Scattering of SH Waves Induced by Interaction between a Truncated Semicircular Canyon and a Lined Tunnel

Abstract

Seismic wave propagation is affected by both irregular surface terrains and underground tunnels, resulting in the amplification or attenuation of ground motion. Hence, it is crucial to tackle the scattering issue of plane shear horizontal (SH) waves by topographical features and subsurface facilities during an earthquake. In this study, a series solution is formulated to address the scattering issue of SH waves due to the interaction between a truncated semicircular canyon and a lined tunnel. Based on the wave-function expansion method and the classical mirror image method, wave-function expressions are established in different polar coordinate systems. Furthermore, the region-matching technique is adopted to determine the unknown coefficients in algebraic equations. A thorough parametric analysis in both the frequency and the time domain is undertaken to demonstrate the effect of the interaction between the irregular surface canyon and the underground lined tunnel on ground motion. The numerical results indicate a pronounced amplifying effect on ground motion in the presence of a tunnel. Under SH wave vertical incidence, the peak ground displacements beyond the canyon are observed at the canyon shoulder where the tunnel is located.