关键词: 软弱覆盖层, 土石坝, 地震动, 动力离心模型试验, 传播规律

Abstract: The anti-seismic stability of dams built on overburden is a key challenge. In order to reveal the law of ground motion propagation in the overburden and the phenomenon of dam instability, centrifuge shaking table model tests were carried out by inputting site wave and windowed sine wave successively based on a prototype project. It is found that when the target peak acceleration of site wave is 0.53g, the peak acceleration of site wave transmitted to the dam crest is 0.773g and the acceleration amplification factor is 1.39 due to the energy loss and the filtering effect of the weak overburden. The acceleration amplification factor is less than the recommended value of 2.0 in the code. In the test of inputting windowed sine wave, the amplification factor of dam crest acceleration is 1.46, which also shows that the weak overburden has a certain attenuation effect on ground motion propagation. The dam seismic subsidence deformation revealed in the two tests conforms to the general law. However, due to the large thickness of the soft sand layer, the overall seismic subsidence rate is high. There is no obvious damage to the dam body after the first test, and some phenomena are observed such as a large number of rockfill falling, dam crest subsidence, dam slope extrusion arch, core wall cracking in the second test. Although limited by the test conditions, the size effect and boundary effect of the model may have some influence on the test results, some findings in the tests can provide a reference for the dynamically numerical simulation of dam resting on soft overburden.

Key words: soft overburden, earth rock dam, ground motion, dynamic centrifuge tests, propagation behavior