COMPARATIVE STUDY ON TUNNEL LINING CONCRETE STRENGTHENED WITH CARBON-FIBER COMPOSITE CABLES AND SHEETS

Abstract

Most lining concretes of road tunnels in Japan have been gradually deteriorated by aging and various environmental effects. The study focuses on a strengthening system for tunnel lining concrete (TLC) subjected to external forces. Carbon fiber (CF) sheets are often used in TLC for preventing concrete exfoliation. The strengthening effect of CF sheet for TLC was not sufficiently known. The experimental study conducted a mock-up loading test to examine failure mode and load-capacity of the TLC model bonding CF sheet. In addition, the study prepared TLC models strengthened with near-surface mounted (NSM) technique using carbon-fiber composite cables (CFCC). The strengthening effects of CF sheet and NSM-CFCC were quantified and compared via the mock-up loading test. The experimental study revealed that the TLC model bonding CF sheet failed by intermediate-crack-induced debonding at around 100 kN, and the load carrying capacity was almost equivalent to the capacity of non-strengthened TLC model. On the other hand, the NSM-CFCC strengthened TLC model indicated higher ductility after concrete cracking and superior load capacity. The experimental study confirmed the NSM-CFCC as an effective strengthening system for TLC members.