An extensive shaking table study of the progression of damage caused by liquefaction in a concrete-faced rockfill dam on deep overburden

Understanding the seismic damage evolution of concrete-faced rockfill dams (CFRDs) on deep overburden is essential for seismic safety assessment in high-intensity earthquake regions. This study conducted a large-scale shaking table test to investigate the progressive development of overburden liquefaction and dam deformation under bidirectional seismic excitation. The Hilbert–Huang transform (HHT) and marginal spectrum were used to identify time–frequency energy transmission characteristics. The results show that overburden liquefaction produces a pronounced seismic shielding effect, reducing the horizontal acceleration amplification factor at the dam crest from 1.43 under 0.1 g shaking to 0.57 under 0.8 g shaking. The dominant horizontal frequency shifts from 8–10 Hz to 2–3 Hz, indicating substantial stiffness degradation. The liquefied overburden acts as a highly damped low-pass filter, attenuating high-frequency shear waves while vertical energy remains amplified. Damage evolves from initial densification and shear deformation to plastic softening and overall reshaping, causing crest flattening, lateral spreading, and face slab–rockfill voiding. The maximum cumulative crest displacement reaches 15.7 mm under 0.8 g shaking. These findings provide physical evidence for seismic design and risk assessment of CFRDs founded on deep overburden.