Spatial seismic response of non-uniform wide river valley with multistage slopes in lower reaches of Yangtze River

The geological conditions of the wide river valley in the lower reaches of the Yangtze River are characterized by complex site conditions due to the presence of multistage slopes and non-uniform stratigraphy. Considering such conditions, a finite element analysis model for multistage slopes in wide river valleys was developed. The model is based on the ABAQUS software platform, and a viscoplastic memorial nested yield surface model of soft soil is used to simulate the nonlinear dynamic properties of soils. The spatial variability characteristics of the seismic response at different depths of stratigraphy and the ground surface under the influence of traveling wave and overlying water pressure are investigated. Results show that the seismic response at different locations on the ground surface of the river valley site varies significantly, and the change pattern is consistent with topographic relief. The seismic response produces abrupt changes at the top of the multistage slopes, topographic relief, and lenticular body. The response spectrum of the ground surface exhibits characteristics of multiple peaks and a strong response over a wide range of periods, and the peak acceleration at the bottom of the river valley on both sides exceeds that on the ground surface. A comparison between the calculated and simplified model results ignoring topographic relief and soil non-uniformity further reveals the spatial variability of the seismic responses of the non-uniform wide river valley site.