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Abstract Taking the San-I No. 1 tunnel damaged by the 1999 Chi-Chi earthquake for example，the associated failure mechanism is studied by means of numerical analysis and related investigation results. Numerical simulation results reveal that，in accordance with all depths of damage sections close to 0.25 wavelengths of incident waves；the combination of tunnel depth and wavelength causes wave reflection from ground surface and wave scattering from tunnel periphery，and leads to particularly pronounced amplification of earthquake-induced stress of lining，that results in lining damages. The four significant damage patterns of lining are also elucidated，including the longitudinal cracks，circumferential cracks or construction joint dislocation，circularity-spalling of lining concrete，as well as oblique cracks and associated spalling of lining concrete. The earthquake-induced exceeding axial-and flexural stresses caused by the S wave with vertical and 45? incident angle yield to the longitudinal cracks. The tensile failure caused by horizontally propagating P wave and the stress increment caused by Love wave dominate the circumferential cracks or construction joint dislocation. The stress increment caused by the S waves with 45? incident angle，occurred nearby opening refuges and amplified while a tunnel subjected to significantly horizontal stress results in the circularity-like spalling. The propagating S wave induced distinct strains in-between of the soft and hard rock layer lead to the oblique cracks and associated spalling. This study clarifies the earthquake-induced damage patterns of rock tunnels and associated affecting factors，which is conductive to aseismic design for tunnels.
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Received: 23 April 2010
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2011, Vol. 30 
