Analysis of circular tunnels due to seismic P-wave propagation, with emphasis on unreinforced concrete liners

A set of closed-form expressions to calculate tunnel liner forces due to compressional seismic P-wave propagation is presented. The results are compared against a state-of-practice method that considers only shear S-waves, and verified against dynamic numerical analyses. Under the realistic assumption of full-slip conditions at the liner-rock mass interface, it is shown that P-waves can lead to significantly higher axial hoop forces compared to S-waves, and can be critical for tunnels bored through areas of irregular topography/geological stratigraphy. The findings are of particular interest for the analysis of unreinforced concrete tunnel liners, where earthquake effects can be a governing factor.