Experimental study on the mechanical performance of unilaterally cracked tunnel lining strengthened with fiber reinforced plastics

Abstract

Adhering fiber reinforced plastics (FRP) is a typical method for reinforcing cracked tunnel linings. Due to the influence of the asymmetric effect, the mechanical response of FRP-strengthened lining with unsymmetric cracks is not known. Investigating the mechanical performance and strengthening mechanisms of FRP-strengthened linings with unilateral cracks is critical in guiding the reinforcing strategy. In this study, a series of model tests were conducted, two unilaterally cracked linings strengthened with FRP for different ranges (unilateral and full-span strengthening), and one intact lining was tested. The deformation field and damage behavior during the test process were monitored by digital image correlation analysis and acoustic emission technology. Results show that the unilaterally strengthened lining exhibits 30% higher bearing capacity and energy-dissipation capability than the full-span strengthened lining. During the damage process, a comparable percentage (50%) of tensile and shear cracks developed in all the lining specimens. However, compared to the unilateral strengthening, the extra FRP strengthening resulted in a higher severity of cracking. In addition, the strengthening mechanism of FRP-strengthened lining was analyzed based on the section-moment and section-stiffness of the linings. The full-span strengthening caused a greater stress concentration near the pre-crack, resulting in greater section moments and stiffness decay rate, contributing to structural failure. For tunnel linings with unilateral cracking, extra FRP strengthening may compromise reinforcement efficiency.

Graphical abstract

Keywords

model test / tunnel lining / unsymmetrical crack / FRP strengthening / mechanical performance / strengthening mechanism

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