Shaking table tests on topographic effects of circular-arc valleys

As a typical locally irregular topography, the valley can change the seismic properties within the local site, which is usually called the topographic effects. This phenomenon has been confirmed by numerous ground shaking observations and earthquake damage records. However, the current knowledge on the site effects of the valley is focused on analytical or numerical methods, lacking the experimental data from physical models. In this study, a free-field shaking table model test method considering the valley effects is established, and a series of shaking table tests on the topographic effects of valleys are carried out. Three sets of circular-arc valley topographies with depth-to-width ratios of 1/8, 1/4 and 1/3 are designed, and the free-field tests under the flat field are used as a reference to compare the topographic effects of the valley site, and the effects of different topographic conditions on the valley effects are investigated. The results show that the valley effects cause the amplification of the ground acceleration response at the local site, and the amplification effects are most significant at the valley top, while the acceleration response within the valley gradually increases from the valley bottom to the valley top. The ground acceleration amplification effects caused by the valley topography are more significant with the increase in the incident frequency. The amplification effects of the valley topography gradually increase with the increase of depth-to-width ratio. The research results can provide a scientific basis for the seismic safety analysis of structures around valleys.