Analytical study of saturation effects on seismic vertical amplification of a soil layer

An analysis is presented of saturation effects on the amplification of a single soil layer to vertical earthquake excitation. Rigorous solutions for various responses are derived based on Biot's theory and the concept of homogeneous pore fluid. The transfer function of the layer is described as a function of degree of saturation, soil properties, layer thickness and loading frequency. Numerical examples are given to illustrate the influence of saturation on the motion amplification. The present study indicates that partial saturation of soils may always lead to a larger amplification compared with a full saturation model, and consequently provides a physical insight into an array observation on vertical site amplification during the Kobe earthquake of 1995.