Simplified analysis of the lining behavior during earthquakes in deep rock tunnels

The sizing of the lining of a tunnel requires to consider not only the static loads transmitted from the surrounding rock, but also the effects of earthquakes on the stresses and strains of the lining. The detailed evaluation of the interaction earthquake-lining using numerical methods typically requires very long calculation time and can be limited to the verification of the project final configuration. In this study a simplified procedure for the assessment of the effects of an earthquake on the tunnel lining is presented. This procedure is based on the calculation method Einstein and Schwartz and quickly allows the estimation of maximum moments induced by the earthquake in the lining. Through this procedure it was possible to develop a parametric analysis that allowed to evaluate the pseudo-static loads that is necessary to consider on the rock around the tunnel, according to the earthquake characteristics and to the geomechanic quality of the rock mass. A final calculation example illustrates the modalities for the analysis of a tunnel lining in the presence of a defined earthquake, using the charts developed in the present paper.