Amplification Effect of Rockfill Dam with Overburden Under Far-Field Long-Period Earthquakes

An increasing number of rockfill dams are constructed on deep overburden in strong seismic areas. And, strong earthquakes tend to generate seismic load rich in low-frequency components. These will bring great challenges to the seismic safety of dams on deep overburden, which have large natural vibration periods. However, few studies have been conducted on this issue. In this paper, a series of studies on the dynamic amplification effect of dams on deep overburden are carried out in conjunction with the spectral characteristics of seismic load. The effects of overburden thickness and seismic intensity are also involved. The results show that the peak accelerations of dam crest and dam–foundation interface under the far-field long-period earthquakes are over 2.50 and 3.50[Formula: see text]times higher than those of the ordinary (short-period) earthquakes, respectively. The natural vibration period of the dam–foundation system is prolonged during the seismic process and gradually converges to the dominant period of the far-field earthquakes, which induces the resonance effect more easily and leads to a significant increase in the acceleration with the increase in thickness of the overburden or seismic intensity. Specifically, the acceleration amplification coefficient of the dam–foundation interface is over 60% higher for the dam with 300[Formula: see text]m overburden compared with the dam with 100[Formula: see text]m overburden. Notably, the acceleration of the dam–foundation interface under 0.1[Formula: see text]g far-field earthquake even exceeds that under 0.3[Formula: see text]g ordinary earthquake. This study can provide important reference for the seismic safety design of rockfill dams on deep overburden in strong earthquake areas.