山岭隧道受震损害类型与原因之案例研究

 以1999年台湾集集地震造成完工通车仅1 a的三义壹号铁路隧道损害为例，应用隧道受震数值分析成果及相关研究，探讨隧道受震损害的原因。研究成果显示，受震损害区段皆落于埋深接近0.25倍岩体波长的范围内，即隧道埋深与岩体特性的组合强化震波受地表自由面反射与隧道散射的效应，导致衬砌受震引起应力大幅增加而造成破坏。而衬砌损害可归纳为4种类型：纵向裂缝、环向裂缝或环向施工缝错动、环状剥落以及斜向裂缝与剥落。分析隧道施工地质记录及震后检测结果显示，衬砌纵向裂缝主要受地盘深处上传的S波垂直方向或45?入射导致衬砌轴力与弯矩受震增加而影响。环向裂缝或环向施工缝错动则受到水平方向P波造成的张力破坏以及乐夫波造成衬砌应力增加的影响。环状剥落系隧道承受较显著的水平方向应力下，S波45?入射导致衬砌应力增量以及避车洞开口结构配置的影响。而斜向裂缝则受S波通过软硬地盘互层的应变差异以及隧道衬砌结构刚度特性所致。研究成果表明隧道受震损害原因与影响因素，可为山岭隧道耐震分析与设计提供参考。

CASE STUDY OF EARTHQUAKE-INDUCED DAMAGE PATTERNS OF ROCK TUNNEL AND ASSOCIATED REASON

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.