Inelastic response of 3-D underground structures in rock under seismic loading

This paper describes the development of a numerical approach to compute the inelastic response of three-dimensional underground structures (mainly tunnels) to seismic loading. The solution is obtained using the finite element method for the surrounding rock medium and the boundary element method for the shell liner, both in the time domain. It is assumed that there is no interaction between the rock medium and the concrete liner. This enables one to analyze the two different bodies separately and determine the response of the liner by imposing on it the displacements of the rock cavity computed under the influence of the seismic waves. Both the rock medium and the concrete liner are assumed to behave inelastically on the basis of the continuum damage mechanics theory. The seismic waves are assumed to have any arbitrary time variation and direction of propagation. The proposed methodology is used to determine the response of various underground structures under various types of loading including the seismic one. Through parametric studies, the influence of the most critical parameters affecting the structural response is determined and critically discussed.