A numerical study on the 2D behavior of the single and layered clayey basins

In this numerical study the effects of the stratification and change in material type on the dynamic behavior of the clayey basins are investigated. For this purpose two kinds of single and double layer basin models with the total depth of 100 m and width of 2 km have been selected. The single layer basins consist of soft, medium and stiff clayey materials, while double layer basins consist of a stiff sandy sub-layer overlaid by one of the soft, medium and stiff clayey soil layer. A range of bedrock inclinations at the valley sides from slighter (10^{circ }) and (20^{circ }) to steeper (30^{circ }) and (40^{circ }) are selected. A numerical study using finite difference based nonlinear code which utilizes appropriate static and dynamic boundary conditions, and includes hysteresis damping formulation based on user defined degradation curves is conducted using real earthquake motions of different strength and frequency content. The results of the 2D analyses show the differences in dynamic behavior of single and double layer basins from the aspect of amount and position of the maximum amplification and resonance period. It was seen that the shallower lateral parts of the basins are sensitive to lower periods while inner parts are sensitive to higher periods. Among other differences, the most important difference between the behavior of single and double layer basins was seen at the resonance period of the inner parts of the basins.