About the author:

China Railway 18th Bureau Group Third Engineering Co., Ltd., Zhuozhou, Hebei 072750, China

Abstract:

During the long⁃term use of tunnel lining concrete, spalling defects may occur which seriouslyaffect the safety and stability of the tunnel. To explore the early identification methods of spalling defectsin tunnel lining concrete, the vibration characteristics and risk assessment methods of spalling defectswere studied through indoor experiments. The results show that as the spalling area of the defect expands,the lowest⁃order modal frequency of the tunnel lining significantly decreases, indicating a reduction in theoverall stiffness of the lining. The low⁃order modes are more sensitive to changes in the interface adhesionstate and are suitable as discriminant indicators for spalling assessment. In contrast, the high⁃ordermodes, due to their small frequency spacing and severe modal overlap, are not conducive to accuratelyidentifying the trend of changes and are not suitable as the main evaluation basis. The vibration signals atthe defect areas of the lining concrete exhibit significant low⁃frequency characteristics, especially in areaswith a higher risk of spalling,where the enhancement of low⁃frequency components and the weakening ofhigh⁃frequency components in the vibration signals are obvious, indicating that low⁃frequency signals havean important indicative role in the earlywarning of lining spalling.