Abstract: Saturated soil layer, located below underground water level, is a two-phase medium(fluid-saturated porous medium). We take into account the interaction between water and soil for wave propagation. In order to consider the coupled effect of soil and water in saturated soil, we introduce Biot’s theory of fluid-saturated porous media to seismic response of soil layer, calculating seismic response of the layer. On the basis of finite difference method and artificial transmitting boundary method, we put forward a method for seismic response analysis for soil layer of two-phase medium. Monitoring well No.3 of Xiangtang array is taken as an example. Furthermore, we use the new method to calculate soil seismic response at the array, and compare the results with results from equivalent linearization method, as well as actual records from intense earthquakes. Results show that both the new method and equivalent linearization method could reflect time-history curves and response spectrum data, which is similar to measured data; theoretical model of the new method is superior to single phase method, with less difference between calculated data and measured data.

Key words: seismic response of soil layer, saturated two-phase medium, time-domain analysis, ground motion parameter, groundwater