Effect of Underground Structure on PGA at Ground Surface Considering Linear and Nonlinear Behavior for the Soil

In this paper, a numerical model was first verified against dynamic centrifuge tests results performed on an underground subway tunnel and then, the effect of underground structure on peak ground acceleration (PGA) at the ground surface investigated considering linear and nonlinear behavior for the soil. The results show that in the range of natural frequency of the system, nonlinear model shows deamplification of PGA with respected to the freefield. Whereas, linear model shows opposite trend. Out of the range of natural frequency of the system, linear and nonlinear models predict same results and for both model, underground tunnel resulted in amplification of low frequencies and deamplification of high frequencies with respected to the freefield.