Exploratory study of ultra-high performance fiber reinforced concrete tunnel lining segments with varying steel fiber lengths and dosages

• The performance of 1/3 scale tunnel lining segments made with UHPFRC was explored.
• Tunnel lining segments with short fibers showed improved peak load and strain hardening.
• Tunnel lining segments with longer fibers showed more stable post-peak (strain-softening).
• The thrust load test showed that fiber-reinforced segments had improved cracking behavior.
• UHPFRC tunnel linings can be beneficial, especially in corrosion prone environments.

Ultra-high performance fiber-reinforced concrete (UHPFRC) is an emerging material exhibiting superior mechanical and durability properties. However, its application in precast concrete tunnel linings is lagging due to lack of experimental data and adequate design provisions. This study is a preliminary investigation of UHPFRC tunnel lining segments incorporating various steel fiber lengths and dosages. The mechanical performance of UHPFRC tunnel lining segments was investigated. Flexural and edge-point load tests were conducted on 1/3-scale UHPFRC tunnel lining segments to evaluate its bending and thrust load resistance. The main studied variables were the steel fiber lengths and dosages. Results showed that UHPFRC tunnel lining segments incorporating shorter steel fibers exhibited higher cracking and peak loads compared to that of similar segments made with longer fibers. Furthermore, the shorter fibers enhanced the strain hardening phase, leading to more stable multiple micro-cracks and higher resistance to growth of macro-cracks. Conversely, longer steel fibers better improved the post-peak strain softening of the lining segments, achieving more ductile failure. The load carrying capacity of UHPFRC lining segments linearly increased with higher fiber dosage and followed the rule of mixtures. Moreover, steel fibers enhanced the cracking behavior under both thrust load and concentrated load compared to that of segments without fibers.