Seismic Response Analysis Of Deep Soft Soil Site And Large Scale Shaking Table Test

In this paper, an offshore artificial island located in a highly seismic zone of our country was selected as a prototype to carry out the large-scale shaking table test. Firstly, the seismic response of the artificial island was explored, and then the possibility of seismic subsidence of the artificial island was studied, finally, the seismic subsidence was calculated quantitively. This research laid a solid foundation for the study to deformation coordinated design of bridge-island-tunnel, the conclusions are as follows.A typical artificial island site is a soft soil interlayered one, the soft soil layered in this site can absorbs and filters the seismic waves. On one hand, the soft soil layer can absorb the earthquake energy significantly, leading to the decrease of the PGA (Peak Ground Acceleration), on the other hand, the soft soil layer has an effect to amplify the low frequency and suppress the high frequency component of seismic waves. With the increase of the amplitude of input motion, the ARS (acceleration response spectrum) of the typical artificial island site increases, yet an decrease is observed in the amplification factor spectrum, at the same time, the spectrum changes from a unimodal spectrum to multimodal one gradully.At the same saturated soil layer, the excess pore water pressure increases with the decrease of elevation. The excess pore water pressure can be decomposed into two parts: baseline and shock. The "baseline" part increases gradually first, followed by a decrease trend. The "shock" part of the excess pore water has some intrinsic link to the displacement-time history.Seismic settlement is observed in both the typical artificial island site (soft soil interlayered site) and the overlaying embankment, and the quantity of seismic settlement increase linearly with the increase of amplitude of input seismic waves. The settlement is triggered by the soft soil layer primarily. Composite pile foundation has an obvious effect to alleviate the seismic settlement,28percent of decrease is recorded compared to the natural foundation. But the composite pile can intensify the seismic response of the typical artificial island. The seismic settlement of the embankment doesn’t exceed the permissible value of the specification even under strong earthquake.