Centrifugal model tests on mainshock response directionality and aftershock effect of slopes

A centrifugal model shaking table test with gravity of 50 times is carried out on a sandy slope containing an inclined bedrock interface to investigate the characteristics of changes in slope response and deformation under the action of the main shock-aftershock sequence. Firstly, the acceleration amplification effect of the mainshock is discussed through the time and spectral analysis, then the relationship between the mainshock response directionality and the amplification coefficient together with the mechanism of the truncation effect is explained using a model for rigid wedge-shaped sliding body. Finally, the aftershock effect and its influence are explored through the cumulative deformation. The results show that the amplification effect is frequency-dependent. The low-frequency part of the response is amplified to different degrees with the increase of elevation, while the amplification coefficient defined by PGA needs to be combined with the consideration of the response directionality due to the difference between downslope and upslope. The truncation effect and its relations with the response directionality reflect the coupling effect of deformation and response of the slope. The analysis of the aftershock effect points out that the total displacement increment of certain parts caused by aftershock can be comparable to that caused by the mainshock. This additional influence of aftershocks should be considered in engineering design.