Mechanical Behavior of Ultrahigh-Performance Concrete Tunnel Lining Segments

Abstract

Ultrahigh-performance concrete (UHPC) is a novel material demonstrating superior mechanical, durability and sustainability performance. However, its implementation in massive structures is hampered by its high initial cost and the lack of stakeholders’ confidence, especially in developing countries. Therefore, the present study explores, for the first time, a novel application of UHPC, incorporating hybrid steel fibers in precast tunnel lining segments. Reduced scale curved tunnel lining segments were cast using UHPC incorporating hybrid 8 mm and 16 mm steel fibers at dosages of 1%, 2% and 3% by mixture volume. Flexural and thrust load tests were conducted to investigate the mechanical behavior of UHPC tunnel lining segments thus produced. It was observed that the flow of UHPC mixtures decreased due to steel fibers addition, yet steel fibers increased the mechanical and durability properties. Flexural tests on lining segments showed that both the strain hardening (multiple cracking) and strain softening (post-peak behavior) phases were enhanced due to hybrid addition of steel fibers in comparison with the control segments without fibers. Specimens incorporating 3% of hybrid steel fibers achieved 57% increase in ultimate load carrying capacity and exhibited multiple cracking patterns compared to that of identical UHPC segments with 1% fibers. Moreover, segments without fibers incurred excessive cracking and spalling of concrete at the base under the thrust load test. However, more stable behavior was observed for segments incorporating steel fibers under the thrust load, indicating its capability to resist typical thrust loads during tunnel lining field installation. This study highlights the potential use of UHPC with hybrid steel fibers for improved structural behavior. Moreover, the use of UHPC allows producing structural members with reduced cross-sectional dimensions, leading to reduced overall structural weight and increased clear space.

Influence of Fiber Addition on the Properties of High-Performance Concrete

“…Not only are the values of the flexural strength reflected in the studies on FRC, but the failure modes for specimens in flexural tests show similarities with other research. Abbas et al [66] tested tunnel lining segments using UHPC with fiber dosage where the crack developed during the progression of load in the middle part of the sample.…”

Structural and environmental performance of recycled steel fiber reinforced concrete segment under the thrust force of the tunnel boring machine jacks

“…Adding fibers improve the mechanical structure behavior and reduce the overall construction cost by reducing the rebars number. 5,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] The durability and structural performance of tunnel lining segments were investigated by Abbas et al 13 This study was performed on full-scale samples that compared the performance of the steel fiber reinforced concrete (SFRC) segment with the conventional reinforced concrete (RC) segment. Finally, it was concluded that due to the presence of fibers in the concrete volume, the postcracking behavior of SFRC samples has been significantly better and has improved compared to conventional samples.…”

“…[25][26][27][28] Abbas and Nehdi conducted thrust load test to study the behavior of precast UHPC segments. 19 They observed that the segments without fibers incurred excessive cracks and concrete spalling under the thrust loads. However, a better performance was observed for segments with steel fibers, indicating their capability to resist typical thrust loads.…”

“…Various studies were conducted concerning the structural performance of precast concrete tunnel lining (PCTL) segments and the impact of the tunnel boring machine (TBM) thrust jacks. Adding fibers improve the mechanical structure behavior and reduce the overall construction cost by reducing the rebars number 5,8–24 . The durability and structural performance of tunnel lining segments were investigated by Abbas et al 13 This study was performed on full‐scale samples that compared the performance of the steel fiber reinforced concrete (SFRC) segment with the conventional reinforced concrete (RC) segment.…”

Prediction of the Interface Shear Strength between Ultra-High-Performance Concrete and Normal Concrete Using Artificial Neural Networks

“…Recent decades have witnessed the emergence of ultra-high-performance concrete (UHPC) as a promising cementitious material in buildings [1], bridges [2], and tunnels [3], etc., due to its excellent tensile and compressive strength [4], agreed post-cracking behaviors [5], and enhanced durability [6]. Extensive application of UHPC materials to fully replace normal-strength concrete (NC) would render the cost prohibitively high [7].…”