Study on Seismic Spectrum and Amplification Effect of Soft Soil in Tianjin New Coastal Area

Tianjin new coastal area has a large area of soft soil with high salinity and high humidity. This kind of foundation has unique spectral characteristics and amplification effect on ground motion, which is a deep factor to increase earthquake damage. Based on the geotechnical data of Tianjin new coastal, we established a simplified calculation model and adopted a nonlinear method to study the seismic spectrum and amplification effect of three typical soft soil foundation with different thickness in Tianjin new coastal area, which real earthquake motion EL-Centro seismic wave passing through, that is in order to provide a basis for the seismic design of engineering structures in this area. The results show that: The soft soil foundation in Tianjin new coastal area has an obvious amplification effect on EL-Centro wave within 8HZ, while the seismic wave greater than 8HZ rapidly attenuates after filtering through the soft soil, and the amplitude greatly reduced. After the EL-Centro wave passes through the three types of soft soil, the acceleration, velocity and displacement coefficient are always in the state of amplification. The amplification coefficient is the largest in the muddy soil, followed by the muddy clay and the smallest in the silty clay. The softer the soil, the more obvious the amplification effect will be. Except the displacement amplification coefficient does not change much with the increase of soft soil thickness, the acceleration and velocity coefficients increase gradually with the increase of soft soil thickness, and the amplification effect is obvious after reaching the surface.