered alluvial deposit, seismic response, gravel column, optimization of foundation treatment