ABSTRACT
The paper focuses on the evaluation of the effect of earthquake on underground structures using the finite element method. The dynamic effects can be addressed either by a fully dynamic approach or using a pseudo-static calculation. Fully dynamic calculations are based on a direct application of recorded accelerations to the actual computational model of the tunnel. In the pseudo-static analysis the effect of earthquake is transformed into an equivalent shear strain constant within individual soil layers. These are introduced in the form of displacements prescribed along the vertical boundaries of the FEM model in a usual static manner. This also implies the basic assumption of the geometry and material parameters of the geological profile not varying in the horizontal direction. In both cases it is generally accepted that vertical propagation of the pressure and shear waves can be described as a time-dependent 1D analysis of so called free-field column. Example comparing both approaches together with popular analytical methods is presented to highlight their advantages as well as drawbacks.
