Dynamic Response Characteristics of Layer Structure Slope Based On Transfer Function Analysis

Through the shaking table test, this paper proposes a conclusion about the failure process of layer slopes under earthquake with different structures and lithology. Meanwhile, by using the transfer function of white noise signal input, the first modal damping of side slope model was deduced. The relationship between the damping ratio change and the model structure during the damage process of the model was analyzed. The test results indicate that the instability mechanism of four types of slope under earthquake can be concluded as: The hard rock bedding slope is caused by bedding slope drift - bottom collapse and bending instability. The hard rock anti-dipping slope is caused by trailing edge pull apart and middle-bottom part shear and slide type instability. The soft rock bedding slope results from bedding slope drift - bottom extrude - layer slip instability. The soft rock anti-dipping slope results from bending-located and shear type instability. Additionally, the dump change characteristic of the side slope model indicates that larger first modal damping changing happens in hard rock structure. As the earthquake becomes stronger, the damping of slope system will increase sharply in the development of failure surface. However, the damping ratio change characteristic of the soft rock slope is relatively gentle, which means the soft rock is less sensitive to the strength of the earthquake. The abrupt damping ratio change of the anti-dipping slope indicates the structural alternation of which is more obvious during an earthquake. Which gives a good explanation that why more earthquakes have occurred in hard rock slopes and why the earthquakes were stronger in anti-dipping slopes, as shown in 5.12 Wenchuan earthquake, 2008.