Seismic Response of Horizontal Soil Layers

Methods of analysis of the response of soil deposits during earthquakes are presented. These methods include linear elastic analyses, a bilinear analysis, and an equivalent linear analysis. All these methods require that: (1) The surface of the layer, the interface between any two sublayers and the base of the layer be essentially horizontal, (2) the material properties of the layer be constant along any horizontal plane, and (3) the applied seismic excitation be also horizontal. The closed-form solutions are utilized to evaluate the accuracy and stability of the lumped-mass analysis and criteria for the accuracy and stability of the lumped-mass representation are proposed. A lumped-mass representation is also used for the analysis of soil layers having bilinear stress-strain characteristics. Finally, a procedure is outlined for obtaining equivalent linear parameters for soils with bilinear stress-strain characteristics. The results obtained by this procedure are shown to be in good agreement with those determined by the bilinear solution.