Finite element versus simplified methods in the seismic analysis of underground structures

Seismic analysis of buried tunnels is considered herein. A comparison of results is carried out between a detailed finite element analysis and several simplified models for hand calculation. The finite element analysis is conducted by superimposing the free field motions and the interaction motions. The latter are calculated in a plane strain geometry taking into account the influence of adjacent structures with an approximation for 3-D effects and for soil non-linearities. Simplified models give, in general, conservative results, although better approximations are obtained by modelling the tunnel bends, where stress concentration occurs.