3-D SEISMIC RESPONSE ANALYSIS OF LONG LINED TUNNELS IN HALF-SPACE

The dynamic response of infinitely long lined tunnels with a uniform c ross-section buried into an elastic or viscoelastic half-space to body and surface harmonic seismic waves is numerically determined by a spe cial direct boundary element method in the frequency domain. The waves have an arbitrary direction of propagation with respect to the axis o f the tunnel and this renders the problem three-dimensional, However, this problem is effectively reduced to a two-dimensional one by a coor dinate transformation and appropriate integration of the full-space dy namic fundamental solution along the direction of the tunnel axis. Qua dratic isoparametric boundary line elements and advanced numerical int egration techniques for the treatment of singular integrals produce re sults of high accuracy. Numerical results are presented for the case o f an infinitely long lined tunnel of circular cross-section and compar ed against those of a full three-dimensional boundary element analysis , as well as those of other methods. Thus the proposed method is illus trated and its merits demonstrated.