Study of ground motion effect of trapezoidal valley site based on centrifuge shaking table test

Studying the seismic effects of valley site has critical guiding significance for site selection and aseismic design. Based on the analysis of centrifuge shaking table tests, the ground motion response pattern of the trapezoidal valley was studied. The results showed that there was a certain amplification effect of ground motion in the bedrock valley site. The amplification effect varied with the change of terrain, but the amplification effect was not significant. Different site locations had a small influence on the response spectrum. In the bedrock-overburden model, an obvious increase of the ground motion magnification was observed at the bedrock surface. Different magnifications were found under different input ground motions. The amplification effect of the ground motion was particularly evident on different sites when the frequency band was in the range of 0.5-2.5 s. In this frequency band, the frequency range of ground motion amplification was increased significantly, which was different from the pure bedrock sites. In the case of the pure bedrock sites, although the shape of the response spectrum was somewhat different for individual sites, the plateau value and characteristic period of the response spectrum were similar. Due to the terrain effect of the valley site, the amplification factors of the peak surface acceleration of the valley site changed with the change of the terrain. The higher the terrace levels of the valley, the greater its magnification, and the amplification of valley bottom was the smallest. With the increase of the input ground motion intensity, the higher the terrace levels, the higher the plateau value, and the greater the characteristic period of the response spectrum.